Quantum experiment undermines the notion of objective reality
Physicists have long suspected that quantum mechanics allows two observers to observe different, conflicting realities. Now they’ve performed the first experiment that proves it by experimental realisation of what was previously a thought-experiment called ‘Wigner’s Friend’.
From MIT Technology Review.
From MIT Technology Review.
Comments (523)
The experiment produces an unambiguous result. It turns out that both realities can coexist even though they produce irreconcilable outcomes, just as Wigner predicted.
So, they can co-exist as long as there is something that can be agreed about between observers. So, we might be talking about the same thing despite having differing views about it.
In that case, you have drawn the exact opposite conclusion to what the experiment suggests.
If it said something as quotidian as you think it said, there would be no point in doing the experiment, and certainly nothing to write a story about.
The same paragraph makes the point that the two observers see two different things, which are irreconcilable. It is those observations which are at issue.
Yes; but, there can be no modality without the observer effect on a macroscopic scale concerning n>1 observers, such as has been demonstrated here? So, what's the big fuss about?
I don't believe in objective reality so this is a bit moot for me. But I'm very interested in QM so I feel the need to comment.
I think it's overstating to say that Wigner and his friend experience conflicting realities. Rather, the friend just has more information than Wigner. The difference can be interpreted as purely epistemological. Wigner knows that his friend knows which way the spin goes, but Wigner doesn't know which way. So Wigner models the lab as a superposition while the friend does not.
I can't see anything new in Wigner's thought experiment. To me it sounds the same as observing that, if we put another cat in the box with Schrodinger's first cat, but the two are separated by a transparent, airtight wall, so that the second cat doesn't get poisoned if the vial breaks, then the second cat (Wigner's friend) knows whether the first cat is alive or dead, but Schrodinger (Wigner) does not.
I can't see what there is to experiment on. I suppose I'll have to read the paper to find out, but I don't know when I'll get time to do that..
As I said to W., if it were that simple then it wouldn’t rate a comment.
I think to resort to Schodinger’s famous simile, it’s as if Bob observes a live cat, and Alice a dead one - and they’re both right.
Is that what the paper does - create a situation where both observers have the same level of detail in their knowledge, and the details contradict each other? That would be a much stronger result than anything contemplated in Wigner's thought experiment, which seems to rely on a belief in 'objective collapse' to have any interest at all..
Good to to see the experiment done. But as you might expect, the main interpretations already have standard answers for this. For example, Many Worlds has those observers in different world branches, RQM allows observers to have different accounts of the event as long as they don't compare their results, and Copenhagen would not regard the friend's interaction as a measurement (for Wigner).
Quoting andrewk
That would be a hidden variables theory (and thus non-local).
I've downloaded the full paper from arxiv and will see what I can make of it.
Cool. Perhaps @fdrake would like to give his thoughts as well?
That is what the MIT abstract says that it does:
——
Quoting Andrew M
I don’t regard that as an explanation so much as a cop-out.
So much for freedom of choice.
Right so perhaps you could correct your title to
Quantum experiment is interpretable in a way that I'd already decided was true before the experiment was even done.
It takes a theory to beat a theory.
Quoting Banno
Freedom of choice refers to an experimenter being able to choose what experiment to perform. All mainstream interpretations accept that assumption.
The assumption of reality, as defined in Bell test experiments, just means counterfactual definiteness. Most interpretations, including Many Worlds and Copenhagen, reject counterfactual definiteness. Bohmian Mechanics accepts it.
Anyway, Bohmian mechanics seems to be the interpretation that asserts counterfactual definiteness. There are other interpretations that do, but not very mainstream ones. It would be interesting to describe the experiment from that perspective.
Quoting Wayfarer
It isn't a live and dead cat, a blatant contradiction which cannot arise. Bob observes the cat and knows if it is dead or alive. Alice measures the cat still in superposition. That's very different than Alice measuring a dead cat and Bob a live one.
It is more complicated than what AndrewK says, one knowing the answer and the other not. The real conflict is that Bob knows the one answer, and Alice knows there are still two answers.
This sort of thing has been going on long ago. I can entangle a pair of particles. Bob measures one and Alice (far away) measures the 2nd one to still be in superposition. The difference here is they seem to be doing to the same object, instead of leveraging entanglement.
Quoting noAxioms
If you reject "objective reality", is there any interpretation other than Many Worlds which is acceptable?
That the photon's state is in superposition. The other measurement is not in superposition with the photon. I suppose you can word it that the result of that known measurement is in superposition.
Anyway, yes, they can take the photon and do an experiment on it where it interferes with itself, without measuring the state. If they have learned of the result of the measurement taken by the other, this superposition is not observed.
Yes, the superposition exists. The suggestion that a measurement cannot have taken place is false. The article does suggest this, but QM rules do not under any interpretation. From the beginning, Schrodinger's cat is in superposition despite the measurement obviously having taken place.
Are they at odds? Schrodinger's reality is not at odds with that of the cat, and never has been. You can put a human in the box watching the cat if your interpretation insists that humans are special, but I assure you that none of the measurements mentioned by that article were made by humans. Humans learn of the results (of probably thousands of runs) only well after the fact.
No interpretation is a cop out, but MWI cannot have those observers in different world branches since they communicate. Alice knows the polarity and tells Bob that she does. Bob knows that the particle is still in superposition and tells Alice so. That cannot happen if the two are in different branches.
Most interpretations reject it. You take away Bohmian mechanics and Stochastic and Transactional interpretations, the latter two being interpretations with which I am not familiar. But all the ones you hear about (Copenhagen, MWI, Consistent histories, objective collapse, Wigner, QBism and Relational) all reject an objective reality. I have a personal preference for Relational, but I don't assert the other ones must be wrong.
If most interpretations reject objective reality, then how is the article referred to in the op saying anything new?
They're not. They're spinning it as something new. But if they've actually disproven the principle of counterfactual definiteness like the wording of the article implies (but does not actually state), then I'd like to hear from the side of those that assert it, like a Bohmian guy interpreting the results. I don't know enough about the interpretation to know how they interpret a superposition state.
First, before even reading the article, it's worth noting that among the many ways that I'm a relativist is that I'm a "perspectivalist." I don't actually like that term, because it suggests that I'm necessarily talking about the perspectives of persons when that's only a subset of it. I think that things are relative to "points of reference" (human perspectives, in particular places at particular times, being one set of points of reference) . . . although I don't like that term, either, because for one I don't want to suggest realism about points, and also people think of "frame of reference" in the physics sense, which is a more limited idea than my view. I haven't thought of/don't know a better term to use for it yet, though, so I use "perspectivalism."
At any rate, on to the article:
So first, this is partially because I don't know enough about how it is achieved, perhaps, but I've always been skeptical of the notion that we conduct experiments where we know with any degree of certainty that we're looking at a single photon, electron, etc. at a time. For one, obviously we can't check such things with our unaided senses. We have to rely on what machines are telling us is the case, and they can only tell us what we've constructed them to tell us, in whatever manner we've devised for them to indirectly tell us something.
The problem is both a control issue--how do we really know that we're only releasing a single photon, electron, etc.? And a knowledge issue--how do we know for sure that (a) we do finally have a correct model of subatomic structure (it turned out to be the case not too long ago that we didn't have the correct model), and (b) we do have a complete model, so that we know with any certainty that there aren't other things going on--other sorts of phenomena that we're simply not aware of yet?
Aside from that, what this experiment is actually doing is taking a pair of supposedly entangled photons (I say supposedly because I'm not sure how we're observationally confirming that that's what we have) and splitting them so that Bob observes m re his photon, x, and Alice observes n re her photon, y. Theory has it that x and y should have a specific relationship, and m and n are not consistent with the relationship x and y are supposed to have.
So the first obvious question is this: if we're observing x and y to have a different relationship than they're supposed to have (and this is supposing that we're observing both x and y, which from my scan of the experiment (the actual paper is here, by the way: https://arxiv.org/pdf/1902.05080v1.pdf), on the one side we're actually observing the classic "interference pattern," we're not really observing the properties of a single photon), then the theoretical notion that x and y would be incompatible with respect to m and n is simply wrong, and insisting that it's correct is an example of theory worship.
The bottom line is that Bob and Alice are observing two different things in response to two different things (we're talking about two different photons). The supposed problem arises because of what theory proposes about what they should be observing about their two different things. Curiously, we interpret this as the theory being correct rather than noting that theory doesn't gel with what we actually observe, thus we are going to need to revise our theory at some point.
Thank you for the thoughtful post. I agree about your point on theory worship.
As Mark Twain said of reports of his death, the conclusion that reality is inconsistent is greatly exaggerated. Let us begin with a simple observation. Assuming that the experiment has been adequately described, there is no dispute over the observed facts. Everyone reading of the experiment will agree that the observations on each side are exactly as reported. There is no evidence supporting the claim that reality is self-contradictory -- because no one has observed that what is, is not.. The contradiction lies in the conclusions drawn from the two sides of the experiment. As these conclusions are based on interpretive assumptions made about self-consistent facts, it is these assumptions, and not reality, that is drawn into question.
As I have not yet read the original work, but only the cited MIT Technology Report article, I can offer no detailed analysis of the experiment -- as I have for experiments allegedly supporting the "Delayed Choice" and "Quantum Erasers" myths. (https://www.youtube.com/watch?v=F-PAjJcRVCs). I suspect that my response to the detailed experiment would rest on the fact that quantum observations do not reveal the prior state of the "observed" system, but the interaction of that system with the experimental apparatus. Thus, in Wigner's Friend experiments, neither Wigner nor his friend obtain unambiguous information about the prior state of the system. Rather, each obtains information about the interaction of that system with their (different) local measurement apparatus.
In response to a recent question on my quantum erasure video, I outlined by views on quantum entanglement, which may be relevant here:
People gonna keep thinking quantum observers are people.
iI my opinion, as others have said, this experiment, by itself, does not disprove the existence of an 'objective reality' anymore than QM does. After all, Wigner's friend is a well-known feature of QM, so it is not really prove anything new.
For instance, an interpretation like the de Broglie-Bohm theory can explain that experiment.
I agree that QBism, Copenaghen interpretation (CI), RQM in their own ways reject 'realism'. But how about MWI. In MWI, the only 'truly real thing' is the universal wave-function (UW). The UW never collapses in MWI. It rejects counterfactual definiteness. But the UW is still objective.
Also, the 'objective collapse' theories like the Ghirardi-Rimini-Weber model or Penrose's interpretation claim that the wave-function is real IMO. But during measurements, the wave-function localizes to a definite position. AFAIK, these theories all predict that this 'localization' occurs at some length scale (even if they differ in the precise way that occurs) spontaneously - another name for these models is 'spontaneous collapse' theories. Hence, I would not say that 'counterfactual definiteness'='objective reality', strictly speaking.
There are different 'flavors' of CI. For instance, see these papers by Michel Bitbol: http://www.bourbaphy.fr/bitbol.pdf and https://core.ac.uk/download/pdf/148348264.pdf. In brief, in my own understanding, Bitbol thinks that the wave-function is not a 'description' of reality, but it is a tool of the experimenter that enables her to make probabilistic predictions. In other words, QM, according to Bitbol is perspectival: it makes predictions of what the experimenter herself will observe. This does not mean that the observer creates reality but, rather, that the measurement is made by a peculiar perspective, namely that of the observer's. According to Bitbol this was also the position of Bohr himself. Note, however, that this interpretation does not take an ontological position on the 'objective reality'. In some sense, CI, in this 'flavor', is a statement on the limitations of science. Science cannot give us knowledge of 'reality as it is', but in its relation to the observations (in the first paper Bitbol compares Bohr's views on QM with Kant's philosophy).
This is rather similar to Rovelli's RQM. The difference is that according Rovelli each physical object has its own 'perspective'.
Thanks! Helpful clarification of my hamfisted attempt at an allegory.
Quoting Andrew M
What if the theory that needs to be ‘beaten’ is not a theory at all but an untestable metaphysical postulate? Then it might be better to simply ignore it, or proceed as if it says nothing.
Quoting Mr Phil O'Sophy
The point is that two observers see different things which cannot be reconciled, but that neither of which can be shown to be incorrect.
Quoting boundless
However the point of the article is the claim that what was previously only a thought experiment has now been experimentally realised.
Quoting boundless
I have been reading those papers from Bitbol, and this is the interpretation that makes the most sense to me also. A point that Bitbol makes is that there is an ineliminably subjective aspect to knowledge, generally - measurements are always made from a point of view or perspective. But scientific philosophy doesn’t want to acknowledge that, it wants to believe that it’s seeing reality as it is in itself, as Boundless notes. This the conceit that is being exposed by these conundrums.
I really do understand that. I understand that Schrodinger spun that yarn with a certain sense of sarcasm, in order to try and illustrate the bizarre implications of QM.
“What did you do to the cat, Erwin? It looks half dead!’ ~ Ms Schrodinger.
That is at the very least a disputed issue.
I think the Copenhagen interpretation is not compatible with the usual folk notion of 'objective reality'. It denies that there is any fact of the matter about where a particle is between observations.
Presumably quantum phenomena were happening long before there were people.
The reports of the experiment are very new, so that could explain the lack of commentary. But it also means the article has not been peer-reviewed. I suggest people wait for that before they start trying to draw metaphysical conclusions from it. Further, the article is so new that nobody has really had time to analyse it fully yet.
Luboš Motl writes that the experiment is not described in enough detail to enable full peer analysis. He also challenges some of the assumptions, and hypothesises that if they were replaced with more standard assumptions, the claimed anomaly would disappear.
But Proietti and co’s result suggests that objective reality does not exist. In other words, the experiment suggests that one or more of the assumptions—the idea that there is a reality we can agree on, the idea that we have freedom of choice, or the idea of locality—must be wrong.
So, according to the article, the notion of objective reality has not been unequivocally undermined, as your headline asserts. It might be the notion of freedom of choice or the idea of locality which have been undermined; the article only claims that it must be that one of the three is wrong.
Right! And this, if confirmed, would a wonderful thing :wink:
However, since all interpretations of QM give (almost) the same predictions, we cannot use that experiment to falsify or verify one in particular.
Quoting Wayfarer
Correct. The point of Bitbol is that in the case of Wigner's friend experiment, Wigner's friend sees a definite experimental outcome, whereas according to Wigner there is a superposition (which includes his friend, too).
But the point is that you cannot really make this comparison until Wigner asks to his friend to tell the precise outcome he has seen. The two perspective are different and they are both 'right'.
Each observer has her own perspective. When they communicate the two perspectives are not separate anymore. At this point, we can make a reasonable comparison.
Rovelli's view is similar, but according to him we can define a perspective with all physical systems. In Rovelli's view, communication is replaced by a physical interaction.
In fact, in both cases before the communication (in Bitbol's version of CI) or the physical interaction (in Rovelli's RQM), a comparison is impossible.
Given that, it appears to me that the article says nothing new.
Experiments have already 'confirmed' Bell's Theorem, which says that one of QM, locality and counterfactual definiteness (similar to freedom of choice) must be wrong. Since we haven 't given up on QM, that means CFD or locality must be wrong. And if we accept that, then the Proietti result gives us no reason to accept that objective reality doesn't exist.
Caveat - it's a couple of years since I read Bell's paper, so I may be misremembering.
If that's right, then belief in 'objective reality' goes back to being a metaphysical question - which is where I feel it belongs.
This is the issue at the heart of the 'observer problem'. This very issue was why Einstein asked (dismissively) 'Doesn't the moon exist when we're not looking at it?' See Does the Universe Exist if we're Not Looking?
Except 'observation' has been occurring since before humans existed, all a 'measurement' is (AFAIK) is a mapping from a superposition of eigenstates of a quantum operator to a single eigenstate of a quantum operator. In that framework, an observable is just a (Hermitian) linear operator on quantum states. None of these objects are people, and none of them have to occur due to an experimental measurement.
Reality happens outside of the lab too.
But you're not seeing why there is a controversy about this issue. You're simply adopting, or assuming, the perspective of scientific realism, without showing any indication that you understand what exactly about the discoveries of 20th c physics threw this into question.
You will find many titles in the science sections of bookstores with variations on the theme of 'what is real?' Why do you think that might be?
Tell me why people are required for the natural formation of salt (which requires quantum mechanical effects due to the ionic bond). Specifically tell me why a person needs to have something to do with the electron orbiting around the sodium atom in its outer orbital to make it donate that electron to the chlorine atom, filling its outer orbital. Where are the people involved? Why are people needed for the formation of ionic bonds? What role do we play in the formation of ionic bonds in compounds that existed long before the first human?
Do you know why, and in what circumstances, Albert Einstein asked the question 'Does the moon continue to exist if we're not looking at it?'
//discussed in this thread.//
Yes, it was an analogy to express suspicion about the physical intuition underlying particles existing in superposition. Einstein saw quantum mechanics as more of a mathematical trick than a physical theory, and was notoriously hostile to it in public. It's actually intended to be a reductio as absurdum to the idea that reality depends upon an observer; achieved by equating the notion of an observer with that of a human. Einstein thought that nature worked deterministically everywhere.
Bohr; who had a more relational view and a higher opinion of the physicality of the wavefunction; eventually was vindicated, and he famously said:
Note, not just the experimental apparatus humans make, but systems; like the composite system of a sodium atom and a nearby chlorine atom, jointly constraining and driving the location of the outer orbital electron of the sodium atom to join the outer orbital of the chlorine atom, thereby making a compound with properties neither atom had by itself.
Nature is suffused with interaction top to bottom, labs and their measurements are a relatively novel mode of interaction for it.
Quoting fdrake
Whereas, that is what is called into question - that's why it is controversial and why it provoked so many impassioned arguments. (Werner Heisenberg recalls being reduced to tears on occasions by the vehemence of the debates surrounding the famous 1927 Solvay conference were many of these issues came to a head.)
What Einstein couldn't accept was any place given to the role of the observer in the determination of the outcome. He demanded that any truly scientific account must be strictly objective, with no reference to the observer - hence, 'mind-independent'. This is what he thought was the criterion for what is scientifically acceptable, and was why he asked the question.
Later, the EPR paradox was intended by him to be the final nail in the coffin for Bohr's interpretation - but as is now known, when it was finally experimentally tested long after Einstein's death it again undermined realism.
Quoting fdrake
Instruments take measurements, but only humans are observers, which is why Niels Bohr would say things like 'nothing exists until it is measured'.
Agree. MWI says there is an objective reality, but it is entirely in superposition, and measurement just entangles the measurer with the measured thing. It does not collapse any wave function. Hence there is no defined state of anything (like dead cat), and hence no counterfactual (or even factual) definiteness.
Oh no, I think it makes the point than an observer need not be human quite nicely. The next bolded bit, which leads on from it, extends the logic to every physical process. IE - a physical process can 'observe' another one, and a human doesn't have to mediate between them.
This ties back into my demand for you to describe what necessary role humans play in the formation of the ionic bond in sodium chloride - the only right answer is none at all.
I don't think that subjective and objective are particularly useful terms. At what point does objective light reflecting from an object become a subjective interpretation of that object's properties? The whole dichotomy has way too much baggage to be useful. It paints a picture of a person standing apart from the world and passively contemplating the 'raw data' of their senses, whereas reality builds emergent structures out of itself within circumscribed developmental environments. The felt roughness of sandpaper does nothing to destroy its grain; we are of the world as much as we are in it.
Notice that Bohr says that ‘the objective world of nineteenth century science’ has become untenable. I think he’s correct in saying that, but isn’t it very much the substance of his disagreements with Einstein?
On the other hand, from a metaphysical perspective one could argue as philosopher and perceptual researcher Evan Thompson does:
"The problem cannot be ‘How do we go from mind-independent nature to subjectivity and
consciousness?’ because natural objects and properties are not intrinsically identifiable ; they are identifiable only in relation to the ‘conceptual imputations’ of intersubjective experience."
"If we had a complete, canonical, objective, physicalist account of the natural world, including all
the physical facts of the brain and the organism, would it conceptually or logically entail the subjective facts of consciousness? If this account would not entail these facts, then consciousness must be an additional, non-natural property of the world. One problem with this whole way of setting up the issue, however, is that it presupposes we can make sense of the very notion of a single, canonical, physicalist description of the world, which is highly doubtful, and that in arriving (or at any rate
approaching) such a description, we are attaining a viewpoint that does not in any way
presuppose our own cognition and lived experience."
Quoting Joshs
On account of 'absence of own-being'.
Where in Thomson's writing is that passage from?
That seems to be fundamental, there cannot be any fact of the matter about where a particle is between observations. To me that says that the particle, as a particle, is a product of the observation process. Maybe we shouldn't think of the particle as a particle, if it doesn't exist as we would think that a particle exists. Actually, I've heard that from physicists, that they just call it a particle, but it isn't really a particle in any normal sense of the word. That's my in depth understanding of "particle" physics.
The main postulate of MWI is that the universe is represented by a unitarily evolving quantum state interpreted realistically. It provides empirical predictions that have been thoroughly and successfully tested (so far).
What I think you mean is that one of the theory's predictions can not be tested (that there are many worlds), at least at this point. But that prediction can only be eliminated by changing either the physical theory (as with Bohmian Mechanics, Objective collapse) or by interpreting the quantum state in some other way (as with Copenhagen, RQM, etc.) Neither of those changes are trivial and they have various consequences that need to be considered on their own merits.
Quoting noAxioms
In the experiment, Alice can communicate to Bob that she has measured a definite polarity (without the polarity itself being revealed) while the lab she is in remains isolated (and Bob does not communicate back, which would presumably constitute a measurement entangling him with Alice). So there are actually three MWI branches here. One where Alice measures a horizontal polarization, one where she measures a vertical polarization, and one that is the superposition of those two branches where Bob detects interference (and knows that Alice has made a measurement).
Sure that's part of it. Are you aware of Sabine Hossfielder's recent book, Lost in Math? And all of the huge arguments going on about whether string theory is or isn't science? I know these are not about exactly the same issue as the 'many-worlds interpretation' but they're metaphysical ideas arising from science, rather than testable hypotheses as such.
I don't think 'the Copenhagen interpretation' is, or attempts to be, a scientific hypothesis. It is just a collection of aphorisms and philosophical reflections, principally by Bohr and Heisenberg, which are about what you can and can't say on the basis of the discoveries of quantum mechanics. One of the appealing features of this 'interpretation' is that it's not masquerading as science - it's actually quite a modest attitude - whereas the 'many worlds interpretation' is presented as scientific when I really doubt that it is. (Anyway I know that I have zero credentials in this matter, I will bow out at this point and attend to more pressing mundane issues.)
https://evanthompsondotme.files.wordpress.com/2012/11/jcs-empathy.pdf
Maybe so, but the end goal is to have rigorously defined theories that can be experimentally distinguished. Part of that task is identifying the assumptions made by the various interpretations (like counterfactual definiteness, free choice, locality, observer-dependence, etc.). Researchers in quantum foundations use this data to come up with no-go theorems and experiments such as that in the OP.
Interestingly, the OP experiment is based on Deutsch's version of Wigner's friend which he proposed specifically to distinguish experimentally between Copenhagen and MWI. Caslav Brukner (mentioned in the OP article) discusses this in https://arxiv.org/abs/1507.05255.
Well, here 'freedom of choice' does not refer to 'free will'. Rather, it is a denial of Superdeterminism (the link is to Wikipedia article), that is the idea that choices were pre-determined at the beginning of the universe. It is actually stronger than 'simple' determinism (like the one that de Broglie-Bohm interpretation (dBB) accepts), because the 'history' of events in the universe is 'already written' at the beginning of the universe. Superdeterminism is a known 'loophole' of Bell's theorem.
According to Bell's theorem, one cannot accept the predictions of QM, counterfactual definiteness (the view that we can speak meaningfully of experiments that have not been performed) and locality (assuming that superdeterminism is not true). dBB does not accept locality.
Note, however, that even if one does not accept counterfactual definiteness, one can still accept an 'objective reality', hence the article is mistaken in that claim. For instance, MWI accepts an 'objective reality', which is the quantum state of the entire universe but does not accept counterfactual definiteness. Objective collapse theories accept an 'objective reality' but do not accept counterfactual definiteness because results of experiments are seen as random (according to these theories, wave-functions are real, physical objects that 'collapse' at the measurement).
Quoting noAxioms
Yeah! BTW, I believe that other than the very problematic concept of 'many worlds', MWI has a serious problem, check: https://arxiv.org/abs/1210.8447. The usual claim that the 'preferred basis problem' is solved by decoherence. But it is not correct. Decoherence solves the 'preferred basis problem' (in fact, 'for all practical purposes' in my feeble understanding) only if you already assume that there is a well-defined factorization in the Hilbert space (which is the only 'reality' in MWI, AFAIK). Without well defined subsystems, the factorization is completely arbitrary (also, it should be added that, in fact, one has no, a priori, reasons to do a factorization in the first place).
I do not know how MWI-supporters handles this in a non-circular way.
I also add that MWI and RQM are close. The difference being that RQM does not accept the reality of the 'universal wavefunction' because, in RQM, wave-functions are well-defined in relation to a specific physical system (the 'observer' in this interpretation).
Very interesting quote by Bohr, thanks for sharing! At that time, he seems to have held a view similar to Carlo Rovelli (who believes that you can define a 'perspective' for every physical system).
Nonetheless, the main problem with this view is that if the wave-function is considered to be information or a 'mathematical tool' (as in my understanding Rovelli does), then it is difficult to understand how we can speak of 'information' related to a non-conscious observer. This is, in fact, Michel Bitbol's point.
Apparently, however, Bohr changed his views over time. Check, for instance, this paper by Bitbol that I linked before:
Quoting boundless
In other words, according to Bitbol, Bohr's views are similar to Kant's philosophy. While RQM is right in saying that QM is about 'perspectives', according to Bitbol these perspectives are well-defined only for conscious observers.
The abstract of the paper:
And the paper itself is titled "Experimental rejection of observer-independence in the quantum world".
I have to disagree about the restrictions to communication you convey above. Alice knows the result of a measurement, and that makes for 2 Alice's now, one for each result. Those two version of Alice, being in different worlds, cannot communicate or otherwise be aware of each other. But they behave exactly identically because they're keeping that knowledge a secret. To Bob, Alice is in superposition of knowing those two states, and Bob can thus communicate two-way with both Alice's since they, by acting identically, are completely coherent. They can make out if they want. In reality, humans are incapable of this coherence, which is why they never use humans to play the role of Alice or Bob.
Anyway, point is, Alice learning of the measurement results splits Alice, but does not split the universe, as is commonly assumed. Bob, being able to speak to both versions of Alice, is still in a common world. So yes to the three worlds if you count them that way: One for each Alice, and one for Bob. But there is obviously communication between the Bob world and both Alice worlds, but Bob cannot pass a message from one Alice to the other. With the communication, Bob's world is clearly not isolated from Alice's world, and hence doesn't really count as a separate world.
Quoting boundless
I actually don't know the terminology that well, in particular 'factorization'.
So perhaps I don't understand the problem here.
I'm an RQM guy myself, and yes, nothing is just 'real', things are only real in relation to something else, so how can the universal wave be real when there is nothing to which it is real in relation? The view would be self inconsistent if it were to be otherwise.
Close. It isn't philosophy at all. The 'interpretation', unlike other philosophical interpretations of QM, is just a scientific statement concerning what is known about a system. Hence it is, as far as Bohr, Heisenberg, and Schrodinger are concerned, just an epistemological statement, not a metaphysical interpretation. There are plenty who take that epistemological wording also as some kind of statement of reality, but Copenhagen was not intended to be used this way.
So the taking of a measurement changes what we know, solidifying some possibilities and eliminating others, and hence collapses the wave function of the possible states of the thing. The wave function is not real, it just represents possibilities for something unknown. There is a wave function of places where I likely left my car keys, with some more probable than others. When I find them (or even when I look certain places and don't yet find them), that wave function changes since my knowledge of the system has been changed.
The wiki table on interpretations lists Copenhagen as a non-local interpretation, and I don't understand that. My knowledge of a system doesn't change due to an event that happens elsewhere. But I suppose that my knowledge of a distant system (like the distant half of an entangled pair) changes immediately upon my measurement of its local sibling, so maybe that's why they list it as a non-local interpretation.
Well we know that physical processes interact with others, it is not so surprising that their interaction can effect all involved or produce novel phenomena. This maxim applies more generally than in quantum physics - ecosystems can couple and interact, so can social groups. The details depend on the specifics.
I think that nature is inherently relational only sits oddly with intuitions that relations are somehow derivative or less important then their relata; like the two poles of subject and object, where everything interesting lays between.
Quoting Wayfarer
Quantum phenomena undermine some aspects of determinism, relativity undermines absolute space and time. Sub specie aeternitas this requires us think of nature in the wake of discovery in both fields, but also when things are big enough or slow enough where the weirdness of either or both does not apply. Objectivity there, I think, means something like invariant of perspective - observer/frame independence. We know nature is not either in many circumstances. The trick is then in giving an immanent account of 'perspectival' dependence without making humans a necessary constituent of nature.
It does not help that the usual words we use to discuss these topics are perception analogies.
Ok! I'll try to give an explanation.
In MWI, there is only a quantum system, the universe itself. Its quantum state is a vector in a Hilbert space.
Now, consider a complex quantum system, that is a quantum system like, say, a pair of particles. Let us call them P1 and P2. To each particle is associated a Hilbert space, say, respectively, H1 and H2. To the total system we associate the Hilbert space, H, which is the tensor product of H1 and H2. So, the quantum state of the total system is a ray in the Hilbert space H, which is 'factorizable' into H1 and H2, the Hilbert spaces related to each particle. Here, the factorization is well-defined by the two particles themselves.
In the case of MWI, however, the only real system is the universe itself. Without additional structure, you can't speak about subsystems. So, you need a factorization, i.e. a decomposition of the Hilbert space related to the universe (which, however, we can argue that is needed a-posteriori because we observe subsystems. A-priori, there is no reason to even do a factorization). But even if we make a factorization we see that such a factorization is arbitrary and in some factorizations literally nothing happens (I suggest to read Scwindt's pre-print. I do not claim to have understood it completely, but IMO it explains well the point...). Since, however, in principle, the factorization is arbitrary, we can choose such factorizations where nothing happens.
The point is that people claim that MWI is more elegant than other interpretations because there is only one real thing, the wave-function of the universe, which never collapses. On the other hand, this is a moot point because in order to explain the multiplicity we observe you need to factorize/decompose the Hilbert space associated with the quantum state of the universe in a given way. MWI by itself however simply cannot do that (as I said, I do not know if MWI supporters have offered a counter-argument).
The only way 'out' seems to introduce an additional structure in the Hilbert space of the universe. But, at this point, how is MWI really 'simpler' than, for instance, the de Broglie-Bohm interpretation (which is an example of 'way out' offered in the paper)? In the de Broglie-Bohm interpretation, you still have the universal wave-function but you also have the particles that define the factorization/decomposition (that is, the theory itself offers you the actual subsystems). The other 'way out' that offers the paper is the Copenaghen interpretation. Of course, there are others but the paper offer these two.
To summarize, MWI claims that the only real thing is the 'universal wavefunction'. But without introducing additional structure it seems that there is no way to explain the 'multiplicity' we observe - to do that we need actual subsystems that introduce a factorization/decomposition.
Quoting noAxioms
Yeah! Speaking of myself, I lean towards either RQM or (some versions of) Copenaghen.
Information and probability are dual notions; wherever you have a probability distribution you have an entropy. The connection between the two is particularly intimate for discrete random variables - like when there is a given probability of being in one of countably many eigenstates of an operator. Quantum entropy measures the degree of mixing in a state; how close it is to behaving in a singular eigenstate (unless I'm misinterpreting, I am both rusty and mostly uneducated here). Information measures are derivable from probability distributions, but the process of mapping a distribution to an entropy value is not invertible - so the two notions can't be taken as inter-definable. As in, if you have an entropy, you have a single number, which could be generated from lots of different quantum states and probability distributions.
I'm sure there are problems, but I think there are good reasons to believe that information is just as much a part of nature as wave functions.
I'm tired of debating whether nature is inside our theories of it or not. Imagining that nature is all we have to say about it is a pointless retrojection; it has been around longer than theory and impresses itself upon us even when we have no account of it. Yes, you will probably say, science produces truths, but more profoundly those truths are indexed to our theories and that those truths attain their sense solely within our theories.
The questions we ask nature are thus muted after leaving our lips; nature's behaviour becomes covered by the silent fog of our understanding, we could never ask questions of it, only of our relation to it. Our theories' mediating status between us and natural phenomena becomes bloated and complacent, it takes the target of theorisation to be the theory produced and not what domain is actually theorised.
Don't put our understanding in the way of our understanding. Questioning and inquiry are themselves ways to relate to nature.
Friend: "Yeah, I know which one!"
Wigner: "No, you don't, it's either dead or alive."
Friend: "I'm telling you it's dead."
Wigner: "Oh, I see, indeed yes, it's dead."
The funny stuff aside; how can you "measure" a superposition or how can a measurement be in a superposition? I thought any observation causes the wave function to collapse in a single eigenstate and a measurement, I would think, involves an observation.
I'm a bit unclear on what the article means what it says:
Quoting technology review
I thought that saying a system is in a superposition is a description of its possible states and not a statement of its actual state if you would measure it.
What am I missing here?
https://www.google.com/amp/s/amp.livescience.com/63595-schrodinger-uncertainty-relation-temperature.html
We seem to have a situation where one observer sees a certain situation, and another sees a contradictory situation. A sees p, B sees ~p.
It's worth reminding ourselves that this is not new. The same thing can happen in relativistic physics where one observer will see events in a different sequence to another.
But of course what happens in relativistic is that a set of equations are used to translate between the observations. SO although A sees p and B sees ~p, A will also see that B sees ~p, and B will also see that A will see p.
That is, A and B agree that: A sees p, yet that B sees ~p.
Now it seems to me that objective reality has here not so much been undermined as redefined.
A corollary: this fits in with a view of language, logic and mathematics such that we choose a grammar for our descriptions that suits our purposes.
But humans provide perspective, a point of view, which in an ineliminable pole in the knowledge of anything. The philosophical issue revolves around the attempt NOT to face that.
Well, yeah this more or less what Rovelli says. In his pre-print 'Relational interpretation of Quantum Mechanics' (see here: https://arxiv.org/pdf/quant-ph/9609002.pdf), he writes (p.3):
This certainly avoids the problem of introducing a 'special' role of consciousness. In fact, the 'observer' in RQM is not really different from a 'reference frame' in classical or relativistic physics, i.e. any possible physical system.
But, interestingly, for all practical purposes Rovelli's position is not very different from Bitbol's proposal, in the sense that Bitbol does not think that consciousness has an 'ontological role'. It does not 'change' reality (as IMO actually say the 'consciousness collapse interpretation' held by Von Neumann, Wigner, Wheeler etc). Rather, it just says all our knowledge is 'situated', in the sense that it comes from a certain perspective and we cannot neglect this. So what I observe is the universe 'seen by me' and from that perspective I am indeed sort of special: not in the sense that I am the 'creator' of what I observe but simply because 'I' am the 'point of view'. So, at least for what is observed in the 'perspectives' of human beings the two models are indistinguishable.
Note, that, however Bitbol's view goes a bit ahead than Rovelli's (note that Bitbol is strongly influenced by Kant and phenomenology). According to Bitbol, knowledge starts from conscious experience. This means that consciousness itself defines automatically a perspective. Hence, each of us 'observers' reality from a precise viewpoint. Note that, in this case, the 'perspective' is easily identified. We do not know how 'reality' is 'seen' from the viewpoint of 'a pen on my table' (in fact, we cannot even know what if such a perspective makes sense).
As I said, however, Bitbol does not claim that we 'create' reality. Rather the situation here is much like in Kant. We cannot know how reality is independently from our perspective. We just cannot 'neglect' it completely. Why? Because, conscious experience is the starting point of all inquiry.
To summarize, for Bitbol and Rovelli, QM tells us that knowledge is perspectival. But Bitbol sees a link between this and Kantian philosophy and phenomenology which (in a different context) also say that 'perspective', which, in this case, is conscious experience. So, according to Bitbol this is also true for QM: we cannot know the 'world as it is', but only from our 'situated' experience.
I do not know if Bitbol is right here but IMO he raises very interesting point. Also, Bernard d'Espagnat has a similar view, see: https://arxiv.org/pdf/1101.4545.pdf
Yeah, I agree. Bell's theorem then implies that one between predictions of QM, counterfactual definiteness and locality must be abandoned. Most physicists believe that it is counterfactual definiteness that is to be abandoned. Hence, the 'claim' of this experiment is not really different from the implication of Bell's theorem.
Quoting noAxioms
Well, I think that probably different 'Copenaghists' would give different responses (after all, there is no agreement among them about the right interpretation of the wave-function). But, I suspect that this problem might be avoided using the same argument that (IMO) is used by RQM, that is, reasoning with 'perspectives'. After I make a measurement, I am sure about the outcome of the other measurement. But until I actually receive the confirmation of it, such an event (the measurement) is outside my perspective.
I do not know however if this argument is really enough to avoid non-locality.
(Note that, more or less, this is the reasoning that is employed to avoid the 'block universe' interpretation of Relativity. In that case, the point is that each 'observer' can define 'its' own plane of simultaneity, i.e. its own present. But if we believe that all these events are 'actually real', then it is not too hard to show that it would imply that we are in 'block world': https://en.wikipedia.org/wiki/Rietdijk–Putnam_argument).
As an aside, a note in that table says that the de Broglie-Bohm interpretation is compatible with relativity. This is IMO wrong. The point is maybe that we cannot observe any violation of relativity via the transmission of faster than light signals. But this does not mean that dBB is actually compatible with it (BTW, non-locality is not the only reason (or even the main) that dBB is not my own favorite interpretation. But I would digress too much here).
Maybe that's because questioning and inquiry are ways to relate to themselves. Maybe the in-between IS where nature is.
Scientists who interpret what they do via Kantain thinking talk about a real world that we mirror through our constructions of it, or as you say, 'mediating between us and natural phenomena".
Postmodern thinking would say instead that the purpose and effect of knowledge is not to represent what is, but to adaptively interact with and thus transform what it theorizes about.
What science does, then , is pragmatically reorganize a world in ways that we can make more or less useful to us. What we get right or wrong, true or false , only makes sense in relation to our changing theoretical norms. As Heidegger says "A science's level of development is determined by the
extent to which it is capable of a crisis in its basic concepts."
Certainly scientists are under no obligation, nor would it be at all helpful for most, to inquire into their presuppositions when they do science. The nature of the way empirical questions are formulated isn't designed for such understanding, which is then left unexamined and implicit. But then one could argue that a field like physics is applied philosophy. Each new scientific advance implies an unexamined shift in philosophical underpinnings. Thats why a history of physics, from Aristotle and the Scholastics through Galileo,and Newton to Einstein parallels the history of philosophy.
(will also serve as a reply to our Heideggerian friend @Joshs)
This more general theme is precisely what I was reacting to in the thread. There's a weak, and I think very agreeable account and a strong, and I think very important to undermine account.
The weak claim goes something like this; all knowledge derives from interpretation, if we know anything about anything, it has to be an interpretation of that thing. Grant for the sake of argument that experiences are also interpretations of stuff; if you pat a dog, the topography and consistency of their hair leaves its impression through your sense of touch. Interpretations are always simplifications and approximations, with a required background to understand them and a necessary set of presuppositions on which they develop. Another way of stating this is that the way we theorise is through the creation of concepts; and we use concepts to make sense of things. Moreover, experience informs the tailoring of concepts.
The strong claim goes like this: it starts with the weak claim; all knowledge derives from interpretation - I agree with all you said, but that is not the end of the story. Consider that every relation that we have with any other thing is an interpretation; interpretations are the trace of our experience and history in our living bodies. When asked the question; what does your knowledge and experience consist of? You may say it consists of interpretations. What of the things we experience in the world? Those too are interpretations with a certain thingliness associated with them. Whenever we interact with anything, all that is generated is an interpretation, and all thought consists in a chain of such interpretations evaluated with a logic of links you might call a theory. Whenever we encounter an object, that object is an interpretation from a certain perspective; it is a contextually circumscribed concept. As Josh put it above:
Quoting Joshs
I believe in the weak claim, I believe in the emphasis portrayed in the strong claim on the dogged pursuit of where our concepts come from. What I don't believe is the characterisation of interpretation, knowledge, or interaction induced through:
Specifically, I disagree with:
(1) (I don't like that) The substitution of interpretations for the targets of interpretations; (rather I believe) knowledge must always be knowledge of its target.
(2) The claim that the target of an interpretation, or knowledge or theory, is consigned to a realm beyond our experience because all experience is interpretation.
Instead I want to emphasise that interpretation is a relationship between its target and a perspective; reasoning consists in the development of this relationship, but its standards of relevance are dictated by the demands the target places on our inquiry; as Lakatos puts it nature can always 'Shout NO!'. We understand nature through theories and interpretations, we don't just have access to theories and interpretations, theories, interpretations and experiences are how we access their targets.
The emphasis I put on quantum phenomena occurring long before our accounts of quantum phenomena were written, and long before the first vestige of quantum mechanics was developing in the canon theoretical physics, is to ape a famous argument that attempts to undermine (2). The argument is usually called the 'arche-fossil' and it was advanced by Meillassoux is the first few chapters of his 'After Finitude, an Essay on the Necessity of Contingency'. The strong account, as I termed it, Meillassoux calls 'correlationism'; stated in one line, correlationism is the belief that we can never have knowledge about thought or being, only of the relationship between them.
Kant fits in here as a correlationist, but he still has the noumenon. The nounmenon, even if we can never have determinate knowledge about it, can be the subject of imagination. Whether you believe that the role of the noumenon in Kant is negative; in that it simply marks the boundary of our possible knowledge; or positive; in that it refers to an uninterpreted reality which subsists beneath our interaction with it, there is still something other than interpretation which we are dimly aware of. Whether this noumenon can 'Shout no!' to our theories or whether it casts no shadow upon our interpretations and experiences is the substance of my disagreement with the 'strong account'. I believe that nature can 'Shout no!' (as Lakatos puts it) when we ask it well formed questions, and I believe that the capacity for it to shout no is a necessary component of a good account of knowledge, interpretation, and the ontology of our being in the world.
The strong account, or strong correlationism for Meillassoux, does away with the relevance of the noumenon; what is the point in it if we can never have experiential or interpretive access to it? Our interpretations persist in the relation of thought and being and never take inspiration from that which is outwith the relation between the two. That is to say, never from nature; even if it 'Shouts no!', we're necessarily deaf to its cry, for its cry would be another interpretation.
Meillassoux summarises this position like:
[quote=Meillassoux, After Finitude Chapter 1, Ancestrality]We said above that, since Kant, objectivity is no longer defined with reference to the object in itself (in terms of the statement’s adequation or resemblance to what it designates), but rather with reference to the possible universality of an objective statement. “It is the intersubjectivity of the ancestral statement – the fact that it should by right be verifiable by any member of the scientific community – that guarantees its objectivity, and hence its ‘truth’. It cannot be anything else, since its referent, taken literally, is unthinkable[/quote]
Meillassoux considers a class of statement called an 'ancestral statement' whose meaningfulness undermines the strong correlationist account. For an example, consider 'the age of the universe is approximately 13.8 billion years'. The precise logic Meillassoux ascribes to the interpretation of this kind of statement for those who believe in the strong account/correlationism is as follows:
The literal truth of the statement, not just 'for us' for Meillassoux entails numerous unpleasant things for a correlationist to square themselves with.
Needless to say, there are problems here. Being the incorrigible simpleton that I am, when I believe the statement 'The universe is 13.8 billion years old', I'm actually believing in its literal truth, and not the correlationist transformation of the statement; 'The universe is 13.8 billion years old for us/our current theories/whatever'. Moreover, though I have given no argument of this, I believe that the ability to accept the literal truth of that statement and moreover that it has a meaning at all are indicative that thought really can 'aim for that which is outside of it', and that our inquiries are meaningful only when they can admit the possibility of nature 'Shouting no!'.
How does this relate to the discussion in this thread? Well, firstly, it relates to the equation of a quantum observer with a human. Secondly, it relates to the equation of an observer-quantum state system as a human-quantum state system, and lastly it relates to the equation of a 'perspective' in an observer-quantum state system with anything like the usual meaning of worldview or theoretical background we would give to it. The debate about these terms and their application in the philosophy here is a lot broader than quantum mechanics; though I do very much appreciate the explicit reference to Kant, @boundless.
I’m pretty sure that’s not true. It is simplistic. The point in respect of sub-atomic particles, is that they’re not in some undetermined location prior to measurement -they’re literally not in any definite location until the measurement is taken. Otherwise, there would be nothing to discuss.
[quote=fdrake] * that being is not co-extensive with manifestation, since events have occurred in the past which were not manifest to anyone[/quote]
I don't know if you took a look at the essay about Wheeler's 'Delayed Choice' I pointed to, but it explicitly address this issue. It describes a version of the delayed-choice thought-experiment where the light source is a distant quasar, and the place of the slits in the screen is taken by distant galaxies, which bend the light as it travels.
The 'delayed choice' and it's associated 'weirdness' has been the subject of extensive reporting in the popular science media in the last decade.
Quoting fdrake
It's not so much 'correlationism' as the incorrigible realism that each of us is born with. What you're not seeing is the role the mind/brain plays in the statement about the age of the Universe (or anything else, for that matter.) But what this type of realism assumes is just what Kant means by 'transcendental realism':
The problem is, empiricism has bet the house on the fact that what it conceives of as nature, the real world, and so on, is what is finally and fundamentally real. But QM continues to throw this into doubt. Hence the controversy!
"You've got the knives on the left!"
"No, you have!"
I do agree that the claim 'the universe is 13.8 billion years old' is something produced by our theories and understandings. But I also believe that it is literally true. In terms of your quote:
I believe it's important to emphasise that nature also informs our sensibility and strikes accord with it. The impulse Husserl expressed that phenomenology (a discipline heavily indebted to Kant) is 'relearning how to see' is basically correct; with the addendum that reality can teach us how to see better when we give ourselves the goal of understanding it.
You seem to want to paint me as a pre-critical realist; I'm not, I know that experience is 'theory ladened' and informed by what we know, what we've experienced, our habits and the structure of our bodies; but I will insist that it is also informed by the objects we experience.
Quoting Wayfarer
The same thing happened with special relativity; and people make the same mistake that the relativity of simultaneity is property of a human perspective; more properly it's a property of motion that can't adequately be accounted for while assuming the speed of light is infinite, the relativity of simultaneity is still something natural, it just takes really fast relative motions to have meaningful effects.
With that in mind, that different observers of quantum states can disagree on precisely what state the system is in is also not a property of a uniquely human perspective; other systems can serve as observers, and systems can serve as observers to coupled systems of observers and other systems. These are facts of nature that need no appeal to human cognition to explain; only an appeal to the randomness of the quantum state. Of course we need to cognise it to understand it, it's a theory; but it still describes some natural phenomenon.
You've misread Kant here.
He's giving an empirically realist account in this context, in which phenomena are as they appear (or would appear if we were present), rather than being something which can be detached from how they would appear in our experiences. He's not trying to suggest things don't exist without us or are beyond our explanation-- indeed, his point is the exact opposite.
Kant doesn't fit the scientism bill, but this point is compatible with accounts scientism, which reduces the world to a set of things known to us. After all, that's what scientism thinks: that the while world is constituted by things which appear in our experience (as se out in our given theory).
Wouldn't dispute it for a moment. Kant himself devised the nebular hypothesis, he was a scientist as well as a philosopher. But you go further when you speak of systems as if they're observers. They're not. Observers are beings, and the word 'being' is significant in this context.
Rovelli makes the same point in the paper boundless linked, as does Bohr in the quote I gave earlier. It's convenient to talk of these things in terms of human perspectives and related terms, because that's how the common relevant vocabulary works, but they go to pains to distinguish observer from human. Whether a system is a being or not is probably outside the scope of the thread, I would tentatively say that it generally is, but it's more adequately described as an interacting connection of flows; what matters more is its image in the category of becoming rather than of being.
Maybe the same could be said of a wave function; the only observables are the states (and derived quantities) and their frequency of occurrence through experiment, but I'd be quite happy to think of a wave function as a being or a property of a being.
Don't think it's relevant really, things induce quantum effects in other things; hence ionic bonding and the arche-fossil reference for when this relationship is anthropomorphised too much.
That is my understanding. And the abstract of the paper doesn't say a superposition is detected. I suspect there is some over-interpretation of the experiment's implications going on here.
At the risk of being annoyingly meta, I think there are multiple interpretations possible of the many-worlds interpretation of QM.
One can take a 'splitting' interpretation, in which worlds branch off when a measurement is made, or one can take the interpretation that all the different worlds exist in superposition from the outset, each one having a definite state of everything, and what happens when we make a measurement is that we narrow our knowledge of which possible worlds we could be in.
Under the non-splitting interpretation, if Alice measures spin as V, then Alice knows she is in a V-world, whereas Bob doesn't know whether he is in a V-world or an H-world, but knows that Alice does know. There are two Alices and two corresponding Bobs, but the knowledge of the two Alices is different whereas that of the two Bobs is the same.
But note that they're not actually identical since they each have a different memory of what they measured. What Bob can do is reverse Alice's polarity measurement while retaining the record that the measurement occurred, which is identical for both Alices. This means that the two Alices will merge without memory of the polarity result and with all records of the polarity result having been erased. That is, there will be only one world branch again, with multiple histories, and with the record that a definite polarity result was measured by Alice.
This is analogous to the double-slit experiment where the single particle detected on the back screen had two distinct path histories (one for each each slit).
Quoting noAxioms
Yes.
Quoting noAxioms
Agreed. Alice's worlds are separate from each other, but they are in superposition in Bob's world.
It's illustrated in the article's image of the experiment (Figure 2 in the paper). Bob's friend's measurement occurs in the gray box (with a record that a definite result occurred). There are detectors on the far right after the beam splitter that Bob observes (and similarly for Alice on the far left). The statistics collected from the detectors over multiple runs indicate quantum interference which means that Bob's friend's measurement in the isolated box was in superposition. It's analogous to the interference pattern in the double-slit experiment which indicates that the emitted particle was in superposition when it passed through the slits.
What this experiment challenges is the idea of objective collapse. Instead collapse is observer-dependent - there is collapse for Bob's friend but not collapse for Bob.
It's actually even "less" than that in these experiments. The two observers are not observing the same thing and reaching different conclusions about it. They're observing two different things. X in state m and y in state n. The issues arise merely due to theory about what the relationship between x and y should be, what the values of m and n should be per the theory.
Thank you for giving this excellent counter-argument! :wink:
I am too reticent to accept completely what people like Bitbol, d'Espagnat etc are positing (and in some sense even Rovelli). In fact, I share your concerns. But IMO correlationism says something really 'deep' about our knowledge, so to speak. Meilassaux's argument is very strong but IMO it does not really refute the 'correlationist' argument. I am not trying to be difficult (I am sorry if I am giving this impression) but IMO Meilassaux's argument refutes the strongest form of 'correlationism', that is: there is no mind-independent reality.
IMO, a weaker form of 'correlationism' is, in fact, right. Let me explain this briefly. First, let's define 'direct knowledge' as a form of knowledge that is not based on inference but it is immediate. I believe that for this form of knowledge the 'correlationist' is right. We cannot 'neglect' its 'perspectival nature'. On the other hand, there is another type of knowledge, based on inference that is necessary for science. For instance, if we accept the reasonable assumption that we can know by inference, it seems hard to deny. We can say that we cannot be 'absolutely certain' about it, but it is difficult to think that all our inferences about something independent from our own perspective cannot give us knowledge.
Now, let me give a longer answer (I hope that isn't too unclear)...
Let me begin again from Rovelli's Relational interpretation (it is a somewhat long answer, sorry!). According to Rovelli, there is no truly 'absolute' perspective. But here whatever physical system has its own 'perspective'. So there are no 'observer-dependent' states. A 'perspective from no-where' or 'God's eye view' is impossible. Rovelli writes in his pre-print 'Relational Quantum Mechanics' (p. 1 and p.15):
If the above is true then we simply cannot have a 'perspective'-independent knowledge. Rather all knowledge is 'perspectival' by necessity. Does this mean that there are only 'perspective' and nothing else? That is: can we still speak about 'absolute' properties of things? For instance, can we speak of an intrinsic property of an object O? Or all properties of O are relational, i.e. defined only in relation to other objects?
I believe that if Rovelli is right, then we simply cannot know intrinsic properties of objects (or maybe even that there are no intrinsic properties...). I honestly do not know if this 'makes sense', so to speak. But in my opinion this is quite interesting*.
Given the above, how can we make sense of the sentence: 'the universe is 13.8 billions years old'? If we accept Rovelli's interpretation, IMO we cannot even speak of 'the universe as a whole'. Why? Because, there is nothing outside that can be used to define a relation (this is very reminiscent of Kant's antinomies about the universe). So, fine! But as you say cosmology is very effective so it is hard to think that even such statement is perspectival. On the other hand, we should not forget that even that statement is made according to a 'perspective', the reference frame where the Cosmic Wave Background is isotropic, that is the 'co-moving reference frame' (check: https://en.wikipedia.org/wiki/Age_of_the_universehttps://en.wikipedia.org/wiki/Cosmic_time ). So, strictly speaking it is still 'perspectival'.
Even Relativity itself seems to suggest this, if we want to avoid the 'block world'. In the 'insight' article 'Block universe, refuting a common argument' on physicsforums, the 'block world hypothesis' is criticized because the assumption that the 'present' of each 'observers' is 'fixed' (in fact, the 'block universe' would follow if you accept relativity of simultaneity and this assumption). The reason why such an assumption is rejected is because of the velocity of light speed limit: no information is available outside the light cone, so only events in the past light cone are really 'fixed'.
So, ok, let us now accept all of this reasoning. Does all of this suggest an absurd form of relativism? The point is that although there are perspectives, one can still speak of 'shared truths'. 'The universe is 13.8 billions of years old in the 'co-moving' reference frame' is true for everyone, because it specifies the appropriate context. Also, from the reference frame of the Earth we can know the age of the universe in that reference frame. So, we actually can know other 'perspectives'. Hence, despite the fact that we cannot have a 'view from no-where' we still are able to make statements valid in the various 'perspectives'.
OK. Now let us bring our consciousness inside all of this. We have accepted that we cannot speak of 'perspective-independent' states. Our consciousness arguably gives us another perspective. So, we actually see everything from this 'perspective'. If the above is right, we can know by inference what is true according to other 'perspectives'.
But Kant reasoned that 'the world that appears to us' is (in part) conditioned by our a-priori forms, categories etc and, therefore, we cannot neglect the contribution of these a-priori forms. Hence, So, even if the 'correlationist' position seems absurd it cannot be really rejected. Statements about other perspectives become 'hypotheses'. How all of this escapes the charge of being 'epistemic solipsism' is unclear to me - it is IMO an 'aporia'. (It is epistemic because Kant accepts that we do not create the world but at the same time we cannot know it independently by our own a-priori forms, categories and so on)
We might try to say that our perspective is itself conditioned by the 'external world'. I'd agree. But still IMO does not actually overcome all of these difficulties. Rather, we have a changing perspective rather than an unchanging one. But still I cannot see a real refutation of the 'correlationist' view.
It might be said, however, that taking very seriously 'correlationism' is due to a sort of 'excessive skepticism'. That is, while it is true that we cannot completely neglect our 'situatedness' we can still say that statements about the world independently by our minds are reasonably true (after all, your concerns are well-justified IMO). But again, I do not see a true 'refutation' here so to speak.
What is fascinating however is that it seems that all this reasoning is suggesting that we should take into account a perspectival thinking. That is, it seems to suggest that all 'true statements' we make are context-dependent, so to speak even if we do not accept the 'correlationist' position. We are always 'forced' to specify the context in which a statement is true. (And also we should not neglect too easily our own perspective!)
As I said, maybe, however, we can accept a weaker form of the correlationist position by distinguishing something like 'direct knowledge' and 'knowledge based on inference'. The correlationist position is applicable to 'direct knowledge'. But he is wrong if he is too skeptical about 'knowledge based on inference' (which enables us to say, for instance, what happened during the evolution of the universe...).
[*As an aside, I find fascinating that David Bohm already by 1957 - only five years after the publication of his 'deterministic' interpretation of QM - arrived at a similar conclusion with the concept of 'qualitative infinity of nature'. According to him, all our knowledge is valid only in a specific context. For instance, classical mechanics is not 'wrong'. Rather, it has a limited validity. And according to Bohm all physical theories must be of limited validity. The difference with Rovelli's view might be that Bohm assumes that there is a perspective-independent reality but it is unknowable. Rovelli does not. But I am not an expert on both. So, I won't digress any longer...]
In summary, I agree with the 'correlationist' is right in believing that all our knowledge being with our 'situated' lived experience (which is changing and conditioned by the 'external world'). I agree also with him that we cannot neglect completely the 'contribution' of our mind. So, 'direct knowledge', i.e. immediate non-inferential knowledge, occurs within this aforementioned perspective.
But I disagree with him if he denies that we absolutely cannot know anything except the world as it appears to us. In fact, I believe that we can be reasonably sure that we can have a (partial) indirect, inferential knowledge of what is 'outside' our situated experience.
But, interestingly, it seems that a 'perspectival' reasoning (somewhat analogous) to the one of the correlationist can be applied to science. And one wonders if there is a link :chin:
Obviously this would not be possible if it did not assume a real world whose functioning produced specific constraints on thinking. So this intermediate claim considers post-Nietzscheans to have gone too far in their relativism. On the other hand ,it rejects the rationalism of Lakatos and Popper, who assume fixed norms as underlying scientific practice.
I suspect such an intermediate position is more appealing to scientists like Lee Smolen and Ilya Prigogine than the Popperian-Lakatos Kantian one.
As I'm guessing you're well aware, Rovelli's main observation exactly describes the Wigner's friend scenario that this thread is about. But it's worth shining a light on. Also of interest, Rovelli commented on the OP experiment in a recent New Scientist article:
Quoting Rovelli in New Scientist (Quantum experiment suggests there really are ‘alternative facts’)
The relevant question about our networks of inferential knowledge is whether they are vindicated solely by virtue of being intersubjectively validated or whether a knowledge claim's intersubjective validation tracks how nature behaves. Scientists don't produce theory or experiment, usually, for the purpose[ of intersubjective validation, they validate claims about the world using shared methodologies. Even repeating an experiment is done to assess whether a claim is true, consistent with the available evidence, or neither of these things.
Quoting boundless
It's worthwhile to remember here that our discussion about intersubjective validation relates to the phenomena of quantum mechanics only analogically. Is a scientific theory a quantum observer? Is a research practice a quantum observer? No to both of these things, scientists don't fire scientific theories at particles to determine their state. Can a chlorine atom serve as an observer for a sodium atom when forming an ionic bond? I think, absolutely, and the latter is the run of the mill kind of quantum interaction that's been going on since things have been going on.
Even when all properties are relational, we can still be in the state where Alice agrees that Bob sees X, Bob agrees that Alice sees not-X, or that one was in a superposition or whatever. The general logic here is about as banal as @Banno portrayed it outside of the QM context and @Andrew M portrayed it within the context of the paper in the OP. Collapse is observer dependent, great, we have established something about nature.
Quoting boundless
I would remind any reader that a view from somewhere is a view of something. The context dependence of the production of a theory; through whatever intersubjective validation mechanisms you like; does nothing to diminish the truth of well established claims using methods consistent with the theory (or theoretical context).
Quoting boundless
Yes, the calculation of the age of the universe is done with respect to a reference frame in which its expansion is isotropic. But:
You can still make ancestral statements within the frame; its history goes back well before the advent of humans; before the advent of the distinction between unconditioned datum ('raw experience' or 'direct knowledge') and conditioned factum ('processed experience' or influence from a category of the understanding). The more relevant point here is that we can make sense of statements which describe events anterior to the the genesis of the a-priori; of conditioning sensibility.
Meillassoux discusses this point in terms a distinction between 'the lacunary nature of the given' (say that we only see one side of an object when looking at it) and 'occurrences which are not contemporaneous with any given':
The strategy here is to locate the conditioning sensibility within a time concept or becoming concept; whereby the conditioning sensibility passes from a state of nonbeing to a state of being. (I'm quoting out of order from the book because I think it fits the flow of our discussion better) It is tempting to say that the existence of such an ancestral state of affairs is a merely empirical matter, which does nothing to change the relationship between the forms of sensibility and their conditioned facts - as I believe @Wayfarer likes to emphasise. However, the interpretation of the ancestral statement; and the required condition for it to make sense; is that we imagine a time before there was a conditioning transcendental subject, a time in which the sensibility's conditioning becomes an event. We need to be able to say that a transcendental subject occurs for the occurrence of the conditioning relationship the sensibility has upon our interpretations. As he puts it: (quoting out of order since it fits our discussion better)
What this argument reveals is that the conditions of possibility for the sense of ancestral statements require us to be able to think of a world indifferent to any given; any conditioning sensibility or emergent system of intersubjective validation. The meaningfulness of ancestral statements requires us to adjust our sophisticated intuitions about the a-priori nature of the correlation between thought and being to include the ability to interpret, since we inhabit, a world radically indifferent to any conceptual distinction. Nature becomes a curmudgeonly gainsayer who can refuse to yield to any determination of theory or sensibility; it will shout "NO!" whenever it bloody well likes and may not speak our language.
If nature does not speak our language then it will not exist for us except as it is translated into our language. Then we will hear nature's 'no' as we interpret any affirmation or negative, as relative to a particular account. That is, its refusal to yield to a determination of theory or sensibility will nonetheless by a refusal that is recognized, that makes sense, and this can only take place through an authorizing scheme. This language-dependency is not unique to human sense-making. A form of it inheres in the sense-making of all living, self-organizing systems. What disturbs a living system only appears as a disturbance, a 'no', in relation to the norms that system sets up via its produced environment.
I agree with you here. And IMO the 'weak correlationist' does not have a problem with it.
Quoting fdrake
Well, I agree again :wink: I mean, 'perspectival knowledge' about something is still knowledge about that. BTW, I agree that objective reality is redefined...when you specify the 'perspective', that is when you give the appropriate context then the statement becomes true for all.
[On the other hand, there might be the problem of how can we talk about objects that do not have any intrinsic property. It seems that a defining (i.e. 'essential') property of an object (i.e. the property that makes an object that object) is intrinsic, not relational...but maybe this is off-topic...]
Quoting fdrake
Agreed!
Quoting fdrake
Yeah! And I agree with you that such a knowledge does tell you something about the object of knowledge. Still, however, you cannot completely remove the fact that it is 'perspectival'. In fact, I cannot think that it is really possible to deny it.
BTW, cosmology is also not the study about 'the universe' in the sense of 'everything'. In fact, in cosmology you neglect small-scale perturbations.
Quoting fdrake
Again, I think I, in fact, agree with you. And I believe that the 'weak correlationist' does not deny the validity of ancestral statements. Rather, as you said before he only says that ancestral statements are made within a frame. Of course, this does not make them invalid!
I really do not think that 'weak correlationism' is more (or much more) than this.
[Also, I believe that the distinction between 'direct' and 'indirect' that I made in my previous post knowledge is apt. This should not be taken to mean that knowledge of e.g. what is observed in other perspective is devalued (unless one wants to become an epistemic solipsist of sorts) but only that it is indirect...]
Thank you for emphasizing that!
Regarding the fact that cosmology is not a 'theory of everything', I suggest this nice talk about Carlo Rovelli: https://www.youtube.com/watch?v=TzmykSv6OBY (especially around minute 7 - it is a hour-long talk).
Also the response to the first question in the Q&A section of that talk is interesting since it gives the idea of how much 'perspectival' is RQM, see: https://www.youtube.com/watch?v=TiXzq4G10mk (the first question ends around 2:30). Anyway, the whole video is very good.
Maybe also @Andrew M and @noAxioms might find the above linked videos interesting.
How is this not simply Popper's 'falsification' at work? In saying that, I'm not implying any belittlement of that principle, I think it is profoundly important. But the point of the principle is explicitly to differentiate empiricism from metaphysics, and here I think we're dealing with the latter.
Quoting fdrake
But that can't be true, or else mathematical physics would not have been as brilliantly successful as it has been (not to mention all of the other successes of mathematical science). As to why this is the case, Einstein himself said that 'the most incomprehensible thing about the universe is that it is comprehensible', and Eugene Wigner wrote his well-known essay, 'the unreasonable efficiency of mathematics in the natural sciences' on the same topic.
I think the basic issue with Meillassoux' analysis, is that it doesn't properly grasp the meaning of 'a priori'. The priority of the categories of the understanding (and so on) is not a temporal priority. It's that in order to understand anything, in order to exercise reason, then the axioms of reason, the laws of thought must hold true. So they're prior to empirical science, in the sense that empirical science has to assume them in order to begin to theorise about anything.
Because we now naturally view everything through an evolutionary perspective, then it's also natural to assume that logic, reason and language are an evolved capacity - which in the temporal sense they obviously are. Then we further think, well the Universe is vast and 13.8 billion years old, whereas us tiny specks ('chemical scum' in Hawking's charming phrase) are like insignificant blips in a vast and largely incomprehensible Universe. Hence 'Science reveals a time that not only does not need conscious time but that allows the latter to arise at a determinate point in its own flux.'
Whereas the classical understanding was that because we're able to reason and discern causal laws and principles, then the mind's capacity to reason must correspond to a kind of sovereign reason that governs the Cosmos. (Of course that sounds far too close to natural theology to be PC in today's world.)
But in my view, Meillassoux' attitude is precisely that which is subject to Bohr's criticism when he said that 'the objective world of nineteenth-century science [is] not the whole reality.' Meillassoux is insisting that this 'wholly objective view' is ultimately authoritative, but again it doesn't acknowledge the role which the human mind, or rather, the rational intellect, plays in the construction of that scientific world-view, because it continues to insist that it must be based on something that exists independently of the mind. That is the basic error that crept into Western cultural discourse through Galileo and Descartes, and which quantum mechanics is now showing to be incorrect - but no matter how many times it does so, what Heisenberg termed 'dogmatic realism' will always find a way to deny it.
Thanks boundless - they're excellent videos and well worth watching for anyone with an interest in the philosophical aspects of QM. Fun quote from Rovelli at 36 mins: "When I told Max (Tegmark) that he was a relationist, he told me that he is going to convince me that I'm, without knowing, a Many World believer." Anyway, Rovelli has a slide at 40:15 that says:
Quoting RQM - Rovelli
My questions are:
1. Is this just a semantic difference with Many Worlds? (That is, there are nonetheless many physical branches, but there are only deemed to be facts relative to an observer's branch.)
2. If not, then what is the substantial physical difference and what explains physical interference effects? (Many Worlds would explain it as physical interference between branches.)
I was wondering if you would answer a few questions for me before I respond in more detail:
(1) Do you believe that ionic bonds happen without human intervention?
(2) Do you believe they happened before the advent of humans?
(3) Do you believe that human ratiocination can find order in nature because the human mind and the regularity in nature jointly participate in some eternal cosmic logos? If so, how do you think that works?
(4) Do you believe in anything like the distinction between primary and secondary qualities? Primary qualities being like mass, tensile strength, temperature and so on. Secondary qualities being heaviness, sturdiness, warmth and so on.
Collapse mathematically is a mapping from an operator's spectrum to a one of its eigenstates right (a projection map)? Whether this collapse has a physical interpretation, and what that physical interpretation is, are where all the knots are AFAIK.
In principle, it doesn't matter whether it's an 'ionic bond' or any other chemical or physical relationship. The ionic bond is just an illustrative example.
In response, it is perfectly possible to have a realist view of the empirical domain - the age of the earth, the universe, the solar system and so on. I take a realist view of all such facts. But it doesn't obviate the point, which is that the human mind - your mind and mine - is an essential pole in any such statement, even statements of empirical fact - which is the basic claim of transcendental idealism. So empirical knowledge, even knowledge of the early cosmos, is still the analysis of phenomena, of what appears.
There's a passage in Magee's book on Schopenhauer that I've quoted previously. It's a bit lengthy but it does articulate the exact point, from a passage discussing some of the objections to Kant, and Schopenhauer's response.
Bryan Magee Schopenhauer's Philosophy, Pp 106-107
Notice that whether we speaking of the ancient universe, an ionic bond, or a pencil on your desk, the same general observation applies.
Quoting fdrake
Have a glance at the two paragraphs below this heading in the SEP entry on Schopenhauer.
As the article states, this is a 'perennial philosophical reflection'. I mean - how is it that maths is predictive? What is the nature of number, and why, by being able to understand mathematical ratios, have so many profound discoveries been made by science? I'm not asking that to elicit an answer, and I don't claim to have an answer, other than to say that reason or the rational faculty obviously discloses facts about reality which can't be discovered by any other means. And furthermore that I don't believe it is meaningful to depict the consilience between mathematical logic and the properties of nature in terms of either mere chance, or biological necessity.
Quoting fdrake
That distinction was essential to Galileo and subsequent science and philosophy. But even though it has been extraordinarily fruitful, it's also deceptive, because of the ramifications that it has for philosophy. Chiefly, this is because it results in what has been called 'the reign of quantity', the notion that only what is mathematically quantifiable is real, because then the mind and judgement and intellect and much else besides is covertly assigned to the domain of 'secondary qualities' (and then we wonder why there's a "hard problem"!) You will notice that this emphasis on the reality of the quantitative is a very widespread assumption in modern culture. But, as Robert M. Pirsig said, what is really wanting is a true 'metaphysics of quality' - and this is just what such an attitude excludes.
I think we habitually adopt the outlook of scientific realism, without acknowledging the sense in which that too is a construct - vorstellung, in Schopenhauer's terminology. That doesn't mean it's all in the mind in an obvious sense, but that the subjective or mental pole is fundamental to it, and that pole is never objectively disclosed.
(Michel Bitbol has written a lot about this, as I have recently discovered, courtesy of some links provided by boundless.)
Ideally I want to know whether you think 'Ionic bonds happened before there were humans' makes sense when interpreted literally, even if that interpretation is misguided or shows an insufficient deference to the role the transcendental subject plays in apperception.
Quoting Wayfarer
Quoting Wayfarer
Does taking a realist view mean you believe "Ionic bonds happened before the advent of humans"? I have a realist view and find this largely unproblematic to believe, even with the caveats related to 'ionic bonds' as a concept being the product of our understanding. They also just happened to happen long before they were theorised.
Ionic bonds happened before the advent of humans, yes or no? Ionic bonding would have occurred even if humans never existed, yes or no?
Sounds like if H is also factorizable into H3 and H4 instead of just H1 and H2, H3 and H4 'exist' as much as the other two, and yet cannot exist in different worlds from H1 and H2, only in different worlds from each other. I think I got the gist of your explanation in your post, but it seems that RQM might suffer from some similar issues.
Quoting boundlessDon't know what simultaneity has to do with it. Relativity seems to work fine with a defined preferred present, even if there is no way to determine it in SR. I suppose that with spooky action at a distance, a preferred foliation would unambiguously label one event as the cause and the other as an effect, but as the experiment that Wayfarer linked shows, there is no spooky action. The distant person (Alice) can make the measurement and Bob (local) know it because it was a scheduled thing. And yet Bod can measure his half of the pair and verify it is still in superposition. QM demands this, so it is not an interpretation.thing. The OP sort of disproves and spooky action at a distance. Alice knows that Bob will take a measurement in one second, and knows the result she will learn tomorrow when Bob reports it, and yet Bob verifies continued superposition, and then an hour later he actually measures the polarity. The superposition doesn't go away due to Alice's action. Therefore there is no spooky action at a distance. No?
The table says it denies locality. OK, I see the note [15] which seems to claim a sort of loophole in Bell inequality. I do suppose that relativity has an implication of locality since without it, events with cause/effect relationship are ambiguously ordered. Not sure if relativity theory forbids that explicitly. A nice unified theory would be nice. The sort of 'weak' non-locality required by dBB interpretation claims to be Lorentz invariant, so that means causes and effects are unambiguously ordered, no? Not an expert, but if Alice and Bob both measure their entangled polarities fairly 'simultaneously', it seems the order of events is hardly Lorentz invariant. So maybe I just don't understand that note.
If Alice discards the result like that, then it wasn't done. Memory of having done it doesn't change that. A mirror doesn't reflect a photon. It measures it and sends a new photon out at the new angle and same polarity, and is afterwards unaffected by having done that. It doesn't count as a measurement since the photon is still in superposition.
Yes.
Yeah they are very good and the quote is very funny :wink:
Quoting Andrew M
I believe that Rovelli himself treats the wave-function as not descriptive. So, he would not say that there are 'many physical branches'. I am inclined to agree with this but I understand that it is somewhat problematic. As I said elsewhere, honestly I am a bit averse to the idea behind 'Many Worlds' (i.e. that "whatever can happen, does happen"). But that's subjective.
Anyway, even if one accepts the 'existence' of 'many physical branches' there is still a crucial difference IMO between MWI and RQM - and this is a more 'technical' objection if you will. In MWI, the 'only real thing' is the quantum state of the universe. This leads to some problems as I mentioned to NoAxioms. Check for instance this paper by JM Schwindt: https://arxiv.org/abs/1210.8447.
Here Schwindt says that even if one accepts that decoherence solves the 'preferred basis problem' once a factorization of the Hilbert space is done that allows for instance to 'decompose' the universe into the measured physical system and its environment (BTW, as I understand it, decoherence solves this 'for all practical purposes' in fact but let's assume we are content with it). But as you might have noticed, decoherence is based on the assumption that a factorization is already made. The point is that Hilbert space by itself is structureless and this raises a lot of problems. Firstly, why we would make a factorization in the first place? This is a need that, of course, we have but it is an a-posteriori requirement based on our experience that a propri is not needed in the theory. Secondly, assuming that we do not regard that a problem, we need to factorize. What happens, however, is that factorization is arbitrary and in some factorizations 'nothing happens' (no interaction etc). Hence, even if we do the factorization the theory itself does not justify that we experience change and so on. So, to avoid this, it seems that we need to accept all possible factorizations: MWI becomes a Many-Many World Interpretation where all histories of all factorizations 'exist' (like the one we are 'experiencing').
Now, I do not know if a version of this problem might appear in RQM (which AFAIK does not even use decoherence). The reason is that in MWI you regard the entire universe as the single 'real system' and you need to add an 'additional structure' in order to decompose the universe into subsystems. In RQM, the subsystems are the 'primary' because they are given by experience (in MWI, instead you try to derive experience from the universal wavefunction).
In other words, factorization is something that you do not need to justify simply because it is so to speak given by experience. (Also the comparison between RQM and Everett's theory in the SEP article about RQM might be interesting here...)
Check also this discussion on physicsforums: https://www.physicsforums.com/threads/why-does-nothing-happen-in-mwi.822848/
Honestly, I do not know if MWI-supporters have found a solution to this problem.
Quoting Andrew M
Well, yeah I honestly do not know how you can explain that if you assume that the wave-function is not 'real'. So, I unfortunately cannot give you a response.
If the wave-function is taken as 'real', then the situation is still different from MWI IMO (as I explained above, hoping that it made some sense LOL...). Mauro Dorato apparently tried to explain RQM in terms of dispositions, check: https://arxiv.org/pdf/1309.0132.pdf
I'll answer to this now. I try to answer to the rest of your post ASAP.
Anyway, as I said also to AndrewM I think that the problem is even deeper. Consider now that you want to identify H1 as the Hilbert space of physical system that is measured and H2 as the Hilbert space of the 'environment' (that is 'the Universe minus the system').
In MWI, you just have H. The theory itself does not tell give you any way to decompose H a-priori. Of course, we observe that something happens and, therefore, we need a factorization/decomposition (but note that the basic ontology of MWI is simply H, which is a-priori without any structure). But here we have two problems:
1) if we factorize, we note that the factorization is completely arbitrary. And in some factorizations you get into a 'situation' where nothing happens. No measurement, no interactions etc. So it just appears that the measurement is due to a sort of illusion due to a bad choice of 'decomposing' the universe.
2) even if you accept the above, then you have to accept that all factorizations/decompositions are actual. So you end up in the situation you mentioned: a Many-Many world situation where all decompositions and all histories related to each of them 'exist' like the one you are living.
As I (tentatively) said to AndrewM:
Quoting boundless
Check also this discussion on physicsforums: https://www.physicsforums.com/threads/why-does-nothing-happen-in-mwi.822848/
I am not Wayfarer, but I try to give an answer from a 'Kantian' or 'quasi-Kantian' viewpoint.
A 'moderate correlationist' (i.e. neither 'weak' nor 'strong') might say 'a la Kant' that while humans (or more generally sentient beings) do not 'create' reality, the 'world as it appears' to us is just our representation. In other words, it is given by the sum of the 'noumenon' (which is unkowable) and our mind. So, to your questions he might answer: for the first 'yes' in the sense that 'things in themselves'* exist independently and 'no' for the second in the sense that 'Ionic bondings' are 'empirical things in themselves' (and hence part of the 'representation'): see the fifth note here https://plato.stanford.edu/entries/kant-transcendental-idealism/notes.html (these are the notes to the SEP article on Kant's transcendental idealism).
*Note that Kant used the plural and hence he allowed the possibility that the 'noumenon' could be made of a plurality of things (and hence, this would put him quite close to the 'transcendental realist' camp). Schopenhauer denied that plurality could be a feature of the 'thing in itself' (hence, he used the singular), claiming that it is a category of our intellect.
A 'strong correlationist' might say that it appears that ionic bonding would exist before the advent of sentient beings. I believe that Schopenhauer is a 'stronger correlationist' than Kant, because he says explicitly that you cannot even think about the universe where no sentient being exist and the previous story of the universe is actually related to the opening of the 'first eye' (i.e. the appearance of the first conscious being) and he also believed that the 'thing in itself' was singular.
BTW, similar remarks have been made by e.g. John Wheeler with his idea of 'Participatory Anthropic Principle' (check the 'Variants' section in the article on Wiki about the anthropic principle, which also mention Schopenhauer) and this interview with Andrei Linde (especially after minute 6). So, it seems that some physicist do embrace this sort of idea (there is also the 'Many-minds interpretation', a version of the MWI where minds have a special role).
In any case, what is common in Kantian-like philosophies is a sort of paradoxical situation of 'external objects'. Since they are regarded the cause of our sensorial experience, they must exist independently by us as the 'empirical things in themselves' (hence 'empirical [i]realism[/I]'). At the same time, however, they are still 'inside' the representation. Check also how Kelley L. Ross deals with this issue of 'empirical realism': http://www.friesian.com/kant.htm#idealism.
Yes, the relationship between empirical exteriority and transcendental interiority is exactly what this kind of argument challenges.
Why is the question being asked? What lead to the asking of the question? What is the issue? Isn’t it because physics itself has challenged the idea of ‘observer-independence?’
Quoting fdrake
You can’t get a y/n answer to that question. Yes, there is evidence of the history of the cosmos prior to the evolution of h.sapiens. But all of that evidence exists in an interpretive framework which presumes a perspective. Thatt perspective is generally implicit, bracketed out. But physics has made that ‘bracketing out’ explicit - hence the interpretive issue.
Yeah, I should have specify that :smile:
With decoherence, which is key to my preferred interpretation, collapse does not happen, unless we want to call a rapid but continuous evolution from one state to another a collapse.
The claim that something exists mind-independently does not commit one to the claim that it is conceptually inaccessible. We conceptualise the world and thereby come to know it. You're continually confusing the ability to conceptualise X with X's existence. The reason for me continuing to pursue the question is because I hope that we agree that the ability to conceptualise X is different from X existing; and I want to bring that to a point by inviting you to consider a scenario in which one of our concepts continues to operate; ionic bonding; its reference class continues to have exemplars; the formation of sodium chloride; but we are not around to see it.
Quoting Wayfarer
The interpretive issue is not whether the term 'ionic bonding' in 'ionic bonding occurred prior to humans existing' is a result of human conceptualisation; we do have a theory of ionic bonding; the interpretive issue is that a condition for the possibility of the meaning of the statement 'ionic bonding occurred prior to humans existing' requires there to exist a reality prior to the existence of humans. Of course our theories about ionic bonding are a theoretical construct, but ionic bonding itself is not.
The substitution of 'the conception of X' for 'X' is completely illegitimate in all cases for any empirical realist; you already know that X's existence is not dependent upon the conception of X.
This is why I have been harping on about nature shouting 'no', and perhaps in a language we don't understand. We inhabit a reality which is not intrinsically concept ladened; it is independent of our conceptions of it; just like an uninhabited landscape exists and we do not populate it simply by thinking about it.
It frustrates me somewhat that in order to defend the mind dependence of quantum observers you defend a Kantian position of transcendental idealism which grants the real an autonomy in excess of the phenomena constitutive of our interaction with it. If you are operating under the presumption of empirical realism, the literal interpretation of 'ionic bonding occurred prior to the advent of humans' is something which must make sense for you even if you think the claim is false.
Thanks, I am a noob in this kind of discussion.
I am not confusing anything. Why do you think Neils. Bohr found it necessary to say that ‘if you haven’t been shocked by quantum physics, then you don’t understand it?’ It’s precisely because it calls into question our innate realism. You have a commitment to the reality of the domain of sense-experience, but you don’t see the way in which the mind itself imbues that domain with reality.
Notice that snippet from Magee which refers to the ‘inborn realism that arises from the natural disposition of the intellect’. That’s what you’re arguing on the basis of. And it’s not stupid or deficient to see it in those terms. It’s simply that it’s been called into question by science itself. That is what, I say, Bohr says is ‘shocking’.
Quoting fdrake
I don’t think the claim is false, but that it’s ‘a claim’!
Does this mean you disagree with the claim 'The existence of X is different from our ability to conceptualise X'?
The analysis of a theme or entity, then, is a creative synthesis between this background we bring to that analysis and the constraints the theme or entity places upon any adequate conceptualisation of it. This requires an ontological distinction between concepts and what they explicate; of ideas and objects (broadly construed to include processes, interactions etc). The distinction between an object and the concepts we use in our interaction or theorisation of it is the very ground for error; and while this error can be conceptualised to improve our theorisations, the possibility of this error marks that the distinction between concepts and what is conceptualised is not merely conceptual, it is real. The mismatches between the goals of our inquiry and the products of our inquiry are rooted in this ontological excess the objects have with respect to our ideas of them. That is to say, in targeting our inquiry towards an entity or theme simpliciter, the distinctions between it and our conception of it operate to tailor our conceptions of it toward greater accuracy. Yes, we operate from a perspective, but this perspective is a vantage point upon domains which do not depend upon our perspective to exist.
Quoting Wayfarer
We may emphasise the constraints that we bring to any perspective; the whole structure of the sensibility of the transcendental ego can be thus construed; but to hypostatise those constraints as imbuing nature with reality is to forget the distinction between the concept and what it conceptualises.
If anything, this is paying a great disrespect to the power of human reasoning; we can grasp problems from the very beginning of being until its end, we can conceptualise that which unfolds irrelevant of our conceptualisation through providing an adequate account of what is conceptualised. The creative and analytic power of our minds is done a great injustice by believing that nature is parasitic upon our conceptions of it; rather nature is expressed through any adequate conception of it. The distinction between the concept and what is conceptualised saturates any inquiry worthy of its name; the accuracy of our conceptions demands no less.
The true problem of epistemology is not the fact of our conditioning sensibility, it is how the conditioning sensibility can arrive at or contribute to an adequate conceptualisation. Any conceptualisation which is not a pure fiction is driven by the operative distinctions between it and its goal. Nature only becomes understood through our attunement to it, by relearning how to see when it shouts 'no!'.
"What is conceptualized" is the markings of a duck/rabbit. Even markings are a fusion of form and formless matter.
If you're claiming the formless has some independent existence, what's the basis of that claim? How do you know that?
Lines - still drawn.
Could you elaborate?
Half hearted questions get half hearted answers.
I was asking for the signs you take as proof that there is an independent formlessness.
Personally I think it's just all made of eggs. All the way down. No one can doubt the formlessness of eggs in their ineluctable succulence intruding into my anxious mouth.
This is the nub of the issue.
I think you’re arguing from the general perspective of representative realism: that concepts represent (or fail to represent) some principle or phenomena. So in this picture of representative realism, there is the thinking subject and then there's the domain of objects, energies and forces which we confront, analyse, and attempt to understand.
This is also clear from:
Quoting fdrake
So again, here, there's the concept in the mind and the reality to which it refers, more or less adequately - right?
Quoting fdrake
I said before that this is basically the principle of falsification, no? We have the left-hand side, which is an equation or descriptive hypothesis, and the right-hand side, which is the observation or experimental result. "Nature shouting 'no'" is when we predict X but we get Y, or no result, or at any rate, something other than what we predicted. Or we find that the entire hypothesis or model has to be abandoned due to a fundamental paradigm shift, such as when the theory of ether was displaced by the theory of relativity.
The problem that brought us to this point in the discussion, however, can't be conceptualised this way, or rather, it eludes being captured within this kind of framework. It has forced scientists to say things like:
It is the 'absolute fact' that I'm taking issue with. Whereas, I *think* your positing a 'transcendent real' that we're always working on getting a more and more adequate conceptualisation of, as a kind of domain of (at least potentially) absolute fact.
One last snippet, from theoretical physicist Andrei Linde:
(Paul Davies, The Goldilocks Enigma: Why is the Universe Just Right for Life, p 271)
I'm not saying that. What I'm saying is that every claim about 'what exists' has a subjective pole or aspect, and that this is never made manifest - it's tacit. But it is what the whole 'observer problem' has brought into focus. So the bone I'm picking with scientific realism, is that the presumption that the universe exists with no observers in it, covertly still includes an observer or perspective. Because without a perspective, a sense of scale, a sense of what is near or far, what is large or small - then what can be said to 'exist'? We have this picture of the empty universe, but this picture still implies an observer who provides that sense of scale and relationship within which all judgements about 'what exists' become meaningful. (That's partially why Wheeler named his approach 'the participatory universe' - it's because he realised that we participate in the 'creating' of the Universe=> 'it from bit'.)
As I mentioned previously, boundless linked some papers from a French philosopher of science called Michel Bitbol. He actually spells all this out in far greater detail than I'm able to. In particular, It is Never Known but it is the Knower: Consciousness and the Blind Spot of Science. That's one of the arguments I've been pursuing on this forum since I first signed up, glad to see it's not just me. :wink:
[quote=Bitbol]Science has a huge blind spot in the midst of it, and, like every blind spot, it is ignored by the blinded subject. This blind spot is something obvious but that remains virtually unseen: our situation, our experience, ourselves in the most intimate acceptation of this pronoun. Usually, the blind spot of science is concealed by scientists in the future of their discipline. They believe that in the future, something that is still inconceivable today will allow objective knowledge to account for subjectivity. But this belief is unwarranted, and it triggers virtually all the so-called “foundational problems” of objective science.[/quote]
A fun quote to roll out for those mystic bullshitters who like to illegitimately invoke Wheeler from time to time to add a bit of scientific prestige to their scat.
Science tells us that the Universe existed long before the advent of humans. Of course that judgement is made by humans. But the truth as to whether or not the Universe actually did exist before the advent of humans is independent of human judgement, because belief does not equate to truth or actuality.
So, we are left with what it seems reasonable to believe; and it certainly seems most reasonable to believe that the Universe existed prior to the advent of humans. What is your motivation for wanting to muddy the waters by complicating the issue beyond what seems obviously plausible to believe?
Of course I am also well aware of, and fully acknowledge, the difficulties involved in talking coherently about the noumenal, but those difficulties are on account of the fact that we can form the idea of things in themselves independent of our perceptions and perspectives, but not any clear idea of how those things might be. We can conceive of the idea of the in itself, but we cannot conceive what the in itself definitely is, beyond its just being, vaguely, the in itself, for obvious reasons.
By reverse, I just mean that the measurement process can be undone by applying appropriate (inverse) unitary transformations.
Quoting noAxioms
It seems to me that a measurement was nonetheless done, even when the original state of the mirror is restored. Of course, the experimenter may not care about that since it didn't entangle them with the photon and because the information has been erased. I think we agree on the mechanics. Or do you see more to it than that?
Thanks - that would be my reading as well.
Quoting boundless
As I see it, the decompositions that are of interest are those that are robust to interactions with the environment. So the ordinary objects of our experience, by virtue of being persistent and observable, are robust. That physical structure has emerged through an evolutionary process (as underpinned by decoherence), it's not a priori.
In other words, as you say above and Rovelli mentions in his talk, we start from the structure that we observe in our experience and work from there. It's not a Platonic endeavor. Now RQM is not solipsistic. It generalizes from individuals, to humans, to things, and ultimately to all systems and composites of systems that can interact. I think that MWI just takes that one step further and sees the universe itself as a system with a reference frame and a quantum state that can be described. So you don't need an excursion through arbitrary decompositions to take that final step.
But on the idea that nothing happens in the Everettian universe, I think that is true in one sense. If one person is pulling on a rope from one end and someone else is pulling with equal force from the other end then there is a high-level abstract sense in which nothing is happening. But there's obviously a lot going on at lower levels. If the universe is itself in superposition then, similarly, in that frame of reference, nothing is happening - there's no time, no dynamics, etc. But it doesn't follow that under the hood, in the reference frames of subsystems, that nothing is happening.
You might be interested in the following article that addresses this issue:
Quoting Quantum Experiment Shows How Time ‘Emerges’ from Entanglement
Quoting boundless
No worries! This is the difficulty for me regarding RQM. I can understand how MWI works, but not RQM in this regard.
Quoting boundless
Maybe a related idea here is to regard values in non-interacting systems in terms of potential. So, for Wigner, interference indicates that the friend has made an actual measurement in their reference frame but the measurement only has a potential value for Wigner until an interaction actualizes it for him (in accordance with the principle of locality).
That is distinct from a hidden variable theory that supposes that the friend has made an actual measurement that is merely unknown to Wigner, with the Bell inequality issues that that would entail.
Thanks for the quote! That's interesting :smile:
Well, I actually one who apparently misinterpreted him (and I am very sorry for that if he never embraced that idea)...
But what about the idea of the 'Participatory Anthropic Principle'? Maybe he just changed his mind during his life? :chin:
Actually such an idea is also attributed to him by his critics. So, it seems strange that he never endorsed it. For instance, in 'Why information can't be the basis of reality', John Horgan writes:
and also in 'Do Our Questions create the World' :
Had also John Horgan misattributed such a view to Wheeler?
:up:
Quoting Andrew M
I see! Yeah, you are right. Schwindt's paper only refutes the idea behind something like 'pure MWI', that is Hilbert space without any structure is the only reality [edit: I meant a version of MWI where you start from the 'universal wavefunction' alone].
If one introduces a substructure (as dictated by experience) and does not have any problem with that, then you are right it seems that those problems do not apply.
Quoting Andrew M
Interesting analogy, thanks! I'll read the paper.
Quoting Andrew M
Yeah, that's a nice way IMO to avoid issues with relativity.
And BTW, as I said to NoAxioms a similar problem arises in Relativity, if one wants to avoid the 'block universe idea' as suggested by Rietdijk-Putnam argument(here's the link to the Wikipedia article). There is a very nice 'insight article' on Physics Forums that gives a counter-argument (which is reminiscent of the reasoning on which, for instance, RQM is based): https://www.physicsforums.com/insights/block-universe-refuting-common-argument/.
Well, I agree that a preferred frame is not actually incompatible with the predictions of Relativity. So, in this sense we can say that SR is not incompatible with such an idea. But, I was referring to the 'standard presentation' of SR, so to speak, where you do not define a 'preferred frame'.
Anyway, I'd agree with what you say here. But IMO problems with locality arise if you introduce hidden variables.
Quoting noAxioms
Well, AFAIK in dBB you need to somehow define a way to define an 'absolute simultaneity'. Lorentz invariance is not the real problem. In fact, I read that you can define some form of 'absolute simultaneity' and at the same time not violate Lorentz invariance. But IMO that's a bit agains the 'spirit' of Relativity, so to speak (I am not saying that this is necessarily bad, of course...).
But in any case, non-locality is inevitable in dBB IMO. To avoid it, you either need 'retrocausality' or 'superdeterminism' but I find both ideas untenable.
See the article on Wikipedia about 'Von_Neumann-Wigner interpretation' (there is however a nice discussion about Von Neumann's ideas on physics forums: https://www.physicsforums.com/threads/where-does-von-neumann-say-that-consciousness-causes-collapse.884128/.)
As I already mentioned, a separate (but somewhat analogous) strand is 'Many-minds interpretation' (a form of MWI where the 'splitting' occurs in the minds of the observers). See also the 'Everett plus minds' section in the article 'Everettian Interpretations of Quantum Mechanics' in the Internet Encyclopedia of Philosophy.
[Edit: after some reflection, I am now not so sure that 'Many minds' can be said to be a form of 'idealism'. Still, mind does have a 'special' role. Sorry for the late edit!]
Note that I do have some reservations about these ideas myself (well, maybe I fall in the 'transcendental realist' camp according to Kant...). But I find very interesting that these idealistic or quasi-idealistic ideas now are taken seriously among physicists (and philosophers of physics) themselves. I believe that is something that is worth of serious attention.
This pre-print by d'Espagnat might also be of interest: https://arxiv.org/pdf/1101.4545.pdf.
P.S.
Quoting boundless
For those interested in Schopenhauer's views, the passage I referred to is quoted here: https://partiallyexaminedlife.com/2015/05/01/schopenhauers-idealism-how-time-began-with-the-first-eye-opening/
Great thread Wayfarer, thanks for that.
I don't feel qualified to comment on this study in particular, but remain convinced that whatever the true nature of reality might be we've only begun to grasp it. The history of science suggests that the group consensus understanding of reality will likely be overturned in a radical fashion many more times before we're done.
As example, when will science be completed? When will the scientists hold a press conference to announce they've finished their work? Most people I've asked this question to reply, thousands of years or never.
If true, it logically follows that we currently know close to nothing in relation to what can be known, and especially in relation to all properties of reality, including those properties which will never be known.
If true, it logically follows that ignorance is a defining characteristic of the human condition. Thus, the most reasoned question would seem to be, what is our relationship with this ignorance? Intellectual relationship is one level of relationship, but typically a relatively shallow business. The more important question would seem to be, what is our emotional relationship with this state of ignorance.
Denial.
With that in mind, giving all these interpretations of the observer effect in quantum mechanics to support the claim 'Conceptualisation of X is necessary for X's existence' is stretching an analogy well beyond its bounds. Exactly the same can be said for motion in special relativity (though to be fair motion has been relative motion since Galileo), every instance of motion (or rest) defines a frame that things move with respect to, and our human cognition is no more required for this than for two raindrops to fall side by side.
Quoting Wayfarer
No, I don't think this is quite right. How are scientific, or indeed philosophical, hypotheses made? How do you generate relevant ideas which provide a good account of something? This goes for the design of experiments which test hypotheses as well as the formulation of hypothesis and theories. You need to take your cues from the thing in order to analyse it well.
As much as I dislike the subject/object distinction, I will use it here to make the point, It is not as if a subject stands inertly by throwing theories at the object until something sticks, the subject tries to create concepts that express the nature of a thing within a desired context of analysis. Rovelli's example in the talk @boundless linked is relevant here; when you model a pendulum as a simple harmonic oscillator you don't really care about how reflective it is, what it's made of, the 'love stories' of bacteria within it and so on, you care about its pendulum motion. And how do you form an account of the pendulum motion? By trying to see what drives it.
The properties of the object suffuse any account which accurately expresses them; within a behavioural regime.
Quoting Wayfarer
You seem to be under the impression that 'absolute facts' are like 'absolute simultaneity' or 'absolute space' or 'a quantum superposition randomly being mapped to one of its eigenstates due to some interaction'; we both agree that absolute simultaneity, absolute space and some absolute 'quantum state' are flawed notions (though the first two are fine approximations when dealing with low velocities). This is just science. The relationship between any of these things and the claim 'X's existence is dependent upon its conceptualisation' is only analogical, but for some reason you continue to cite scientific studies that allegedly 'show' the existence of X is dependent upon its conceptualisation. This allegedly is important, because you seem to have forgotten the relationship between frame dependence of motion and observer dependence of quantum state relate to the correlationist epistemological framework is an analogy. An analogy furnished through our common vocabulary of relation and constraint taking its cues from words related to perspective/perception/viewpoint and so on, but an analogy nevertheless.
I have seen you claim, elsewhere, about the problems of reductionism in science; people trying to 'define away' experience and so on. The strategy of your argument here is an excellent example of inappropriate reductionism; you seek to explain frame dependence of motion and observer dependence of quantum state/properties as being mere instances of conceptual relations between thought and object. Far from respecting in precisely what ways frame dependence and observer dependence are perspectival in their own terms, you jump to the conclusion that frame dependence and observer dependence are perspectival in precisely the same sense that a conceptual framework apprehends its topic.
In terms of the metaphysics here, you are also being a reductionist. The relationship between thought and being is just one relationship with its own properties; the relative motion of raindrops is another; the dependence of an ecosystem on soil qualities is another. No doubt you would cite all these dependences as instances of the relationship between thought and being; whereas the appropriate conclusion to draw is that nature has relations in the territory which are not exhausted by the fact that we may mirror them (in a behavioural regime) through the relation of concepts.
In terms of personal taste, I really don't get how you could look at something like the OP paper and the frame dependence of special relativity and think 'look! more instances of the same thing I already suspect is true! more evidence that everything depends upon its conceptualisation.' The relationship between thought and being does not have a monopoly on the character of relationships; clouds do not think rain.
Edit: I would like to point out that while there probably are analogous properties regarding the relationship of thought and being to other interactions; perhaps a spider's behavioural instincts which classify vibrations in their web; a neat one to one mapping which preserves all properties between reference frames/quantum observers and our garden variety conceptualisation of things is unlikely to hold.
Have their been physicists who placed consciousness in a central role in their quantum theory? Yes. Does that alone give you, I don't know, comfort? Could you say what it means to you?
I'm just not on this site as often as I used to be.
Quoting Andrew M
I compared what Alice did to what the mirror did since neither seems to collapse the wave function. There is still but one mirror and Alice, and somewhere down a pipe there is a state in superposition still. Sounds like no measurement was done, even if both the mirror and Alice have a green light over their heads indicating that yes, the event was noticed and measured, but no state from that measurement was retained.
So yes, green light says the measurement was nonetheless done. I agree with that.
How does this fact sit with the experiment in the OP? Bob sees Alice not even in superposition, but with a green light. She truthfully says "Yep, I did it, but can't remember what I saw". Not sure how a mirror might retain a history of a photon going by without a polarity measurement being taken, but I'm sure it can be arranged. From Bob's POV, no measurement was taken. It seems not contradictory at all for Bob to find the state of the photon still in superposition, despite the conflict wording in the article.
So that's what I see in it.
The article goes too far in interpreting the situation.
Not defining something undetectable (in SR) is fine, and I suppose the standard presentation of SR is that there isn't one. But GR, to the embarrassment of Einstein, had to admit to an apparent preferred foliation (which is not an inertial frame), so SR would actually be sort of wrong if it asserted that no preferred local frame can exist, and SR has never been shown to be wrong.
GR shows that the variable isn't hidden, but only because real spacetime doesn't conform to SR's nice flat uniform gravity special case.
A preferred foliation is one thing. A preferred moment (presentism) is more of an offense to relativity. I've created a thread defending presentism against attacks from the relativity side and thought I held my ground OK, but I thought of another interesting one:
If presentism is true, what is the rate of advancement of objective time? Equivalently, by how much is say a clock that tracks GMT dilated? It isn't moving very fast, but it's the depth of the gravity well I'm interested in. I thought of this when I tried to look it up. The absolutists sort of group together like the flood geologists and put out all this propaganda against Einstein, but none of those denial sites quote this absolute dilation factor, which you think would be one of their flagship points like the absolute frame. But they evade the topic. Why is that? Must be embarrasing...
The one from GR is not enough?
Yes, I know about the superdeterminism loophole. I also dismiss it enough to state that Bell eliminated locality and counterfactual definiteness from both being true. I see none of the listed interpretations hold both to be true, utilizing the superdeterminism loophole, so it seems the world agrees with that assessment.
‘Thought and object’. It is just that instinctive division which is called. Into question by ‘the observer probllem’. Anyway - thanks for your considered criticism, I appreciate the time you have taken.
If you are willing to collapse the distinction between the two, rather than merely and only 'inhabiting' the relation as correlationists describe, then the arche-fossil is successful; it at the very least forces a correlationist to choose between idealism and absurdity.
That there is no material reality prior to the existence of humans is certainly one way to find the argument instructive.
Anyway, was fun, even though I doubt I convinced you, I understand the arche-fossil argument in a lot more detail through rehearsing it with a willing antagonist. Thanks. :)
Nice find with the PF article and I fully agree with it. I was going to mention the Andromeda paradox and the idea of potentiality in relation to it in my previous post. So we seem to thinking along similar lines here.
It also reminds me of Aristotle's future sea battle example where he contrasts potential and actual:
Quoting Aristotle, On Interpretation, §9
--
Quoting noAxioms
Yes, I agree - it's just what quantum mechanics predicts will happen and so it's not contradictory (or unexpected) at all. But it does challenge objective collapse theories since they modify the standard formulation.
Because pop-science writers are generally trash.
Do you mean that some geometries in GR require such a foliation (rather than simply allow)?
AFAIK, there are attempts to reconcile dBB and SR that use a preferred foliation (which is not prohibited by Lorentz symmetry) but I think that this does not satisfy many people because it goes against the 'spirit' of Relativity.
Quoting noAxioms
But is there a real difference between the two? I mean, If the structure of space-time requires such a foliation, IMO I can define a frame where all these events are present. For such a frame, there is an absolute simultaneity, which is precisely the reason why AFAIK Lorentz aether theory is criticized.
Quoting noAxioms
I'd agree with the objection you are making. But IMO what you are saying is also a clue that one cannot make an absolute simultaneity (or rather, it is possible but would be 'hidden'...).
Quoting noAxioms
I don't know!
Quoting noAxioms
:up:
Great. Interestingly, I discovered that the same point is made by Carlo Rovelli to defend his 'relational' view, see: https://www.youtube.com/watch?v=vbYeAaCloiM. At 4:55, Valentini makes the same question that he made in the other video (namely that different observers might disagree about what happens) and at 53:52 Rovelli answers by citing the Andromeda Paradox - so we are in good company :wink: . It is a very good discussion, BTW (other than Rovelli and Valentini, also Saunders and Wallace (and others) participate in the discussion). This might also be of interest to @noAxioms.
Quoting Andrew M
Very interesting, thanks!
In fact, some time ago I read a philosophy of science paper that tried to use the potential-actual distinction in SR in order to avoid situations like Andromeda Paradox. Unfortunately, I do not remember neither the title nor the author :sad:
Quoting Andrew M
Unfortunately, I know very little about objective collapse theories. Anyway, I agree with you. It would be interesting to see how these theories deal with this experiment.
I do not understand your point, actually.
On one hand, I agree that pop-science is not always reliable. On the other hand, in this case, it seems that you are saying that John Wheeler never proposed the idea of the 'participatory anthropic principle' (or 'participatory universe') even if there are a lot of sources that claim otherwise. Am I right?
Or you're suggesting that is their interpretation of the 'participatory anthropic principle' problematic? If so, what did he really mean?
Thanks in advance!
Since none of this is new (it is demanded by QM right from the early days), how do any of the objective collapse interpretations get around this? Does this experiment change something? Did they expect a different result? I don't think so.
Quoting boundless
The expansion of space is uniform only under one foliation. It isn't absolutely uniform since it seems resistant to local mass, but only under one foliation does the expansion switch to accelerating everywhere at once. Essentially, only the the frame that corresponds locally to that foliation has the property of isotropy both in what is and in appearance.
It apparently goes against the spirit of SR, and it pained Einstein to not keep that in GR. Physics is different in other frames since non-local observations are allowed in GR.
Of course. One objectively orders any pair of events, and other may or may not attach an ontological status to each event (has or has not yet happened). A preferred foliation has no such ontological status. There is still spacetime with all events having equal ontology. Presentism has no spacetime, only space, with only current events existing (happening) and not any of the others. That sounds like a huge difference of reality to me.
I don't understand this comment. Under presentism, there is no spacetime. Only objectively current events are present, and the other events don't exist, so can't be present.
No, there would still be an absolute simultaneity. I can still sync remote clocks. I just find it difficult to build a clock that is designed to run in a location of known dilation and have it compensate for that in order to record the passage of absoute time. If it were possible to do that, the objective age of the universe could be known, but we only know the figure (13.8 BY) in dilated Earth time, which is obviously running slow. The universe is older than that, but by how much is the question.
Thanks for the very informative answer! I need some time to think about all of this :smile:
I forgot to say that I actually read the article and I found it very intriguing :smile:
I did some further research on Wheeler. I found this article: https://plus.maths.org/content/it-bit - it quotes a paper by Wheeler himself.
He certainly IMHO thought that 'information' (which he believes to be 'immaterial') plays a central role and is more 'fundamental' than matter.
But he did not seem to give a 'special role' to human observers (he seemed to have a more general idea of observer).
I am still not sure about the 'participatory anthropic principle' thing.
https://what-buddha-said.net/library/pdfs/wheeler_law_without_law.pdf
The basic idea behind the participatory universe idea is simply that what 'participates' with the universe is itself - which includes the equipment used to make a measurement (which belongs to the universe...). From the paper: "Registering equipment operating in the here and now has an undeniable part in bringing about that which appears to have happened". An 'observer' is a piece of apparatus, that's it. This, incidentally, was Bohr's position, which Wheeler understood very well.
(cf. Wheeler's comments on Bohr concept of the 'phenomenon, in the cited paper': "a phenomenon is not yet a phenomenon until it is brought to a close by an irreversible act of amplification such as the blackening of a grain of silver bromide emulsion or the triggering of a photodetector". Incidentally, this was also the point of difference between Einstein and Bohr: Einstein refused to believe the act of measurement qua equipmental intervention - or 'participation', in Wheeler's overblown vocabulary - could determine the results of a measurement, while Bohr figured this was the only consistent way to explain the results).
Thank you very much!
Actually in the article I linked, there is in it a link to a paper by Wigner himself: https://jawarchive.files.wordpress.com/2012/03/informationquantumphysics.pdf.
They would predict that Wigner would not see interference for sufficiently complex friend systems. So the options are to either accept the experiment's result as falsifying their theory or else show that the experiment isn't scaled up enough to trigger a physical collapse by their criterion.
For a brief discussion of that prediction in one of the experiment's referenced papers, see https://arxiv.org/abs/1507.05255 (p18, point 1).
I actually thought about it but, unfortunately, I did not arrive at a satisfying conclusion.
Quoting noAxioms
Ok, that's right. Maybe the point is that the foliation is not directly observable. As you say, we can observe only a "frame that corresponds locally to that foliation has the property of isotropy both in what is and in appearance". Just a guess. As I said, I am quite at loss.
Quoting noAxioms
I see...but if this does mean that non-locality is compatible with GR (as it is usually understood) why people consider non-locality problematic?
Quoting noAxioms
Well, yeah, you are right.
But IMO this leads either to the 'Andromeda Paradox'/Riedtjik-Putnam argument scenario or some form of retro-causality.
Quoting noAxioms
OK, I also agree with you on this.
Anyway, Antony Valentini proposed that cosmological observations might help to solve interpretational problems in QM. The de Broglie-Bohm interpretation actually makes the same predictions of QM only if the 'quantum equilibrium hypothesis' is satisfied, i.e. if the modulus square of the wave-function corresponds to the actual probability distribution (this assures that dBB satisfies the Born Rule). However, in general, this might be not true. Hence his proposal: maybe at the earliest stages of the evolution of the Universe, that hypothesis was not satisfied and - as a consequence - we should see empirical evidence against the Born Rule.
Here is the link to his talk (at the same conference): https://www.youtube.com/watch?v=XYZV9crCZM8.
Here the link to the Q&A session: https://www.youtube.com/watch?v=8qnuNLB61RA.
I suggest these videos also to @Andrew M.
According to the 'no signaling' theorem, if predictions of QM are satisfied there cannot be any direct evidence of violation of locality. Hence, it just seems that there is a sort of 'conspiracy' if there are non-local influence. This is actually one of the reasons I do not think dBB is true. But, interestingly, according to Valentini, this might be a clue that dBB is, instead, right: the fact that the world seems 'local' is due to the fact that the 'quantum equilibrium hypotesis' is true. IMO, his proposal however makes perfect sense in the light of dBB.
[Another reason for which I do not accept dBB is its 'strange' ontology. dBB is, in fact, characterized by both particles and the wave-function. In my understanding, particles have no role except moving in a way 'dictated' by the wave-function*. The wave-function seems to do all the job. Furthermore, the wave-function is not a field in real space but lives in the 3N-dimensional 'configuration space' where N is the number of particles. This prompted some proponents to adopt a 'nomological' view of the wave-function. But IMO this is still odd: laws are generally understood to not be dynamical objects and if the wave-function is merely a law, it just seems that there is no reason why particles move in that way. In fact, some think that the wave-function is better understood as representing dispositions: https://arxiv.org/abs/1406.1371.
*This is not true if one introduces the 'quantum potential' AFAIK. But even in this case, you still have a weird ontology where you have to make sense of particles living in our usual 3-dimensional world and an equally real field that lives in a 3N-dimensional world. And also some dBB supporters are critical of the 'quantum potential' formulation, see: https://plato.stanford.edu/entries/qm-bohm/#QuanPote
Also, I am a bit puzzled by the asymmetry between position and other observables. QM is perfectly 'symmetrical' with them, i.e. it treats them equally. For dBB, instead, position is somewhat 'special'. The counter-argument that is found in the SEP article on 'Bohmian mechanics' does not convince me. ]
Good find! I'll read it :smile:
Yes, another great discussion! I also liked Wallace's explanation of the wave function at 11:25.
So here's the setup and exchange between Valentini and Rovelli:
Here's also the relevant passage from the Physics Forum Insights article that you linked to earlier: The Block Universe – Refuting a Common Argument.
So we can see Rovelli's reasoning in the above exchange. For Alice on Andromeda, Carlo on Earth only potentially exists until a local interaction (say, a telescopic observation at light speed) brings him into her present (and then past). Similarly, for Bob the superintelligent being in the future, Carlo is only potentially at the conference until a local interaction decoheres the superposition (say, Bob talks to Carlo).
A further thought here is that I think this allows a representational interpretation of the wave function for RQM in terms of what is actual and potential for any given observer. What is locally entangled with an observer is actual (the past and present, measurements and interactions), what is not is potential (the future, spacelike separated regions, superpositions).
Thank you very much for the transcription!
Quoting Andrew M
:up:
Quoting Andrew M
Yeah, I'd agree. Both the representionalist and the non-representionalist views are possible. Rovelli himself wrote against a 'realistic' interpretation of the wave-function: https://arxiv.org/abs/1508.05533.
Actually, this interpretation of the wave-function is also held by some Copenaghists. For instance, Abner Shminoy wrote in the older version of the SEP on Bell's Theorem:
The link is to the section 'Philosophical Comments' of the article - Shimony lists other possible positions.
There are different takes. For IMHO a very interesting Neo-Kantian non-representionalist reading (among the 'Copenaghists'), check this article of Michel Bitbol (I already quoted it in this thread - I quote it again here for convenience): http://www.bourbaphy.fr/bitbol.pdf (according to him, Bohr's epistemology was close to Kant's views...). Or, if one prefers the video of the talk: https://www.youtube.com/watch?v=pYRLapWBqJY.
Another instance of interpretation of the wave-function in terms of potentiality-actuality can be found in this paper by Kastner et al: https://arxiv.org/abs/1709.03595.
That is one thin explanation. If what Alice did wasn't complex enough to objectively collapse the wave function, she should be able to measure the subsequent superposition herself and not leave it to Bob. Of course, QM theory won't allow that, so the 'thin' explanation see to go against QM itself.
Of course maybe I just don't understand this explanation. I have not read your link and am not sure that I would find the answer there satisfactory.
It seems not to be. It would probably violate SR if it was.
Yes. What is: Space is expanding everywhere equally(ish) at all simultaneous points. I say 'ish' because it expands more in empty places than crowded places, but not more in any particular direction. This isn't true in other frames.
Appearance: Space appears to be expanding equally at all points at some fixed distance from any observation point. So space is expanding close by, but not expanding say 6 billion light years away. Doing these sorts of measurements is how they determined the acceleration of expansion in the first place. You can't measure what is now, but you can measure how it appears now.
All of relativity seems to depend on locality, while QM interpretations might have other ideas. It is why I resist interpretations that discard locality in favor of counterfactual definiteness. I just don't see how relativity can make sense without locality. One can blatantly change the past, not just events outside one's future light cone.
That and the fact that counterfactual definiteness has all sorts of seemingly paradoxical philosophical baggage that goes away if you don't accept the principle.
Don't get your Dutch names wrong... I've got one myself.
The Andromeda thing and the Rietdijk-Putnam thing are pretty much the same, and are only paradoxical if you try to combine assumptions from both interpretations of time. All that proves is that they are not both correct.
Presentism demands an objective ordering of events (although no particular one), but a preferred folation does not demand a preferred moment in time.
Way to kill an afternoon, eh? Thank you for the link. Not sure how much I'm interested in sinking an interpretation that I've already listed as low probability. I'd rather see them sink RQM. Always best to have ones own cage rattled once in a while.
Same impression!
Quoting noAxioms
Ok, thanks! I think I'll revise GR and cosmology. I admittedly do not know very much about both.
Quoting noAxioms
:up: I agree! I would add the 'no signaling' theorem.
Quoting noAxioms
Ops! Sorry!
Quoting noAxioms
Right :smile:
Quoting noAxioms
Maybe dBB requires a preferred moment in time and not just a preferred foliation, then! (alternatively, a preferred foliation without a preferred moment in time and retro-causality.)
Quoting noAxioms
LOL, yeah!
Quoting noAxioms
You're welcome :wink:
Quoting noAxioms
I see! That's perfectly reasonable :smile:
Actually, I admit that dBB (in some forms*) is my third favorite interpretation. After all, it is still somewhat 'odd' but at the same time counterfactual definiteness is very intuitive. But as I mentioned before I find (among other things) this 'oddness' as an indication that some kind of 'paradigm change' is required. Also, it seems that, in general, there is a trend to more and more 'counter-intuitiveness' in physics...Hence, I lean towards RQM and Copenaghen.
*(I do not like the purely 'nomological' view where there is no physical explanation of the movements of the particles - I prefer the 'dispositionalist' version. Also, I think that I am in the minority but I find the 'quantum potential' formulation interesting - after all, the 'classical limit' becomes quite intuitive if the contribution of the wave-function is seen as additional force.)
Obective collapse theories (such as GRW and Penrose's) are physically different theories to standard QM. I don't know what specific explanations they would give for this particular experiment. But they make predictions for Wigner's friend-style experiments that make them experimentally differentiable from standard QM.
As Brukner says in that link (my italics):
Quoting On the quantum measurement problem - Caslav Brukner
Quoting noAxioms
I'd be curious to know your thoughts about the RQM questions from my earlier exchange with boundless here.
Thanks for the links! I had a quick skim. I find Rovelli's approach more natural than either of those. Bitbol's approach seems overly metaphysical and Kastner's approach is non-local.
Quoting boundless
Thanks, that was interesting. So my suggestion differs in at least two ways. First, as with Rovelli, I think that quantum mechanics is local. Second, as with Aristotle, potentialities don't "do" anything, only actual systems do.
Instead, the term "potential" provides a natural way for Wigner and his friend to describe the scenario from their own perspective and also to describe the scenario from the other's perspective.
So when the friend (Alice) measures spin up, that actualizes (i.e., realizes) the particle's spin potential for her. But she also knows that both the spin and her subsequent measurement of the spin are only potentials for Wigner until Wigner measures the friend's system in that basis.
The actual/potential terminology combined with RQM's relationalism provides an ordinary language abstraction over the underlying mechanics. That abstraction preserves locality, factual definiteness, freedom of choice and, crucially, a referent within the universe that provides a view from somewhere (i.e., the system's reference frame).
There is a paragraph in the essay on Kastner's paper which says:
So - they don't exist in space-time, but they're real. Here is key idea, I think - which is the idea that there can be degrees of reality, that things can be more or less real.
That intuitively maps against the idea of the probability wave also, as the probability wave is literally a distribution of possibilities or likelihoods.
I think there reason that this is so hugely controversial is that in Western philosophy, the idea of 'degrees of reality' was abandoned by the later medievals (largely due to Duns Scotus.) So in the modern picture, something is either real, or it isn't - which maps against the classical atomist idea where a particle is 1 and the void is 0. But if things can be more or less real, then it expands the notion of ontology along a different dimension, so to speak, to include the axis from the unmanifest to the manifest. And that concept, I contend, had largely dropped out of Western discourse by the time of the Scientific Revolution.
Some more passages from Wheeler's article, Law without Law:
I think this is perfectly in keeping with the regular use of the word 'phenomenon' i.e. 'what appears', however what is novel, is the distinction of the phenomenal from 'the unobserved'. Note that in Wheeler's depiction, it is not strictly speaking accurate to say that 'unobserved' means simply 'existing unperceived', as the act of observation is the very 'participation' that he introduces.
Bad news for the 'arche-fossil'!
It is after this that the cautionary note about "consciousness" is introduced. However, here, Wheeler makes it clear that he means by "consciousness" "what is happening in the mind of the individual observer". This doesn't detract from the pivotal role of the observer in the "participatory universe".
... Really? You didn't even tag me man! And you seem to have forgotten a few things from the paper, selectively choosing what to emphasise.
Initiate close reading mode:
After your first quote, Wheeler clarifies his notion of 'recording' or 'observation':
(my italics)
Firstly, observation is characterised as 'an irreversible act of amplification'. Secondly, he clearly ascribes the role of 'irreversible acts of amplification' to the lab equipment, rather than human consciousness. (without mentioning the previous quote @StreetlightX gave)
He also draws a large distinction between 'elementary quantum phenomenon', like the observation of a single photon dispelling its superposed histories, and macroscopic phenomena:
he goes on to clarify that rather than defining the past with respect to the present, the quantum observation determines the trajectory it took. Prior to the observation it makes no sense to speak of the route the photon took. He clarifies:
This is much distinct from giving any sort of being, even theoretical, to the past; it is saying that for quantum states/trajectories it makes no sense to talk of their past trajectory without their observation. Moreover just after introducing his idea of a 'participatory universe', he immediately gives the clarifying note; a caution; that this should not be interpreted in terms of consciousness.
He then reiterates his previous clarification between an anthropomorphic sense of 'observation' and his preferred description of it:
To super-duper-mega-ultra emphasise that it is not the cognition of humans which 'creates' the 'past' of quantum phenomena, he even says of cognition/interpretation:
IE, the 'measurement' is a nonconceptual thing, it is not a property of a human relating to a quantum state, it's a physical interaction which is analogised with conception or perception using perspectival vocabulary to explain it.
Of whether the requirement of observation for a quantum phenomenon to take on a determinate character renders reality some composition of ideas and perceptions. He firstly (and before the quotes we've discussed) makes an analogy with Berkeley:
.
he concludes this analogy in a later section:
These theme of multiple quantum processes is exactly mirrored in his distinction between 'elementary quantum phenomena' and 'macroscopic' phenomena which he has previously discussed. Not only does Wheeler reject the dependence of observation upon consciousness, he explicitly rejects transferring the account of subjective idealism which hold in analogy for elementary quantum phenomena - which he is using to explain observer dependence to those who do not understand it - to systems of multiple quantum processes; esp. the macroscopic. How you can cite the article for support of your position when it goes to pains to refute it baffles me.
But we do certainly know that most observers are not humans, or human consciousness and so on. How can we make sense of the idea that everything is observer dependent plus the idea that observers are not human consciousnesses? (rather, recall, interpretation for Wheeler occurs after observation!) Wheeler characterises such a question as requiring more 'knowledge of the universe', IE he thinks it's something that might be true or false about nature that 'everything' is created through some system of observation. But we can say that our reality would not be transformed by such an understanding, in a similar way to Dr. Johnson's foot-pain not being alleviated from the discovery that mostly things are made of empty space.
end close reading mode.
That observer dependence isn't consciousness for Wheeler, and that he compares the discovery of the observer dependence of quantum phenomena to the discovery of that matter is largely empty space, suggest that he takes a realist stance towards observer dependence. That is, observer dependence is not an epistemic or conceptual relation toward a phenomenon; just a map; it is a mode of nature interacting with itself; observer dependence is 'in the territory' too.
Also adjoin that he thinks macroscopic phenomena are largely 'untouched' by quantum effects; ancestral statements can easily be produced. They can even be produced about the photon whose past was determined by observation; how long did it take to get here? Longer than the lifetime of human history.
All you've demonstrated is that you didn't read Wheeler's paper closely, and that you didn't actually understand the arche-fossil argument (which is my fault). Perhaps I should make a thread on it.
Lab equipment, instruments, and so on, are all simply adjuncts and extensions to human sensory capabilities. An instrument can register a measurement, but it's not an observation until it is, in fact, observed:
Consider figure 7 in the Wheeler paper, the caption of which is 'what we call 'reality' symbolised by the letter "R" in the diagram, consists of an elaborate paper-mache construction of imagination and theory fitted between a few iron posts of observation.'
An elaborate paper mache construction!
Look at the question he asks in the very passage you've quoted:
Are there? He doesn't answer the question. The paper, and the footnotes, are littered with aporia, with open and unanswered questions. He compares physics to a motor vehicle, where all we've done is 'turn the starter motor over'.
Quoting fdrake
You're right, I didn't read it as closely as I should have, but at the same time, I don't see how it supports anything like a realist ontology. It has many references to the 'role of the observer'.
You've quoted two passages, one from Bohr, one from Wheeler, both of which call into question the objectivity of scientific observation, as if they support the objectivity of scientific observation. So - who is not reading what? :-)
Quoting fdrake
How can an observation that happens now, effect the path the particle has taken before being observed. That is the conundrum of the 'delayed choice experiment'.
What I am arguing is that, you take 'the world out there' as independently real, always existing, regardless of any observation by us. You assume this so naturally, that anything that appears to threaten it is treated with intense annoyance; it pushes buttons. But we know even from cognitive science that this can't be the case. Everything we see and know are after all received sensations and perceptions which are organised by the brain into a gestalt. That is what reality is, you can no more get outside it than step outside your own body. It's just that physics itself, the hardest of hard sciences, is now starting to drive this home.
They only 'show' this when you misinterpret the observer. Like this:
Quoting Wayfarer
See? Claiming observer=human again. Bohr and Wheeler have gone to pains to say that this isn't so. This is the only thing stopping you from seeing 'observers' - which recall for Wheeler are 'irreversible events of amplification' - as part of nature. Going back to the start; like a sodium atom and chlorine atom acting as observers for the electron in the outer shell of the sodium atom by constraining its distribution of trajectories in forming an ionic bond.
But looking at the original quote from Bohr again:
Where Bohr says 'it doesn't make any difference what the observer is', I think this is drive home the point that the act of observation cannot be removed from the picture - no matter what you call 'observation'! - and furthermore, that 'observation' is irreducibly subjective in nature ('every physical process may be said to have objective or subjective features'). So unless you subscribe to pan-psychism, i.e. that even elementary particles are subjects of experience - then to all intents and purposes, the role of the observer is always at least implicitly a human agent.
(Why is that a problem, again?)
Which is similar to the point made by Wheeler:
Wheeler is known for the phrase 'participatory universe', which is what? To take it from the horse's mouth:
It's exactly observation, in the human sense, which is removed in that picture. The sodium and chlorine atoms aren't having human experience of observation when the interact with each other.
Subjectivity, in other worlds, is understood as more than just being our ideas or the presence of experience. To be an observer, one does not need our ideas, our experiences, to even be consciousness at all. They just have to be a distinct point of reference compared to others.
The realisation here is not "humans experiences creates things", but rather that any interaction is a result of the particular entities involved. In other words, its always an interaction in which the participants have an effect (thus, there can be no experiment performed without our measuring equipment having an impact). We cannot set up a system of "objective rules" which push around and constrain inert objects. Those involved, whether they be our experiences, tree, equipment or atoms, always constitute the conditions of the given interaction itself.
There is an ambiguity in 'Copenaghen Interpretation' (CI) that creates endless debates like this one :smile:
In CI, measurements are explained via the 'collapse' of the wave-function. The problem is, however, that CI is simply ambiguous on it. In fact, I would say that there is no 'Copenaghen Interpretation' at all. It is rather a 'class' of very different views that are, so to speak, 'grouped' together.
But where is the ambiguity? The problem is that the formalism of the theory alone does not identify what is the 'observer'. Yet, in order to explain the wave-function collapse you need to posit an 'observer'. If not, we cannot explain why our 'everyday world' looks classical, so to speak.
Anyway, let's see the proposed solutions to this intrinsic ambiguity of CI.
Firstly, one might try to say that, indeed, there are physical objects that count as 'observers'. For instance, objects that are able to store and process 'information', like e.g. computers, registering devices, brains etc. If I am not mistaken this is the view of Wheeler. The 'universe' is 'participatory' in this view because each of these 'observers' can 'modify' reality by 'collapsing' the wave-function.
Secondly, another possible way to deal with this is to go with RQM (Relational Quantum Mechanics) as Rovelli et al do. Here, all physical systems can be 'observers' and the 'measurement' is simply a physical interaction. This is because, according to Rovelli, there is nothing special about computers, etc:
(Source: https://arxiv.org/pdf/quant-ph/9609002.pdf ; emphasis mine)
But Rovelli's RQM is, in fact, not classified as 'CI'. Why? Rovelli claims that QM is complete, whereas for CI you still need to consider something as classical.
Or one might argue that, for instance, you cannot have a well-defined concept of information without relating it to some form of consciousness (not necessarily human, in fact). And you end up with the 'Consciousness causes collapse' interpretation
Or a Kantian-like interpretation like the one proposed by Bitbol and others (and possibly of Bohr at least for some parts of his life, if Bitbol is right...) if you do not like the idea that consciousness really 'modifies' reality (but it is nevertheless necessary to have an 'observer').
Of course, if one is really pragmatic one can simply choose to ignore the problem (but maybe this is not satisfactory for someone philosophically inclined). Finally, one can choose other interpretations of QM.
You're definitely welcome.
I can understand the unease with Bitbol's approach. But note that consciousness in his interpretation does not 'do' anything, in fact. It does not affect physical reality. It simply define the 'perspective' of the 'observer'. In a way analogous to Kant, Bitbol in fact IMO says that the 'quantum world' is indeterminate. But it is not a denial of it and neither he claims that it is 'modified' by consciousness. But as I said, I can hear your unease because I share it (even if I do like Kantian-like philosophies).
Regarding Kaster's approach I am not sure to call it 'non-local'. In the paper, Kastner et al explain (page 5):
Shimony's take, instead, seems definitely 'non-local'. But maybe he meant something like Kastner et all above (as did maybe other proponents of an 'Aristotelian-like' reading of CI).
Quoting Andrew M
I feel I am in agreement!
Quoting Andrew M
:up:
To be more complete, in fact I lean towards RQM and CI. The problem I have with RQM is that 'information' maybe is not something well-defined in relation to all physical systems. But as I said in my previous post, this is a quite controversial point. If 'information' is something that can be defined in relation to all physical system, then RQM is IMO the best choice.
If not, maybe something like Bitbol's interpretation (with maybe some elements of 'actuality/potentiality' dualism) would be best.
I am simply undecided.
I am definitely very ignorant about Information Theory, but I believe that the status of 'Shannon information' is somewhat controversial. The point is that there is a disagreement e.g. whether it is objective or subjective etc.
On this issue, maybe some might find interesting this paper by Basil Hiley (who collaborated with Bohm for many time): https://pdfs.semanticscholar.org/bb05/2740074f3e6b19f685315c9ddb994b563e29.pdf.
OK, my comment assumed it was an interpretation. But if the the different theory is experimentally differentiable from standard QM, then by all means let's devise the experiment.
My comment on that is about how Copenhagen deals with those implications, but since I understand that 'interpretation' to be an epistemological one, it doesn't really have implications for physical reality, only about what one observer might know vs another.
From that exchange then:
Quoting Andrew M
They're almost the same thing, with different definitions of 'is real'. RQM says this world is real to me and a different world is real to anything else (the cat say), so they're both talking about different worlds. MWI says they're all equally real, and RQM says none are real, only that there are relations between worlds and observers. Neither requires an observer to by anything more sentient than a speck of dust, and I find any interpretation that requires otherwise to border on religion. Even Copenhagen, an epistemological interpretation, can be applied to the dust speck. It 'knows' about the wind because it reacts to it, and thus has a relationship with it. It is real in a way that something unmeasured isn't.
Still, there are very 'real' differences between MWI and RQM, and I don't see how either Rovelli and Tegmark are going to convince the other that they hold the opposite view. I have yet to view the video since I tend not to get my information from such sources.
I don't consider it a price to discard these things. Quite the opposite. All the threads on forums such as this one discussing some form of "why is there something, not nothing" take for a premise that there is something, and then run into all sorts of valid contradictions that follow from it. So it appears that the notion, however intuitive, of there being something is the thing with the price to pay. My answer to the above question is that perhaps there isn't anything, and thus there is no need to have to explain its being.
[quote=boundless]But as I mentioned before I find (among other things) this 'oddness' as an indication that some kind of 'paradigm change' is required. Also, it seems that, in general, there is a trend to more and more 'counter-intuitiveness' in physics...[/quote]Boundless echoes my mistrust of such intuitions. My username carries an implication of not taking any of them as a premise, at least not without explicitly calling them out. I'm always on the search for assumptions I don't even know I'm making and are thus unseen biases.
A lot of people had no trouble getting rid of absolute simultaneity when relativity came into acceptance a century ago. Some still cling to it religiously.
Well it seems a real difference. There 'are' no branches at all in RQM, and they are 'are' in MWI. That's the huge difference such that I doubt an adherent to either interpretation can be convinced that they also hold to the other. Even the relations don't exist.
I always reach for integers and the simplest cases for many of my examples. I claim that 7 is indeed 2 less than 9, but I don't claim that that particular relation between 7 and 9 exists as a real fact. Is it still counterfactually definite if I word the claim that way?
What is interference? It seems to be 'maybe' as an answer to a question not yet asked, a measurement not yet taken. So X = square root of 2 is 1.414 but also -1.414 and both those values can work through my equation until a choice must be make before the mathematics can continue. That's a measurement, and now there are two equations that proceed in different directions using a now real value for X instead of one in superposition.
That's a cheesy description of superposition, but I feel it fails as an analogy of interference since the two values never seem to interact with each other. I like the question and it deserves a better answer than that.
It seems too simple since they are discreet values, which a wave function really does describe a wave that yields an interference pattern when the wave for path-A is added to wave for path-B, which yields an interference pattern in 2D but only a flat scalar in 1D. So my X probably needs to be more complex than a simple scalar with two discreet values that satisfy a polynomial.
Quoting boundless
Bitbol is interesting to me because I’m more interested in philosophy than physics.
The price to pay for that is subjectivism/relativism/nihilism.
My view is that naturalism as a stance assumes the reality of the world (or rather, the sensory domain). There is nothing the matter with so doing, in fact, it's an essential methodological step. The problems start when the fact that it's a methodological step is forgotten, and it is mistaken for a metaphysical principle, or a statement about the real nature of things. In other words, methodological naturalism is interpreted as a metaphysical principle, which it is not. That is the whole issue, in a nutshell. (One way to avoid that is positivism, which says that only statements made on the basis of methodological naturalism are meaningful - but as has become evident, this too results in self-contradiction.) But the net result is, that the primacy of metaphysics has once again asserted itself through these conundrums posed by physics.
easy to demonstrate with a football
the QB throws the foot ball to his reciever who turns around at the last second to catch it .
the QB throws the ball and it spins clockwise direction as he sees it get further and further away
the receiver sees it coming but its spinning counter clockwise.NOT clockwise
the ball never stopped or changed directions between the two players
BOTH see opposite directions at the same time and both are correct.
both see the ball but the QB sees it get smaller as it gets further away and the receiver sees it get bigger as it gets closer
bigger and smaller
closer and further
If the QB hands the ball to his receiver , at the same time, then both are doing opposite actions at the same time in the same motion
one hands it over and the other takes it over at the same time
this can be construed as opposite or complimentary AT THE SAME TIME
black comes from white
white makes black
white reflects and black absorbs at the same time and they also oppose at the same time they complement by the way of contrast
white is an absolute and so is black
you cant get whiter than white or blacker than black
https://cdn-images-1.medium.com/max/1600/1*V377-3x7cHjr9HCebFGHJw.png
the wave and matter are at two poles of same item wave starts at blue and ends solid at black . It starts as emphty space and positive potential at WHITE with no density
the number 1 is both a positive number and a neg at the same time
1x1=1
1/1=1
multiplication is a positive and its opposite negative is division at the same time
white is a positive and black its negative
Forget about looking into a mirror, that might get real complicated.
the reflection of the sun setting across the ocean always goes from the sun, to the water and towards your POV
If the 2nd person stands 25 feet away on the same beach at the same time , BOTH will observe the lights reflection on the water at he same time and it only leads to the person who is observing it . It doesnt go to both place and it does go to both places AT THE SAME TIME but the lights reflection will not be at both places at the same time .in the same relative locations.
opposites are both subjective and objective based only on ones SUBJECTIVE POV
Why should the acknowledgement of absolute nothing (more aptly no-thing) entail "subjectivism/relativism/nihilism"?
Naturalism is not merely a 'methodological step"; it is the step from the dead to the living; it is a phenomenological step. There is no phenomenological nothing just as there is no absolute something!
'So what?' I say; the absolute is nothing to us except an unthinkable thought rife with every paradox that both afflicts and invigorates the mind. Affliction or invigoration? Fallacy of misplaced concreteness or the principled placement of phenomenal ashlar?
Physics, being a phenomenology, knows no metaphysics beyond its own bounds. not all walls are prisons; there is no boundless freedom.
There are no metaphysical principles; can you name one? If metaphysics is not phenomenology informed by science (itself a phenomenology) then what can it be but thought tying its own Gordian Knot?
Legend has it that Alexander circumvented the common afflictions of delusory puzzlement and cut the seminal Gordian Knot with a single blow of his sword.
There is a time to remember and a time to forget; but beyond that it is always time to remember to forget false hope.
You're welcome.
Anyway, I am not @noAxioms, but I believe that his point was not 'nihilistic'.
Basically, according to RQM you can only define a state of a system S in relation to something else. In other words, when you speak of the state of S you always need to specify the 'perspective' according to which you are making such a description. You can't avoid that.
So, RQM seems to imply that while there are 'individual' systems like S, their states are meaningfully defined only in relation to something else.
In other words, RQM threatens the view that physical objects have some intrinsic properties. If true, the very concept of 'object' becomes problematic for it seems difficult to speak of objects that do not have any intrinsic properties. But if S does not have any intrinsic properties, what does S, S?
I do not believe that RQM per se goes as far as denying that we can speak of individual objects, i.e. a 'no-thing' view, so to speak. After all, perspectives here are defined in relation to these objects. But it certainly comes close to this idea: ultimately there are no 'objects' (which should not be taken as saying that 'there is no reality'). Rather objects are useful abstractions or approximations :smile:
Thank you :blush:
With this I agree. I often characterize it the way Bohr did: as a description of what can be known, and not at all a description of what is. It is rather a jumping board by which a description of what is might be bounded. Others take their interpretation of what is and label it Copenhagen because it fits within these bounds.
I thought the difference between the various interpretations often focuses on the treatment of the Heisenburg Cut. The Wigner's friend scenario basically puts one observer on either side of that cut, and drives out many of the differences between the interpretations.
Isn't there a problem with this view in that without earlier collapse, none of these registered devices could possibly exist in the first place? If understanding of a measurement is what causes the collapse, how could the thing doing the understanding come about to do it? A chicken/egg problem.
That definition of 'measurement' is hardly confined in RQM. With the exception of anthropocentric Wigner interpretation, I think all the interpretations assume something along these lines, and even Wigner backed down from his own interpretation due to it reducing to solipsism.
OK, that is a point about CI. To know something about system X, I must exist, and I am classical, thus something needs to exist in a classic sense. MWI falls under CI then?
The Wigner interpretation I referenced.
How does this interpretation get around the chicken/egg problem if an observer is necessary for an observer to collapse out of a system? I presume Bitbol does not consider a dust mote to be an observer?
Existential nihilism perhaps. Life still has meaning, even if that meaning isn't objective. Even a typical theist doesn't really consider say morality to be objective. Don't kill because God says it's wrong. 'Don't do it because I said so' is relative to the thing saying so, not objective.
This is as opposed to objective morality where God tells you not to do wrong things, and a good god doesn't do them either. The morality is a higher authority than God if it is objective, which makes for a weaker god if it answers to this higher objectivity.
Yes, it seems something along the lines of those 3 views is a price paid. If a view you find distasteful is more sound than one you'd like to be the case, does comfort trump logic?
Surely you have a spin on the whole 'why is there something' debate, else you'd have to face the subjectivism yourself.
Is time a property of the universe or does the universe, like any other object, exist in time? Only with the latter does it make sense for it to have come into being, in which case one has to posit a way that came about. Is there a first cause? RQM doesn't posit this 'being', so it doesn't have to answer to the conundrum.
Quoting boundless
My post above sort of indicates that while I don't mean to be nihilistic, I'm not sure the view doesn't lead necessarily to that camp.
I'm talking about what one individual observer sees when looking into the mirror. My right arm appears to be my left arm.
It is meaningful to say that there are individual systems like S? That sounds an awful lot like counterfactual definiteness. A system with states still in complete superposition is still an existing system. There was no description of S existing in relation to R. Just 'there is a system S', which sounds more like MWI and not RQM.
I tend to go whole-hog on the implications of the interpretation, so I found less reason than you did to counter the suggestion of a sort of nihilism.
S does have intrinsic properties. I'm just balking at the suggestion that there is S, unqualified.
? I would say we can only speak of objects. There is no 'no thing' view. That would be the objective view, things that exist without the relation, or with only an objective relation.
Yeah! Bohr's IMO was not an ontological position. And yet, 'Copenaghen Interpretation' is often used to denote one.
Quoting noAxioms
I agree with this. Maybe Wigner himself however thought that all conscious observers are 'classical', i.e. according to him in the thought experiment Wigner's friend causes the collapse also with the respect to Wigner.
Quoting noAxioms
Bingo! That's IMO the billion dollar question for all versions of CI. Classicality is both the result of collapse and the necessary condition of it.
Note, though, that if you accept the versions of CI where consciousness has a special role and you do not have a physicalist theory of consciousness the argument you are making does not really apply. Why? Because, consciousness is not a result of a physical process. That's the point that, for instance, Bitbol makes (also @Wayfarer makes this point in my understanding).
Quoting noAxioms
I am not completely sure. Take Wheeler's view for instance. While not giving a special role to consciousness, he nevertheless gives a special role to the act of registration. So, it seems that in CI 'measurement' is at least given by both the interaction and the act of registration. Does this make sense to you?
Quoting noAxioms
I agree on the first part. Regarding the question, instead, I would say that MWI is CI plus universal wave-function.
Quoting noAxioms
Yep!
Quoting noAxioms
Yes, Bitbol does not consider a dust mote to be an observer. In my understanding, Bitbol thinks that only conscious beings can be observers.
FWIW, I am not a 'physicalist' myself but I am not convinced that consciousness has a special role in QM.
Quoting noAxioms
Oh, I see. I believe that it does not necessary lead to nihilism or relativism. After all, there is still the possibility of inter-subjective agreement on ethical matters (so in some sense we can still talk about 'objective ethics') in a similar way that there is inter-subjective agreement on scientific matters. [Maybe this is too off-topic, though]
Quoting noAxioms
So S defines a perspective and [i]everything[/I] (i.e. all its properties) about it is defined in relation to other systems? Is there something about S that is not defined in relation to other systems?
Another question, maybe problematic: How is S in relation to itself?
Quoting noAxioms
I'd agree with you if by 'intrinsic properties' you mean properties that distinguish S from other systems.
Quoting noAxioms
In this case, we would have that both S is associated with a perspective and everything about it is defined in relation to other objects. I am not sure if this position is fully consistent but it is very fascinating! :smile:
Actually I read your account of Rovelli's 'observer' again, and there's something about it I can't buy. It says "I use the word “observer” in the sense in which it is conventionally used in Galilean relativity when we say that an object has a velocity “with respect to a certain observer”. The observer can be any physical object having a definite state of motion'.
But this simply means, anything that moves with respect to anything else is 'an observer'. And I don't see how 'an observer' can be 'a table lamp' or a rock or dust mote or whatever.. I think this must be mistaken. I think what this is trying to do, is preserve a sense of scientific realism in the absence of observers - which is precisely the problem! It is one thing to say that "all motion is relative motion" but another thing to say that "all objects are observers". It seems to me to deny the issue rather than solve it.
I’ll spell out my bottom line - that all measurement or observation has a subjective aspect, i.e. it is undertaken by a subject, and the subject is (obviously) never disclosed in the act of observation, because observation is always of objects or at least of the objective domain. As Bitbol says, the inability to recognise the ubiquitous presence of the subject is precisely the blind spot of modern science. Philosophers (including Kant and Schopenhauer) understand this but many scientists do not, because it’s not, by definition, a scientific issue. But the fact that it becomes a subject of discussion here is because scientists are perhaps operating at ‘the limit of objectivity’.
Quoting noAxioms
I think there's little understanding of the idea of 'first cause' nowadays. Because science has habituated us to thinking of causality in terms of material and efficient causation, then we can only conceive of 'first cause' as something at the temporal beginning of the sequence. But I think the original notion of the first cause is of a different order or kind to material and efficient causes.
Does CI explicitly define measurement far enough to classify it in general as a 'registered device'? I thought it left measurement fairly undefined, allowing all sorts of interpretations on the spectrum from interaction through information processing and full on has-a-soul.
Yes, that's the full-on definition. It is outside methodological naturalism, but not outside science. Wigner concluded that the interpretation led to solipsism partly because other consciousnesses will collapse waves functions differently, and that puts each of these consciousnesses in different physical worlds. If that's not the view, then you don't exist until I collapse you, and that again makes for solipsism.
Not really. I don't formally know what Wheeler means by 'registration'. I tried to look it up but found the term only fairly well buried in papers beyond my ability to absorb. I used the word above, but only to echo the notion of a system that meets some unstated qualification of processing the information of measurement.
What I like has little to do with it. I'm interested in what works: is self consistent.
Well it works I suppose. If consciousness is not a classical physical thing, then there's no chicken/egg problem. Still, how does it manage to collapse a state of total superposition into a state with matter present, let alone matter that can host consciousness? Collapse seems not to be in any way a function of will. I cannot will a measurement of vertical polarization, yet I would seem to need to do that to find my physical host.
Oh good, then you might take a stab at my questions, even though they're geared towards a Wigner sort of setup. Are you saying that consciousness is not physical?
If there's not another topic to discuss it, then why not here? I'm in no way against inter-subjective agreements. I just don't think that makes things objective. We both see the same moon, sort of, but the moon's existence is still relative. It totally doesn't exist to something that has taken no measurement of it, but it also doesn't stop existing to us if everybody looks away for a moment. It cannot be un-measured.
S can define a perspective, yes. S is perhaps a collapsed state at some event say. Doesn't matter what the system is. The collapsed state here might be the two of us looking at a moon, and might be a moonless Earth without either of us, or it might be empty space between galaxies. In MWI speak, those are all existing worlds, and the we only exist in the first one, so the moon exists relative to that S and not to other potential states for the same collapsed S at that event.
S always exists to itself it would seem. The live cat measures a live cat, never the dead one, let alone no-cat. I don't see how that is problematic.
Since I am not really an event, I'm also not a defined measured state S. Relative to parts of me, other parts are in superposition. This does not in any way impede my classic functionality, but it does mean that lacking a defined state, I lack a defined state and thus a defined identity, which was never a problem to my view, so I don't care. But one has to be careful when trying to pinpoint an intersubjectivity between two systems. So each of us measures a past state of the other, not a current one. These are nitpicks since the parts in superposition are trivial differences.
You need to define S. This collection of atoms currently has an arbitrary box drawn around them and is designated as S or 'noAxioms' for the moment, even though many of those atoms come and go continuously. You may have a different idea if you have a different philosophy of mind and identity. For me, at best, my identity is the stuff in that abstract box drawn around a bunch of matter near a certain event, and the entire worldline that led to that event. That definition only works because I cannot subjectively split or merge. It wouldn't work for an amoeba, starfish, or a candle flame.
I would love to talk philosophy with a sentient amoeba.
Maybe it isn't consistent. Hence the appreciated cage rattling.
An observer is one who takes notice of (and this means pays attention to) the thing which is observed.
That sounds like a reference frame, which A) doesn't require an object stationary in that frame to define it, and B) has nothing to do with what causes a wave function to collapse. Rovelli says this in the context of equating that 'observer' to the mechanism that collapses/splits a wave function? I think not the latter. An observer is a point of view, but not necessarily something at that point observing, and not something that has an effect.. Just a point from which a description can be made. It does imply a partially collapsed state, so it isn't really defined without the table lamp, stationary or otherwise.
I kind of agree with this terminology being ambiguous, which is why I hesitate to use the word observation. Wave function collapse has presumably been going on long before any object has been capable of being this sort of 'observer'. So if I claim the table lamp takes a measurement of the air heating it, I'm not laying claim that it has subjective experience.
Is that an answer? It is a of a different order or kind. OK, I can agree with that, but it isn't a specific answer. Indeed, I think it is a category error to treat the universe as an object, which, like all objects, doesn't exist, comes into being, and then exists (for a duration). 'Exists' means something different than how we use it for objects. But what does it mean actually? I find it to hold no distinction. An existing object is distinct from a non-existing one, but that is the object category. It seems not to apply to a universe category. That's just me and my relativist mindset. I'm sure you see a distinction, but you haven't really identified what 'order or kind' we're talking about here.
Yes, it seems she is simply talking about a logical consequence there. If the cafe closes then no-one can eat there. But her characterizing a logical consequence as an instantaneous and acausal effect, or a form of global non-locality, is a category mistake.
All that is physically going on are systems interacting locally with other systems. The time of closure of the cafe is system-dependent and is determined by physical interactions.
Quoting boundless
Fair enough! As it happens, I also find Aristotle's form/matter distinction useful for considering information. A physical system, being substantial, can be abstracted in terms of its matter and form (or state). Which provides a natural isomorphism between a physical system and a point in state space.
Thanks! My own reading of RQM for a while was as a relational semantics abstracting over a Many Worlds dynamics. But as boundless also suggested, I think Rovelli would reject an underlying Many Worlds dynamics.
Quoting noAxioms
I recall that you accept Tegmark's mathematical universe hypothesis, so that would seem to follow. :-)
Quoting noAxioms
OK, but that seems like a nonphysical answer. Just to follow up a bit further, suppose we have an equal path-length Mach-Zehnder interferometer that sends every emitted photon to detector 1.
Now since RQM respects locality, it raises a question of what is physically going on in the interferometer prior to detection of the photon. MWI says there is amplitude for a photon on each path which results in subsequent interference at the final beam splitter. But it seems that RQM can't explain it that way since it raises the prospect of branches.
Quoting Wayfarer
Simply substitute system for observer if that helps. That is how Rovelli is using the term.
That's why I don't get this:
[quote=Carlos Rovelli]For instance, I say that my hand moves at a velocity v with respect to the lamp on my table. Velocity is a relational notion (in Galilean as well as in special relativistic physics), and thus it is always (explicitly or implicitly) referred to something; it is traditional to denote this something as the observer, but it is important in the following discussion to keep in mind that the observer can be a table lamp.[/quote]
I think I understand what a reference frame is. But I don't understand how an inanimate object can be regarded as equivalent to 'an observer'.
Ask yourself this: NASA sends out a probe, as it often does, which whizzes by Saturn, all the while recording data, but then its radio link with Earth fails. It keeps registering data for an indefinite period of time - years, perhaps - but does that any of that data comprise an observation, without it having been sent to, and interpreted by, the scientists who sent the probe? I say not.
There's a distinction between 'data' and 'information'. Until data is organised and contextualised, it doesn't become information. That is the difference between them, and I think it's being obfuscated by these arguments.
For similar reasons, I'm dubious of the following:
I mean, according to this definition, every single thing that is arrayed in respect of some other object (for example, any atom) has, or conveys, information. I think this definition is so broad as to be meaningless. I don't believe 'information' has a single definition. Shannon's definition of information was specifically given in the context of transmission of electronic information through a physical medium, so that definition has certain boundary conditions, so to speak. To generalise from that to information in such an amorphous sense, seems illegitimate to me.
The whole problem in this debate is "what is the role of the observer", is it not? And the paradox is that science knows that "the observer" - h. sapiens - is a latecomer on the scene, we're the proverbial lighting of a match at the end of a vast aeon of time. So it doesn't make any sense, from that point of view, that "the observer" should have such a central role in any physical observation.
But the problem is simply that when you make such a statement, you're looking at "the observer" from the outside - in other words, treating "the observer" as another object - here, the solar system, or whatever, and there, h. sapiens.
But how can you assume that perspective? Because we never get outside of the perspective of being an observer. "Observation" in the broader sense, includes everything, not because lamps and rocks and atoms are conscious (which is nonsense), but because everything we know is ultimately and irrevocably a cognitive act. We're knowing beings, and everything we know is based on observation (and reasoning based on observation). Then, as Bitbol points out, we overlook or forget the "role of the observer" in all of this, assuming that we're viewing the world as if from no perspective or no point of view. Seeing that requires a gestalt shift, an aha moment, which some get, and some don't.
I can't see any evidence in the article you cited that the notion of "observer'' in QM is thought as having anything to do with being "an intentional being".
I hope you realize that an observer, without something observing is contradictory.
Quoting noAxioms
A measurement is a comparison, between something observed, and a scale (an ideal). A table lamp does not measure.
Quoting Andrew M
The problem is that anything within that "system" needs to be interpreted according to standards before the system has any observational value. The "system" has no observational value without those human standards.
Quoting Janus
Since "observer", as commonly used, requires that one notices what occurs, the notion that something other than an intentional being could be an observer needs to be supported. Suppose a machine records, as in wayfarer's example, or an object is changed by an event. How does this qualify as noticing what occurs? When that information in the machine, or the changes in the object, are interpreted, the interpretation requires basic assumptions about the relationship between the machine or object doing the recording, and the event being documented. The "observation" of the event is not complete without those assumptions. So the machine or object, on its own, is just changing, it is not observing.
I agree that 'observer' is a poor choice of words in Rovelli's interpretation. That's why in some of my former posts I preferred the more general word 'perspective'.
Anyway, note that there is a problem of self-reference even in Relational approach(es). I suggest you to read section four of the SEP article about 'Relational Quantum Mechanics': https://plato.stanford.edu/entries/qm-relational/#SelRefSelMea. It is a discussion about the possibility of self-measurement. (Maybe @Andrew M and @noAxioms will find it intriguing too!)
Quoting Wayfarer
Well, I think that I agree in part with this. But as you say, it's not by definition a scientific issue :smile:
So, I do not think that your reasoning here is really affected by what interpretation of QM is 'right'. (After all, Kant and Schopenhauer did not knew QM)
At the same time, what I find fascinating is that with the advent of QM and with the introduction of interpretations like the Von Neumann-Wheeler a.k.a 'consciousness causes collapse', Bitbol's (and d'Espagnat) etc and also Many Minds, this issue has become of interest of scientists themselves.
I agree that knowledge is perspectival and since we are conscious, it is at least in some but very deep sense, 'subjective'. But at the same time, my fear is that, if we embrace this kind of reasoning completely, we end up to deny 'reality' completely.
In terms of the noted parable of the blind men and an elephant (here the Wikipedia article), the risk is to deny the 'elephant' instead of denying the 'perspectival' (in this case 'subjective') character of knowledge. In other words, my fear is that we fall into the other extreme, so to speak :smile:
How does this work? Do you think the observer's intention somehow acts on a superposition to constrain it - tightening the distribution of states or collapsing it to a single one?
Yes, you are right. That's one difference between Wigner's original proposal and Bitbol's take (other than a less 'ontological' take on what the 'collapse' is) and possibly also QBism (but I admit that I do not understand it very well). Here an article by Bitbol about the Wigner's friend scenario: https://core.ac.uk/download/pdf/148348264.pdf. An excerpt:
Oddly, I think that Bitbol's view seems a mixture of CI and RQM, but in fact I think it is still a form of CI. In usual formulations of CI, there is only a 'classical world'. Yet, Bitbol's point is that Wigner still has to consider his friend in superposition. In other words, just like in the case of Rovelli, in Bitbol's take of CI, there is no single 'history', so to speak. As Bitbol points out in the other article I linked before (i.e. this: http://www.bourbaphy.fr/bitbol.pdf):
Quoting noAxioms
Yes, I agree with you on the ambiguity of CI. But some proposals to resolve it, involve that registering devices 'collapse' the wave-function. If true, I believe you need the physical interaction and the act of registration.
Quoting noAxioms
Yes, that's my concern too. Regarding consciousness, I believe that science can give us some knowledge of it. But it cannot give us the full story.
Quoting noAxioms
I see. Me too, actually. So do not trust my word :wink:
Quoting noAxioms
Me too. And unfortunately, I do not know if it is really self-consistent (honestly, I do have a similar concern for RQM).
Quoting noAxioms
According to Bitbol, collapse is due to an increase of knowledge. It is not a physical process. The wave-function is regarded as a tool.
Of course, it becomes more problematic if a minimalist take on the wave-function is untenable.
Regarding your question how is possible that matter can host a 'non-physical mind', I just do not know how to answer. And that's one of the reason why giving a special role to consciousness in a [i]scientific[/I] theory is for me problematic.
Quoting noAxioms
Well, yes and I also believe in free-will. [But I am a bit unwilling to explain why I think so here... :smile: Anyway, in brief, for example, I believe that this is a consequence to both the so-called 'hard problem of consciousness' and my acceptance of free-will (because I do not believe that free-will, if is real as I think it is, can be explained in purely physical terms...).]
At the same time even if I have this belief, I am not so sure that giving consciousness a so special role in a scientific theory is a very good idea. But, oddly, the fact that this has been done in various ways fascinates me.
Quoting noAxioms
Ok...Yes, I agree that inter-subjectivity and objectivity in the usual sense are different. What moral relativism denies, however, is that there are no universal ethical truths. I find it somewhat irrational, actually. In a sense, it is somewhat dogmatic: 'perspectivism' does not entail that it is impossible to find something that is considered 'good' for everyone. Also, it has absurd consequences: I believe that, indeed, there are actions that can be considered good/bad by everyone. And I do not believe that rejecting 'objectivity' in the usual sense denies that. (I referred to a discussion on ethics when I referred to 'off-topic')
Regarding the example of the Moon, I am a bit perplexed however. If the Moon is completely non-existent for anybody that has not measured it, how can I say that measurement is an interaction?
Quoting noAxioms
Intuitively I would agree with you! But look at the link I gave to Wayfarer of the SEP article on RQM :smile:
Quoting noAxioms
Ok!
Quoting noAxioms
Ok thanks, I see. But it seems that this kind of definition of 'S' (or whatever physical object you have in mind) presupposes that can be used to all perspectives.
Take for instance even an electron. Its state might be different for the various 'perspectives'. But for all physical systems it is indeed an 'electron'. So, you need something invariant, after all. Can we still have invariants if we do not have something perspective-independent? I am struggling with this point and I am not arrived to a solution.
Quoting noAxioms
Well, me too! But as Wittgenstein remarked, we might not be able to understand a lion, let alone an amoeba :sad:
Quoting noAxioms
Thanks!
Mmm, I see!
Also, both she and Shimony are in fact clear that 'potentialities' for them are in some sense non-local.
Quoting Andrew M
Agreed!
Let me, however, ask you the same question that I asked to noAxioms.
Consider an electron. According to RQM, its state is 'perspective'-dependent. But all of them are in agreement that it is an 'electron'. So, is 'out there' something identifiable as an 'electron' even when is not measured? What I am saying is that it seems we need after all something invariant, equal to all perspectives. Is this compatible with RQM? :smile:
Just a curiosity...
Interestingly, it seems that RQM agrees with the Consistent Histories interpretation about the lack of a 'single history'. From the SEP article on Consistent Histories, section 11.4:
Well, I really find this interpretation (at least as it is presented there) somewhat difficult to understand. So, I still have not formed an idea about it. In fact, I somehow have a problem to really distinguish it from MWI.
What do you think of Consistent Histories?
As far as I can tell the notion of an observer in QM is a specialized one; so 'observer' would be a metaphor, not a literal definition in strict accordance with everyday.usage.
Quoting fdrake
Isn’t that the very kind of question that the article in the OP addresses? That two observers observing what ought to be the same event each see something different?
Recall Figure 7 in the Wheeler article again - that what we call ‘reality’ is in part a construction (‘between the ‘iron posts’ of observations). That is what I take Schopenhauer to mean by ‘Vorstellung’ and Buddhist philosophers by ‘vikalpa’ or ‘Vijñ?na’. This is *not* to say that ‘everything is in the mind’ but, as Wheeler is saying, that the mind has an inextricable role in ‘constructing’ reality, and that we can’t see without it (hence, also, Kant).
Naturalism starts with the perspective ‘I - it’, the division of subject and object. But that is part of the construction, it is a learned cognition that is acquired in early childhood. That’s what I mean by saying that naturalism ‘assumes the world’ - it assumes that the division of subject and object is fundamentally real, but in actuality, reality is not something we’re outside of, or apart from. That sense of being apart from, or outside of, reality, is what I refer to as ‘the illusion of otherness’. In modern thought, generally, that is one of the base assumptions, but here we are beginning to see it break down. And that really is an epochal shift, make no mistake.
That still leaves a vast domain of phenomena about which there can be objective agreement (‘iron posts’). But the objective domain is not (in Buddhist terms) ‘self-existent’. Perception or cognition is a foundational aspect, but it is never a ‘that’, it only ever appears as the subject, as the ‘unknown knower’.
Note this encyclopaedia snippet on ‘objective idealism’:
Sort of. Tegmark takes the MWI position that the structure (the universal wave function) exists, and thus he has to explain its 'being'. I don't buy into Platonic existence of numbers, and to both of us, the universal wave function is a mathematical thing, so same category.
It is very physical if you consider the physical universe to be a mathematical thing. The answer is still lousy, but I find it to be a very physical answer.
Does RQM have branches? That is more an MWI thing. Prior to that measurement, there is no collapse, so the wave function puts the photon on both paths, not on 'either' path. The photon in this state can interfere with itself on both paths (to detector 1 and to detector 2) after the final beam splitter resulting in one wave function that yields almost all of the probability of measurement on detector 1 and none on detector 2.
That's not so much a description of RQM as it is a description of QM. I don't know where you might suggest locality comes into play. Nothing is being affected faster than light or anything, unlike what apparently goes on in some delayed choice experiments.
He's not saying that the lamp is taking note of the hand motion. He's just saying that the motion is relative to the motion of the lamp, be it noticed or not. The word 'observer' is being used in place of reference frame.
An inertial reference frame doesn't even need an origin. 20 things can all have identical velocity in some inertial frame and some other thing will have identical velocity relative to any of them, so in this sense they're all the same 'observer' as Rovelli uses the term. It doesn't work for accelerating frames, so 20 things can all be different parts (let's say rivets of a ship) of some rigid accelerating object and those 20 parts will have different velocities in any frame in which they are moving. So an 'observer' in an accelerating situation like that needs to be a specific point like one of those 20 objects or any other coordinate in that accelerating frame.
Not the way Rovelli is defining the word. I personally dislike such usage because it encourages exactly such misinterpretations.
It is warmer than the same lamp measuring colder air. The air temperature has had an effect on the lamp. One system has effected the 2nd, and that's the second definition of measurement that @boundless gave.
OK, that's what you meant by the self reference issue. Theorem aside, it seems quite intuitive that an aparatus cannot measure all of its own states since the taking of that measurement changes those states. This seems a little analogous to Heisenberg uncertainty where the more you know about one aspect of yourself, the less the can be known about some other aspect.
None of this means I cannot collapse my own state in sufficient hindsight, which is sort of what I meant with my first reply to this issue.
Quoting noAxioms
The problem is that the definition of "observer' is not consistent with what the observer really is, in practise. The reference frame, which is supposed as the "observer", is inherently a human perspective. Any reference frame is. So to define "observer" in such a way that the observer might be something independent from a human perspective is to falsely define "observer", i.e. to define "observer" in a way which is inconsistent with what an observer really is in practise.
Quoting noAxioms
You cannot say that the lamp is warmer, unless you, or some other human being actually measures to see that it is warmer. Even if you conclude deductively that the lamp was exposed to warm air, therefore it is warmer, this still requires certain premises, and a human being to observe that it was exposed to the warm air, and apply the premises to make the deductive conclusion. You cannot get away from the need of human presence to make an observation, simply by asserting that an object can make an observation without a human presence. Even if the object did make the observation in that way, such an observation would be absolutely useless to any human being. We can't simply assume that an object made a specific observation without confirming that it did, but then it's a human observation. The only observations which are useful to us are the ones which we interpret using our assumptions and logical principles, but then the observation is not made by an object, it is made by the human being which makes the interpretation.
Quoting boundless
This isn't the QM I know. There is no 'big difference' between the two cases. The cat is both dead and alive (superposition), not either dead or alive (result of an unobserved coin toss). The latter probability function is said expression of ignorace about how the coin toss turned out, but the probability function of the cat is not ignorance. It really is dead and alive until measured, else it could not interfere with itself. Of course, being a classic object, it is not easily going to interfere with itself, but quantum states very much do, so it seems to be a mistake to qualify the probability function as a mere expression of ignorance.
Maybe the colleague (Wigner's friend) changed that (being a conscious being that the cat apparently isn't), and that explains this assertion above. This I suppose cannot be disproved since there is no way to prevent the decoherence of something as classic as a human, but it also goes for the cat of course. They seem to allow the inconsistency of having a cat in superposition but not a lab assistant.
What does the measurement chain have to do with it? I shoot a photon through the slits and it makes a mark on the screen. That's a measurement even though it might be a minute before the operator bothers to look and learn of the result. The result is not being kept hidden in a box to prevent decoherence. If consciousness causes collapse, it doesn't imply that knowledge causes it. The conscious guy is in the room, ignorant of the result of the measurement, but nevertheless present. The collapse occurs because of that presence, no? If it is awareness, then I should be able to measure a thing but not take note of the result, and find the thing still in superposition later on. But that doesn't happen. It seems a falsification for the 'conscious knowledge' causing collapse idea.
I'm just trying to shoot holes in what I think might be being described in these quotes.
More of that quote:
So what? Only the table lamp is the privileged object for the table lamp. We are no more a natural end to the chain of reactions than is the table lamp. The reactions continue right on through us to affect other things. I have a hard time thinking of any causal chain that is initiated (rather than propagated) and cannot think of any that can end ever (per conservation of information). Radioactive decay might be an example of a new causal chain. Depends on interpretation.
OK, but I can substitute "table lamp" for "US" everywhere in that bit and it still holds. If "WE" are not special, why bring US up all the time like that?
I didn't get that from reading that bit.
OK, so take caution when the term is used below:
Without a description of what constitutes that registration act then, I have no idea what he's talking about.
If CI is taken as an epistemological interpretation, I suppose this is true in a way, but it seems trivial to falsify. Alice (a simple device) measures the spin on one of an entangled pair, and prints the result of that measurement on a little paper that ejects face down on the table. Human Bob sees the paper but has gained no knowledge of the result, only knowledge that the measurement has taken place. He now measures the other particle of that pair and is is no longer in superposition. His lack of knowledge did not prevent the collapse of the wave function of his sample The device (Alice) has no knowledge since it retains no state of the incident after finishing its little printout. Does the unseen paper have the knowledge? It certainly contains the (hidden) information, but does it have 'knowledge'? If it does, why that anthropocentric choice of words?
Well, so do I, but my definition might be different than yours, so it isn't saying much. I will to be on the other side of these jail bars, so physics, deterministic or otherwise, very much does get in my way on that account, but few consider such restriction to be an example of lack of free will.
[But I am a bit unwilling to explain why I think so here... :smile:.]Agree, this would be too far off topic. There are always other threads about such things.
Double negative. It denies that there are universal ethical truths. I'm sure you meant that.
Actually, I find that any particular rule is probably meaningless for most situations. 'Torture of babies is bad' has no application to the vast majority of things where 'torture' and 'babies' are both meaningless or at least poorly defined. Note my use of 'things' instead of the already restrictive word 'everybody' which detracts from the universality of the rule. A universal rule should not only apply to things that are member of 'everybody'.
Same here. I don't necessarily deny objective morality, just playing devil's advocate.
Don't understand your, um, misunderstanding. How can it exist unmeasured? I've not measured the 2nd even larger moon, so it doesn't exist, and that seems not a problem to you. Nobody can be on this Earth (can exist relative to me say) and not have measured the moon. We have an inter-subjective agreement about that. Similarly, if one has not measured the moon (or has measured that bigger one), then that person cannot establish any inter-subjective relationship with me. It would be a contradiction.
The article says a complete measurement of ones self cannot be taken, not that you can't measure yourself. My pants size is a measurement of myself. :sad:
I don't have a definition of S. It seems arbitrary. It is fairly easy to do for a human, but less so for other things. The ease of defining human X (and equating that definition to the same X at some other time) allows the existence of a legal identity of X. You can't do that with amoebas and flames.
I think there are interactions between two electrons (like both being part of the same Helium) that ambiguates which one is which when one of the two changes state (like exits the atom). So yes, an electron departed, but it wasn't necessarily a particular electron. This is not a measurement thing. Of course there is no way to measure which one stayed and which one left. I'm just saying that metaphysically, it seems that electrons don't have identities, and thus act like a distinct 'system S'.
Not sure if we're talking about the same thing here. Most of my relation with the electron is 'it is there', and relative to some other observer, it isn't there, or anywhere, just like the moon. To any two intersubective observers, they should agree on the electron being there or not, even if viewed from different frames. Isn't 'it is there' an invariant between said intersubjective perspectives? One says it is northbound and the other says eastbound, but both say it is there. That relation is not invariant between perspectives that are not intersubjective.
We should if it is sentient. I just want to talk to an alien that reproduces by suddenly falling into two halves. There is so much stuff that we find intuitive only because we don't do that, and talking to such a being would drive out all those inbred biases in not just us, but the amoeba as well. It would learn from us. The flame is even worse, because two flames can merge into one. Even the amoeba can't do that. We may well be able to talk to the flame some day soon because any AI entity (say an intelligent virtual being) would benefit from working that way
Appreciate the good discussion. Been a while for me.
From some (most) perspectives, there is no 'it' to be an electron. To consider an electron is to have already assumed a perspective where it exists. It is a measurement already taken.
Hard to understand is my current state of affairs. I don't get a clear statement about how it differs from the others.
The man on the street, sure, but to philosophers and physicists who know their QM, that faith in there being an actual state of affairs is not very deeply rooted at all. Those roots were discarded a century ago. There are interpretations that support it and interpretations that do not. That this interpretation lists itself among the latter is hardly contrary to established belief. Yes, it seems a lot like MWI and I'd like to see a thing that spells out where the two differ in metaphysics, and not just terminology.
From a quick glance at the wiki chart, both have universal wave function, but only MWI considers that wave function to be real. MWI is deterministic and CHI is not, but it isn't clear from the linked article why not.
I have a problem with worlds of non-equal weights in MWI, and I'm not sure if the interpretation addresses that, or if CHI has a similar problem.
I think this was addressed to me. An observer occupies all reference frames, but is stationary in only one of them. Without an actual observer doing an act of observing, relative velocities of rocks and table lamps and such are still defined, just not noticed in any conscious way. You seem to continue the classic definition of 'observer' here rather than the one being described by, Rovelli was it?
Ah, ok! I see. S can have a 'partial knowledge' of its own state, but not complete. This makes sense.
Quoting noAxioms
No worries!
Quoting noAxioms
Well, I think that you actually pointed to the 'big difference': quantum probabilities are not explainable in terms of ignorance :smile:
Quoting noAxioms
I see. Maybe I misunderstood.
But, I still believe instead that here for Wigner also his friend is in superposition. That's why I referred to Bitbol's take as a sort of middle ground between CI and RQM.
Quoting noAxioms
This is a very good point and I'll think about it :smile:
Quoting noAxioms
Yes, that's the reasoning of RQM. According to RQM all physical systems are good 'end points'. Bitbol, however, notes that 'our' knowledge is always made from 'our' perspective. So, for 'us' there is a special 'end point': us. According to him, this reflects an intrinsic limitation of our knowledge: we cannot know, in principle, what is 'seen' from other perspective. The 'starting point' for our knowledge is lived experience. We cannot totally 'disregard' this and, therefore, we should not speak of how the world is 'for an experimental apparatus'. On the other hand, we can have knowledge of other human (at least) perspectives because they are qualitatively (very) akin to ours.
As you say, however, at the level of practice this does not make any difference. After all, in RQM it is still true that for 'our' perspective, 'we' are 'special'. And our knowledge is perspectival. In a 'Kantian-like' philosophy it is impossible to know 'things as they are' because phenomena (in our immediate experience) are conditioned by a-priori categories of our mind. So, for Bitbol, we can only be (almost) sure about our perspective.
Note however, that I do not believe that accepting a 'Kantian-like' philosophy requires that you have to choose a determinate interpretation of QM. (After all, Kant himself did not know QM)
Quoting noAxioms
I believe that the registration act involves 'something' that is able to store information. E.g., a computer that stores '0' ('1') for spin 'up' ('down') when the spin of an electron is measured. But anyway, if one follows Rovelli in saying that everything can store information in that way, I believe that Wheeler's CI becomes RQM.
Quoting noAxioms
Another excellent point. This in fact seems to go against Bitbol's interpretation. Maybe the 'counter-objection' is that when Bob sees the piece of paper at that point he knows that there is no superposition and, therefore, the situation is now more or less like the unseen coin. I don't know if this makes sense, though.
I agree that claiming that the piece of paper has knowledge is an anthropocentric choice.
Quoting noAxioms
Agreed! I agree that 'free will' is not 'complete free-will'. But in my opinion, it is not just an 'effective free will' a la what's is required in Bell's theorem to avoid superdeterminism, for instance. I believe that we have some autonomy - our actions cannot be (entirely) explained via physical processes (after all, I believe that neither determinism nor randomness nor some combination of the two are compatible with a 'real free will'). But as you say, it is O.T. :smile:
Quoting noAxioms
Yes, sorry.
Quoting noAxioms
Ok. I think I see what you mean. Ethical statements are contextual. If there were no human beings (or more generally 'sentient beings' if one accepts that there are non-human sentient beings and those beings have some kind of 'ethics'), there would probably be no ethical truths.
Quoting noAxioms
Ok!
Quoting noAxioms
Yes, I agree that everybody on this Earth measure the Moon and, therefore, we all agree on its existence. But let's consider an alien who never measured it. Suppose that he visits our Solar System and 'measures' the Moon. So, at this point he agrees with us about the existence of the Moon. But before that, is it right to say that for him the Moon is simply non-existent?
Quoting noAxioms
LOL. You are right! :smile:
Quoting noAxioms
Ok, I see. Good point!
Oddly, this point might be made by Bitbol himself. Since we cannot define S but it is very easy to define our own 'perspective', then it is not very natural to define the the perspective of a pen.
Quoting noAxioms
I think I agree!
Quoting noAxioms
Right, I agree.
But I am not sure that we can say that the unobserved electron does not exist.
In other words, let O be an 'observer'. What is the ontological status of unobserved systems according to O? :smile:
Quoting noAxioms
:up:
Yeah, I actually agree with you that a (partial) understanding of other sentient beings. I was a bit joking. Wittgenstein was far too extreme. Language, culture etc are not such an insurmountable barrier.
Quoting noAxioms
Ditto :wink:
Well, according to Rovelli there is no 'observer problem' in the sense of CI. According to his interpretation, 'observer' is actually an excessively anthropomorphic expression to denote whatever physical system. Rovelli tries to do that in order to overcome the ambiguity present in CI about what an 'observer' is (in CI it is strictly speaking unspecified...).
But maybe even Rovelli's solution is problematic. After all (as it came up in my discussion with noAxioms) defining a 'physical system' is arbitrary. Let's take the example of the pen on my table. It can be argued that I can define my 'physical system' as both the pen and the 'pen + my table'. But also the 'pen tip' can define a 'physical system'. In other words, it might be argued that there is an undesirable explosion of the number of 'perspectives'. (Maybe it is more like an 'inelegance' rather than a problem, however...)
Sorry, I can understand this but only in part. But I am just not sure that this is satisfactory. I mean, according to RQM, measurement involves an interaction. Are you saying that according to RQM the measurement process 'creates' the 'electron' 'out of nothing'? (this is actually a problem that can be raised to any form of CI)
Quoting noAxioms
Ok, same here. As far as I understand it, the main difference between MWI and CH is that the universal wave-function is unreal and that CH is indeterministic (as you pointed out). My problem is with the first part, in fact. I think I'll have to re-read that article.
Quoting noAxioms
Agreed!
Quoting noAxioms
I believe that in CH is more or less like MWI + Born Rule. In MWI, all results are equally 'real'. In CH, apparently there is the additional axiom that a particular result is 'selected' with a probability given by the Born Rule. I just do not get the unreality of the universal wave-function. I can appreciate the philosophical reason behind considering it 'unreal' (i.e. do not consider unrealized experimental results as 'real') but IMO this makes somewhat questionable its introduction in the first place.
Quoting noAxioms
Well, yeah that is one of the problems of MWI. In the case of CH, it seems that 'histories' have non-equal weight and you consider only the 'history' that you observe as 'real'. Not sure that this is really tenable, though.
The article says that an external system can take this more 'full measurement' of some system, but not any system containing the system being measured. I don't understand this since Heisenberg's uncertainty says that even an external system can't do that. So they must mean something else when discussing the sort of information they expect from this 'self measurement'.
Under any 'consciousness causes collapse' or other anthropocentric take, the friend, being conscious, cannot be in superposition. In any other interpretation, the friend very much can be.
The view cannot be falsified given that they've never put anything more complex than a barely visible dust mote in local superposition. Until they can put a human in a box, the interpretation remains valid.
Just thought of this: Per time symmetry, is there such a thing as radioactive un-decay, and would such an event constitute an end to a causal chain? If not, I don't think the decay can constitute an uncaused event.
I have a hard time figuring out what Bitbol finds special about us. I am special to me, but everything has a relationship like that with itself. Another human ('us' but not 'me') measuring something gives me no more or less knowledge of that measurement than a dot on an unseen paper, and the wave function collapses either way. Wigner's friend just doesn't change that, so there is no 'us', just 'me', which is solipsism if you posit any QM significance to that.
Sorry. You can see I have little patience for anthropocentrism. I'm biased all to hell.
I see no such thing in any way that QM changed.
I was going to make Rovelli's point. If something changes state at all, it stores that information in its changed state. A prism is an example of something that sort of interacts with a photon without a state change (storage of the information). The photon is absorbed and immediately a new one is emitted in the same direction, leaving no state change to the prism and a change to the photon for the tiny delay in its journey. The prism does not store the information, and thus does not collapse the wave function of the photon. Objects that do change state don't seem to need to perform an act of registration to be affected like that, so that wording is still a bit unclear to me.
Bob's knowledge of the paper means nothing: The device may have randomly declined to take a measurement and emit a blank paper. Bob can tell if it happened by measuring superposition or not. So the device taking the measurement, and not Bob's knowledge of that action is what collapses the wave function.
I agree that claiming that the piece of paper has knowledge is an anthropocentric choice.
For the alien not to measure the moon, he'd have to put the moon (and everything else) in Schrodinger's box, which is best achieved by making a ship that is one, inside out. Zero information can penetrate from outside to inside the box. He opens the box randomly at some location which happens to be here, and there is some vast wave function of what he might find here that collapses quite improbably to us and our moon. Far more likely it collapses to empty space. Depend on from what distance he came, but it would have to be from over 5 billion light years away because the moon (or the whole solar system) needs to be unmeasured from the start. He'd have to come from a helluva longer distance to find no galaxy here. How far must I travel now to find a place where I have zero information about what is there? A lot further than the event horizon. It cannot be done. We see stuff that is 22 BLY away, which is not possible to reach ever. But the moon is young enough that it can be done.
Before that there is no moon to be nonexistent. He can equally declare torrid-planet Vulcan to not exist. In both cases, he's just making stuff up.
I don't follow. The perspective of the pen seems the same as that of a human being there. The pen just pays a lot less attention. I honestly give humans or any living thing no special regard in this topic.
Cool. Few agree with that. It is controversial.
Kind of hard not to observe an electron. Its state might be hidden if put in a box, but we put it there so we know its there. If not in the box, it interacts with other things and that makes it exist. I cannot escape that interaction.
An unobserved system is in superposition of possible states that follow from the last observed state of the system. The real trick is how to go about not observing it for any length of time. Hence our alien showing up in an inside-out Schrodinger's space ship.
Suppose you wanted to measure the diameter of a pizza. The way to do that is to put the pizza in front of you and hold a tape measure up to it, but the act of putting the pizza in front of you already performed the pizza/not-pizza measurement. I could in theory walk into a dark room, hold out the tape, have the lights turned on and hope by improbable chance that a pizza appears directly under that tape, but that is not likely to happen if I had zero knowledge of the presence of a pizza in that dark room.
So the electron is like that. Maybe I shot it and want to measure where it goes, or any other property of it, but to do that, I'm not taking a measurement of a random volume of space and hoping an electron appears in it. I probably already have a specific one in mind, meaning the measurement of its mere existence has already been done.
I have more of a problem with MWI having a real wave function because it makes for a weighted reality of each of the worlds. One world seems to exist more than the other, but existence seems not to be anything but a True/False state. How cat X exist twice as hard as Y? So maybe CH resolves that problem for me.
I don't see why it needs to posit indeterminism or not.
Equally weighted then, but why do we find ourselves in a world where far more 'likely' collapses occur than the 'unlikely' ones? If all results are equally real, why are the probabilities of measuring those results unequal?
Sounds like RQM. My history is real to me. My future is not, thus 'I' am defined as this endpoint event along with its history, plus an arbitrary designation of which events are 'me' and which ones are 'other stuff'. There's nothing in physics to make that designation.
Information preservation seems to prevent multiple histories from culminating in the same state
It depends, I think you keep reading it that an observer is required to be a human and measurement
is a form of conceptualisation. I also think you believe that conceptualisation is how a human consciousness intervenes in quantum processes. You also seem to argue for 'X exists requires that X is conceptualised' through a largely transcendental idealist perspective - even though the point you're seeking to demonstrate is much closer to subjective idealism, and you're using an empirically realist conception of scientific methodology to do all this.
This is a self reinforcing collection of equivocations. For example, one moment of it is that evidence for only humans being observers is read into the supporting articles you provide by your interpretation of the word 'subjective' being necessarily associated with consciousness. This is even rejected in the paper discussed by the OP (as well as all the other articles we've discussed).
We both agree on the data, I don't agree with your equivocations, and I don't agree with the strategy you use that paints me as disagreeing with the data (or that the arche-fossil argument is refuted through it) while substituting your idiosyncratic interpretation of the terms in the data for its results; all the while reserving a primordial realm of meaning for philosophical contemplation which isn't touched by the 'mechanistic', merely empirical, inquiry of science. Can't have it both ways.
What human beings and table lamps have in common is that they are substantial and have form. What RQM says is that that form is relative to the observer, not intrinsic, so a point-of-view is explicitly recognized.
But RQM also says that an observer is internal to the universe. As a consequence, RQM allows an observer to be part of a system that is itself being observed by another observer. That is the scenario that the Wigner's friend thought experiment presents.
But we don't need RQM in order to recognize that. We observe others in everyday life and they can observe us. The principle is the same.
Quoting Metaphysician Undercover
Which is fine. The point is only that QM is an abstract theory about the mechanics of physical systems generally, regardless of the specific systems one is interested in modelling (which will include context-specific information).
Yes, it alludes to the self-referential problems associated with predicting what oneself is going to do in the future. Fortunately, you can usually just choose!
Quoting boundless
Yes. Whereas, in my view, potential just means that the value has not been actualized yet for the observer (which would require a local interaction).
It's like the problem of non-referring sentences. The sentence "The King of France is wise" has a potential use but not an actual use until the appropriate physical conditions occur (i.e., a King of France is installed). As a consequence, you have to be careful about the logic applied to such statements.
Quoting boundless
My own view is that there is a universal quantum state that is invariant, but RQM seems to reject that. Though perhaps another invariant is that we are all human beings with similar physical structures so we should always be able to agree that there are electrons and on the form of an electron.
Quoting boundless
Basically the same as you. I think almost all of these views can end up looking like Many Worlds when you dig into them. It makes sense in a way since they all depend on unitary QM. Though I think RQM would say that a history can be indefinite rather than there being multiple histories.
The problem is that the above doesn't really make sense on a single-world interpretation, at least in my view. What I'm interested in is whether there is a way for the photon to travel on only one path but yet have physical interference still occur. And also while avoiding hidden variables.
One thought here is the idea of reflection. When Alice looks in the mirror and raises her left arm, it appears in the mirror that she is raising her right arm. Now Alice's action and her reflection are both the results of local physical processes. Bob, observing from afar, might receive light signals directly from Alice and indirectly via the mirror that end up superimposing for him, so it seems that Alice is raising both her left and right arms at the same time. That would be a physical interference effect. However when Bob and Alice interact, he discovers and they agree that she was raising her left arm.
It makes perfect sense. The photon cannot take one path, unmeasured. That would be the counterfactual definiteness that any local interpretation denies.
That's your brain interpreting it that way. The reflection very much still appears to raise the arm on the same side, but appears to have switched front to back. This doesn't seem to change the point you're making.
I don't see that as superimposing or interference. Bob perhaps sees two images facing in different directions, but not one image facing in both directions. Bob cannot tell which is the reflection, and technically they're both images, modified by mirrors and lenses and such, so none of those images is Alice.
I didn't think my analogy was very good either. I like that we're both trying. I suspect there isn't a classic analogy.
Quoting Metaphysician Undercover
"Observer" does seem to imply a studied separation or distance form what is observed, and that seems inappropriate in the context of lived experience. I don't know much about QM, but I have tended to think of reality as virtual or potential until the advent of experience, in the sense of underlying or providing the conditions for actual experience.
I have somewhat of a taste for Whitehead's notion of pan-experientialism; the idea that experience or relation appertains to all entities and is thus the 'substance' of reality. Another way Whitehead expresses this is with his notion of concrescence. So, it might be better to say that experience rather than observation collapses the wave function. Experience can be a very broad term even in ordinary usage: as when we say things like "The cliff face experienced the erosive effects of the wind and rain".
Quoting Wayfarer
I can't see how the question of "mind-independence' really has anything to do with QM. If you want to say that 'having a perspective' is what collapses the wave function, and if to have a perspective is to be in relation, then in accordance with what I wrote above about the ubiquitous nature of experience it is fine to say that a particular cliff being eroded by the wind and rain has a unique particular perspective on the world. No other cliff erodes the way each cliff does.
I really believe that you don't see the problem. One of the things Bohr said, and it's a bona fide quotation, is that 'Anyone who is not shocked by quantum theory has not understood it.' And I don't think you see anything shocking about it - ergo ...
Another Bohr quote is that 'a thing does not exist until it's measured'. The Wheeler 'Law without Law' article draws on the same point, where it says 'a phenomenon is not a phenomenon until it has been brought to a close by an irreversible act of amplification'. OK, this might be a photographic plate or some other device, but in all cases, the act of measurement or observation is intrinsic to it.
But look at the definition of 'device': "a thing made or adapted for a particular purpose, especially a piece of mechanical or electronic equipment". Devices are made by an observer, to complement or supplement the natural senses, and their operation and raison d'être are entirely dependent on the observer. And, as I noted already, 'data' does not become 'information' until it is interpreted in a context - until someone is informed by it. An automatic weather station contains only data, which do not become information until they're observed.
Quoting fdrake
Yes, quantum physics does suggest 'subjective idealism'. Hence the controversy! But that is not exactly news - Sir James Jeans and Arthur Eddington both wrote books on it between the wars ('the universe seems more a great mind than a great machine'). Paul Davies and other science writers have been commenting on it for decades - I read 'The Matter Myth' in, oh, about 1989.
All of the arguments that are being deployed here are specifically to avoid the implication of the role of the observer which seems the unavoidable inference. But many think it's solved, or that it's a non-problem, because of 'presumptive realism', which is that 'common sense simply insists that the Universe exists when we're not observing it. Everyone know this is true.' But this is precisely why Bohr said that 'quantum mechanics is shocking'. This is why Einstein felt compelled to ask the question about 'does the moon continue to exist when we're not looking at it?', and why Einstein and Bohr went on to debate the point for 30 years.
The initial philosophical problem has never been solved, it's simply been continually obfuscated. What I'm arguing is that there is an irreducible subjective element to all science and all observation, which is the constructive (in the Kantian sense) activities of the mind. 'Modern thought' believes that it has bracketed this out by arriving at a purely quantitative and completely impersonal description of the Universe - the so-called 'view from nowhere'. However physics shows us that even the view from nowhere is still a view, and that a view requires a viewer. But people would rather believe in an infinite number of parallel universes than face up to it.
Quoting Andrew M
And what they DON'T share is 'the ability to form a perspective'.
Right, but we support abstract theories with empirical evidence gathered from observations. If, what is called an "observer" is not really an observer by rigorous standards, then the biases inherent within that definition of "observer" must be accounted for or else "empirical evidence" will not really be empirical evidence.
"You say that to all the boys" who disagree with you. the "problem" as you see it exists only on your particular set of presuppositions, which apparently you cannot see that others don't share.
Quoting Wayfarer
You didn't attempt to address my solution to the problem, which is along the lines of:
"Quoting Wayfarer
that is, the implication here is panpsychism or pan-experientialism; nature itself is both mental and physical "all the way down". The irony is that your thinking consists in reacting to an outmoded paradigm; the idea that the universe is a dead mechanism. You accept this no longer apt idea in order to assert that human subjects are special, and you reject any idea that nature itself has an ineliminable subjective part to it.
So you keep mechanical nature and then project the subjective part into the "beyond" somewhere. But QM has no truck with any beyond, and thus your thinking on this, which is firmly founded on the empirical observations of physicists, and yet which nonetheless rejects any empirical explanations, seems inapt. Your position seems quite inconsistent and confused, in other words.
I'm not the one advancing an incredibly contentious idea about quantum mechanics requiring human minds to work. Note, this is not just the claim that humans can act as observers; but that only humans can act as observers. I'm indifferent to the matter of whether we can, but strongly convinced that other things can observe too; as is consistent with everything we've read in the thread and referenced. Moreover, I believe that if human consciousness can act as an observer, our sentience will have much less to do with that than the fact that our consciousness comes equipped with systems of macroscopic objects in our bodies.
The claim that only humans can act as observers, conversely, is inconsistent with everything we've read. Perhaps you should be more surprised; your view is inconsistent with the sources you used to form it.
Quoting Wayfarer
This is extremely inconsistent with the claim that only humans can act as observers. Lab equipment also, trivially, works. And I do not believe you think lab equipment is sentient. The only way I can make sense of your claim now is that you believe that something being a derivative of human action imparts it observer status; but this thereby means non-human things can be observers.
Is your claim that observing objects must be derived from humans or be humans, or is your claim that only human consciousness can be an observer?
Quoting Wayfarer
This is irrelevant to whether lab equipment, or other physical processes, can act as observers. It's also inconsistent with the notion that probability distributions have entropy notions derivable from them. If anything, the 'data' comes after an 'informational' relation obtains between a system and an observer. A pair of electrons can be entangled with each other, thus giving information about the other's state, but they could also be in superposition prior to measurement; data derives from observing the state (or superposition) of something, not just having information about it. You'v got things the wrong way round here; information is much weaker than data.
Quoting Wayfarer
Except no, it doesn't, and the role consciousness and ideas play in quantum processes has been declared either irrelevant or non-central in every single source we've read in the thread. Also note 'seems like' in the quote, it would not surprise me if this was another analogy you have misinterpreted.
Quoting Wayfarer
You continue to display a deaf ear for metaphor, and we've covered this. That quote is intended to be a reductio on the claim that observers constrain or realise quantum system dynamics; Bohr did not think that only human consciousness could be an observer, and he disagreed with Einstein in that debate not because Bohr thought only humans could be observers, but because he thought (rightly) a proper account of quantum phenomena requires one to tackle observer dependence. You have mistaken Einsten's exaggerated caricature of Bohr's position for Bohr's position (which has been revealed previously by looking at quotes from Bohr, he took something close to a relational view around the time).
Quoting Wayfarer
Ah yes, that unforgettable Kantian thesis, subjective idealism. It is almost as if he never argued against subjective idealism in the Critique of Pure reason.
Information = data, measurement = conception = observation, empirically real = subjectively ideal, misrepresenting all the sources we've analysed together in the thread, presuming that I'm some ancient Cartesian and responding as such. grumble grumble
If you read me with more care you'd see that while yes, I'm a materialist of some sort, but I have strong sympathies for the relational interpretation of QM. IE; I fully agree with you that observers and systems need to be considered together. This is the grand charge you're saying I don't understand, but the relational character of nature is something I think is very important to see. You just think that I don't understand the issues here because I'm not using the above series of equivocations.
Though, I don't claim to be an expert on quantum mechanics.
After some reflection, I am not convinced by this explanation.
The first section says:
In other words, from its own perspective, O is 'meta-theoretical', i.e. QM can describe anything but not everything. It must be applied in a particular context or 'perspective'. The only way for observers to know about themselves is to consider themselves in relation to others. This makes somewhat sense to me, actually.
Quoting noAxioms
I agree that this is the usual understanding. But in Bitbol's case, it seems that he faithfully follows the remark: "QM can describe anything but not everything". In other words, Wigner can apply QM even to his friend. The 'measurement' for Wigner takes place when he actually enters in the lab.
There is, however a problem here. If Wigner asks his friend before entering in the lab if he sees a definite result, it appears that at this point Wigner already knows that everything in the lab is in a definite state. So, superposition is now destroyed. At this point, it seems it is not very different from the classical case of an unseen coin. The problem is that Wigner still does not know in which state the lab is (including is friend). But it seems that when he enters Wigner and his friend must be in agreement! So for them, S is in the 'up' state.
Let's consider the RQM explanation. O = 'Wigner's friend'. O'= 'Wigner'. If O' 'asks' O if the state of S is definite (let's say spin 'up' or spin 'down'), and O answers 'yes', it seems that now according to O, S is in a definite state, let's say 'up', but at the same time for O' the state is definite but it is either 'up' or 'down'. In MWI terms, for O' there are still two non-interfering branches. Yet, when O' enters, there must be an agreement between them.
But what happened to the 'other branch' in O' (or Wigner's in Bitbol's interpretation)?
(edit: I am not sure that there is no more interference for O' (or 'Wigner) when O (or Wigner's friend) says that he sees a definite state to O')
Quoting noAxioms
I do not think that it is reversible, hence I'd say that time symmetry is broken!
Quoting noAxioms
But in that case this is not a relevant information for Bob. So, to him the state is still undefined (even if he does not believe that...knowledge is not belief). If, instead, the measurement apparatus works perfectly, he really knows that the state is definite (but we fall in the aforementioned problem, where according to Bob, there are two possible states of 'Alice').
Quoting noAxioms
I agree that the Moon and everything else are in the Schrodinger's box. But this means that in some sense there is 'something' that corresponds to the Moon in the perspective of the alien. When the alien 'opens the box', the Moon 'collapses' in a definite state according to him. But this seems to imply that the Moon in some sense 'exists' before the measurement.
Quoting noAxioms
I see. But I would say that the comparison is apt for Vulcan and the definite state of the Moon, not the Moon.
Quoting noAxioms
Quoting noAxioms
Quoting noAxioms
Ok. So, you endorse some kind of 'panpsychism' or 'panexperientalism'? (see: https://en.wikipedia.org/wiki/Panpsychism#Panexperientialism)
Actually, I agree with you that it seems that Wheeler's take is somewhat ambiguous. More precisely, it seems somewhat arbitrary to think that registering devices are 'special'. I can understand taking sentient beings (including non-humans ones if any) as special. But honestly, it seems that Wheeler's model is somewhat an artificial way to avoid either some form of RQM and giving a special status to conscious observers.
I believe that what Bitbol's find fascinating is that QM seems to force the idea that knowledge is perspectival. This is also what Rovelli finds fascinating of QM. The difference is that according to Rovelli, you can define a perspective for everything, whereas for Bitbol this is not true.
Note, however, that Bitbol's take seems in some sense 'skeptical'. Since we 'directly' know only how the world appears to us, we cannot really 'know' how the world appears to a non-sentient object (if such a thing is meaningful). So, if Bitbol can be charged with some form of anthropocentrism, I believe that his kind of anthropocentrism is not the usually criticized one: it is not due to some wishful thinking that we are 'special' but, rather, it is due to an epistemic reason, namely that we 'directly' know the world as it appears to us. In other words, Bitbol (and in a similar way d'Espagnat) does not deny a mind-independent reality (whether independent of 'my' mind or 'our' minds), but he says that it is inaccessible.
Quoting noAxioms
Well, first electrons are identical particles according to QM (if we do not accept hidden variables). Furthermore, QFT seems to give some support to this kind of view: electrons are just excitations of a field. So, it seems justifiable to think that an electron does really have an identity.
Quoting noAxioms
Well, yes. So, it must 'exist' even if unobserved!
Quoting noAxioms
Quoting noAxioms
I see. Then maybe we are in agreement! The unobserved electron is not really non-existent. More precisely, it does not exist in a definite state. So, before measurement it simply does not make sense to talk about electrons in definite states.
Quoting noAxioms
Ok, I see. This for me shows that it is paradoxical to talk about an universal wave-function (whether an epistemic tool or a real entity).
Quoting noAxioms
IMO, because results of observations are random.
Quoting noAxioms
Agreed! That's definitely a problem for MWI.
Quoting noAxioms
Yes, I agree. It does not seems very different from RQM.
Well, I am not persuaded that it says just that. As I said to noAxioms in my previous post, it seems that the only way for O to have 'information' about 'himself' (or better 'itself', to avoid anthropomorphic language as RQM does) it must consider 'himself'/'itself' as an object to another system. To me this somewhat makes sense.
Quoting Andrew M
Ok.
Let me ask a question that I posed to noAxioms. According to RQM, the state of S (let's say that S is an electron) is observed dependent. To be more precise, S can have a definite state, e.g. spin 'up', for O but not for O'. For O' it is still in a superposition. Now O' can ask O if 'it' 'sees' S in a definite state. O answers 'yes'. So, now it seems that according to O' the state of S 'collapsed' to a definite result. O' does not know which one, however. It seems that, at this point, for O, S has spin 'up' but for O', the spin can be either 'up' or 'down'. So, it seems that there are two 'branches' (using MWI language). But when O' 'opens the box' (or 'enters the room', as Wigner does in the Wigner's friend scenario), O' must agree with O according to RQM. But why? How is this justified in RQM? I mean: how the 'disappearance' of the 'other branch' is justified under RQM?
(edit: I am not sure that there is no more interference for O' when O says that he sees a definite state to O')
Quoting Andrew M
That's my problem exactly. It seems that there is an ambiguity about the 'unobserved' objects in RQM.
Considering that the electron 'exists' but not in an undefined state IMO solves at least part of this issue.
Quoting Andrew M
Ok, I agree!
In my opinion Wheeler's view is a bit ambiguous. At times he suggests some form of 'panpsychism'. In other places, he seems to suggest that an 'observer' can be a sufficiently complex physical object. By 'sufficient complex physical object', I mean that such an object must be able to store and process information. And maybe, he considers that these objects are somehow sentient.
But IMO, he does not give a 'special role' to human consciousness (or animal consciousness...).
Personally, I prefer either Bitbol's approach, where you can define perspectives to sentient beings, or Rovelli's approach where you can define a perspective to everything (and might relate Rovelli's view to a form of panpsychism).
I am too fascinated by panpsychism, pan-experientialism etc. But it too does have problems IMO.
In case you are interested, for a criticism of panpsychism, I suggest this article by Bitbol: https://www.academia.edu/36160525/BEYOND_PANPSYCHISM_THE_RADICALITY_OF_PHENOMENOLOGY. It is a bit long but very interesting IMO. Anyway, criticism to panpsychism can be found at pages 7-13.
(He also criticizes emergentism, at pages 6-7)
But a discussion on consciousness maybe is off-topic...
Do you think any other kinds of beings that we know of can actually do physics? It seems obvious that animals must be excluded. Computers can perform calculations, but again they're human artifacts. So do you have an alternative?
Acknowledging the centrality of the human is actually a gesture of humility. It's the idea that we can attain complete knowledge that his hubristic. That's why I say the Copenhagen approach is a modest attitude.
Quoting fdrake
Human beings - not specifically 'human consciousness' - are observers, and they create devices to amplify their natural abilities. There are no 'observing objects' - there are measuring and recording devices but as I've said I don't think recording data amounts to 'an observation' until its interpreted.
You know yourself that there are no 'atomic facts' - that facts are only meaningful in an interpretive framework. I mean, physics comprises facts about the universe, but those facts are always embedded in theory.
Quoting fdrake
I'm quite familiar with Kant's critique of subjective idealism. As I said before, my inclination is to objective idealism.
Regarding idealism in mid-war physics, see Eddington, [url=https://en.wikipedia.org/wiki/James_Jeans#Idealism]James Jeans, and for contemporary examples Richard Conn Henry and Bernard D'Espagnat.
Quoting boundless
I think because it's controversial and counter-intuitive - like there's a conclusion he wishes to avoid.
The issue is not about who ("who" here to be taken in the broadest possible sense) is capable of "doing physics" but about who can act as an "observer" to collapse the wave function. Not many people can "do physics"; do you think those people are the only ones capable of collapsing the wave function (in general, not merely in the laboratory, of course)?
"Observer" is this context must be being used in a specialized sense. You haven't responded to my suggestion that 'experience' might be used less ambiguously.
It is true that my tendency to 'include the subject' is rejected by mainstream science. The wiki entry on the subject says the same, with these footnotes:
[quote=Heisenberg]Of course the introduction of the observer must not be misunderstood to imply that some kind of subjective features are to be brought into the description of nature. The observer has, rather, only the function of registering decisions, i.e., processes in space and time, and it does not matter whether the observer is an apparatus or a human being; but the registration, i.e., the transition from the "possible" to the "actual," is absolutely necessary here and cannot be omitted from the interpretation of quantum theory.[/quote]
-John Stewart Bell, 1981, Quantum Mechanics for Cosmologists.
My issue with these statements is that it takes too restrictive a view of what 'observation' entails. Because it seems to me that the very experiment that is the subject of this thread calls into question the whole notion that nature exists in a given state, whether or not observed. The whole point is that there is not a single, objective 'state of affairs' that is apprehended differently by different observers. Again, if that were the case, there would be nothing to discuss. Whereas, 'The experiment produces an unambiguous result. It turns out that both realities can coexist even though they produce irreconcilable outcomes.' In other words, two observers report different outcomes which are irreconcilable but correct.
So there's not a particular, observer-independent state which is, or is not, apprehended by the observer. Again the act of observation is implicated in determining the outcome, which is the point at issue. So I'm wondering if the problem with the quotes above is this: that they embody the (natural) viewpoint, that the outcome or object and the observer are two different things. So how could what happens in the mind of the observer effect what happens? It seems a ridiculous proposition when viewed that way. But I think perhaps it's because there is in reality, one situation which includes the observation and the result. Let's consider that.
For RQM, the path travelled is only counterfactually indefinite for the observer outside the interferometer. It says nothing about what the full-silvered mirrors within the interferometer might measure (the result of which gets subsequently erased by the final beam splitter). Bell's Theorem is inapplicable for RQM because there are no hidden variables in the observer's reference frame.
Of course, if the photon did travel only one path for the full-silvered mirrors, that still leaves open the question of what produces interference for the observer. But, logically, a one path explanation has not been closed off.
Quoting noAxioms
Yes. Physically it's a front/back reflection. And it can also potentially be perceived as a 3D object that is half rotated around the up/down axis and reflected left/right. Perhaps a 2D/3D gestalt effect.
Quoting noAxioms
Thanks, problems noted!
...yet another exhibition of Wayfarer's attempt to assasinate language for his equivocal woo: as if the attempt to unduly restrict 'observation' to nothing but humans is not among the most severve 'restrictions' one could arbitrarily place on interpretations on QM. Newspeak for the pseudoscientific cause: war is peace, inclusivity is 'too restrictive'. And that's to say nothing of this arrogrant reverse-speak where the height of hubris is passed off, bewilderingly, as 'humility':
Quoting Wayfarer
Hot garbage.
Right! I think we're in agreement.
Quoting Metaphysician Undercover
Yes, the term observer has two uses, so we should always pay attention to the context to avoid equivocation. If an inanimate object is called an observer, then no intentionality is implied, it's just a reference frame. Whereas human observers have an intentional view (and can additionally serve as a reference frame).
Yes. This seems to align with Wittgenstein's private language argument. Our language develops via interactions with other people and things in the world. By which we come to learn things about ourselves as well.
Quoting boundless
I don't think there is another branch for RQM. A superposition merely indicates that there is no actual value for O' prior to an interaction. The reason that O' will agree with O is simply that an interaction allows the value that O has obtained to also become actual for O'. This does not constitute a hidden variable because the rule is that the value only exists as the result of a local interaction between the two systems.
As for why that should make a difference, my thought is that there are many possible spacetime paths between the present moment for O' and the measurement event for O. Similar to the Andromeda paradox, perhaps the time of the event for O can potentially be in the future of O' (until fixed in the past of O' by an interaction).
Quoting boundless
There is still interference. See Brukner's discussion on this below:
Quoting On the quantum measurement problem, p18 - Caslav Brukner
[quote=noAxioms]Under any 'consciousness causes collapse' or other anthropocentric take, the friend, being conscious, cannot be in superposition. In any other interpretation, the friend very much can be.[/quote]
My comment is applicable to your reply. Wigner's friend is is superposition in relation to Wigner. The friend measuring himself sees no such thing and cannot detect his own interference with himself in the other state. In other words, Alice (the friend) is in superposition of having measured vertical and horizontal polarization. Bob (Wigner) sees this and can see Alice interfere with herself (per the OP) yet Alice cannot detect this self-interference. Perhaps that's what they mean by inability to self-measure. Alice needs Bob to tell her she's in this superposition of states.
I grouped this with your quote above because it mentions dealing with the description of a different observer. In the consciousness-causes-collapse interpretation, maybe the consciousness is that introduced second observer.
No he doesn't. The friend in superposition would also indicate that. Wigner does not learn from that answer that the lab is in a definite state. This is of course assuming that the friend (and the rest of the lab) is very capable of keeping the result a secret, which is why Alice is never a human in such experiments.
Not if Wigner is unaffected by the actual measurement result, and not the mere taking of it. It is not the case of the classic unseen coin.
If decoherence has occurred, then Wigner has effectively taken a measurement, and the lab is in one state. If Wigner doesn't know the result, that's just an epistemological problem. The result is fact at that point, known or not. A tossed coin between my hand and arm is not in superposition just because I don't know which side is up.
I disagree with all of this, assuming O can keep a secret, which only certain lab instruments can do. With actual humans, O' and O need not communicate at all. O's measurement affects O' at nearly light speed because no lab is a Schrodinger's box.
Decoherence can be temporarily prevented with distance, but then O and O' cannot communicate. This has been demonstrated with entangled pairs.
I'd bet otherwise, but what do I know? They create some exotic new element in a particle accelerator somewhere. Isn't that un-decay of a sort? Perhaps not. The exotic nucleus decays before it can even acquire some electrons and write home to its mommy that it has grown up and become an atom. I digress. The thing decays into different pieces than the pieces that that they probably smashed together to make it. If it can be the same pieces, that's un-decay in my book.
Exactly. Wigner learning that his friend took the measurement is not relevant information. What's relevant is being affected by the result of that measurement (and not even the knowledge of that result). Being affected by it puts him in the causal chain of that measurement and entangles Wigner (Bob) with the state of the thing measured.
This is what happens in the OP, where the fact that the measurement is done is simply not relevant information to the other observer, and thus the other observer still can measure superposition.
What? All this assumes perfect lab equipment. Bob knows the measurement was done (by something else), and yet that irrelevant information does not change the superposition state of the thing measured to Bob. He doesn't need to know or believe anything. He can measure the superposition of the thing directly.
Concerning the counterfactual existence of the moon:
It most very likely does not. Our moon, or us for that matter, are unlikely things to find in a random sample of totally unknown space. This location (which is known from inside the box due to inertial calculations) is in total superposition of anything that might have evolved from the known state of this area say 8 billion years ago. There wasn't even a galaxy here, but with really good instruments, perhaps it could be computed that there would be. So he's probably not going to pop into totally empty space like he would if he came from even further away.
Intuitive but not so if the principle of counterfactual definiteness is wrong. Think of it from a MWI perspective. The moon exists in that interpretation, but only in a tiny percentage of possible worlds that might stem from the state (past light cone) of where our alien shut himself in that ship 8 billion light years away. Most of those worlds have no moon, and far fewer have humans. He's not at all likely to witness either of them, but it is hard to imagine finding humans and no moon.
Why any difference? OK, I don't think the torrid planet is going to happen naturally, but perhaps the Vulcans that live there find it convenient for some reason, so they made it that way. It could happen.
What? Where'd you get that? More the opposite. Living things are just arrangements of atoms just like pens. There's nothing experiential required to collapse a wave function.
The interaction is observation. I did not describe an unobserved electron in that bit you quoted. So the unobserved electron is not really unobserved in those examples.
Right. Even after observation, the state is only somewhat more definite. Never totally definite, as per Heisenberg.
OK, that sort of determinism. MWI is deterministic because the entire universal wave function is one completely deterministic thing. Consistent histories is not, but I don't know it well enough to say why. With RQM, it sort of depends on how you word things. Observations appear random in every interpretation, so none is deterministic in any sort of subjective way.
It’s because the view that we can arrive at a completely objective understanding of nature, is what is hubristic. We learned we cannot fully determine the nature of the presumed 'ultimate constituents of reality'. So Heisenberg's response to that is a modest one: 'What we observe is not nature itself, but nature exposed to our method of questioning.' Who was it who said 'nature loves to hide?' You see, it leaves space; actually it leaves uncertainty, in a somewhat broader sense, which is salutary, as far as I'm concerned.
Quoting fdrake
Another question: why do you think Bohr made that statement about the fact that quantum physics is 'shocking'? Why do you think he would have said that? What was shocking about it?
Which is fine and dandy, except your position is as far removed from Heisenberg's as can be: you're not arguing from some position of epistemological humility: you're arguing that consciousness (or subjectivity or intentionality or mind ... concepts which, because you have no coherent way of sharply defining, are all collapsed into each other in one big, useless mess) is inherent to quantum processes as such.
Frankly, I don't even think you have a coherent idea of what you want to argue - the epistolomological or ontological claim - each very different, each with utterly different implications - so long as you can somehow work whatever fuzzy notion of subjectivity/intentionality/consciousness/mind (again, amalgamated into a indistinct blob of concepts) into the science in some way or another. Which is why you can mangle quotes from Wheeler, Heisenberg, Einstein, Bhor or whoever, and why you're completely incapable of answering the questions posed by fdrake in any way than invoking completely irrelevant rhetorical questions like 'WhY ArEnT YoU ShOcKed?'.
It's true: when we encounter objects, we use our perceptual system. The appearance is our response to the outside, to the thing we are encountering. All it means is our observations will entail how something appears to us (essentially, Kant).
It doesn't mean what we are observing is somewhat not present outside ourselves or not "objective". At most it means there might be more to what we have observed, other "objective" aspects of a thing our system of perception doesn't pick up-- e.g. colours to bees, smells to dogs, echolocation of bat, etc.
The story is not one of experiences creating things that are only themselves, but of how our experiences are/can be a limited in their grasp of "objective" reality. Our cone of vision is limited. Objective reality extends beyond it. We live in a world where flowers are colours bees see, we each have a particular smell a dog senses and trees have an echolocation profile to bats-- all "objectively."
The fact we don't sense those doesn't make them any less of the things we do observe.
Bohr did have a ying-yang symbol on his family coat of arms, and I can't see how this was not significant. The ying-yang symbol represented 'complementarity' which Bohr regarded as his signal philosophical insight. And you didn't answer the question, so I'll take a shot at it. QM was 'shocking' because it undermined what Bohr described as the 'Victorian' commitment to the possibility of absolute objectivity, which all boils down to 'mind-independence'.
Tertium non datur. Bohr at least was not so juvenile as to think that the latter conclusion ("all boils down to 'mind-independence") at all follows from his declaration of 'shock'. Your usual mis/nonreading claptrap. Not even your - as usual, unconxteualized - citations mean what you want them to.
I respond to you the way I do because your posts on this topic are frequently scientifically dishonest, conceptually loose, and full to the brim with (non-)argument-by-allusion. The two instances of double-speak I pointed out are emblematic of all your posts on this topic.
It's all ad homs, it's all you have. And that's a misspelling.
But 'an observation' in this context, is not a matter of what an individual thinks. It is embedded in a context of theory and practice, of which scientific instruments are a part. That is why there are peer-reviewed journals and consensus. "An observation", in this context, is a data-point, one piece of information that is interpreted in the light of theory. That is how 'consciousness' manifests in this context, and the sense in which 'observation' is meaningful.
If by 'this context' you mean Wheeler, there is no point, not a single mention - quote it, I fucking dare you - at which Wheeler even remotely refers observation to 'a piece of information interpreted in the light of theory (it's this qualification, which I've italicized, which is an utter fib on your part). Every single one of Wheeler's examples deals with registration by scientific instruments which interact with - and thus 'participate' with - the quantum phenomenon in question:
"The observing device in the here and now... has an irretrievable consequence for what one has the right to say about a photon that was given out long before there was any life in the universe" ; And repeated again two pages later: "Registering equipment operating in the here and now has an undeniable part in brining about that which appears to have happened"; And early on: "Bohr emphasized that ... we are dealing with two different experiments... the one with the half-silvered mirror removed ... [and] the one with the half-silvered mirror in place"; Elsewhere and most significantly: "A phenomenon is not yet a phenomenon until it has been brought to a close by an irreversible act of amplification such as the blackening of a grain of silver bromide emulsion or the triggering of a photo detector";
At every point is 'observation' linked to, and articulated in terms of, the physical set-up of the scientific apparatus in place. At no point is the wider body of 'theory' as set out by a community of scientists invoked necessary to bring about a quantum phenomenon: the phenomenon is 'brought to a close' by the interaction with the instruments: it goes no further, and certainly requires no 'consciousness' to swoop in from out of nowhere to make it an observation. And all this to say nothing about your attempt to insulate Wheeler's unequivocal statement about consciousness by once again skewing, with zero warrant, the statement to refer to 'what happens inside an individual observer's mind': no, it refers quite unambitiously, before your twisted attempt at blatant sophistry, to consciousnesses having a role in the 'quantum phenomenon' tout court - Wheeler is about as clear and blunt as can possibly be on this point:
"Does the record [of an act of registration] subsequently enter into the 'consciousness' of some person, animal, or computer? Is that the first step in translating the measurement into "meaning" [note how the measurement is deliberately and distinctly separated from meaning, unlike your sophistic attempt to run the two together - SX] - meaning regarded as "the joint product of all the evidence that is available to those who communicate"? Then that is a separate part of the story, important but not to be confused with 'quantum phenomenon'" - a deliberate confusion which you bathe in from head to toe.
Thanks for clearing up the issue of the interference. It makes more sense now.
Quoting Andrew M
Very interesting point :up:
Quoting Andrew M
Ok, I see. Much confusion about this arises probably from an unconscious tendency to think in terms of a 'singular history' (i.e. a fixed present for everyone...), so to speak. But that's precisely what both Relativity (if one does not want to endorse the idea of a 'block universe') and RQM question. It is, however, simply very difficult (or impossible?) to 'overcome' that tendency...
Quoting noAxioms
Ok, I see.
I actually made that comment following this remark of yours:
Quoting noAxioms
My point was that a 'panexperientialist' might agree with this remark. I believe that for some forms of 'panexperientialism', there are degrees of 'sentience' and ours is just more complex. This is more or less the point of views like psycho-physical parallelism.
Anyway, sorry for the misunderstanding! I will answer in detail to your post later.
(BTW, unfortunately, I will soon have less time available so I will probably leave the discussion...)
And at no point, could that apparatus have been set up without a guiding theory. If there were no theory to test, then no apparatus would have been set up. Open and shut. And theory is the product of reason - that is the way that consciousness manifests.
Why was that? Why would Einstein be unhappy about that?
Oh look an Einstein quote, right on fucking cue. Another rhetorical (non)-argument-by-allusion. Next stop, bookshop stocklists.
If all this is true then there's as much difference between classical physics and QM as there is between religion and science.
Also, to declare there's no objective reality from such an experiment seems to let logic off the hook. As if to say logic, as it is, can't fail. We probably need to work on our logic too before we reject objective reality so soon.
That is an exact analogy. It is why the question is vexed. It was expected that 'bacteria' (fundamental particles) would be found. It was precisely because of the 'observer effect' that the whole issue is so very controversial. The quarry - atomic particles in this case - were found not to have an independent reality, and they were supposed to be the fundamental building blocks of nature.
I will put something to you. Bohr said, as I said, that 'Quantum physics is shocking'. This is why it's shocking. It's shocking because it seems to imply that the these supposed 'fundamental building blocks' depend for their existence on observation, that they don't exist independently until they're measured. That is the problem in a nutshell. The disgust you're expressing towards me, actually is that 'shock'. I'm actually causing you to seriously consider the outrageous implication of quantum physics, which I sincerely, hand-on-heart believe you haven't actually seen up until now. The revulsion your expressing towards me, is exactly what drove a lot of the heat and passion in the debates over quantum. Heisenberg said he was driven to tears over it, because it genuinely is shocking.
I don't think fdrake has seen this point, either. That's not me 'being a shithead'. or a troll, or an internet crank. I have read a fair amount, I consider myself a responsible correspondent, and this is what I think the issue is.
Now the issue is that any information collected by the "reference frame", as "inanimate object", needs to be interpreted by human beings before it is useful as observational evidence. The interpretation is theory laden. So the idea that a reference frame can give observational information which is independent of intentionality is false.
The problem is that the theory laden interpretation cannot account for all the possibilities. For example, I put a dish of water in the sun, as my observer. I measure that water every fifteen minutes and derive a rate of evaporation as the day progresses. But I am assuming that evaporation is the only thing happening, I don't know if something else happened to the water, like a creature went and drank some when I wasn't looking. So the inanimate reference frame, as an observer, is only as good, and reliable, as the principles used to interpret the information.
Well, maybe you are right. But IMO, it suggests that the only that 'Alice' can know about herself is to consider herself in relation to 'someone else'. I am still leaning to this 'stronger' implication :smile:
Quoting noAxioms
Quoting noAxioms
Ok, I apparently almost agree! (see later)
Quoting noAxioms
Are you sure about this?
IMHO decoherence alone cannot, strictly speaking, give you a definite outcome. More precisely, it removes the superposition but it is not enough to 'select' a specific 'branch'. That's why MWI supporters like decoherence. Decoherence explains the absence of superposition. But the are still the non-interfering branches.
In my understanding, Consistent Histories instead says that interference disappears due to decoherence and a definite outcome is 'selected' probabilistically via the Born Rule.
Quoting noAxioms
Our disagreement is probably due to my possible misunderstanding of decoherence, then. AFAIK, decoherence can explain the disappearance of superposition, not the 'selection' of a specific branch.
On the other hand, if no decoherence occurs and O 'tells' O' that 'he' (O) sees a definite result then for O' there is still superposition.
Quoting noAxioms
Ok, I see your point. You're probably right, actually!
Quoting noAxioms
Quoting noAxioms
Quoting noAxioms
:up:
Quoting noAxioms
Quoting noAxioms
Quoting noAxioms
Ok, thank you again! I believe that now I see your point. So, there is at best a 'probability' of finding the Moon but not 'the Moon'.
So this means that the Moon is a possible outcome of the 'measurement'. The same goes for an electron, an atom and so on. 'Measurements' are random process but at the same time they can give only a class of result.
If one accepts counterfactual definiteness, this is explained by the fact that we, indeed, find something already there. If not, it is still undeniable that there are regularities. So, I wonder how we can explain them, if we can (unfortunately, this leads us to metaphysics...).
Maybe, reasoning in terms of potentiality/actuality can help here (e.g. see the quotation of Shimony here) at least in terms suggested by Andrew M here (but maybe his take is not really different from your model :smile: ...).
Quoting noAxioms
Ok, sorry!
Quoting noAxioms
Agreed! Good point! (I have a tendency to forget it, for some reasons...)
Quoting noAxioms
Agreed (except in the case of some hidden variables interpretations but I think that was implicit...)
Those mirrors don't take any measurement since they retain zero state from the light that reflects from them. If they did take a measurement, the photon would take only one path and not interfere with itself at the final beam splitter. That would effectively be putting a detector on each of the slits in the double slit setup. No interference is observed in such a case.
The perception as a rotation is an illusion made possible by our near bilateral symmetry. But my wife in the mirror looks sort of unfamiliar to me, and my cat is unrecognizable. I don't look that way to myself because I rarely see myself, only my reflection.
Not sure why this aspect of the discussion is relevant to the topic. We seem to have gotten off track. I was expressing my dissatisfaction at the analogy, as I have with my own.
I've seen that people use the word 'know' a lot when talking about observation/information transmission/interactions involving energy exchange, but 'know' looks to be used in different contexts to where just 'correlation' would be appropriate - like, if 2 particles are entangled, it doesn't seem typical to say that one particle 'knows' the state (distribution) of the other. Examples in this thread are the use of 'Alice knows that Bob knows...' towards the start in the discussion between @boundless, @noAxioms and @Andrew M.
What do you mean when you use 'know' in this sense? What is the (range of appropriate) physical interpretation(s) of it, if it has one?
I completely reject that. Your criticisms are ad hominem, they're not supported by any references or sources, and they're solely informed by prejudice. You can continue to rant, but that is the last thing I will say to you.
That seems to work. I considered myself in relation to that alien who came from far away and has yet to observe what's here. To that alien, I am very much in a superposition of lots of states, most of which do not contain a 'me'. So it is a state of superposition of 'here' more than it is a state of superposition of 'me'. I don't need the alien to tell me that such a superposition state exists. He's still in his box, but conveying what he knows is outside, which is very little.
Sure about my statement that decoherence is a measurement? The two are almost synonyms.
Some nucleus in the moon is in superposition of decayed/not-decayed. That decay (or lack of it) affects its environment, so it cannot be contained. The immediately surrounding matter is quickly in a completely different state because of it, so the wave function collapses into a definite outcome for at least that matter in state A or B. That's a measurement taken of the decay event by the surrounding matter. That's decoherence of the atom in superposition, entangling the matter around it into its superposition. Same thing. Within a second or two, that superposition state entangles me as well, even at this distance, and the fact of what happened to that atom becomes a definite outcome to me.
MWI is misrepresented if it has a concept of branches with identities. There is never a specific branch. The measurement is taken by nearby matter but not yet by something further away, so it is still in superposition from that PoV. That's an RQM description, but MWI never really has distinct worlds. The cat is both dead and alive (same world to Schrodinger, different worlds to the cat). Opening the box entangles Schrodinger with the cat and now there are two of both, at least from their PoV. Each Schrodinger I suppose finds himself entangled with a specific branch, but there is no identity to the branch, only the wave function of some arbitrary system, which is different to different observers.
A quote from Tegmark on the subject: https://arxiv.org/pdf/quant-ph/9709032.pdf
"[MWI (per Everett) does not posit that] at certain magic instances, the the world undergoes some sort of metaphysical “split” into two branches that subsequently never interact."
Same thing, different spin.
With interpretations where selecting goes on, I suppose that needs explaining. Here are all these possibilities, and only one becomes real and the rest discarded. What makes that choice?
I leave it to them. MWI makes them all real, and RQM doesn't really have selections that happen. A measurement isn't really done by any observer who is but an event with only a history, but not the ability to 'select'. I cannot measure the photon, but I can have already measured it, so no 'selection' is ever done. At least that's how I interpret RQM.
Bob's knowledge of the action can be obtained without consulting the device that did the action, so that information passed on by the device is not relevant. Bob has independent access to this information already.
It might be purple and tiny, but if there's one and there are locals living on what it orbits, then I suppose to them it would also be 'the moon' just like it is for us. There's a probability for finding that purple one and a probability of finding me.
If at any time I take any measure at all of the alien's approaching ship, then there is a 100% chance that the alien that steps out will find me. This is unremarkable. From a MWI perspective, the alien, upon opening his door will 'split' into every possible world that could be found and all those worlds would see the alien. That is decoherence of the state of 'here' from massive superposition to something concrete.
I cannot measure the moon right now and not find it, so that limits my possible class of results, sure. The alien measuring the same thing will likely get no-solar-system here since he never measured one in the first place like I did. My measurement collapsed a much simpler wave function that has almost zero possibility of no-moon.
Example? I measure the moon twice and find it both times? Be freaky to get a different result. But I find it because I has already measured it prior, so its existence to me is about as defined as it can be.
Isn't the "quantum phenomenon" itself completely theoretical? There are some things, like wave interference which can be observed with the human eyes, and some things like the photoelectric effect which are observed by the interaction with instruments, all the rest, what we call the quantum phenomenon is just theory. Isn't it?
:up:
Quoting noAxioms
I think you're mixing the issue of how the result at the detectors is calculated (by summing path amplitudes) with the question of what physically happens in the interferometer. RQM doesn't claim that the photon would take both paths, only that accounts of an event can differ for different observers which is a weaker claim.
Quoting Metaphysician Undercover
I'm not sure I understand your claim. Your example seems to merely raise ordinary epistemic issues around observations and experiments. There's always the possibility of some factor undermining your conclusion regardless of how careful you are or how you define your terms. For example, perhaps you observed the dish all day, but there was leak in the dish resulting in you recording an incorrect evaporation rate.
Quoting fdrake
"Know" would generally indicate that a measurement had been made and the result stored. As you suggest, the spin values of an entangled particle pair would be correlated but not known until a measurement occurs.
RQM indeed does not claim anything about what path is taken. Any statement about the path taken (such as it taking one or the other) would be a counterfactual one, and RQM is not a counterfactual interpretation. So perhaps I was in error stating that it takes both paths. Statements about unmeasured things are meaningless in RQM.
Right, that's the point, there are epistemic issues with "observations" no matter how you define the term. Sometimes the "observer" might be focused so as to miss many possibly relevant factors. In a human observer, this is one's attention. The person might observe with eyes and not ears, or vise versa, and miss some relevant information. In the case of an observing machine, its capabilities are limited by the intent of the design.
Well, I agree with was said by Andrew M.
Quoting noAxioms
Ok, I think we agree on this :smile:
Quoting noAxioms
I agree with what you said here. But I am not sure that it solves the 'measurement problem' completely. It explains why we do not observe superposition. AND it explains why a single outcome is observed.
BUT you need an additional assumption in order to explain why only one outcome actually occurs.
Quoting noAxioms
Not sure why you think you are disagreeing with me. If by 'universe' in MWI you mean the 'universal wavefunction' then I agree with you and Tegmark. But this is not normally what one means by 'world' or even 'universe', so, in fact, I think that one can definitely say that there is splitting. And this is for me a reason to not accept MWI.
Well, I know that some supporters of MWI consider only one branch as 'real' and other branches as 'unreal' ( e.g. apparently Hawking and Weinberg are supporters of this 'flavor' of MWI, see the Wikipedia article on MWI). But unfortunately, MWI cannot IMO justify that without an additional axiom (as in Consistent Histories, where there is the axiom that a 'history' is selected probabilistically. In dBB one 'branch' is occupied by particles).
My point is that this version of MWI simply does not explain why the 'other branches' are 'unreal'.
On the other hand, Deutch, DeWitt etc consider all branches as physical, 'real'. So it is not just me that understands MWI in that way.
Quoting noAxioms
In dBB you have particles. In CI it is left unexplained, I think. In Consistent Histories it is an additional axiom in my understanding (and, therefore, it is left unexplained IMO).
Quoting noAxioms
My point was exactly this.
Quoting noAxioms
I do not understand this. Take the double-slit experiment. When you observe that an electron passes through slit A then you either explain this observation of a single outcome via a selection or you accept that the 'other history' is equally true as in MWI. So, I believe that both CI and RQM leave it unexplained.
Quoting noAxioms
Ok, agreed!
Quoting noAxioms
Ok, I see.
Quoting noAxioms
I agree again. My point however is that there is no explanation why there is a probability of finding a Moon, an electron or whatever in the first place. If one accepts hidden-variables this is of course explained.
Quoting noAxioms
Right, you find the Moon again because you already measured it. As you say it is not that remarkable. It is more remarkable that you find an electron probabilistically when you perform a measurement without hidden variables.
Quoting noAxioms
This is actually my understanding of Rovelli's own view.
Also, Rovelli makes a similar point in this article: https://arxiv.org/pdf/quant-ph/0604064.pdf ('Relational EPR')...for locality (at the end of page 3):
Quoting Metaphysician Undercover
This is a very interesting point. Maybe this is also the point of @Wafarer, in fact (regardless of 'idealism'). I am not sure that this applies to RQM where measurement is understood simply as a physical interaction, in fact. But this is IMO relevant for CI.
Just a curiosity: has anyone ever suggested an interpretation where the 'universal wavefunction' is real (like in MWI) and a single branch is 'selected' by a probabilistic rule (as in Consistent Histories as I understand it)?
This would be similar to the 'unreal' interpretation of MWI referenced in the Wikipedia article about MWI where only one branch is 'real' and the others are not. The only difference is that here there is an explicit axiom of a probabilistic selection.
It seems strange that you should say this, when it seems that you are proposing a narrower conception of "observation".
Quoting Wayfarer
What exactly do you mean by "given state"? Would saying that nature does not exist in a given state mean that nature is "really" not anything, that there is no 'way things are' at all? If there were no "objective states of affairs that are apprehended differently by different observers", then how could there be any commonality of observation at all? Where would the commonality that is obviously attained originate? If there are no "ways things are", then what is science studying, and how would science then be possible at all?
Quoting Wayfarer
So, is there "a way the act of observation is" which all by itself enables the outcomes to be consistently determined and consistently agreed upon?
If all you want to say here is that human experience is always already concept-laden, then I would agree.
The salient question is as to what conclusions you want to draw from that obvious fact of human experience and what further assumptions and lines of reasoning you would use to attempt to sustain any conclusions you want to maintain. I am yet to see you do that, to be honest.
I think we observe it every day, but you take it as an ordinary observation. A rainbow is quite impossible to see without superposition. The lens of my eye would not work without it. Most directly, Bob in the OP is able to directly measure superposition even after Alice has taken a measurement.
If your interpretation says that a single outcome occurs.
I never used the word 'universe' in what you quoted since it means such different things to different people.
There is splitting of a sort in RQM also. To me, the photon is polarized vertical. Relative to another me, the photon is horizontal. Relative to a 3rd reference, there's not even a me or a photon. Sounds like those are separate worlds, some connected more than others.
That very much goes against the Everett postulate. It is a different interpretation and should have a different name.
OK, I see better now what CH proposes that is unique. You'd think they'd put that in plain language in the introduction somewhere. How is what Hawking and Weinberg push different from the CH view then? Why add a 2nd postulate when the first one perfectly predicts the experience we have?
That's why I like RQM which is the main Everett postulate: "All isolated systems evolve according to the
Schrodinger equation" without MWI's secondary metaphysical postulate that said equation is real. The latter postulate makes no change to the evolution of the equation and thus 'what happens', and thus isn't needed to explain what the experience would be.
So the inhabitants of those 'other branches' don't continue to post in their forums philosophical discussions about how their world being more real than ours? The Schrodinger equation says they very much do, and none of these additional postulates make any modifications to that.
I'm not sure that Everett did. It was a physics interpretation of QM, not necessarily making any metaphysical assertion. MWI as we know it might have been built on Everett's work, but I don't believe he called it 'MWI'.
I figured. That one is hard to explain. RQM says such and such is real to a second thing, say 'me', but 'me' needs definition. A worldline doesn't work because it isn't defined after a certain point. So that point (one event) is 'me', and that event cannot take a measurement. It may or may not have an abstract worldline leading up to it, but none has a worldline leading from it. Hence an event (me) can have already taken a measurement, but it cannot take a new one. Such new measurement are taken by future events, and the future does not exist to 'me', thus 'I' cannot take a new measurement, only something else which will happen to include 'me' as part of its past worldline. So 'I' do not select anything and thus what is real never changes for me. One of my future events (say one that measures a vertical polarity) can have already measured that polarity and that event considers that state of affairs to be real to it, but it never becomes real to (is selected by) any particular 'me' event, which, being an event, cannot flow through the selection process to its future, however much it might intuitively anticipate doing so.
That was a very eternalist way of describing things, but I cannot think of a way to do it in presentist terms. I consider 'observers' (that to which a reality relates) to be events in RQM, and consequently almost anything can be such an event. Humans are not special at all. Not sure if empty space is a valid event since there is nothing there to take a measurement of anything. It has to be something capable of being affected by state.
I never observe an electron passing through a slit. If I do, it goes through one and doesn't interfere with itself. So I don't get this scenario. What I have observed is where the electron hit the screen, or the pattern from many such electrons. At no point does any local interpretation of QM interpret the electron taking one path to get there. I think pilot wave theory might assert it, but they've really shot that one to hell when they put a partition between the two slits
Take a point exactly 50 billion LY north. There is a nearly pure wavefunction describing what exists there, and one set of solutions to that wave function is finding a moon like ours nearby, or just an electron, or whatever. If there was a way for 'me' to just suddenly teleport and take a measure of that point, under MWI, I (a whole multitude of 'I', however many it takes) would measure every one of these possibilities. Under RQM, each of these possibilities would be real to the 'me' that appears there. Same story, but different wording. Both views also say that to an observer on that moon or at any of the other possible states there, I'd probably not suddenly appear in front of them. My appearance there is as unlikely as is theirs to me.
How does one go about 'finding' an electron? What sort of measurement are we talking about here? With the moon, sure, you look up on a clear day and see if there's one there, but for an electron, it seems more difficult to not find one since they're everywhere. OK, 50 BLY away I might not find one in a sample radius since odds are I encounter fairly empty space, but I'm not sure if that's what you mean.
Such an interpretation would seem to propose counterfactual definiteness. Somewhere off to the side, some measurement is taken by not-me and causes some state to be real and the other results not.
From the Rovelli bit you quoted in the post above:
[quote=Rovelli]Even beyond its foundational role in relativistic field theories, locality constitutes, therefore, the base of the relational methodology: an observer cannot, and must not, account for events involving systems located out of its causal neighborhood (or light-cone).10[/quote]
An interpretation that such selecting of reality is going on outside of some privileged light cone is doing exactly this: accounting for events involving systems located out of its light cone. As such, the interpretation bears little resemblance to local interpretations like MWI or CH as I understand it.
Per you post above, it seemed that Hawking and Weinberg posited something along these lines, so I wonder what they'd say to my point here.
Well, yes, with this I agree.
Quoting noAxioms
Again, I agree. But this is IMO the position of RQM. On the other hand, I do not believe that there is only one 'version' of RQM. In fact, I believe that there are different relational approaches to QM. So, maybe some versions accept that all outcomes occur.
Quoting noAxioms
Yeah, but when MWI-supporters deny that there is a 'splitting', they actually do not usually deny that there is a splitting that others have in mind IMO (of course, there are exceptions).
Quoting noAxioms
But this is a different issue, IMO. Yes, there is a splitting in this sense. What I meant is that for each reference, there is no splitting. In your example of the polarization, if 'I' observe a horizontal polarization the observation of a vertical polarization does not occur in RQM (for 'me'). In MWI, it does.
Quoting noAxioms
I agree. Furthermore, I do not see a real justification for treating other 'worlds' as 'unreal'.
Quoting noAxioms
IMO, the difference is that in the MWI 'version' of Hawking and Weinberg the axiom is not stated (in fact, my 'proposed interpretation' consisted to add this axiom). Also, the wave-function in CH is not real (I wonder what this actually means in practice).
Quoting noAxioms
Ok!
Quoting noAxioms
Agreed! I believe that there is some controversy on Everett's own views.
Quoting noAxioms
Well, you have a good point here about presentism. Maybe it does not lead to 'eternalism' but some persistence over time seems required. Regarding empty space, I am not sure if it can be an 'observer' in RQM.
What about QFT? In QFT, the 'vacuum state' is not really 'void'. So, maybe quantum fields can be used as 'events'? (hope this makes sense)
Quoting noAxioms
Correct! I would have said that, sorry. Anyway, I do not believe that this affect my point. I would say that the point where the screen is hit is 'selected randomly'.
Quoting noAxioms
Ok, I see your point but I am not sure that this is right. Or rather: if you explain 'measurement' in terms of decoherence, then you are right. No selection happens. So, each 'outcome' happens.
For me this is problematic and, in fact, this is one of the main reasons - if not the main reason - why I do not accept MWI. But that's just me.
Quoting noAxioms
Very good point!
If true, I wonder if this is the reason why in CH, the universal wave-function is considered unreal.
As I said previously, I am sorry but I think I'll answer much more slowly in the following days :sad:
There is certainly no one version of probably any of the interpretations, but there are probably some fundamental features that characterize each. Take that away and it isn't really a different version of something (like RQM), but rather a whole different interpretation. So sure, all outcomes occur, but they don't all occur to a given X (or anything else). They very much occur (are real) to things Y that interact with (measure) them.
Tegmark is kind of funny this way. An MWI person might refer to 'universe' as the one universal wave function and all these resulting worlds, but Tegmark often uses 'multiverse' splitting into universes so that it falls under his type-3 multiverse. But other times he speaks of worlds and one universe.
Tegmark also argues effectively that the 'split' is never a full separation into separate disjoint worlds, and others (e.g. Wayfarer) often do, which I feel misrepresents the view. To quote Tegmark again (same link):
"According to the MWI, there is, was and always will be only one wavefunction, and only decoherence calculations, not postulates, can tell us when it is a good approximation to treat two terms as non-interacting."
So worlds don't actually split off, but different terms simply become sufficiently decoherent for their interaction to become negligible.
Everything in that paper seems to apply to RQM since it seems to separate out the needless metaphysical assertions piled on top of the one postulate. Section III-C seems to offer a choice between effectively MWI and RQM, making RQM a valid offshoot of MWI physics.
Sounds good.
It isn't stated in MWI because it doesn't need it. All worlds are real, so none of them is in need of selection over the other. It's only when you have a metaphysical selecting (dice throwing as Einstein disdained) that such a postulate is introduced.
Everett was forced to reign in his views in order to gain acceptance. It was dumbed-down to a reasonably finite number of worlds, not this full blown Hilbert space thing. That has since been put back, but I wonder what else never was. It's not like Everett really ever contributed much after being driven from the physics community like he was. He needed more of the PR engine that was behind Einstein. His thinking was too out-of-box for the time.
I think information preservation principle gives the persistence needed. If I measure the photon and then the big boot hits me from the sky (Python-style) before I can pass on the findings, was the measurement done? Information preservation says yes, the boot doesn't erase that.
Agree. Nothing to collapse a wave function.
Maybe so. Not up on QFT enough to comment with anything but the ignorance PoV.
I say it isn't selected at all.
Ok, I see. For 'Wigner's friend' only one outcome occurs. For 'Wigner' there is still a superposition (of both his friend and the physical system).
Quoting noAxioms
Yeah, in fact I was familiar with his 'multiverse' terminology.
Quoting noAxioms
Agreed. Now that you mention it, I remember reading a discussion in physicsforums where this issue came. And I was surprised in reading that in principle the various branches could still interfere after the 'split'. So, I actually forgot this.
Quoting noAxioms
Interesting. I think I'll read the paper, then :smile:
Quoting noAxioms
Excellent!
The issue here is how to interpret the wave-function. If you interpret it as 'real' (or 'representational'), then you are right, there is no selection and the 'other branches' are still 'real' after the measurement.
If, instead, the wave-function is not treated as real/representational (as I think Rovelli does), it does not give a description of reality. There is a single outcome given by a probabilistic law. Maybe in this case, the word 'selection' is apt and it creates only confusion. The process of the 'collapse' here is treated like in CI (where it is an 'axiom' and is not explained e.g. in terms of decoherence).
Note that what is said in my quote above is compatible with both interpretations of the wave-function!
Quoting noAxioms
Agreed!
Quoting noAxioms
I see. His proposal was certainly revolutionary (regardless whether one agrees with him or not).
Quoting noAxioms
Interesting idea! Maybe you are right!
Quoting noAxioms
Yep. This is certainly the case for QM.
Quoting noAxioms
Yeah, I too do not know very much about QFT.
Quoting noAxioms
If one sees the wave-function as real then there is no selection, I agree. Otherwise, there is a 'selection'.
Don't you see that this is the whole point of the article in the OP? Read the title of the thread again - it is literally what the experiment is about.
I asked before, why did Niels Bohr say that 'if you're not shocked by quantum physics, then you haven't understood it'? I've tracked down the source of the quote:
In Physics and Beyond Chapter 17, entitled “Positivism, Metaphysics, and Religion (1952)", Heisenberg recounts a conversation he had in Copenhagen with Wolfgang Pauli and Niels Bohr in June 1952. They were reflecting on the interpretation of quantum theory, which had emerged 25 years earlier. Heisenberg recounts Bohr as saying the following:
So - why the shock? What is shocking about it? The books I've read about it include David Lindley's book Uncertainty: Einstein, Heisenberg, Bohr, and the Struggle for the Soul of Science. Why is it called 'the struggle for the soul of science?' It's because of the very question that you're asking. Adam Becker's recent book is called 'What is real?' Why is it called 'what is real?' Isn't it just obvious what is real? Don't we know that? Why is that a question? I don't have any kind of solution but at least I think I understand the problem.
Anyway, I'm logging out for the time being to concentrate on work. Bye.
So, there's is not much incentive for me to make an effort to respond to the few allusions that what you wrote here consists in, when I have little confidence that you will respond in kind, and particularly considering that you apparently now intend to "log out" of the discussion.
I have a rough time with this distinction. Something not real can still be used to describe a real thing. It just isn't the actual thing. I think more on the lines of what is more fundamental. So I exist, but I'm made of more fundamental matter. Matter exists, but the mathematics underneath seem more fundamental. Below that is what, law of form? None of this stuff 'is real' under RQM, but one part really does relate to others.
That doesn't follow from either interpretation of the wave function. It seems to require an additional postulate. A unreal wave function can still describe a multi-state system, and in fact must in order to describe superposition.
[quote=noAxioms]Everett was forced to reign in his views in order to gain acceptance.[/quote]Reign... Brain fart. :yikes:
He was shunned by the physics community after his PHD and went into the defense industry instead, but was asked to present his work 5 years after the paper was published. Somewhere around that time DeWitt coined the MWI term from Everett's original "relative state formulation" which sounds an awful lot like RQM.
That works given a postulate of such selection going on. My statement was an opinion, not an assertion.
Yes, that's a good way to put it.
Quoting Metaphysician Undercover
Agreed. A human observer and an artifact will interact differently with their environment based on their physical characteristics. And no observer will pick up all the information available during an interaction. However since whether or not there is a hole in the dish is a physical characteristic then a subsequent observation could detect it (either because the human observer directs their attention to it or because the machine is modified to detect it).
Quoting boundless
It seems that some objective collapse interpretations might fit the bill:
Quoting Quantum Histories - Adrian Kent
The problem is that in QM we are dealing with the boundaries of "physical characteristics". If having "physical characteristics" is defined as having spatial-temporal presence, then special relativity places electromagnetic energy (light) as the boundary of physical existence. Now we cannot talk about the physical characteristics of the boundary of physical existence. The spatial-temporal presence of light (physical properties) is nonsensical in the context of relativity, that's why it's like a wave (physical property) without an ether.
So, back to the analogy. The dish in this instance, now the boundary, has no physical characteristics. What type of observation could be used to detect holes in the "dish", which has no physical properties? What is necessary is to either release the confines of special relativity, allowing light to have physical properties, and describe those properties, or devise a way of observing non-physical properties.
Just because something has an indeterminate state from an epistomological point, up to when it's observed, does not mean it does not exist "independently". (Also, quantum particles, not atomic). You're confused about the implications of QM experimental results if you think a particle requires an observer to exist. It's a shitty article with an even shittier headline.
Is a particle really there when there's no one to observe it? Yes, otherwise experimental physicists would be out of a job or wouldn't bother to share the results with us.
Or as Dustin Lazarovici reacted to the paper: "A group of physicists claims to have found experimental evidence that there are no objective facts observed in quantum experiments. For some reason, they have still chosen to share the observations from their quantum experiment with the outside world.
...
In particular, it doesn’t mean that measurement outcomes, once obtained, are not objective. It rather reminds us that a measurement is not a purely passive perception but an active interaction that “brings about” a particular outcome and can affect the state of the measured system in the process."
Basically, the only way we would have to let go the assumption of an objective reality is if we were to insist on locality (against this and other experimental results) in which case nothing really exists but thank God it's local! (pace Tim Maudlin)
Could you explain the difference?
What do you mean "from an epistomological point up to when it's observed"?
Are you saying the particles have location and momentum and so forth prior to observation, it's just that the information is unavailable to us?
If so, does that quantum theory have a name? What is it?
What does that mean?
Quantum particles are even smaller, aka subatomic particles, and not properly described as particles but that's language for you.
Quoting frank
An electron orbiting a nucleus is in a superposition around it. It doesn't come into existence because of a quantum measurement establishing its position, it has a position independent of the measurement that we cannot predict but we can probabilistically describe it. Hence we know we do not have to put a measuring device on the moon to establish the position of an electron for an atom in a lab in San Francisco. Epistomologically its position was indeterminate until we measured it.
Quoting frank
I'm saying that wave function collapse is a matter of knowledge. The information isn't entirely unavailable to us, we know it has location and momentum and we know the possible states, we just don't know which one until we measure.
Quoting frank
I'm confused by this as I'm under the impression I'm describing something the various theories agree on.
There are a lot of quantum theories. Some involve a wave function collapse, some don't. The ones that do usually say that it's not appropriate to talk about location prior to the collapse. Waves don't have specific locations the way particles do.
It's definitely not a matter of knowledge.
You're not seeing the problem, again. You're simply asserting that it isn't real.
The attitude of the Copenhagen group is pretty succinct on this: the particle doesn't exist until it's measured. That's the whole problem in a nutshell. Asking 'where is it' or 'what is it' before it's been measured is pointless, because all there is, is probabilities. It's not as if it's there somewhere waiting to be discovered. It's described by the wave function (hence the talk of it being 'smeared out'.)
Almost everyone assumes that there is a real, objective atomic particle which is there whether you observe it or not. But if you read the account of the debates between Einstein-Bohr-Heisenberg and others, this is precisely what is at issue. Bohr explicitly questions whether atoms exist (in any sense other than an explanatory model.) As I've said, this is why Einstein asked (in an exasperated way) 'doesn't the moon continue to exist when we're not looking at it?'
The answer seems obvious, because humans have only been around for less than a million years and the moon is demonstrably millions of years older than that. So it seems an absurd question, asked for polemical reasons, to elicit the answer 'of course it is!' But the question still had to be asked! And again if you read the accounts of the debates in the 20's and 30's, the answer is not nearly so clear-cut as common sense entails. This is why it is a 'revolution' (not that you would know from many of the comments here.)
I think this is why this issue elicits such a heated response. It's because we have a temperamental attachment to the reality of the domain of sensory perception, what is demonstrably and measurably 'out there'. (Isn't that shorthand for what we think is real? 'Out there somewhere'?) After all this is one of the implications of empiricism - that only what can be validated against sensory perception (augmented by scientific instruments) is real. But quantum theory challenges that, precisely because the elements examined by physics have a kind of ambiguous existence. They do not really exist, but they're not non-existent.
.
But I would take issue with this in one particular. Again, it's the role that the act of measurement plays in eliciting a response, which discovers 'the electron' in a particular position. That can be seen as the role of the observer. As Bohr says, this 'seeing' might take place via an instrument or device, but the act of observation is central to it. It 'makes manifest' something which is only 'potentially existent'. And that is arguably the doing of 'res cogitans' (although it not and can never be an object of cognition, for which see Bitbol.)
There are schools of philosophy that accomodate this attitude quite comfortably, although they're usually denigrated on this forum as 'idealist'.
That's only a realism-- the presence of a distinct entity measured at that instance-- it doesn't suppose anything about the rest of reality, particularly unobserved instances which might be present.
Your whole approach of trying to use the appearance experience as a measure of which things can be aid to exist does not work for unobserved presence-- in that situation, we cannot use a standard of observation or not precisely because the state in question is not object to observation.
If we are to propose an unobserved quantum events, atom, person, universe, etc., are knowledge of must be given without observation of it, for our concepts are referring to the unobserved instance in that case. As such, we cannot use our observations to dismiss those instances because they are states present prior to our act of measurement. The addition of us and any measurement device changes what we are dealing with, an instance of an unobserved object to an observed one.
The reason you are degraded as "idealist" is because you are taking exactly the opposite conclusion about the limits of our observation. You try to use it as a measure of things we have not observed: an oxymoron if there ever was one.
When we are dealing with unobserved events, we are dealing with what we haven't seen. A question not of empirical observation of an instance, but a conceptual grasp of something we've not yet seen or measured, much like correctly imagining who is standing behind you in a room, even though you haven't looked or made any other empirical observation of who it is.
The Copenhagen interpretation says that prior to measurement, stuff doesnt have the properties we associate with particles.
I was just talking about Wayfarer's metaphysical error.
There is nothing wrong with suggesting instances of things we don't obsevre have the same properties as instances we do. Indeed, this is how we make commentary on things we don't observe with descriptions like those we have: the unobserved stuff behaves similarly.
But Wayfarer won't get this point until he stops equating things of the world with our experiences and our knowledge of things with empirical observation-- it amuses he complains so much about "scientism," when his own position reduces knowledge of things to purely when they are empirically observed.
But they all do. The particle is somewhere within the range of possibilities provided by the probability field. It is true that by measuring position the thing measured behaves as a particle and not a wave for that measurement but this is a result of it really being neither a wave nor a particle and a limit of language.
This is my first reply with a position. I asked a question previously so that seems an odd start is your reply.
Quoting Wayfarer
This just violates the law of non-contradiction.
Why measure for position to begin with if the theory does not predict it will be there? They all, even the Copenhagen interpretation, assume when measuring position it will return a result.
Heisenberg agreed with me by the way, which is why he uses the term reduction and not collapse.
You asked a question - and then answered it yourself, in the affirmative. ‘Is the particle there when there’s nobody there to observe it?’ is the crux of the problem. So just casually saying ‘yes it is’ indicates you’re not seeing what the issue is - because that is the issue.
Quoting Benkei
That's kind of the point! See the beginning of the forward to Heisenberg’s Philosophy and Physics which specifically mentions Heisenberg's re-introduction of 'potentia' into physics (as per the quote in my earlier post). One interpretation is that this implies there are 'degrees of reality', that what is being predicted by the 'wave function' is a pattern of probabilities, but the probabilities don't pertain to some individual thing which might or might not be there. It's pure potentiality.
It's worth having a read of Heisenberg's 'Debate between Plato and Democritus', given as a conference keynote speech. In that, he talks about the meaning of the word 'exists' in relation to sub-atomic particles:
I think the suggestion that sub-atomic particles don't exist 'in the same way' as stones and flowers is pretty significant - because we would generally assume that something either exists or it doesn't, don't we? Democritus certainly thought so: atoms 1, void 0.
Quoting Benkei
But it's not, otherwise, again, there would be no problem.
Quoting Benkei
It predicts according to statistical probabilities, very accurately. But according to the Copenhagen stance, you can't go behind the observations and say anything about what is really there; you can't assume that there is a real X apart from the observation. (This is why Bohr is sometimes (incorrectly) said to be positivist.)
We may be having a translation problem, but it sounds like you're saying that superposition can be understood as a classical physical state, the particulars of which are only known to us by probability.
If that's what you're saying, you're wrong, but you have a mind-bending journey ahead of you in discovering how bizarre quantum theories really are. I envy you.
Not what I meant. The probability describes the possible outcomes of measurement not that at any given moment before measurement it is accurate to say it has a singular position that we just don't know and will discover through measurement. The measurement just brings out a specific property of the object at the expense of all other possible properties "disappearing".
Yeah, that's true. So your point was that measurement doesn't create anything. It just brings about an alteration. Therefore we shouldn't think of quantum experiments as undermining objectivity.
I agree. Although there is a sense (or two) of "objectivity" that is damaged by quantum experiment and quantum theory.
It's not a limit of language, it's a limit of the principles employed toward understanding the thing. In other words, if the thing cannot be understood, it is because inadequate principles are being employed toward understanding it. Language doesn't have limits in that way. We just make up new words for new things, physicists have no problem making up new words. When you're talking about a thing which you cannot identify (point to), it's very hard to describe that thing. This is not a limit of language, because the thing (just like imaginary things) can be named. Its a limit of the method of observation.
So you aren't suggesting that measurement creates something ex nihilo, You're just saying it creates the type of thing we usually think of as a physical object in the same way an artist creates a statue out of clay. And to the extent that an objective view is populated with regular stuff that does not shift or change by virtue of being measured, quantum theory screws up what we usually think of as objectivity.
Is that true?
Sort of. Wheeler uses the metaphor of paper mache. In any case there isn’t ‘a particle’ lurking there undetected. What is there, is a distribution of possibilities - degrees of potential existence, you might say. Measurement or observation then ‘collapses’ the domain of possibilities - hence the ‘wave-function collapse’. Realists.couldn’t accept that, because they naturally assumed that there had to a real object. But this is why Bohr said of such things that ‘they don’t exist until they’re measured’. That’s the basis of the controversy as laid out in Manjit Kumar's book Quantum.
Quantum physics doesn't give a subjective idealist any leverage. It might have seemed so early on, but not anymore.
There is no implication of non-physical properties. In QM, light quanta (photons) have physical properties. And QM is consistent with special relativity.
Here's the DailyNous link for those quotes. The assumption of reality, as defined in Bell test experiments, is simply that there is a definite value for a measurement that has not been performed (counterfactual definiteness).
Almost all QM interpretations reject counterfactual definiteness, with Bohmian Mechanics being the main exception (as it happens, both the individuals you quoted above hold the Bohmian interpretation).
So what experimental results actually show is that counterfactual definiteness, locality and free choice can't all be true. Those interpretations that assume locality are compatible with special relativity.
It's worth noting that superpositions have been created for objects with up to trillions of atoms (as in the case of the piezoelectric "tuning fork"). Probably most physicists would consider QM to be a universal physical theory (i.e., applicable to everything). Which is part of the point of the Schrodinger's Cat and Wigner's Friend thought experiments.
Sure, QM is consistent with special relativity, but I don't think it's correct to call the properties of a photon "physical". A photon has an effect on physical things, and it might have a physical cause, and it is described by mathematics, but according to special relativity, light does not have spatial-temporal properties. The speed of light is the limit to spatial-temporal properties. So how exactly would you describe these "physical properties" which light quanta have? How does something which is only described by mathematics have physical properties? Say for example "2+6=8", that's something only described by mathematics. How does that have physical properties, other than the symbols which represent the mathematical idea?
Putting this together with your earlier comment that you are not attached to locality, it sounds like you have an affinity to the 'non-local hidden variables' school, of which David Bohm's 'pilot wave' interpretation of QM is perhaps the best-known. In most other popular interpretations, the imprecision about location is not just epistemological.
I like Bohm. I have his book 'Quantum Theory' which is interesting because it was written before the modern Dirac notation for QM with 'bras' and 'kets' became standard.
FWIW Bohm was quite a mystic, and had a famous series of public discussions with Krishnamurti about physics and spirituality.
If we adopt a worldview that the universal wave function IS 'objective reality' - Kant's Noumenon - then we have all the objectivity we could realistically wish for, without even touching on the question of 'whether the moon is there when we are not looking'.
The wave function explains the correlation of observations by independent observers, aka intersubjectivity.
I wonder whether Berkeley would have thought of such a view as confirmation of, or an attack upon, his Idealism. It certainly has no truck with Johnson's rock-kicking approach.
For that matter - are numerical propositions, or even just numbers, objectively real? I would say not. I would say they are deductively valid (or not). So they are used to determine what is objective. If I say there's 6 of something, and you count 5, then I'm objectively mistaken. But, like the nature of the wave-function, the ontological status of number is also a vexed question. (If you doubt it, look at the size of the Wiki entry on philosophy of maths.) Myself, I am inclined to the Platonic view of numbers - that they are real but not materially existent. However, naturalism has problems with that view (see here.)
The reason for the controversy is, in my view, because Enlightenment-era science believed it would be able to discover a real, ultimate, material particle or entity of some kind. But if instead if you have to talk in terms of wave-functions, or fields, or mathematical abstractions, or the act of observing, then it's already game over for that effort - there is no ultimate material unit to act in that role. I think that has something to do with the controversies.
I dare say you are right.
Amazingly, I had not hitherto noticed that the first six letters of 'objective' are 'object'. Strange, for somebody with a keen interest in etymology, as I have.
objective
/?b?d??kt?v/
adjective
adjective: objective
1.
(of a person or their judgement) not influenced by personal feelings or opinions in considering and representing facts.
"historians try to be objective and impartial"
synonyms: impartial, unbiased, unprejudiced, non-partisan, disinterested, non-discriminatory, neutral, uninvolved, even-handed, equitable, fair, fair-minded, just, open-minded, dispassionate, detached, impersonal, unemotional, clinical
"an interviewer must try to be objective"
antonyms: biased, partial, prejudiced
not dependent on the mind for existence; actual.
"a matter of objective fact"
synonyms: factual, actual, real, empirical, verifiable, existing, manifest
"the world of objective knowledge"
antonyms: subjective
2.
Grammar
relating to or denoting a case of nouns and pronouns serving as the object of a transitive verb or a preposition.
noun
noun: objective; plural noun: objectives; noun: the objective; noun: objective lens; plural noun: objective lenses
1.
a thing aimed at or sought; a goal.
"the system has achieved its objective"
synonyms: aim, intention, purpose, target, goal, intent, object, end, end in view, grail, holy grail; More
idea, design, plan, scheme, ambition, aspiration, desire, hope;
the point, the object of the exercise
"our objective is to build a profitable business"
2.
Grammar
the objective case.
3.
the lens in a telescope or microscope nearest to the object observed.
"examine with high power objective"
No mention of 'object' there other than in the sense of 'purpose'.
I was thinking how to reply to this but I think Rovelli's presentation here is better than what I'd be able to come up with:
"If different observers give different accounts of the same sequence of events, then each quantum mechanical description has to be understood as relative to a particular observer. Thus, a quantum mechanical description of a certain system (state and/or values of physical quantities) cannot be taken as an “absolute” (observer independent) description of reality, but rather as a formalization, or codification, of properties of a system relative to a given observer. Quantum mechanics can therefore be viewed as a theory about the states of systems and values of physical quantities relative to other systems.
A quantum description of the state of a system S exists only if some system O (considered as an observer) is actually “describing” S, or, more precisely, has interacted with S. The quantum state of a system is always a state of that system with respect to a certain other system. More precisely: when we say that a physical quantity takes the value v, we should always (explicitly or implicitly) qualify this statement as: the physical quantity takes the value v with respect to the so and so observer.
Therefore, I suggest that in quantum mechanics “state” as well as “value of a variable” – or “outcome of a measurement–” are relational notions in the same sense in which velocity is relational in classical mechanics. We say “the object S has velocity v” meaning “with respect to a reference object O”. Similarly, I maintain that “the system is in such a quantum state” or “q = 1” are always to be understood “with respect to the reference O.” In quantum mechanics all physical variables are relational, as is velocity". (source)
[Quick note, by this point in the paper Rovelli has already set out very clearly that an 'observer' is nothing more than a 'physical object having a definate state of motion', and may well be something as benign as a table lamp. I mention this to head off any waffling idiot who equivocates on 'observer' to mean 'consciousness' or any such trash].
"The word “objectivity” has a somersault history. Its cognates in European languages derive from the Latin adverbial or adjectival form obiectivus/obiective, introduced by fourteenth-century scholastic philosophers such as Duns Scotus and William of Ockham. (The substantive form does not emerge until much later, around the turn of the nineteenth century.) From the very beginning, it was always paired with subiectivus/subiective, but the terms originally meant almost precisely the opposite of what they mean today. “Objective” referred to things as they are presented to consciousness, whereas “subjective” referred to things in themselves.
...Even eighteenth-century dictionaries still preserved echoes of this medieval usage, which rings so bizarrely in modern ears: “Hence a thing is said to exist OBJECTIVELY, objective, when it exists no otherwise than in being known; or in being an Object of the Mind.”" (Daston and Galison, Objectivity).
The physical properties of a photon are able to be measured in the same way as for any other particle. If you want to know a photon's position or speed, you set up an experiment and measure it.
See https://en.wikipedia.org/wiki/Photon#Physical_properties
I believe that if you say that something 'not real' describes 'a real thing' you're just re-asserting a realist/representational view. The 'unreal'/'non-representational' view of the wave-function advocated by Rovelli, Bitbol etc is that the wave-function does not describe anything. It is just a tool.
This is very compatible with the view that collapse is due to an increase of knowledge (i.e. an 'epistemic', not 'ontic' view). But, of course, if the wave-function is not representational in any sense, it is difficult to explain why QM predictions are very good, for instance. In fact, a non-representational view of the wave-function implies that we cannot know anything about the unmeasured objects and the 'collapse' mechanism.
In other words, 'real' and 'representational' should be taken as synonyms (or very close to that) - the point is that there is a biunivocal correspondence between mathematical formalism and reality. In MWI all outcomes occur because you consider the wave-function as real. This is true for the objective collapse theories. In CI there is a spectrum. In dBB theory too this is a controversial issue, actually.
For instance, many dBB-supporters do not consider the wave-function as a 'real field' but as 'nomological'. The point is that the wave-function is a 3N-dimensional function, while particles or (normal) field configurations live in the 3-dimensional space. This paper explains some possible views of this 'nomological' camp: https://arxiv.org/pdf/1406.1371.pdf. The authors distinguish between two possible meaning of 'nomological'. The first is called 'Humeanism' - it is actually a reductive approach: there is no real 'reason' why particles move in the way that move. The wave-function is just a useful tool to 'describe' (or, maybe better, to calculate) the evolving configuration of particles (at least as I understand it) - it is more or less 'non-representational'. This is somewhat ironic because dBB is usually chosen to understand what's going on. Indeed, another 'nomological' view is dispositional, quoting from the article (p.16):
This is entirely different from Humeanism. Now the wave-functions is not indeed a 'physical field'. Yet it represents some physical property. So I would say that the wave-function is indeed 'representational'. It represents a physical, real property - it's not just a tool like in Humeanism. The point is that in Humeanism, the 'wave-function' does not add anything to ontology whereas in dispositionalism, it is related to a physically real disposition.
The point in bringing this distinction between two different 'sub-interpretations' of dBB was simply to explain better what I mean by 'real'. If you think that the wave-function has some ontological meaning, then the wave-function is real/representational. If not, it is just a tool of some sorts.
Edit: a somewhat related discussion on physics forums can be found here: https://www.physicsforums.com/threads/the-reality-of-configuration-space.554543/
Quoting noAxioms
Agreed!
Quoting noAxioms
Interesting. BTW, I knew that Everett's original views are sometimes distinguished from DeWitt's et al interpretation of them. Anyway, the IEP article on 'Everettian interpretations' lists also some Relational interpretations. So, maybe Everett was really a 'relationalist' :wink:
Quoting noAxioms
I fully agree.
Quoting Andrew M
Thanks, interesting. It makes sense.
Schrodinger himself took a 'wave-only' view during his life (he also took a 'non-representational' view for some years). I wonder if he did endorse that view (at least for some years). Maybe, however, he was more close to the 'usual' GRW-like approach.
I think we still use it that way. The 3rd person, objective voice is the world's voice. On analysis, we note that this has to be a construction of the mind.
The subjective view is not supposed to be mental. It's sensual. It has a mental or abstract component, but that's not obvious at first glance.
I believe that the de Broglie-Bohm (dBB) theory should be given more attention. I am not a dBB-supporter but I believe that it is a valid alternative. Interestingly, there are different views about the ontology of dBB. Some like Bohm himself in his original work consider the contribution of the wave-function to the motion of the particle in a similar way to an additional force, given by the Quantum Potential (the link is to Wikipedia article on it).
To my knowledge, most dBB-supporters however do not like this formulation and prefer a first-order formulation (i.e. without second order temporal derivatives, i.e. without accelerations and forces) - The SEP article on 'Bohmian mechanics' has a section that explains why the 'quantum potential' formulation is criticized. But even here there is no consensus about the ontology. Some take the wave-function as a physically real field. Others do not and prefer a 'nomological' approach (but even here in the 'nomological' camp there are different views: check this article https://arxiv.org/pdf/1406.1371.pdf. I commented on it and quoted an excerpt in my previous post).
A somewhat related discussion is found in this thread in physics forums: https://www.physicsforums.com/threads/the-reality-of-configuration-space.554543/ (note that it is not only about dBB, strictly speaking...)
As I said elsewhere, however, I find dBB somewhat 'bizzarre' in its ontology. I am inclined to believe that this shows that some radical 'paradigm change' is necessary. But I nevertheless believe that it is a very interesting theory.
Quoting andrewk
I like him too very much. He really had fascinating ideas during all his career. He really wanted to understand things in depth.
I unfortunately do not have this book (but I believe reviews are generally positive).
Quoting andrewk
Yeah, that's correct. Unfortunately, this is a reason why people are averse of his (especially later) work. Personally, I disagree with them. Even if one is uninterested in spirituality, his later ideas are IMO intriguing.
If there is no objective reality, then what is it that separates observers into individual units in order to have subjective (differing) experiences of the same thing?
Wouldn't the "same thing" be the object (objective reality) and our differing experiences of the "same thing" would be the outcome of our different positions in space-time and life-history (subjective, or unique representations of the "same thing"). I don't see how QM undermines objective reality if it admits that there are objects, or events, that remain the same independent of our observations. It is our observations that are different, not the thing. The fact that two different observers can experience the same thing differently isn't a new idea, or surprising. It is what is expected in an objective world with objects or things, like observers that are an amalgam of their life-history and location in space-time. The frequency at which our brains process information could be different (due to drugs, lack of sleep, age, etc.), which can give rise to different experiences of the same thing.
It's just ironic to see people claim that they don't believe in an objective reality, yet they refer to theories and use language to communicate - as if everyone should experience the words as they experience them and understand what they write and a theory the way they understand it - as if theories and words can remain the same independent of some observers reading them and everyone that reads this theory or article will read the same words that they read and that the author wrote.
What is measured is the effect of the photon. That's the difference between a machine observing and a human being observing, the standards of measurement are being applied to changes in the machine (effects of light energy), they are not being applied to the photon itself. Let's go back to my analogy of measuring water in the dish, as it evaporates in the sun. What is measured is the effect of the sunlight, not the sunlight itself. The point is that there is interpretive theory and logic which lies between the effects on the equipment, and the so-called "physical properties" of the photon. The so-called measurement of the photon is dependent on causal theory. But the equipment has a very focused observational capacity, and can't detect other factors, so it's just like measuring the water in the dish, and figuring that the loss of water is all caused by evaporation.
Quoting andrewk
The problem with this is that a wave without a medium doesn't make sense. If we had a medium for that wave, then we could study the properties of the medium, the waves in the medium, and the whole field (pardon the pun) would be opened up to us. But without the medium the waves don't have objective existence, and the wave-function is just mathematics which predicts the probability of so-called "particles". So by the structure of the mathematical applications, the "particles" are what have real objective existence, and the wave-function uses probabilities to predict the existence of the particles. To switch objective reality, assigning it to the waves instead, would require principles for the existence of the waves, and developing a wave based mathematics, instead of a particle based mathematics.
This is why special relativity may not be the best theory here. It leads us astray by denying the possibility of a medium, when the empirical evidence indicates that the waves are real. So special relativity confines the activity of real physical existence to within the boundary of light, by denying that the waves have real physical existence. Light waves cannot be real. But then the activity of light cannot be understood with the normal descriptive terms that we use to describe physical activity because light activity needs to be described as waves, and a wave without a medium is nonsense. Now we can only understand the activity of light by means of how it affects physical things, and the wave-function is only grounded in this way, the effects of light on things, not by any real waves in a medium. So we do not have the principles to say that the wave-function itself represents real waves.
Quoting StreetlightX
This can't be about observing several quantum events right because the observation would cause a collapse resulting in only one outcome? And since we can't do simultaneous measurements...? To me Wigner and his friend don't have conflicting views but different levels of knowledge. So what sort of sequence of events are we talking about?
I get the point about it being a relational thing and it would be inappropriate to not include the observer in a description of a quantum measurement.
If so, then it would seem that the same principle should apply to an electron. One would be measuring the effect of the electron (on a measurement device), not a property of the electron itself.
Are you singling out the measurement of photons as unique here or claiming a general principle for the measurement of all particles and, by extension, all physical objects?
So you see it like - everything is a quantum system, just sometimes the corrections from quantum mechanics to macroscopic systems are sometimes negligible? Not that there is a particularly strong divide between macroscopic and quantum.
That supposition was rejected more than a century ago given the results of the Michelson-Morley experiment. There is no medium in the model for electromagnetic waves.
Yes. The Schrödinger equation doesn't make a micro/macro distinction or specify a collapse of the wave function. Which is what gives rise to the measurement problem.
Yes, I think that is the case, electrons are measured as effects, and most forms of measurement are like this. But there is varying degrees of soundness in the theories involved. So for example, I think that the theory which makes an electron as part (property) of a molecule, and part of an atom, is quite sound. But a theory which has free, independent electrons is not as sound.
Quoting andrewk
I know, that's the point. The physics of a "wave" is such that a wave can only exist as a vibration in a substance. That's what a wave is. Since there is no such substance with electromagnetic activity, we cannot refer to this as "waves". So it is incorrect to assign objectivity to electromagnetic waves, because they are not waves. If people want to insist on the reality of these waves, then someone needs to do some more serious experimentation to determine the substance which they exist in. It's nonsense to say that there are real waves which do not exist in a substance. A wave can only propagate in a substance.
Not in physics. In physics a wave is a phenomenon that behaves in accordance with the wave equation.
Ah, but is it. A phenomenon is 'what appears'. And what appears are not waves, but patterns that look like waves. The pattern is predicted by an equation that describes a wave. But I don't know if the wave can be considered amongst phenomena. The Wheeler article that was discussed earlier in this thread says that 'no elementary phenomena is a phenomena until it is an observed phenomena'.
I'll correct my statement to say that in physics a wave is a model that is used to predict phenomena, and the model does not require the assumption of any medium.
I don't think physics provides any reason to doubt that the elementary particles (as described in the Standard Model) exist and have measurable physical properties just as everyday macroscopic objects do. Whatever issues QM raises apply to particles and macroscopic objects alike.
(Have a glance at this thread I opened on Physics Forum about this point.)
Quoting Andrew M
Isn’t the ontological status of fundamental particles also precisely what is at issue in all this? The ‘Copenhagen interpretation’ does, after alll, say that ‘the particle doesn’t exist until it’s measured.’ I had the idea that this was the very conundrum that the ‘relative state formation’ was posed to avoid.
To complicate matters, the 'wave function' is, I believe, a misnomer. It's not a 'wave' in the way waves are understood either in physics or in everyday discussion. It is an element of a Hilbert space, and there's really no more user-friendly way to describe it than that. It has nothing to do with electromagnetic waves, gravity waves, sound waves or any other sort of wave, and it's not a solution to the wave equation.
That's one framing of the issue, sure. But, more impartially, what is at issue is the solution to the measurement problem. That is, what does it mean for a physical system to be in a superposition of states given that it will always be measured in a definite state?
No, in my high school physics, that is not how "wave" was defined. Here is what Wikipedia says:
"In physics, a wave is a disturbance that transfers energy through matter or space, with little or no associated mass transport (Mass transfer). Waves consist of oscillations or vibrations of a physical medium or a field, around relatively fixed locations."
Notice two key points: first, "transfers energy", second, "vibrations of a physical medium or field". The problem with "vibrations of a field", is that a "field" is purely mathematical, there has been no physical substance identified which corresponds to "field". Nothing corresponds to "field", it is pure mathematics, so it is nonsense to talk of vibrations of a field. And waves as "vibrations of a field" is something completely imaginary.
Another thing, in relation to the Michelson-Morley experiment. That experiment was completely inadequate because it premised a separation between physical objects and the supposed medium. It did not account for the possibility that objects are part of the medium, that the objects and the space between them are all part of the same medium. And, the empirical evidence, that light waves pass through physical objects, indicates that the objects must be part of the medium.
Quoting Andrew M
I don't agree with this. I've spoken to physicists who say that there is no reason to believe that what they call "particles" in the Standard Model, are actually particles at all. That's just the word that is used. Of course there is something real here which is referred to by the word, but what the word is actually refers to is states of the field. However, the "field" is purely mathematical, with nothing physical corresponding. Therefore it is incorrect to say that these particles actually exist, they are products of the mathematics.
The issue here is that a "field" is an imaginary thing, created by mathematics.
The problem is that you come from an entrenched Aristotelian position that rests on an axiom that everything is 'substance'. As a remedy, I recommend a reading of Nagarjuna, who argues persuasively that there cannot be any such thing as substance.
Or you could listen to Alan Watts about the Prickles and the Goo views of the world,
Right. That's why I said it wasn't 'a kind of phenomena'. (Incidentally check this thread out).)
Quoting Andrew M
That's the interpretive problem in a nutshell.
That's like saying that what we call "apples" aren't actually apples, that's just the word we use. So it's really a semantic issue. If one understands particles in a classical sense (i.e., as having an absolute state) then, I agree, physics gives us no reason to think such things exist. However if one understands particles (and apples) in a quantum/relativistic sense (as having a relative or relational state) then there is no problem - it's a natural fit.
Quoting Metaphysician Undercover
Or, conversely, it's not imaginary since it has physical consequences. Perhaps consider it a manifestation of the measurement problem that can be understood in terms of potentiality.
Quoting frank
I'm not familiar enough with QFT to do so. But here is someone else's explanation that I found helpful.
Quoting Wayfarer
:up:
Quoting boundlessA tool (a map of Paris say) may be just a tool and not be the thing it describes, but it very much still describes Paris. Thus I object to the statement that the tool doesn't describe anything.
I guess I'm not much in that camp since I personally suspect the wave function isn't just a tool.
I would not call what a table lamp does 'epistemic', so again, I do not personal hold view described there.
Disturbingly close, yes, to the point where no arbitrarily close inspection will yield a difference. This is not true of the paper map of Paris.
I don't think there is just the two choices. It is certainly not representational in my opinion, but the wave function has meaning only in relations, not objectively, so it isn't ontological as in 'is real' but more like 'does relate to'. 5 really is less than 7 and that is not just a representational property of the tool that is the integers, and yet the integers don't need to have Platonic realism (ontological meaning) for that relation to be true.
The point remains, that in physics a wave is defined as a vibration in a medium. It is an activity, and when there is activity there is something which is active. We can have a verbal, or mathematical description of a type of activity and that description can stand alone, as activity X, but once we apply the description to something real (use it to describe something), we engage with the underlying assumption that there is something which is involved in that activity. If it helps for you to understand this by referring to Aristotelean "substance", that's fine, but it's just a simple fact about how we describe things. If we describe a movement in the world it is assumed that there is something moving, otherwise we are describing a type of motion, a concept.
I admit that I was wrong to say that a field is completely mathematical, physicists do regard fields (like an electromagnetic field) as real things. The problem is that a field is modeled as force, and therefore potential energy. So the real existence of the field is modeled as the potential for activity in an object. For example, you can map a space with coordinates and show with vectors the force at each point. The force will change as time passes, and this may display a wave-like pattern.
The issue is that this is not the modelling of a wave. It is the modelling of a wave-like force. It is not the activity of a wave which is being modeled, what is being modeled is a force which has the capacity to cause activity in objects. As an analogy, suppose we model the force of a hammer hitting a nail. We model the effects of the hammer on the nail. This is not a modelling of the hammer. Looking at the model of this force, without any other information, we would assume that there is something there (substance, the hammer itself), which hits the nail. But we have no information about that thing other than the force which it applies on the nail, so we have no means for describing that thing itself, until we look directly at it as a thing to observe. Likewise with the modeling of the force within a field. What is modeled is the effects of the force on objects. This indicates a wave-like activity. But until we look at the field itself, as an object, a moving thing (and this means as a wave in a medium), therefore something actually moving rather than the potential for motion, we have no means for properly understanding that thing.
Quoting Andrew M
Well, I wouldn't agree that "there is no problem". Let's assume two distinct ways of using "particle". Now we must avoid equivocation so we need some principles to distinguish between particles in the classical sense and particles in the quantum sense. If we start looking at different particles, when do we cross that line? Take an electron for example. It must be a particle in the classical sense, because the structure of molecules and atoms is dependent on those particles. However, it also appears to be a particle in the quantum sense. And this might appear to be the case for the other parts of an atom. We can't use "particle" in both senses without equivocating, and we cannot say that these parts of the atom are actually both types of "particle", because that would be contradictory.
Quoting Andrew M
OK, so as I explained above to andrewk, I'll accept that a field is assumed to be more than imaginary. The problem is that it is modeled as the potential for activity, rather than a real active thing. So the issue is with the modeling technique, not the assumption that an imaginary thing is real. Therefore there is an inconsistency between the assumption, that the field is a real active thing, and the modeling of the field, as the potential for activity.
Very helpful. Thanks!
No, It doesn't, and it isn't.
EM waves don't have a propagation medium either.
Think that's how it happened. Michaelson-Moorley? Michaelson-Morley, was linked by andrewk earlier in response to MU IIRC.
No worries!
Quoting noAxioms
I see what you mean and IMO this is a good argument against a 'non-representional' reading of the wave-function: it is difficult to accept that the wave-function can have absolutely no ontological meaning and, at the same time, be so useful.
I actually am not sure. On one hand, I am inclined to say that when the 'observation' occurs the other 'branches' do not exist (for the 'observer'). On the other hand, I recognize that the 'non-representational' reading is problematic. Maybe thinking in terms of potentiality/actuality helps.
Quoting noAxioms
Ok, I agree. Bad choice of terms on my part. For the sake of generality, let's just say 'not ontic' instead of 'epistemic' and drop using the word 'knowledge' in favor of 'addition of new 'information'' (for the lack of a better term).
Quoting noAxioms
Again, you are right! I should have said, instead: 'non-representational' means that the wave-function simply does not have any ontological meaning.
Quoting noAxioms
Ok, I see. I am open to the view that there is a 'middle way' between the two positions. At the same time, however, I am not sure if what you are describing here can be applied to the 'version' of RQM that I have in mind where after the observation, for the observer, the other branches do not exist.
BTW, I am sympathetic to some kind of realism for mathematics. I do not believe that mathematics is entirely a product of our minds but, at the same time, the usual version of mathematical Platonism does not convince me. So, maybe mathematical relations are 'real' (but not 'physical'). Interesting view :smile:
I'll now explain why I believe that replacing 'conscious observers' with 'sufficiently complex physical object/system' does not solve anything IMO.
In CI, 'classicality', i.e. having definite values of physical quantities, arises due to collapse of the wave-function. But collapse itself needs in CI a classical physical system, i.e., in this view, a 'sufficiently complex physical system'.
This is a deep issue in CI. Classicality is both a pre-condition to explain 'measurements' and a consequence of measurement. So, the problem of conscious observers is now replaced by another problem: CI cannot explain the arising of classicality - after all, to work CI requires that something must be treated as classical in the first place. Hence, the first occurrence of a 'classical system' is left completely unexplained in CI. Hence as it is said in in an already quoted article by Bitbol (http://www.bourbaphy.fr/bitbol.pdf), according to CI:
This also shows IMO that the problem of the validity of 'ancestral statements' is not solved by replacing 'conscious observers' with 'sufficiently complex physical systems'. CI needs some kind of classical object as a starting point.
If one wants to avoid completely the problems due to giving a special role to conscious observers of some physical systems, one IMO should simply choose another interpretation. After all, there are a lot of interpretations of QM. RQM for instance does not have this problem because it treats all physical systems as 'observers', so there is no problem to explain how 'classicality' arises.
That's what I've been discussing with andrewk, whether EM waves are real waves or not. Andrewk insists that "wave" is defined in physics in such a way that a medium is not required for a wave. But this is contrary to the Wikipedia page on waves in physics, and contrary to what I learned in high school physics, as well. I think andrewk is just fabricating a definition to support an ontological position, and asserting the correctness of that intentionally directed definition.
Quoting fdrake
As I explained to andrewk, the Michelson-Morley experiment was inadequate, using the restrictive premise that objects would be separate from the ether rather than a part of it. That premise is contrary to observational evidence that EM waves penetrate objects. The premise that an object, such as the earth, is independent from the ether is misleading. This is evident in QM, which models the object (particle) as a property of the wave field.
Here's the conclusion from your referenced Wikipedia page. Notice that the experiments were inconclusive. Al that such experiments really show is that the relationship between the proposed ether and the earth, is unknown. Instead of resolving the issue, of the relationship between the ether and physical objects, scientists opted for special relative which provided a way around this problem. However, the problem remained and is amplified in quantum uncertainty. To say that the Michelson-Morley experiment demonstrates the non-existence of ether is a complete misrepresentation. What those experiments demonstrate is that the nature of the ether is not understood
[quote=Wikipedia]From the standpoint of the then current aether models, the experimental results were conflicting. The Fizeau experiment and its 1886 repetition by Michelson and Morley apparently confirmed the stationary aether with partial aether dragging, and refuted complete aether dragging. On the other hand, the much more precise Michelson–Morley experiment (1887) apparently confirmed complete aether dragging and refuted the stationary aether.[A 5] In addition, the Michelson–Morley null result was further substantiated by the null results of other second-order experiments of different kind, namely the Trouton–Noble experiment (1903) and the experiments of Rayleigh and Brace (1902–1904). These problems and their solution led to the development of the Lorentz transformation and special relativity. [/quote]
No, the classical sense (with absolute state) can be rejected altogether. On a relational model such as Rovelli's RQM, particles, atoms and molecules (and apples, desk lamps and human beings) are all quantum systems with relative state.
Quoting Metaphysician Undercover
On a quantum fields model, the fields for each particle type are real whereas it is particles that are potentials between interactions. For example, in the double-slit experiment the photon emitter acts by producing a disturbance in the electromagnetic field that propagates as a wave through the slits and toward the back screen. The wave represents a potential photon and a subsequent measurement actualizes the photon (say, at a slit detector or the back screen).
This is the point of the op then. The classical sense of "object" can be rejected altogether, and we no longer have any objective reality, everything is a "relative state".
Quoting Andrew M
All you are doing here is constructing a double potential. The field itself is constructed as potential, then you layer another potential on top. This method of layering potential is not new in physics. Consider the concept of energy. As the "capacity" to do work, energy is fundamentally a potential, the potential for work. Then there is potential energy, and this is the potential for the potential for work. The double potential does not make energy actual, energy maintains its definition as a potential. Nor does the fact that the fields represent the potential for interaction between particles make the fields actual, they maintain their created status as potential. and we now have a double layer of potential.
Nah man. He ain't duping you bro.
field, n.: something that has a value everywhere in space
From the Wikipedia page cited :
.Quoting Metaphysician Undercover
I don't think there is any such thing as 'the classical sense of an object'. What there has been, at various points in history, is the belief that there are real atoms, which are by definition 'indivisible particles'. But the existence of atoms in that sense has never been universally accepted.
(from the wiki page on Boltzmann.)
In any case, my thumbnail sketch of what quantum physics means, is that there is no 'ultimate object' in the sense proposed by atomism. Which, in turn, raises the question of what the fundamental constituents of nature are, or if indeed that is a valid conception at all. That doesn't imply relativism, either, as natural laws and mathematical logic hold for all observers. But I don't think they can be underwritten with reference to a purported indivisible material unit.
[quote=Werner Heisenberg]all the opponents of the Copenhagen interpretation do agree on one point. It would, in their view, be desirable to return to the reality concept of classical physics or, to use a more general philosophic term, to the ontology of materialism. They would prefer to come back to the idea of an objective real world whose smallest parts exist objectively in the same sense as stones or trees exist, independently of whether or not we observe them.[/quote]
Reference https://www.physicsforums.com/threads/copenhagen-restriction-on-knowledge-or-restriction-on-ontology.968982/
Are you not familiar with the idea of kinetic energy and the difference between that and the idea of potential energy?
Objects and objective reality remain, but counterfactual definiteness, an assumption from classical mechanics, is rejected. In other words, there is no view of an object from nowhere but only in relation to an observer (that is similarly internal to the universe).
As Banno analyzed earlier here, this already has a precedent in relativistic physics which is consistent with an objective reality.
In the case of the Wigner's friend experiment, Wigner sees interference while Wigner's friend sees a definite result. And QM is used to translate between the observations such that Wigner and his friend both agree that Wigner sees interference and Wigner's friend sees a definite result.
Quoting Metaphysician Undercover
The field is not constructed as potential. QFT says that the physical things that we observe emerge from the interactions of more fundamental physical fields. That is, those physical fields (one per particle type) are part of the ontology of QFT.
This emphasizes the fact that what's commonly thought of as objective is a psychic construction which happens to be mostly wrong.
Taking QM into account means we have to change which 3rd person statements we consider to be true. So the OP is really just a matter of semantics.
Yes, but how does that make a difference? Energy is the capacity to do work, therefore a potential. Kinetic energy is actually having that potential by virtue of being active, and potential energy is potentially having that potential. So potential energy is a double layer of potential.
Consider it in Newton's terms, an apple is hanging in the tree, it has potential energy by virtue of gravity and the fact that it could fall. If it is falling, it has kinetic energy, and thereby has the potential to hurt someone, hitting them on the head. The falling apple has the potential to exert force (work). When it's in the tree, it has the potential to fall and thereby has the potential to have the potential to hit someone on the head, double potential.
Quoting Andrew M
Redefining "objective reality" so that contradiction is acceptable in an objective reality is not what I would consider as an acceptable solution.
Quoting Andrew M
As far as I understand "fields", they are always modeled as potentials, and this includes "the more fundamental fields" of QFT. If you understand them as a model of something actual, then I think you misunderstand the ontology of QFT. But perhaps I'm wrong, and you can show me how a field is modeled as something actual. Read what I said above to Janus "energy" refers to a potential.
Well good. Being sure is being closed minded. I try not to be sure about anything, but I do it anyway.
The table lamp does acquire information (physics definition), so I can go with that.
It may or it may not. Wasn't this the thing we said we're not sure about? It seems quite interpretation dependent, even to the point of interpreting the meaning of 'ontological'. Tegmark's mathematical universe says that the wave function is what the universe is. It doesn't just describe it, but it actually is it. That's one kind of ontological statement: mathematics is fundamental, not just descriptive. Another kind would be two different interpretations of this mathematical universe where the mathematical structure has the property of existing (MWI variant) as opposed to RQM, where 'exists' is a relation, not a property. That's a different sort of ontological statement. RQM doesn't say that the universe doesn't exist (isn't nihilistic). It just gives no meaning to the phrase.
And no, neither MWI nor RQM needs to accept this mathematical foundation. I just used the mathematical universe example to illustrate two different kinds of ontology.
Sounds like what I have in mind as well. For me, unicorns don't exist. For the unicorn, I don't exist. You seem to indicate that what I've described is something else.
Or maybe they're physical but not real.
Quoting noAxioms
Ok let's keep 'information', then! :smile:
Quoting noAxioms
Yep!
Quoting noAxioms
Correct! There is a spectrum of views here.
Tegmark's position is that the Hilbert space is the only true reality, whereas our 3 dimensional space is merely an appearance. That's why in his view it is perfectly safe to say that there is no 'real' splitting.
On the other hand, one can even IMO in MWI take a less ontological view about the 'wave-function' (and the Hilbert space). I believe that a purely descriptive position is consistent with MWI.
Quoting noAxioms
Good point! Existence is relational. The 'universe as a whole' is not in relation with anything, so 'existence' here does not apply. This does not imply that the universe 'does not exist', as you say :smile:
In other words, if we take this reasoning seriously we can speak of 'existence' in the presence of relations. If there are no relations, we cannot speak in terms of 'existence' (maybe of a different kind of 'reality', if 'reality' is taken as a more general term than 'existence'...).
Quoting noAxioms
Agreed!
Quoting noAxioms
Thanks for the clarification but I still do not understand how you say that we can avoid some sort of 'selection' here.
To make it simpler, consider a radioactive decay experiment. There are two possibilities: Alice either observes the occurrence of the decay or not. Let's call these two possibilities, 'decay' and 'no decay' respectively. Let's also say that the probability of 'decay' is much less than the one of 'no decay'. Alice performs the measurement. And, say, she observes 'decay'.
If we do not accept the selection, we should accept that there is 'another Alice' that observes, instead, 'no decay'. And - besides the existence of 'another Alice' that observers 'no decay' - we have the different weights problem that occurs in MWI. In fact, this scenario is not very different from MWI. The only difference is that here we do not have a 'universal wave-function'.
On the other hand, if a selection is accepted, there is only one outcome.
BTW, the table on the Wiki article on the interpretations of QM, says that RQM is 'agnostic' about determinism. So, maybe RQM is simply silent about the selection.
[Also, IMHO unicorns here are not a good example. For me, they are simply impossible (but as you say, better not to be too dogmatic about this :wink: ).]
Quoting noAxioms
I believe that 'real' is more general than 'physical'. In fact, I just cannot understand how mathematical relations can be 'physical'. :wink:
Energy is both the capacity to do work and the force that gets work done. The first is potential energy and the second is kinetic energy. I'm not sure if all forms of energy that get work done qualify, according to any conventional definition, as kinetic energy, but in any case we can generalize and call all forms of energy that get work done actual energy as opposed to potential energy.
:up:
Quoting Metaphysician Undercover
There isn't a contradiction. Do you accept the relativity of simultaneity in special relativity? If so, then you already accept that a correct account of events can be reference-frame dependent and not absolute.
Quoting Metaphysician Undercover
Sean Carroll gave a lecture a few years ago entitled, Particles, Fields and The Future of Particle Physics. I recommend listening to his discussion of one of the slides (between 28:00 - 30:40) that includes the line, "Particles are what we see. Fields are what reality is made of." Do you disagree with Carroll's characterization of QFT?
I don't think a superposition is measured as the measurement collapses the superposition. I think, from what I read, the paper reiterates Bell's inequality and that the test setup was rather impressive.
(EDIT: Ah, I see it was linked a couple of pages back. Still, it's a great read and worth mentioning again, I think!)
Some excerpts:
Karen Crowther: "In this ‘real life’ experiment, however, Wigner and his friend are not conscious observers, but pieces of machinery: they are measuring-and-recording devices. Proietti et al. (2019) argue that these devices can act as observers, defining an observer as any physical system that can extract information about another system (by means of an interaction) and can store that information in a physical memory. On this definition, computers and other devices can act as observers, just as humans can.
So, what is the philosophical interest in this particular experiment? The question is what this experiment demonstrates about QM that was not already known from the thought-experiment plus previous experimental results. Plausibly, what it shows is that a scenario analogous to the one imagined by Wigner is in fact physically possible, and in it the observers do record conflicting facts. Thus, the philosophical significance of the experiment is to make Wigner’s own interpretation of his thought-experiment look increasingly implausible: it is difficult to imagine that this experiment would not have been successful if the devices had conscious experiences.
But, on the other hand, the fact remains that these devices are not conscious, and so Wigner could stand resolute in his interpretation. If anything, he could point out that—in the same way that an observation of a non-black, non-raven provides a negligible sliver of confirmation for the claim that ‘all ravens are black’—the success of the experiment even provides inductive support in favour of his interpretation: the ‘observers’ in this experiment are able to record conflicting facts only because they do not experience these facts."
--
Sean Carroll: "There is a long tradition in science journalism—and one must admit that the scientists themselves are fully culpable in keeping the tradition alive—of reporting on experiments that (1) verify exactly the predictions of quantum mechanics as they have been understood for decades, and (2) are nevertheless used to claim that a wholesale reimagining of our view of reality is called for. This weird situation comes about because neither journalists nor professional physicists have been taught, nor have they thought deeply about, the foundations of quantum mechanics. We therefore get situations like the present one, where an intrinsically interesting and impressive example of experimental virtuosity is saddled with a woefully misleading sales pitch."
--
Tim Maudlin: "The way that this experiment is described—in terms of its significance—is complete nonsense. Physicists have become accustomed to spouting nonsense when quantum mechanics is the subject of discussion, which often takes the form of mind-blowing assertions about the loss of “classical reality” or even “classical logic”. The reason we know that all of this is nonsense right off the bat is that the experimental predictions of standard quantum mechanics can be accounted for—in several different ways—by theories that postulate an objective, unique physical reality governed by definite laws and using only classical logic and mathematics. So when the sorts of claims made in the title and abstract of the article are made, one knows immediately that they are unjustified hype."
This paper also discusses the 'neo-Kantian' views of Grete Hermann (link to Wikipedia) who also much time earlier than Bell discovered that not all hidden variables theories are in conflict with the predictions of QM.
Another Kantian-like perspective as I said before is advocated by for instance Bitbol. For convenience I give again the link to Bitbol's paper: http://www.bourbaphy.fr/bitbol.pdf.
Quoting andrewk
Yes, I agree. This experiment does not 'reveal' anything [i]new[/I]. This does not mean that it can be interpreted as an evidence that CFD is problematic, but we already knew that.
You don't seem to understand. Energy is the potential to get work done. We make a judgement concerning a particular aspect of an active thing, its capacity to do work, and call that it's "energy".. You can say that this aspect of the thing is actual, in the sense of "real", just like the judgement that a thing is red is a judgement of something real, but that doesn't change the fact that in the case of "energy" what is being judged is a thing's potential. So all you are saying is that this potential which the active thing is judged to have (called "energy") is something real, actual. When we describe things in terms of "energy", we are describing potential, whether or not we believe that this potential is something real.
Quoting Andrew M
I think that the relativity of simultaneity allows for the same type of contradiction. It allows that it is true that two events are simultaneous, and also true that two events are not simultaneous. That is contradiction, plain and simple. The relativity of simultaneity undermines the objectivity of the law of non-contradiction in a very fundamental way. This law states that the same predication cannot be both true and false at the same time. The relativity of simultaneity allows discretion, choice, in the judgement of "at the same time".
Quoting Andrew M
Whether or not I agree with Carroll that reality is made of fields is irrelevant to the issue here. The question is whether what is represented by "fields" is of the nature of potential or not. As I explained to Janus above, what is represented by the concept "energy" is potential. Many people believe that energy is what reality is made of, but that does not change the fact that what is represented by "energy" is potential. And if we represent reality as composed of potential, that's only half the picture, because it doesn't provide us with a representation of what is actual. You might say that the reality is that there is an endless number of possible worlds, but what makes one of those possible worlds into the one that we live in, the actual world? That's what's missing if you represent the totality of reality as potential, a principle by which there is an actual world. If you cannot give reality to this principle as well, then there is no actual world in your ontology.
Quoting boundless
Well, I was presuming their possibility. It's just a horse-like thing with an evolutionary feature currently found on a narwhal and arguably a rhino (both mammals). It can happen, no? The being a sucker for human female virgins is implausible if there are no humans around, but I think its still a unicorn without that feature (or the blowing of rainbows out it's arse). Pick a different example if you find them impossible.
Radioactive decay is a wonderful example of a lot more than two possibilities since it could decay any time, thus infinite possibilities. Alice detecting it after one second is different than the Alice that measures it after two, but there is one Alice that doesn't measure it at all yet. This isn't to say that the one Alice is less probable. That depends on the half-life of the sample.
For the sake of your example, the device measures the decay destroys the 'when' part of it, so all Alice gets is a yes/no from the device when she makes her single query as to if it's happen already or not. Cat dead or alive so to speak, which as I recall was done in this manner.
I knew where you were going with this. It seems solved by MWI by exactly what you quoted from Tegmark: There isn't actually any metaphysical split. There is but the one wave function with different solutions, and thus one Alice in two unequally weighted states. There are not two separate worlds, one metaphysically weighted more than the other. But the weight never changes from the '1' that it always was.
This argument is a great one against the whole metaphysical split interpretation of MWI.
I thought we were discussing MWI there. Looking back at the exchange, maybe you mean RQM here. Under RQM, the Alice that measured no-decay does not exist in relation to the one that measured decay, so there is no weight problem. There is no selection since there is but the one world in relation to any particular state. The Alice that had measured the decay is not the same event as the pre-measurement Alice, so no selecting took place for either of them. That's at least how I've been wording it.
I noticed that. It seems not to matter. In relation to me (or to anything else), what has happened is what has happened (fixed, in the past), and what will happen is meaningless since none of it can happen to me. Multiple future possibilities will be able to claim me as prior state, but that fact doesn't change if the list of those future possibilities is determined or not. Hence agnostic: it works either way.
"Physicists have long suspected that quantum mechanics allows two observers to observe different, conflicting realities. Now they’ve performed the first experiment that proves it by experimental realisation of what was previously a thought-experiment called ‘Wigner’s Friend’."
in my opinion this is equavalent to in medieval times when people didn't understand something they just said it was magic. I recently watched a video and read some articles on quantum mechanics and one of the recurring things they say is that they don't completely understand the situation. There are 100s of known particles smaller than an electron. How those particles interact with each is a mystery in many ways at this point in history. One of the key things said in these videos is alot of the results can only be predicted using probability and statistics. Probability and Statitistics does not rule out a root cause for something that happens but it just means the future is much harder to predict then a statement where someone says if A occurs then B will happen following that.
Well, yeah in that case it might be a possibility. Who knows :smile:
BTW, regardless unicorns, I believe that the ontological status of possible yet unactualized 'things' it is a very interesting topic. Suppose that X is possible but it is never actualized in the past, the present or the future. Is that possible? Well, yeah, I believe. As I said before I am a free will believer. So, there are choices that I could have made in the past but I chose not to make them. Indeed, they were 'possible'.
Maybe those choices are simply 'unreal'. Yet, they are not 'unreal' in the same sense that dragons are (assuming that they cannot exist). Or in the same sense that the academic career of a dragon is. What makes something possible? What it means for X to be possible?
Using a MWI-like reasoning, one might say that whatever is possible is, in fact, actualized 'somewhere'. But for people like me who do not accept that kind of reasoning, it is an interesting conundrum.
Quoting noAxioms
Ok, well as you say they are all indeed different cases. But suppose that as per above, not everything that is possible actualizes. Hence also in this case, only one 'event' happens. Of course, I am assuming that not everything happens. But note that if you, instead, accept the 'existence' of all those Alice-s, how RQM is really different from MWI (except for the universal wave-function)? I believe that Tegmark pointed this out to Rovelli.
Or maybe it becomes a binary event if the measurement tells only if the decay happened during a certain time interval (I am not sure if you were saying this in the second paragraph).
Quoting noAxioms
I partly disagree. In Tegmark's view, there is no metaphysical split at the level of the universal wave-function. So, in that case there are indeed different 'Alice-s' there. It is not a 'real split' because what is truly real is the universal wave-function.
Quoting noAxioms
Yeah, I was referring to RQM. Pardon the lack of clarity.
Quoting noAxioms
Ok, I think I see what you mean. Nice work!
In MWI, the 'Alice that observed decay' would know that, indeed, 'Alice that observed no-decay' exists. In RQM, however, the answer is, you say, negative. Why? The meaning of 'existence' is different in RQM: it is relational. So, we cannot treat the 'pre-measurement Alice' as the 'Alice that observed decay'. So, a negative answer is perfectly fine.
I know that it is problematic within a relational framework, but it appears that there is no reason to believe that the other event did not occur. It seems a bit 'solipsistic' for 'Alice that observed decay' to declare that 'her' counterpart that observed no-decay is simply real, in this case.
Furthermore, as I said before, I find RQM somewhat vague in the definition of 'perspectives'. According to RQM, every physical system is an 'observer'. Fine, but if we consider, for instance a pen, it can be argued that its parts can be considered a 'physical system'.
So, it seems that there is actually a very, very huge number of 'physical systems' (and, consequently, 'perspectives'). I believe that this is a legitimate criticism to RQM (as legitimate as the criticism to MWI to have too many 'branches').
And if we unite these two aspects we end up with an even more huge number of perspectives!
Quoting noAxioms
Ok, it seems so from a RQM point.
Quoting noAxioms
Well, I believe that we are certainly understanding each other more and more. Not sure about the agreement :wink: Anyway, thank you very much for the very clarifying explanations. Now I feel that I understand RQM much better!
To summarize, I believe that RQM has two serious problems.
1) I believe - as I said previously - that there are indeed too much 'perspectives'. If every physical system defines a 'perspective'/'reference frame' (i.e. is an 'observer' according to Rovelli), then there is an incredibly huge number of perspectives.
2) If after a 'measurement' the measuring physical system becomes something else, we are, indeed, implying that after every physical interaction (for Rovelli, measurements are physical interactions) 'creates' new perspectives.
IMO, these two are very problematic features of RQM. YMMV!
Yes, I was forcing a (still imbalanced) binary event from a non-binary situation.
Sounds pretty similar to me. There is one universal wave function, some solutions including an Alice in one state or another.
Yes, the other Alices don't exist, per definition. We can still, just like the MWI person does, say that the decay measurement doesn't exist relative to the no-decay Alice. She was a real (and even more probable) outcome of the quite real pre-measurement Alice. The unicorn is more difficult due to the vast improbability of one from a 100 million year ago wave function of Earth. Of course humans are near equally as (if not more) unlikely per that same wave function.
Pop quiz: At what distance in the past does the wave function of Earth have the highest probability of there ever being a unicorn today?
Note that above I did treat the pre-measurement Alice as being real to either post-measurement Alice. Both have memory of that state and thus have taken a measurement.
It is not valid to state "the other event did occur" in a relational framework. The statement is an objective one, and has no meaning in a relational framework. It seems to constitute a counterfactual statement just like "The decay occurred". It didn't. It occurred relative to me, but it didn't just 'occur'. Thus just say that the other event occurred to the measurer of the other outcome. I tried to do what with the no-decay Alice above. I carefully avoided a wording like 'she exists' or 'the decay was not measured'. I tried to be careful to always include the relations.
Non-mind idealism of a sort, but not solipsism. If existence hinges on an interactive relation with a subject, then that subject defines its own existence, which is interaction-idealism. But there is symmetry. Everything does it, so it isn't solipsism. The table lamp does it, so it isn't mind-idealism.
A table lamp might measure a different version of me and thus I cease to exist in relation to it, but I always exist relative to myself, so I'm here. Under solipsism, I would not exist because only the table lamp (or whatever the one privileged thing is) counts.
If you get right down to the details, an observer is an event, and a system is not. No pen is in a consistent state with itself since at any given moment, parts of it are separated by about a nanosecond of speed-of-light space, and thus the ball of the pen is in superposition relative to the clicker at the other end. So in that sense, I do not exist as a system with a state. Right now I am completely undefined since no point of me has had time to measure any other part. In hindsight (say a microsecond later), that state is mostly defined and immutable. I mean, suppose that my retina has just measured the decay result from the first photon from the device giving answer to my query. OK, several other parts of the front of me also measured that, but not yet the innards (brain in particular), which are still in superposition of decay happened or not. Relative to different parts of me, the measurement was taken or not. It isn't entirely correct to say that the measurement has been taken relative to me since 'me' is not an event.
As legitimate, yes, but I find neither argument to have any teeth. Yes, it is an obscenely large number. Physics is full of those. One measurement such as a decay has seemingly infinite possibilities (not a discreet list), so even a trivial system already has infinite worlds. If one is to worry about how such a list can be instantiated (where do we find room to put them all?), then you're applying classic wording to a Hilbert-space problem. It is a good argument against the universe as computer simulation hypothesis since the implementation really would need to find room to put it all.
Still, the wave function is a pure function just like it is in MWI. Without interference from outside tweaking the terms, how can it not be deterministic? Sure, RQM doesn't care either way, but the same reasoning that MWI uses also works with RQM.
I'm now arguing against what I said above. I also do not know the meaning of the 'agnostic' designation on the wiki list for RQM.
Agreed! Until yesterday I did not fully understand RQM, I believe. My confusion was about the treatment of the ontological status of Alice: for me the 'Alice' that does the observation was the same as the 'Alice' observed by 'Bob'. Which is not true in RQM.
Quoting noAxioms
Ok!
Quoting noAxioms
I am not sure that I understand you here but I think we agree :wink:
Quoting noAxioms
Ok!
Quoting noAxioms
I would say at the beginning of the history of the Universe (unless one believes to ancient mythologies that actual unicorns wandered on the Earth).
Quoting noAxioms
Ok.
To summarize, in RQM, according to the pre-measurement 'Alice' both 'Alice-s' (or 'Alici' :wink: ) will exist. But both post-measurement 'Alice-s' regard the other one as 'non-existent' and the 'pre-measurement' as having existed in the past. There is no contradiction here because the states are perspective dependent.
Quoting noAxioms
Yeah, sorry! You are correct :smile:
Quoting noAxioms
Ok, I see what you mean. But since yesterday, I am doubting that RQM is really consistent. But maybe the situation is the same as in the case of SR if one does not accept the 'block universe' (well, to be honest, I am not completely sure that even SR without the 'block universe' is really consistent...).
[But if one accepts some sort of panpsychism it is a mind-idealism :lol: Well, I believe that RQM and Process Philosophy can fit nicely together.]
Quoting noAxioms
Yeah in RQM, 'you' according to yourself and 'you' according to the table lamp are different. The table lamp according to itself is different from the table lamp according to you.
Quoting noAxioms
I think I see what you are getting at*. But I do not believe that this really solves the problem that I have in mind. Unless you specify a duration for the events.
Quoting noAxioms
This is not true, however, for CI. In CI, only a specific class of entities can be considered an observer (which kind of 'entity' is subject to interpretation). At the same time, however, Relativity seems to imply something analogous.
Quoting noAxioms
From the perspective of the 'pre-measurement observer' if no 'selection' is made, then I'd agree it is deterministic. But if you consider the perspective of each 'post-measurement observer', the situation changes. For the 'Alice that observed decay' attributing the status of either 'existence' or 'non-existence' to the 'Alice that observed no decay' is meaningless (and vice versa). So, in this sense maybe we should understand the term 'agnostic'.
(sorry for the late edit!)
[quote=Tim Maudlin]What about “objective reality” and “Wigner’s friend” and what-not? Well, the non-local theories that we have—pilot wave theories such as Bohm’s theory, objective collapse theories such as the Ghirardi-Rimini-Weber theory, and the Many Worlds theory of Hugh Everett—all postulate a single objective reality. [/quote]
Qualified with the following caveat:
Likewise Sean Carroll:
Which again begs the question of ‘what is objective’? How does a 'many worlds interpretation' posit a 'single objective reality'? Because if there are indeed infinite numbers of 'other worlds' or parallel dimensions, or if the universe 'splits' into different universes as is implicit in this 'meta-theory', then each of these universes are inaccessible from any other one. So how could they be considered ‘objective' when they can't even be known?
In a sense, the many-worlds hypothesis is a reductio ad absurdum of the notion of objective reality, because everything possible happens in at least one world, so there is no objective fact of the matter about whether any given event happens. What is objective is the god's eye view of all the worlds. But only gods can have that view.
What I said. And the casual way in which this is accepted as an explanation or rationalisation of the 'observer problem' strikes me as either disingenuous or naive. In any case, in no way does it resolve the basic issue of ultimate objectivity.
So it's an objective fact that everything possible is actually happening, at every moment of time, in the many-worlds hypothesis?
Potential energy is the potential to get work done, actual energy is the getting of work done; in any actual doing of work some of the energy is "wasted" and discharged as heat (heat energy which of course itself does other "work").
Think of a nuclear bomb; when it is just sitting there the energy which it "contains" may be activated via a chain reaction of fission is potential, and if the chain reaction is initiated then it will be released as actual energy which will bring about changes in the environment.
You're looking at only half of the picture, and thus failing to see the distinction between potential and actual. If this doesn't clear up your misunderstanding I don't know what else I could add.
Why would you say that?
That's incorrect, energy is the capacity to do work, it is not "the getting of work done". Flowing water for example has a certain amount of kinetic energy, as the capacity to turn a turbine etc. (do work). The energy is there whether or not the turbine is. If we build a dam, the water is held up from flowing, and that held up water has potential energy. Release the water through the flood gate and the potential energy turns to kinetic energy, the capacity to do work. Run it through the turbine and the kinetic energy of the flowing water is transformed into electrical energy (the capacity to do work). Energy is not the getting done of work.
(I've often referred to the Peter Byrne article, The Many Worlds of Hugh Everett, which is an abstract of his book of that name.
Everett did eventually meet with Bohr:
Instead Everett became part of the team whose task it was to figure out the optimal re-entry trajectories for ICBMs. (A difficult and emotionally withdrawn figure, he died young, leaving instructions for his ashes to be put out with the trash.)
Interestingly, the very last line in that essay is a quote from the unedited version of his dissertation:
Which is rather a pregnant phrase, I think.)
I suppose that depends on what one believes that issue to be. It's not an issue I am familiar with - at least not by that name.
Personally, I wouldn't say that, because I think the useful everyday word 'objective' loses its meaning when it is deployed in a philosophical context. But it seems to me that the statement is at least as reasonable as most other statements in which I can recall people using 'objective' in a philosophical context.
Are 'different versions of yourself' objectively real? I suggest that as soon as you say 'that depends', then the argument is lost.
The problem here I think is that there is no real principle whereby we can say that there is "only one which we can ever be aware of". That's what destroys objectivity in many-worlds, that we are aware of only "one world" is an illusion.
Quoting Janus
I've read a heck of a lot about it already, and submitted an extensively researched paper in university on the development of the concept of energy. All you need to do is google "energy" to see that "energy" is the capacity to do work, not "work getting done". I described very clearly the difference between potential energy and kinetic energy in my last post. I conclude that you're hopelessly lost, and helplessly refusing to acknowledge you misunderstanding.
I should reword. Yes, the odds are almost a certainty from the beginning that the unicorn will occur in some world, but I meant given a single measurement giving one random collapse. You only get one try. From the beginning of the universe, there's not even a planet on which a single measurement might hope to collapse a unicorn. I would presume an existing Earth with life already on it would raise the odds of a unicorn considerably from the odds from a blank slate.
Such statements are why I balk at A-series wordings like that. Under RQM, both post-measurement Alici (the plural is so stupid I am compelled to use it) consider the pre-measurement Alice to be part of their history. To pre-measurement Alice, the other two do not exist. The future is unmeasurable and thus doesn't exist to that instance of Alice. So there's no 'will-exist' except to indicate that certain future events (post-measurement Alici) consider certain past events to exist and others (like the one where Alice didn't measure it at all) to not exist.
I agree about the lack of contradiction. I know what you're saying and agree with it, but I don't like the A-series wording of it. 'Will exist' makes it sound like existence is something objective that occurs, and not the relation to something. The future Alici cannot exist ever to the pre-measurement one because there is no 'ever' to that version. She's an event, and events don't move into the future.
I've been on the RQM wagon for a while and I've learned to be careful about how things are worded.
SR is also quite consistent for the same reason: different orderings of events are not contradictory if they're from different perspectives. Meta for instance commits this fallacy by deliberately omitting the perspective references:
The law of non-contradiction says there is only a contradiction if the thing is both true and false in the same way, but it is not the same way here. That part always gets omitted. Nowhere does SR say that that two events are simultaneous, and also not simultaneous. There is in fact no assessment of simultaneity at all between two space-like separated events without a frame reference.
One need not accept a block model of the universe (spacetime) for SR to work. It is more complicated, but it works fine in a space-with-flowing-time model. We digress.
I think that works as well, yes. I seem to have a pretty weak grasp on the panpsychism idea. It doesn't seem to have a consistent interpretation from one person to the next.
Well, 'I', from an RQM standpoint, am an event, despite my whole me being an abstract worldline. So in that event sense, I don't exist to myself, I only have memory of some past consistent state. From a pure event perspective, any two events (the table lamp and I at two specific moments) cannot exist in relation to each other. Neither exists to the other if the two events are space-like separated, and only one might exist to the other if not. It isn't paradoxical since no such mutual existence relation is ever posited.
All different events, so not comparing the same thing. There is no 'the lamp' any more than there is a 'me' making that decision. We're both a series of events, any of which can relate to other events. The fact that a certain event in the past is considered 'also me, yesterday' is an abstract designation I make. There is nothing physical that connects my current state to that past state as opposed to any other random arrangement of matter. Identity is abstract, not real. There are plenty of philosophical arguments that demonstrate this.
I'm sorry, but what was the problem? I thought the lack of duration was exactly what solved the problem.
Not even familiar with the term Process Philosophy, but perhaps I am discussing it anyway. I'm a poet and don't even know it.
OK, I can buy that.
How does MWI handle probabilities in its branching of worlds? For instance if there are two possibilities (+ or -) and each has a probability of 50%, it makes sense to say that two separate branches result.
But what if the probability of + is 51% and the probability of - is 49%? In order to preserve probabilities we would need 100 worlds! (51 +, and 49 -).
It seems rather contrived to me that the number of branches would depend on probabilities like that. Or are some worlds considered to be more "probable" than others? (Which I understand to be a question that might not make sense, because all worlds are considered to be equally "real")
I meant to tag you too in my question but couldn't find a way to do it. I'm still learning the idiosyncrasies of the site.
I meant boundless.
[quote=Tegmark]Everett does not postulate that at certain magic instances, the the world undergoes
some sort of metaphysical “split” into two branches that subsequently never interact.
...
According to the MWI, there is, was and always will be only one wavefunction, and only decoherence calculations, not postulates, can tell us when it is a good approximation to treat two terms as non-interacting.[/quote]
So there are not separate worlds where one exists more than the other. It is all one thing in Hilbert space.
I think it's important too to differentiate between Everett's Interpretation and MWI, as first put forth by DeWitt. Everett's definition of "real" was anything that could affect the results of a future experiment. Everett was also pretty adamant that separate branches could affect one another; the separate branches, according to Everett's (relative State Formulation) https://plato.stanford.edu/entries/qm-everett/interpretation, can and do interact.
I'm not sure why, in MWI, the separate branches are said to not be able to interact with one another. Especially if, as you say, it is all one thing in Hilbert space.
Thanks for the very informative answer, again. I hope I'll can answer tomorrow (if not, I will on Saturday).
I am still confused about regarding 'observers' (as defined in RQM) as 'events' without duration but considering systems as abstractions denoting a stream of events is very interesting (note that I do not regard my confusion as an objection :smile: ...).
(sorry again for the edit... I misread a part of your answer)
Hi,
Quoting i aM
In MWI, you need an additional axiom AFAIK to include the Born Rule. I know that there have been some attempts to derive the Born Rule but I do not know if any of these attempts are regarded to be satisfactory. Note that some deny that such a derivation is necessary (I disagree, though - FWIW).
Quoting i aM
In MWI, the branches can interact. But the likelihood of this interaction is negligible. (By the way, this is another really weird feature of MWI...)
"In MWI, the branches can interact. But the likelihood of this interaction is negligible. (By the way, this is another really weird feature of MWI...)"
I'm not sure how weird it is. As an analogy in the classical world suppose that I forget to blow out a candle before I go to sleep and the house burns down. I'll experience regret because there is some world out there where I did not forget to blow out the candle and the house did not burn down.
That alternative world will have a causal effect on my world in which the house DID burn down. I will be more careful in the future and make sure to blow out candles before I go to sleep (or not light them in the first place!). If no alternative world in which the house did not burn down existed, it would never occur to me to be more careful in the future.
I'm not sure how to put that analogy in direct terms of the wave function, but it allows me to see the possibility of different branches interacting. A possibility which didn't actually occur in my current branch could have a causal effect going forward.
But it is implicit in the formulation. 'Many-worlds implies that all possible alternate histories and futures are real, each representing an actual "world" (or "universe"). In layman's terms, the hypothesis states there is a very large—perhaps infinite[2]—number of universes, and everything that could possibly have happened in our past, but did not, has occurred in the past of some other universe or universes. ...Before many-worlds, reality had always been viewed as a single unfolding history. Many-worlds, however, views historical reality as a many-branched tree, wherein every possible quantum outcome is realised.' (Wiki) Also the Scientific American article on Everett notes that Wheeler advised him to redact passages about 'splitting' from his thesis before it was submitted. The 'many' in 'many worlds' really means 'many'.
For Everett "real" meant "something that could affect the results of an experiment"; and, Everett was pretty clear that these different branches do interact.
I googled and got this first:
"William Rankine (1820–1872) Scotland: first mention of "potential energy" as distinguished from "actual energy". Since kinetic energy was the first form identified, he attached a modifier to the form of energy he discovered. Thus the unfortunate notion that kinetic energy is actual energy and potential energy is energy that has the potential to be actual energy. Energy is energy. No form of energy is any more or less "actual" than any other. The unfortunate terminology is due to Aristotle who applied the dichotomous terms potentiality and actuality to several disciplines — motion (Physics, Physica, ?? ??????), causality (Metaphysics, Metaphysica, ?? ???? ?? ??????), ethics (Nicomachean Ethics, Ethica Nicomachea, ????? ??????????), and physiology (On the Soul, De Anima, ???? ?????)."
From here: https://physics.info/energy/
After reading the above I think we may be talking about different senses of 'actual". I agree with what is expressed in the above passage: that all energy, both energy in potential, as in the example of a nuclear weapon that has not done any work yet, and the actual energy which is released when the weapon is activated are equally real, that is equally actual in that sense. I was using 'actual' in the sense of acting or actualizing.
My point is simply that if you want to say that energy has an actual potential to get things done, then there must be an activation or actualization of that energy when it gets things done. It is the distinction between 'energy at rest' and energy at work.
If I am mistaken in this view I am open to being corrected, but it will need to be something better than
Quoting Metaphysician Undercover
From Sabine Hossenfelder
(I still go with Copenhagen.)
If you are objectively real in your world, then why not the alternative versions of you in their worlds? I am still not seeing what the objection is.
Do you believe it is objectively the case that there are other worlds? You see, I would have thought that if it were objectively the case, then there would be no room for disagreement. But plenty of people disagree with Everett's meta-theory. Therefore, it's a matter of interpretation, and if it's a matter of interpretation, then it's not objective.
I believe that it is objectively the case that either there are other worlds or there are not. No interpretation is involved in what is objectively the case, so I still can't understand your objection. Of course some people will argue that it is not even objectively the case that there is this world. I don't see any difference in principle between the two cases, although there is the epistemological difference that this world is experienced by us. But if there are other versions of us in other worlds, then for them our world would be an "other world".
Then why doesn't everyone agree with the many-worlds hypothesis? According to you, there's no scope for disagreement.
It is usually thought of like that, but it doesn't have to be. Another version is that there is no splitting, but just an infinite number of parallel worlds and for each world W and time t there are infinitely many that are identical to W up to time t, but that differ in some respect after t, which could be because of an observation at that time having a different outcome.
Under that perspective, the 'splitting' is epistemic rather than ontological. We were always in the world in which the measured spin on a particle at midday on 20/4/19 was going to be Up and not the one in which it would be Down, but we didn't know which one we were in until 20/4/19.
Since the differences between this setup and the branching one are by definition unobservable, it is moot which one we believe (if we believe either - I don't agree with the suggestion somewhere above that one has to believe some form of many-worlds).
QFT provides a physical mechanism (mathematically specified) for what is observed that is predictive and testable. It's been extremely successful and many physicists, including Feynman, have won nobel prizes for their work on it.
Regarding non-physical hypotheses, it's not that scientists don't think so. It's that without a physical mechanism, there's nothing to test. One person's speculation is as valid as anyone else's. So a physical mechanism provides a constraint on speculation.
Quoting Metaphysician Undercover
Per the LNC, there is also "and in the same sense". In this case, the reference frames differ. Do you reject special relativity?
Quoting Metaphysician Undercover
The issue was whether fields are real in the ontology of QFT which Carroll's comments confirm.
My reading of RQM (and Rovelli) is that RQM doesn't accept the existence of more than one Alice (or, at least, need not). Per RQM, all that is known to Wigner is that Wigner's friend has made a measurement and that the value is (physically) indefinite for Wigner until it is localized in his reference frame.
Sure, absolutely. I'm not querying whether fields are real or the effectiveness of field theory. The point I was taking issue with was 'Particles are what we see. Fields are what reality is made of.'
The problem is that to say that the ordering is dependent on perspective means that there is no objective truth with respect to the order. Therefore the two propositions "A is prior to B", and "A is not prior to B" may be both true, and this is contradiction That you blame this contradiction on "different perspectives" does not make the contradiction disappear, it's just a sort of rationalization. You're just saying that this contradiction is acceptable, kind of like if I said that the best dinner is beef steak and you said that the best dinner is pork chop, we'd accept this contradiction because it's a matter of perspective. But it doesn't make the contradiction go away
Quoting Janus
It's very simple, energy is the capacity to do work. As a capacity it is a potential. We look at things and attribute "energy" to these things, and energy is a potential which the things have. If you want to say that this potential is "actual", in the sense of being real, that's fine, but it's really just conceptual, it's a value we assign to the thing.
Now, according to the law of conservation of energy, it is not correct to say that the energy ever gets actualized. When the energy "gets things done", it is just transformed from one form to another, remaining as energy, and therefore remaining as potential. Energy is always potential, and never gets actualized because that potential (the capacity to do work) is always conserved in the temporal continuity of existence. That's why some people get hooked on the idea of perpetual motion. This is just the way that we've come to describe motion, we assign it a value, energy, it has proven to be a very useful way.
[Quoting Andrew M
"In the same sense" means using the words in the same way. It has nothing to do with reference frames unless "temporal order" has a different meaning from one reference frame to the next.
Quoting Andrew M
No, the issue was whether or not the thing modeled as "a field" has the nature of potential or not. As I explained to Janus, energy is modeled as potential, but this does not mean that energy is not real. That fields are modeled as potential does not mean that they are not real. However, just like in the example of "energy", potential is the property of something which is actual. So a field would be the property of something because there needs to be something actual which has that potential For example an electromagnetic field is a property of an object.
"This confirms what I said earlier about the non-independence of detectors in Aspect-type experiments. The detector wave functions are related and constrained by a transtemporal symmetry extending through all space-time. So, entanglement does not involve action at a distance, but transtemporal symmetry.?"
... and if the settings on one of the detectors is changed randomly, before a particle has reached it, but not soon enough for any subluminal signal to have reached the other detector...what? The "randomness" used to change the setting on the detector wasn't really "random", but part of the "transtemporal symmetry"?
I understand that energy is conserved, and that it does always "remain as energy" But, why would it not be correct to say that potential energy is actualized? If, as in your example of water held in a dam that is not doing any work, the water is released and does the work of turning the turbine, should be not speak of the energy potential being actualized? You acknowledge that energy may be 'transformed from one form to another". The example of the nuclear weapon, or even better, the fusion reactor makes this even clearer. Matter contains enormous potential energy which can only be actualized via certain technologies.
And to repeat my earlier point; it would seem to make little sense to say that energy is the potential to do work, and yet energy is not capable of doing any actual work. Yet you seem to want to say this, and have as yet, given no argument or explanation for why you want to say it.
When we change the macroscopic setting of a detector, the microscopic details of its multi-electron wave function (our ignorance of which we call "randomness") remain constrained by transtemporal symmetry -- and that wavefunction interacts with the incident quanta to produce the detection event.
That's just the way it's been conceptualized, energy is a property of something moving, just like momentum, and motion does not just disappear, or become something other than motion, as described by Newton's laws. So modern physics does not employ the ancient concept of potential being actualized in the case of the concept energy. There is potential (energy), and this potential remains constant as it takes many different forms.
"Potential" in the sense of "potential being actualized", really has only a philosophical meaning, because its ontology is considered as dubious. Here, "potential" means a possibility rather than a capacity (or power), as in energy. When there are numerous possibilities, and one is actualized, we might say that this specific potential is actualized. But to bring those possibilities into reality, rather than just logical possibilities requires a denial of causal determinism. This is why we need to keep the "potential of energy, as capacity or power, separate from the "potential" of "actualizing a potential", because physics does not have the ontological principles to relate these two. Notice that the former refers to "potential" in a general or universal sense, and the latter requires a particular "potential", so category mistake could occur.
Quoting Janus
This is that ontological gap which we have no principles to form a bridge. To do "actual work" is just a matter of perspective. When is the work actually done, when the water turns the turbine, when the electricity is transmitted through the wires, when it runs the compressor on my fridge, when the cold keeps my food fresh? So, we keep the potential of energy (the capacity to do work) as completely separate from any work actually being done, in order that the conservation principles are maintained. It is important to understand that the concept of "energy" was produced as a conservation principle to compete with Newton's conservation of momentum. The reason why the thing which is conserved, as time passes, has the nature of "potential", goes back to Aristotle's concept of matter, as the thing which does not change as time passes, and matter is designated as potential. So the conceptual structure was already there, by which potential remains constant as time passes.
In the context of QM, consider that the wave-function is analogous to the potential of energy (capacity to work). It must remain constant, continuous, as time passes, according to conservation laws. Then there is a so-called collapse of the wave-function, and this is analogous to actual work being done, a potential being actualized. We cannot relate these two because "actual work being done" would remove potential and violate the conservation law. So we have a gap between the potential, which must always remain constant according to conservation laws, and the "actualizing of a potential", which would remove some of that potential placing it into a different category of "actual", thus violating the conservation law.
Are you saying that by randomly changing the detector settings of one detector the other detector's multi-electron wave function is likewise changed through transtemporal symmetry?
Well, more or less I always understood RQM in that way! :smile: ... After my dialogue with noAxioms, I am not sure about it. In fact, the 'relativization' of existence makes perfect sense in RQM. For each 'Alice' (each 'Wigner's friend') the other(s) cannot be said to 'exist'. But unless one adds a selection postulate, I believe that before the measurement 'Alice'/'Wigner's friend' can safely say that all 'Alice-s'/'Wigner's friends' will remember 'her'/'him'. What do you think?
Quoting noAxioms
Ok, I agree!
Quoting noAxioms
I see what you mean, but 'pre-measurement Alice' can predict that 'she' will be 'remembered' by both 'post-measurement Alici'. This is not too very different from what MWI says. According to this view, MWI and RQM would be similar (not the same, but similar...).
Quoting noAxioms
OK! That's fine. Note however that if one accepts presentism the past and the future do not 'exist'. Only the present does. It is true that the past can be said to 'exist' in the sense that there are data, in the present, about it. At the same time, it is also true that it is possible to make predictions about the future.
So, it seems to me that the relation between the future Alici and the past Alice is more or less the same of the reverse. So, before the experiment, Alice can predict the 'appearance' of the future Alici. So, for her, it seems legitimate to say that a 'split' happens.
Quoting noAxioms
Ok, I agree. But my point was another. If you say that 'your' present exist (the 't=0' 3D hypersurface), then the Andromeda Paradox is unavoidable. The answer to this objection is to not regard what is outside the light cone in the same way of what is inside from an ontological point of view. On the other hand, it seems intuitive to accept the 'existence' of the present (e.g. I will observe the present state of the Sun at t=8 minutes). If you follow your intuition, you end up with the Andromeda Paradox. I am not absolutely certain that the intuition is wrong, though (if not, dBB supporters would be very happy).
Quoting noAxioms
Well, this seems also the implication of presentism plus SR/GR.
Quoting noAxioms
I sort of agree with this (but the reasons are not exactly the same...as I said I have a different view about mind) - it seems that there is some kind continuity without, however, a persisting identity (but we are digressing maybe...). This is not IMO however a complete denial of the existence of 'individuality' (and 'identity' in some sense).
(But I am not sure about this :smile: we are probably digressing here)
Quoting noAxioms
Yeah, it seems so.
Quoting noAxioms
Well, I do not know very much about it. It is a kind of presentist ontology. 'Objects' are not regarded as substantial entities but rather as patterns in succession of events. On the other hand, existence is not defined in a relational way.
Quoting noAxioms
Yeah, there are a lot of different versions of it. The parallelist variety, for instance, holds that everything has both a physical and a 'mental' aspect. The more complex an entity is, the more complex are both its physical and mental sides. In other words, mind and matter are like two sides of the same coin. But this is off-topic :sad:
...
Quoting i aM
But you can explain regret in that way only if you accept the concept of parallel universes, i.e. if you accept the idea that whatever is possible, happens which is precisely what says MWI.
Honestly, I do not find any compelling reason to accept the idea of parallel universes/branches etc.
I'm just giving a classical-world example of how a "branch" consisting of an event which did not occur in my "branch" (me blowing out the candle) could conceivably have a causal effect on the "branch" I inhabit going forward (me being more careful with candles).
We think about possible worlds that did not occur all the time, and those possible worlds which did not occur have causal effects. That is one way that we learn from mistakes. If there were no possible worlds to compare our actual world to, there would be no incentive to ever change behavior, for instance. It probably wouldn't occur to us to change behavior.
Yeah, sorry. I was a bit flippant.
The point is that in your example the interaction would give you some information of the other world(s). In MWI, you would observe superposition due to the interference of the branches (which would be very weird).
The fact we do not observe superposition is explained in MWI using decoherence, which suppresses the interference (well, technically, it renders it negligible...).
Without interaction, there would be no interference. Seems a view that asserts lack of interaction can be falsified. I suppose they get around that by saying that superposition states are not different worlds interacting, but rather just one in that state, to be metaphysically separated at measurement time. There are experiments that demonstrate otherwise.
Please excuse my ignorance. I have done searches for "transtemporal symmetry" and didn't find anything, other than items written by you, in this thread.
In a Bell Inequality experiment, when one of the detectors (Alice's?) is "randomly" altered, after entangled "particles" have left the source, is the reading ultimately registered at the altered detector changed, or does it stay the same as if it hadn't been altered at all, because of this transtemporal symmetry? Or is it that the other detector (Bob's?) somehow recognizes that Alice's detector has been altered and for this reason registers a reading in correlation with Alice's reading.
I recognize that this question is in some fashion a reiteration of my previous question, but I didn't quite grasp your answer. Sorry.
idk, by my understanding decoherence would render interaction between specific separate branches highly improbable. But because there are SO MANY separate branches, it would happen regularly. Sorta like what happens with quantum tunneling.
Exactly so. That's why it is called the theory of relativity and not the theory of objectivity. It's only a problem if you add that additional premise as you are doing.
I didn't really understand most of what you wrote, so I will just try to focus on this passage. What you seem to be ignoring is entropy; which is the continual dissipation of the capacity of energy to do any work, which in theory culminates in so-called 'heat death' the total absence of any potential for energy to do any work. Remember that matter and energy are equivalents, and the form of energy only obtains provided there are differentials in potential which allow energy to "flow'.
My argument has been based on the idea that potential energy consists in virtue of local differentials in potential, and that actual energy consists in the flows that occur. Energy is not lost insofar as new sets of different potentials are always coming into being, but the whole process, according to the second law of thermodynamics, consists in a gradual 'winding down' of differences of potential, and thus a diminishing of potential energy as well as a diminishing of actual energy flows, and consequently a diminishing of work done.
The control typically exercised over detectors in EPRB/Aspect type experiments is to change their orientation. If we change the orientation, then, of course the measured spin will be up or down the new orientation, not the old one.
Still, changing the orientation does not exert control over the details of the detector's electron wave function. The details will be controlled, in part, by the exchange principle and resulting constraints.
Alice's observations can inform her of conditions at Bob's location. If she performs her obseervation, she is informed, but if she does not, she is not informed.
How could an experiment at Alice's location inform us of conditions at Bob's location? Before I try to answer this, it is important to note that it does. Once Alice has measured spin up, she knows that conditions at Bob's location are such that he will measure spin down. Further, it does not matter if she learns of the conditions at Bob's space-time location in a reference frame where she learns of it before Bob does his measurement, or after. All that is important is that an observation at Alice's space-time location can inform us of conditions at Bob's.
I am suggesting that the reason Alice's observation informs her of conditions at Bob's location is symmetry. If we lived in a model world in which Bob's observations must mirror Alice's, then Alice would be able to predict Bob's results from hers without a hint of non-locality. The actual case is more complex, but the principle is the same.
Adding the premise doesn't make it into a problem, it's the thought that there ought to be an objective reality which makes it into a problem. If you don't mind an ontology with no objective reality, then there's no problem.
Quoting Janus
No, entropy is something completely different. Energy is defined as the capacity to do work. Entropy cannot rob energy of this unless it left energy as something other than energy. And entropy does not violate conservation laws.
This may help you understand what I am saying:
There is yet another way of expressing the second law of thermodynamics. This version relates to a concept called entropy. By examining it, we shall see that the directions associated with the second law—heat transfer from hot to cold, for example—are related to the tendency in nature for systems to become disordered and for less energy to be available for use as work. The entropy of a system can in fact be shown to be a measure of its disorder and of the unavailability of energy to do work.
From here: https://opentextbc.ca/physicstestbook2/chapter/entropy-and-the-second-law-of-thermodynamics-disorder-and-the-unavailability-of-energy/
That certain energy is not available to a human being with the desire to use energy, does not mean that this energy is no longer the capacity to do work. That would be contradiction.
You are mixing together, the definition of energy (the capacity to do work), with the relative condition of "available". Whether or not the energy is available to us has no impact on whether or not it is the capacity to do work. Energy on the other side of the world is not available to me, yet it is still the capacity to do work. Here's a quote from you referenced article:
"Recall that the simple definition of energy is the ability to do work. Entropy is a measure of how much energy is not available to do work. Although all forms of energy are interconvertible, and all can be used to do work, it is not always possible, even in principle, to convert the entire available energy into work. That unavailable energy is of interest in thermodynamics, because the field of thermodynamics arose from efforts to convert heat to work."
Entropy has no affect on energy's capacity to do work. The condition "available" just reflects the limits of the system used to harness the energy. Various different ways of harnessing energy (converting it from one form to another in a controlled manner), have differing degrees of efficiency. There is no such thing as one hundred per cent efficiency or else we'd have perpetual motion. The fact that some of the energy is lost into unharnessed forms does not mean that it is not energy. When a system has 85 per cent efficiency, the remaining 15 per cent is still the capacity to do work (energy), despite the fact that it is unavailable, it has just slipped into unharnessed areas because of the limitations of the system..
:up:
Well, that's another good argument IMO against the view that decoherence is enough to solve the measurement problem (even in MWI).
So what Carroll means is that fields are fundamental and particles (and everyday things generally) emerge from the interaction of those underlying fields.
Or, as Wikipedia puts it, "QFT treats particles as excited states (also called quanta) of their underlying fields, which are—in a sense—more fundamental than the basic particles."
The truth of a statement depends on its reference in the world. For example, when it is noon in London, the statement "It is noon" will be true for London observers while false for Sydney observers.
Now consider the train-and-platform scenario (including the two traincar pictures). Per special relativity, the statement "The light reached the front and back of the traincar simultaneously" is true for an observer on the moving traincar while false for an observer on the train platform.
As with the noon example, there is no contradiction when the statement is indexed to an observer (or, equivalentally here, a reference frame).
Quoting Metaphysician Undercover
And that's not the way it's modeled in QFT. In QFT, objects (including particles) emerge from the interactions of more fundamental fields. That is, the existence of the object is dependent on the existence of the fields.
I agree. But that interpretation of RQM would only be a semantic difference from MWI, not a substantial one. My understanding is that RQM is a more abstract interpretation that captures what Rovelli considers to be the key elements of QM and nothing more. For example in his RQM paper he says, "From the point of view discussed here, Bohr’s interpretation, consistent histories interpretations, as well as the many worlds interpretation, are all correct." That is, they all share those key elements (albeit they commit to further things as well that differentiates them from each other, such as many worlds versus a single world).
Quoting boundless
I'm not sure I see the issue you're raising here. But I would agree that post-measurement, Wigner's friend (or friends on a MWI-style reading) would have a memory of themselves prior to measurement.
Regarding a selection postulate for RQM, I think it's just unknown and RQM doesn't commit to anything specific.
‘in a sense’ ;-)
When it comes to this matter, that phrase carries a lot of weight.
Right, we are talking about the temporal ordering of two events, when the light reaches the front of the traincar, and when the light reaches the back. Special relativity allows for contradiction in the ordering of these events. The "noon" example is just a name given to one event, so it's not a proper analogy. What I call "noon" you might call "midnight", and it's just a matter of translation, we are still talking about the same time under different names. Calling the same thing by different names is a matter of identity, not contradiction But in the case of special relativity it is a matter of predication. One event is predicated as prior in relation to the other, and to allow the opposite as well, is contradiction. Noon in Sydney is prior to noon of the same day in London, no matter what your reference is, and.there is no contradiction
Quoting Andrew M
Right, that's why I'm pointing this out as a problem with QFT. The way that fields are modeled, they cannot have reality unless the field is the property of an object. Remove the electromagnetic field from the object which it is a property of, and it's just a piece of theory. If QFT does not model its fields as properties of some object, or objects, they are theories without reality. Physics does not have the principles required to model free standing fields, from which particular existence arises, the fields are dependent on the prior existence of objects. That dependence needs to be included in the models.
Nit-pick: you think that maths, a human invention, is more fundamental than the stuff of which the universe is built? I don't think so.
:up: I completely agree!
Quoting boundless
Quoting Andrew M
Well, I worded it badly. I simply meant that without the selection postulate, it seems that RQM implies the splitting.
Anyway, I agree with you. RQM seems simply silent on this point.
I thought about that and it seems that post-measurement Alice has the same relationship to pre-measurement Alice as the relationship to post-measurement Bob, which is a superpostition of multiple unmeasured states. The perspectives are quite different but the relationships are essentially identical.
Therefore the future does exist to Alice, just not a specific state. The cat exists to Bob, even when in superposition of dead and alive.
This hypersurface exists. So does this different hypersurface. That's just two different things, not a paradox.
Totally agree. Two observers at the same place but different frames might disagree about what is going on at Andromeda, but they'll agree entirely about what has been measured. The light cone from that location is a frame independent thing.
Interesting corollary for a presentist, who by definition cannot observe any existing thing. In 8 minutes, the thing I observe will not be the present state of the sun. It will be an observation of something nonexistent.
Agree that what I said depends on my personal choice for philosophy of mind. Some interpretations do give identities to things. Mine just happens not to.
Not sure how you combine your mind interpretation with your QM one. Does the pre-Alice ontologically become one of the post-measurement Alici to the exclusion of the others because the mind-identity can only follow one of them? That's a very different QM interpretation.
I consider it something discovered, not invented. If invented, pi would not be the same value in another world. OK, odds are the aliens don't express the value in base 10. That base is definitely a human invention.
:up:
Quoting boundless
Maybe it's embarrassed. :yikes:
Quoting noAxioms
Ok! Agreed! :smile:
Quoting noAxioms
Well, I think I see where you are getting at but I am not sure you can really avoid the paradox if you say that all events in the hyper surface are in a definite state. I am not saying you are wrong, I just do not know.
Quoting noAxioms
Yes! In Relativity the ordering of events in every light cone is an invariant (unless one accepts tachyons or any FTL influence).
Quoting noAxioms
Yep! Presentism is somewhat problematic in Relativity. I would say that 'global presentism' is simply incompatible with relativity of simultaneity. Maybe a form of 'local presentism' can be saved but it is surely counter-intuitive (I personally lean towards some form of presentism and I admit that I am troubled by this).
Quoting noAxioms
I see!
Quoting noAxioms
Well, note that I do not currently accept RQM as 'my interpretation'. But it is one of my favorites.
Anyway, I do not believe that the mind is something immutable. So, for me, it is more like a 'stream of consciousnesses'. When I said that, in some sense, 'individuality' is preserved I meant that these 'streams' or 'continuums' are distinguishable. Yet, I do not believe that there is 'something' that 'persists' in the process (a 'substance') - in other words, I do not believe in a substantial identity.
Personally, I do not like the idea of the 'branching'/'splitting' - that's why I am insisting with the 'selection' postulate. On the other hand, I think that this kind of position about the mind is logically consistent with the 'branching' idea. Furthermore, I do not believe that the 'splitting' is a necessary feature of RQM. Before this discussion, I believed that there was a selection postulate in RQM. I now think that the theory is simply silent on it.
+ 1 :wink:
(More precisely, I believe that there is something in maths that is discovered. It cannot be totally invented)
Quoting Wayfarer
Well, possibly! :razz:
I can't answer that, I don't know the heat death scenario
I would have thought that one sense was enough. How many senses are you requiring? ;-)
Quoting Metaphysician Undercover
No, the relative ordering of events necessarily follows from the invariant speed of light in different reference frames. Since the traincar is moving away from the train platform then the light emitted from the middle of the traincar, travelling at velocity c in the train-platform observer's reference frame, will take longer to reach the front of the traincar that is moving away from it than the back of the traincar that is moving toward it.
Quoting boundless
I think splitting might be implied only because Copenhagen and Consistent Histories don't specify any physical mechanism, whereas MWI does. But since some other unknown physical mechanism can't be ruled out at this point, then being silent seems a reasonable option (and treating interference as unactualized potential).
Can you "discover" something that is non-physical? Mathematics is not part of the scientific space-time universe, except trivially. How could you "discover" maths when there's nothing to come upon, and say "Oo look, that seems handy!" Maths is a collection of ideas; I think its emergence into our awareness has surely to be our invention.
As for pi, as soon as you invent numbers, and all the stuff that goes with them, you notice pi as soon as you start considering circles. Bearing in mind that circles - not just things that are roughly circular - occur rarely if at all in the real world....
Well, yeah, this would explain the silence :smile:
Another curiosity: what do you think about the problem of interfering branches in MWI (and maybe in RQM if no selection mechanism is accepted)? As 'I aM' (see here) noted it is true that due to the decoherence the interference term becomes very small. Yet, rigorously, it is not exactly 'zero'. Given the fact that decoherence occurs a lot of times, it seems possible that - sooner or later - interference will be observed. In other words, it seems that decoherence gives (multiple but) definite outcomes only 'for all practical purposes' (I remember to have read that decoherence is said to solve the measurement problem 'only for all practical purposes' but I am not sure that this the reason why it is said so...).
Right, that's the point. The assumption that the speed of light is invariant (which is essential to special relativity), is what produces these contradictions.
It's not a cop out. You can't just through phrases like "heat death" at me, and ask me a complex question concerning the event referred to, without providing me with some description as to what these terms refer to. I personally have no belief in "heat death", I think it's a misguided speculation. So your question is like asking an atheist a complex question about the nature of God. It's pointless.
I assume that there will be no human beings in existence at the "heat death". So if you interpret "the capacity to do work" as "the capacity to do work for human beings" (which is how you seem to interpret it, but not how the definition is intended to be interpreted in physics), then there would be no such energy at the time of the heat death, because there would be no human beings.
You don't seem to understand, all energy is "the capacity to do work" whether it's potential energy or kinetic energy.
So, as I said already, and as indicated in the quote I brought from your referenced article, at the so-called heat death there would still be energy, as the capacity to do work.
https://en.wikipedia.org/wiki/Heat_death_of_the_universe
https://en.wikipedia.org/wiki/Thermodynamic_free_energy
I told you, I don't believe in heat death. And I also told you that I think your description of it, as energy (which is by definition the capacity to do work), that is not available to do work, is contradictory. Why would I want to read up on this? It's like you're telling an atheist to go read some theology. What's the point?
David Wallace has a good discussion of this in his paper Decoherence and Ontology, or: How I Learned To Stop Worrying And Love FAPP.
As he puts it, decoherence gives us quasi-classical worlds (branches) but not actual classical worlds. Which means that decoherence can be treated as irreversible and the worlds as classical for all practical purposes. Nonetheless interference between branches continues to happen in accordance with quantum mechanics.
So the Wigner's friend thought experiment is a good example of this. For the friend, decoherence has occurred (i.e., the friend, measurement and lab have become entangled), but not for Wigner, who continues to detect interference and can, at least in principle, reverse the friend's measurement.
Whereas in the actual experiment of the OP, decoherence hasn't occurred since the photons involved haven't become entangled with their surrounding environment. Sean Carroll discusses this in his DailyNous essay on the experiment.
Quoting Metaphysician Undercover
OK. So do you claim that the light emitted from the middle of the moving traincar towards the front is travelling at c + v (where v is the velocity of the traincar) from the train-platform observer's reference frame?
I don't think that the movement of objects can be satisfactorily related to the movement of light, in the manner suggested by special relativity, because the relationship between the objects and the medium within which the light waves exist, has not been properly established.
So apart from rejecting Lorentz invariance (in favor of Galilean invariance?), I'm not clear on what your model is. When the light is emitted from the middle of the traincar, what do you think the observers on the traincar and train platform see?
I don't understand the question. They see the thing which is emitting the light, as emitting light.
I didn't say that. I said the set of events in a given light cone is frame independent. The ordering of those events is still quite frame dependent.
I have done an advocatus diaboli thread defending the compatibility of relativity and presentism, so I maintain that they're not incompatible. SR says that the preferred frame cannot be determined given the special case after which it is named. But inability to detect such a frame does not mean that there isn't a special one. Presentism doesn't even require it to be a inertial frame, and no presentist that knows their physics seems to assert that it corresponds to such a frame. The foliation is always bent, which has the interesting paradoxical implication that no two stationary observers are simultaneous in each other's inertial frames. I find that hilarious, but not paradoxical.
Do you think light reaches the front and the back of the traincars simultaneously for both observers? If so, then what is the speed of the light? Is it c for the traincar observer, but c + v for the train-platform observer? Or is it c for both of them? Or something else?
As I said, I don't think we have the principles required to precisely measure the various motions of objects in relation to the motions of light because we have not yet determined the relationship between objects and the medium in which the light waves exist.
This is why I resist describing RQM under presentist terms. If time is external to the structure that is the universe, then such selection is an objective act relative to this realm under which time exists, and it isn't really RQM anymore if such an objective action takes place.
With time being part of the structure, no event/state (something to which a relation can be made) 'flows' to a different event, necessitating such a selection. Thus there is no selection postulate.
This isn't an embarrassment, just an implication of a relative interpretation.
Obviously yes, your topic being a prime example.
I choose to interpret it otherwise.
Yet that is exactly how mathematical progress was always made. Nobody found it under a rock or through a telescope. Not even talking about mathematical models of the universe here. I'm just talking about pure mathematics like Calculus, imaginary numbers, 14 dimensional space, and octonions and such. These are not 'come upon', yet are discovered.
Exactly. We notice pi despite the complete absence of any actual circles in nature to measure. Figuring out pi to a lot of precision doesn't involve hunting down an ever closer physical approximation to a circle.
My definition is the same as the one on your referred site. The laws of thermodynamics came into existence following the defining of energy. So you're wrong, energy was understood prior to the second law, and therefore separately from the second law. You really just blabber on, demonstrating that you have absolutely no understanding of this subject
How does one approach the figuring out of pi?
What you are saying is like saying that oxidation is irrelevant to understanding fire, since fire was originally understood separately from oxidation. The annoying blabbering sound is emanating from you, not from me.
Then you don't have a model. Whereas special relativity is a self-consistent model that makes predictions that have been experimentally confirmed in numerous ways. See https://en.wikipedia.org/wiki/Tests_of_special_relativity
Well, consider the context. The idea of the atom was that it was a discrete indivisible point-particle - posited as the ultimate constituent of matter. I mean, ask the person in the street what the Universe is made of, and s/he will probably say 'atoms'. But as we have been discussing, it turns out the nature of the atom is actually rather ambiguous - particles that 'interfere with themselves' or that can appear as waves rather than particles at all. So it seems to me that substituting 'fields' for particles as a kind of ontological basis is a bit of a pea and thimble trick or sleight-of-hand. Which is not to question the efficacy of field theory as it obviously works. But we ought to remember that the same guy who won a Nobel for work in that very field is also famous for saying that 'ultimately nobody understands quantum mechanics.'
It seems like you did not read the quote I posted from your referred site:
That is from the site you referenced on "heat death". Notice, "the ability to do work" is the definition of energy, even today. Also, at the proposed "heat death" there is still energy, therefore the ability to do work. Speculators have simply taken some principles from thermodynamics, and have concluded in an extremely dubious way, that this capacity to do work (energy) becomes unavailable to do work through entropy, until the "proposed heat death" when all energy is unavailable. It is extremely dubious because that conclusion requires some completely unsubstantiated, and improbable premises, concerning the nature of time, human capacities to create systems, and the universe.
Quoting Andrew M
Right, we went through this already, in this very thread. The Michelson-Morley experiments failed to determine the relationship between the wave medium and physical objects, and special relativity gave what appeared to be a simple and satisfactory way around this problem. However, the problems of QM, and wave-particle duality ought to indicate to you that special relativity really is not satisfactory. Without understanding the relationship between objects and the wave medium, we cannot establish the relationship between the wave and the particle in wave-particle duality.
Notice, that to produce the conclusion that there is no wave medium, from the Michelson-Morley experiment, requires the premise that the medium is independent from physical objects. But the conclusions from QM indicate that the particles (physical objects) are a feature of the wave function. So QM actually disproves the premise required to say that the Michelson-Morley experiment demonstrates the non-existence of the medium. Now we need to go back and determine the relationship between the particle (object) and the wave medium, to understand wave-particle duality. But this will never happen if physicists adhere to special relativity and deny that there is a medium.
You're mixing up "medium" with the QM wavefunction. That's a linguistic mistake, which is understandable because the word "wave" is in there.
You also confuse the physical property of "energy", which can really only be defined in mathematical terms in specific contexts with what you say is its linguistic definition, "the ability to do work".
But even linguistically, that is still not quite right. Here is the first sentence from the Wikipedia article on "energy":
"In physics, energy is the quantitative property that must be transferred to an object in order to perform work on, or to heat, the object."
So if you get to a state like "heat death", energy can no longer be transferred. "the quantitative property that must be transferred in order to perform work" is still there, but no such transfer is possible and there is no longer any "ability to do work".
Energy is the ability to do work. If at maximum entropy there is no energy available to do work, then effectively there is no energy on that definition.
Firstly the "ability to do work" is only known about at all insofar as the the activity of energy; that is work being done, is constantly observed.
Secondly, if no energy is any longer available to do work, then there is only the "in principle" inherent potential energy "locked up" in "dead" matter itself, and no energetic activity (heat exchange) at all remaining.
Also, whether or not the "heat death" is a realistic scenario is irrelevant because we have been discussing the current scientific understanding of energy and its implications.
It seems like you have an aversion to discussing things "linguistically".
Quoting i aM
That's interesting, because Wikipedia doesn't even have an entry for "quantitative property". So by defining "energy" as a quantitative property, and not defining "quantitative property", the author of this quote has led me on a wild goose chase. Did you happen to read the footnote to that quote you produced? Some author of self-help books for high school students, Robert L Lehman, arguing that energy is not the capacity to do work. So much for your appeal to authority.
Sorry, you can count me out of your discussion because I discuss things linguistically.
I tried to help you. You think you know alot more than you actually do know.
The problem though is that there is a conservation law, and entropy does not actually decrease the amount of energy. So at maximum entropy there is still the same amount of energy, on that definition. All you have done is created a contradiction, saying that there is energy, but it's no longer the capacity to do work, when energy has already been defined as the capacity to do work. That's why i am sought to change the definition of energy. It's what would be needed to avoid the contradiction. But i am's definition is nonsense, and the definition of energy has already been established as you can see.
The "heat death" is just nonsense, it assumes that the universe has the characteristics of an artificial system, created by human beings. Then it describes the capacity of that system to do work, from the perspective of the human beings who created it, for a particular purpose. So it's nonsense because it requires that the universe is a system created by human beings.
Quantum mechanics provides conclusive evidence that the universe is not the type of system which is required for the heat death. That's why the many worlds interpretation is logically acceptable.
Ok, I see!
Yeah, sorry!
Quoting noAxioms
I am not sure I am following you. In fact, I just am saying that the cause precedes the effect in all reference frames without FTL. Isn't it right? :smile:
Quoting noAxioms
Ok, I see. Interesting, thanks! I wonder if this can be used to reconcile SR with pilot-wave theory... :smile:
Note, however, that the 'presentism' that I had in mind was somehow different. I am not sure of how to explain it - so, I'll leave it for now.
Quoting noAxioms
Ok, I can see the problem! Even the presentism you referred before as compatible with SR seems to imply a unique, well-defined state of the universe (the 'unicity' referred in the SEP article on Consistent Histories) :smile:
(as I said it was not exactly what I had in mind. But I think I'll leave it at least for now...)
Pilot wave is a form of Bohmian mechanics: Pro counterfactual definiteness (objective state) and denial of locality. So I wonder how they interpret spooky action at a distance using pilot waves. I don't know the official line on that. They certainly cannot reproduce spooky action using a classic pilot wave setup like they use for double slit.
It can be frustrating, when you are trying to interact sensibly with an ignorant or stupid person who is being willfully ignore-ant or deliberately obtuse, or just plain stubbornly ignorant and/ or doltish.
It can be frustrating to realize that no matter how much you try to reason with them and encourage them to engage with relevance and rationality with what you are presenting, even if only to cogently criticize it, that there is nothing you can do to stop them coming up with ever more distortions of what you have said, empty rationalizations, evasions and other tactics designed to avoid admitting they are wrong, or seeing that their position is actually ill-informed or even totally vacuous.
Often such people will never stop, they always want to have the last word, no matter how empty that word might be. It can be frustrating to have to admit to yourself that you are powerless to help such people, powerless to stop their flow of bullshit, and it is not always easy to admit that enough is enough, and any further responses from you will just be a waste of time.
There does come a time, though, and hopefully we learn from our wasted efforts and abstain from future interactions with such people altogether (at least insofar as they continue with their ignorant claims or evasive tactics). Unfortunately, I haven't been able to find any 'ignore' function on this site.So it's down (or up) to you! Your brain has an 'ignore' function, although it's not always that easy to actuate and sustain, but definitely worth the effort sometimes. :zip:
On the positive side; there is probably more value in learning to exercise your own 'ignore' function in cases which warrant it, than there would be in electronically avoiding having to see such annoying responses at all. I'm a slow learner; it has taken me a long time to learn to ignore, and even now I still get sucked back in from time to time. :gasp:
Ok! Fine, then we agree :smile:
Quoting noAxioms
Considering that the 'wave-function' is a 3N-dimensional (N being the number of particles) object and the theory predicts that the 'influence' is instantaneous, I do not think that there can be an explanatory dynamical model like - say - the one that uses mediators.
(As an aside, I prefer using the term 'de Broglie-Bohm theory' or 'pilot-wave theory' for various reasons. Among these, 'Bohmian mechanics' is actually the preferred term of a specific sub-school of the dBB-supporters and also downplays the role of de Broglie. It gained success and maybe it is the most used term in literature... :smile: YMMV )
Well, there have been attempts to reconcile SR and PWT. To my knowledge, they involve the use of preferred foliations of space-time or retro-causality. Of course, this is different from saying that PWT can be reconciled with SR in its standard formulation, but the point is that apparently it can be reconciled with Lorentz symmetry.
I was however referring to this way of reconciling SR and PWT via this defense of presentism proposed by NoAxioms:
Quoting noAxioms
Isn't a core idea of SR "relativity of simultaneity", i.e. simultaneity of events is entirely dependent on the reference frame of the observer?
Nice!
Quoting i aM
I believe that it depends on how you define SR. In the usual definition, both preferred foliation of spacetime and retro-causality are incompatible with SR.
Yet, I think that they are both compatible with Lorentz symmetry.