Who here believes in the Many World Interpretation? Why or why not?
The consensus from my fairly recent read of Max Tegmark's Multiverse book among physicists is that the MWI is the correct approach or at least a stochastic probability distribution.
I find it hard to concieve the MWI due to the rather infinite amount of realities there may be; but, so do many mathematicians have qualms with dealing with real infinities.
A quasi deterministic universe always seems more appealing; but, why can't we have determinism within a many worlds interpretation.
Just some ideas that are bouncing around my head on the matter.
I find it hard to concieve the MWI due to the rather infinite amount of realities there may be; but, so do many mathematicians have qualms with dealing with real infinities.
A quasi deterministic universe always seems more appealing; but, why can't we have determinism within a many worlds interpretation.
Just some ideas that are bouncing around my head on the matter.
Comments (324)
Of course, I have pretty much a logical positivist bent on such things.
Not only not the consensus, but apparently not even the majority view.
Quoting Question
Well, the idea that the universe is spatially infinite was commonplace throughout the history of thought, and among today's cosmologists this is probably much closer to a consensus. And that doesn't even require the acceptance of any particular interpretation of quantum mechanics. So I don't think the infinitude of the world - or worlds - is all that controversial.
Quoting Question
MWI is a deterministic theory (in a way).
But I've been out of the loop on that for a long time, too.
For those who haven't seen it, an excellent article on Hugh Everett III in Scientific American.
A report on a straw poll of physicists from Sean Carroll, 'The Most Embarraing Graph in Quantum Physics', showing that the Copenhagen Interpretation is still most popular. (I'm currently reading Manjit Kumar's excellent history of QM and am just up to the section where Heisenberg and Bohr are not speaking on account their differences over interpretation.)
https://www.physicsforums.com/threads/does-quantum-mechanics-obey-causality.881156/
The opinions were interesting.
Never knew the CI was still alive and well.
Initially the equations developed in QM didn't predict anything as much as they resolved certain paradoxes. The structure of the atom was the question.
But the solution presented seemed to contradict a number of beliefs that one would draw from classical physics and thermodynamics. And, furthermore, seemed to border on the incoherent -- and certainly contradicted leading theories of the atom at the time.
Mind you, under the MWI, there is no decoherence. Every reality is essentially a decoherence from the original state (big bang) to the present.
I canno't grasp of a universe without decoherence given how macroscopic events are deterministic and at odds with the randomness and indeterminacy of QM.
(From the Scientific American profile.)
Now, I think it was intolerable for there to be a suggestion that 'the mind of the observer' has a role in the outcome. After all, that torpedoes the whole principle of objectivity. But the only way to get rid of it, was to propose that the Universe actually splits when the observation is made!
So that's another way of saying the same, but I was trying to generalize to allow not just what's on the table, but even new ways of interpreting the postulates. It's good to be aware of that history, but no need to pin oneself down either. I'm not really overly committed to CI, it's just what I'm most familiar with, and makes sense of the postulates.
I could see your point on what motivated Everett, though.
That is what also really annoyed Schrodinger and Einstein. Heisenberg was quite at home with the 'quantum jump' whereas Schrodinger said he 'hated the whole thing'.
Why do you say 'not any longer'? What has changed?
Quantum simulators and topological insulators are the hot thing because quanta being analog it means you don't need a full fledged quantum computer to do a wide variety of calculations. Analog is the more duh!, kick the damned thing approach that, nevertheless, can be incredibly fast, efficient, and even creative. It also means that just understand the analog language of nature could provide a wide variety of cheap and easy to use tools. With the first publication of the 500 states of matter it means the dream of the alchemists should be accomplished within the next century.
A good example of analog quantum mechanics is physicists recently discovered a combination of materials that self-organize to produce what they call quantum logic gates which can then be mixed and matched in a variety of ways to form a full fledged quantum computer. Nature herself, can provide the simulators with a little encouragement because she's a bit vein.
So they believe in a real, physical infinity, as opposed to a mathematical infinity? I thought infinities in physics meant there was a problem with the theory requiring revision. Maybe it's just a personal preference, but infinity seems like zero or imaginary numbers to me. A useful concept that has no real embodiment. For example, there is such a thing as one rock (as in a single, countable, physical object), but there isn't actually zero rocks, anymore than there are physically zero unicorns, that's just a useful conceptual tool.
So this isn't a violation of Occam's razor?
There needs to be empirical evidence backing it up at some point, or else it will always remain an interpretation. If no empirical evidence can ever be given, then it's not scientific, but it's rather metaphysics, akin to saying we're living inside a simulation.
I say "no longer" because it's institutionalized now. While there are those who disagree with an interp, and it's understood that the question of interpretation is not settled (and sometimes posited that it could not be settled), it's not offensive in the sense that it was before. I mean, as I noted, that's what I was taught. So it's not exactly a scientific controversy when it's textbook (even if it is acknowledged that the question is not settled)
I can think of two reasons why that might be the case.
One, scientific thought changes not just with experiments, but with the deaths of those who postulate scientific truths. Many a scientist has gone to their grave against the consensus when their "opponents" won the general agreement of scientists. So the proponents of CI, MWI, Bohm, etc. are dead, and therefore the arguments aren't carried with the same sort of conviction. And, in the meantime, none of them really won out. CI has enjoyed the most renown probably because it was first, more than anything.
Two, the cultural milieu of this particular scientific thread has changed. QM was developed on the continent, where philosophy enjoyed a higher degree of respect within academic institutions. A lot of the questions that drove QM were part of a philosophical concern (not strictly, but partially). They were interested in the nature of reality and the nature of, well, nature. But Americans aren't as patient with these sorts of questions. They tend to enjoy the results of technological progress more than questions about what a scientific theory might mean about the nature of the world. Where these were a part of the scientific tradition, the victors of the two world wars fractured that tradition and had it reborn elsewhere, with different cultural values and educational goals.
Schrodinger, Pauli, Heisenberg, and Eugene Wigner were philosophically inclined and educated. Schrodinger learned Greek and Latin (had some spare time in senior school!) and was influenced by Schopenhauer. In later life, Wigner read on Vedanta, and Heisenberg published well-regarded books on physics and philosophy (from a generaly Platonist perspective). I don't think the contemporary commentators (with exceptions like D'Espagnat, Penrose, Henry Stapp) have any kind philosophical depth; they simply resolve all of the philosophical conundrums by invoking parallel or multiple universes. (You could say that having swept all the philosophical problems under the rug, they need a bigger rug!)
Most likely because they're on the corporate or military-industrial payroll, and they're being paid to shut up and calculate (although again with noble exceptions).
??????!
I don't know how you failed to notice, but Many Worlds is deterministic. In fact, it is the entire point of it!
Many Worlds, is not just deterministic, it is unitary and local. All dynamics is unitary; the Schrödinger Equation is obeyed by all things at all times.
It was in fact Schrödinger who first discovered the other Worlds, but he was reticent to talk about them, because he knew other people would think he was crazy. It was left to Everett to summon the courage to develop the idea, motivated as he was by the desire to unify QM and general relativity. Everett paid the ultimate scientific price for his discovery.
There has been some progress since Everett. The Born Rule is now dropped as an axiom of QM, Decoherence has been discovered, and the quantum computer has been discovered, all as a result of Everett's idea.
If we go a bit further back in time to 1935, the Bohr-Einstein debate was essentially about the nature of science. Einstein was a realist - he thought scientific theories were about what exists in reality; Bohr was an anti-realist. Out of this debate came Einstein's discovery of Entanglement.
I'm going to chalk-up Entanglement to Everett's side of the argument, because it still is an argument between realists and anti-realists.
All quantum interference experiments are evidence of Many Worlds.
A particularly fun experiment is the Elitzur-Vaidman bomb tester. All interaction free measurements are evidence of Many Worlds.
The famous Before-Before experiment is evidence of Many Worlds, as are all experiments on entanglement.
The quantum computer was invented to test Many Worlds.
Quantum Cosmology can't be done outside Many Worlds.
Many who work on quantum foundations will disagree with you that MW is an interpretation, as it has fewer axioms than standard QM.
?????!
Decoherence was discovered and developed under Everettian* quantum mechanics!
*While H. D. Zeh - the discoverer of decoherence - was an Everettian, he developed a flavour of Many Worlds known as "Many Minds".
The old argument from personal incredulity!
Don't take MW seriously, just take the Schrödinger Equation seriously!
@Tom - could I put the question to you: what problem is the 'many worlds' interpretation a solution for? Why is it necessary to invoke 'many worlds'?
Many Worlds does not invoke anything, let alone many worlds.
Your question is like - "What problem does 'elliptical planetary orbits' solve? Why does Newton invoke ellipses?"
Newton never invokes ellipses, they are a consequence of his theory.
MW is notable for its lack of invocations - it does not invoke the Born Rule - it derives it, and it does not invoke wavefunction collapse, or state-vector reduction.
Yet another thing that MW does not invoke is Classical Mechanics, which is required under the Copenhagen Interpretation. Neither does it invoke consciousness to get around "Wigner's Friend" type experiments.
Is the following description accurate?
Newton never invokes ellipses
I had the idea that it was Kepler who discovered the elliptical orbit of the planets.
It was called "The Relative State Formulation" by its originator. "Many Worlds" was a catchy name coined by DeWitt. Those working in foundations, seem to prefer "Everett Interpretation", though recently its started to be called Unitary Quantum Mechanics or even simply Quantum Mechanics
As I said, Many Worlds doesn't invoke anything - it is simply quantum mechanics taken as a universal theory.
The quote you provide rightly states that many worlds are an implication of Unitary Quantum Mechanics. It then wrongly states that they are a hypothesis, though that seems more like sloppy use of language.
Quoting Wayfarer
Kepler invoked ellipses, Newton did not.
I'm sorry; I should have stated that the other way.
What I meant to say in my non-educated understanding is wave function collapse. I don't believe the wavefunction does not collapse in MWI and decoherence is simply the wavefunction striving towards the mean.
I never bought into the idea that you can stand in front of an automatic machine gun and have realities in which it does not fire indefinitely/sporadically/once/none at all.
So how do you know he talked about them?
A martyr to boot. (Although, as a consolation prize, he made a fortune plotting the re-entry paths for ICBM warheads.)
I don't believe that it is possible to fully explain decoherence in English, although as I understand it, the problem it solves is only that it shows that Schrodinger's cat would really be either dead, or alive, but not both, because on macro scales, the effect of the uncertainty principle is cancelled out by the interaction of so many states:
Nature.
Decoherence, however, doesn't solve the 'observer problem' with respect to sub-atomic particles.
"The Interpretation of Quantum Mechanics: Dublin Seminars (1949-1955) and Other Unpublished Essays" Schrödinger 1995. p 19
There exists no alternative explanatory theory to Everett-interpreted quantum mechanics which can reproduce the predictions of quantum theory.
Surprising that the Deutsch acolyte would chime in on this one. ;-)
Yeah, exactly.
Infinite space? Of course. Whether it's "real" and "physical" is down to semantics, I guess*. But the idea that space is infinite is old and, I would think, much less controversial than its opposite. We only got a good grip on the latter concept (of finite space) recently, with the development of topology and modern cosmology. Otherwise it is rather hard to imagine, intuitively.
I forgot which ancient Greek philosopher it was that argued that space must be infinite, because suppose that it rather had a boundary; then on reaching that boundary you could just poke a stick through it.
* But if you think that space is somehow not physical or not real or doesn't count for some other reason, well, once you suppose that space is infinite, it is only natural to suppose that there's an infinite amount of stuff in it - stars, galaxies, etc. - and that's as real and physical as it gets, right? The alternative would violate the Copernican principle, making our finite pocket of the infinite universe very special for no good reason.
Yeah, that's the worst possible reason for rejecting some physics or even an interpretation: that it is strange, incredible, etc. - especially for a wannabe philosopher. I mean, if nothing else, the last 400 or so years of discovery should have taught us that the world is stranger than we can even imagine.
Motion does not have to be constantly sustained by a mover? What have you been smoking, Galileo? :-}
I actually had a guy from Pakistan the US military was teaching nuclear reactor physics too call me a liar when I casually pointed out heavy objects don't fall faster than lighter ones.
Thanks. I haven't found that particular book yet, although there's an extensive discussion of the comparison between Schrodinger and Everett's views in Schrodinger's Philosophy of Quantum Mechanics, Michel Bitbol. It speaks of Schrodinger's adoption of Advaita Vedanta in combination with the philosophy of Schopenhauer, to produce a kind of mystical monism, in which Mind (capital M) is the primary reality. It notes many similarities between the relative state formulation and Schrodinger's wave equation, but also says that:
So, again, because Everett (and Deutsch, and Tegmark) are physicalists, they can only conceive of 'what is real' in terms of what is physical. So their 'many observers' actually do exist, in really-existing parallel worlds. Whereas, here, Schrodinger's philosophy accomodates 'One Mind which may adopt any one of the available points of view'. And that is 'a difference that makes a difference'.
'Many worlds' is a solution for why we observe quantum interference patterns.
When a single photon is fired in the double-slit experiment, the probability that it will be detected at any particular position on the back screen can be calculated by summing over all the possible photon paths to that position.
In MWI, those photon paths are not merely possible, but real. That is, each path is traversed by a photon in a separate world branch. When a photon is observed on the back screen, that is the result of world branches combining in superposition which causes an interference effect.
The difficulty for other interpretations is how to explain those interference effects if the paths are not real. How can merely possible photon paths cause a real interference effect?
So what the many-worlds intepretation does, is to say that it is also in all those other positions, which are viewed or at least viewable by other observers.
The trouble is, I just think it is consequence of the fact that Everett can't accomodate the idea of a mere observation having causal consequences. To admit that, undermines the principle of the 'causal closure of the physical'. It seems to suggest that simply observing something has physical consequences, which is central to the so-called Copenhagen intepretation. So it solves that 'problem' - but at what cost?
The real objection, I think, which is the objection that Einstein had, is that the Copenhagen Interpretation entails a rejection of realism. That is, does the world, in some sense, depend on the mind? Does God play dice? Does the moon only exist when you look at it? Is there spooky action at a distance?
Under MWI, these are all trivially answered in the negative. It is an interpretation that is highly explanatory. Whereas the Copenhagen Interpretation is not well-defined and does not explain why quantum interference effects occur.
You say that MWI is 'highly explanatory' - it may be, but at the cost of assuming an infinite number of parallel universes.
When Everett first showed his paper to Wheeler, 'Wheeler was troubled by Everett’s use of “splitting” humans and cannonballs as scientific metaphors. ...In April 1957 Everett’s thesis committee accepted the abridged version—without the “splits.” Three months later Reviews of Modern Physics published the shortened version, entitled “‘Relative State’ Formulation of Quantum Mechanics.” The same article hints that Bohr never accepted the idea of a real 'split' or plurality of worlds, that perhaps he thought it was intended as an allegory. 'In the spring of 1959 Bohr granted Everett an interview in Copenhagen. They met several times during a six-week period but to little effect: Bohr did not shift his position, and Everett did not reenter quantum physics research.'
https://www.scientificamerican.com/article/hugh-everett-biography/
Under MWI, entanglement is just correlation. In terms of the EPR experiment, there will be a pair of correlated opposite-spin particles on one branch and another pair on another branch and these branches are in superposition. When Alice observes the first particle, a process of decoherence occurs whereby Alice becomes correlated with the pair of particles on one branch (and similarly on the other branch). There is no spooky action at a distance because there is no action happening between the particles at all.
Quoting Wayfarer
Not necessarily infinite. But, yes, a lot. The branching isn't assumed. It's just the natural interpretation. That's what the summing over paths is about. The difficulty is in coming up with a coherent interpretation that omits the other branches. If the other branches aren't real, then what causes the interference effects?
Under MW, entanglement is not just a (statistical) correlation. "Correlation" is the wrong word. It is the anti-explanatory word used by anti-realists to avoid any questions about why their algorithm works, particularly as the algorithm does not apply to reality, but rather what can be said about reality.
Rather, under MW, the physical mechanism by which the right branches encounter each other - in order to preserve conservation laws etc - is termed "information flow" or something similar. The process was fully worked out here: http://xxx.lanl.gov/abs/quant-ph/9906007
Quoting Andrew M
Quite!
Denial is always an option however, and to be consistent, the Copenhagen Interpretation denies all the branches!
Of course "branching" is just shorthand. What troubled Wheeler was branching-by-splitting, which not the current understanding of branching.
I think 'we don't know' is the superior answer. Physics is getting hopelessly entangled in pseudo-metaphysics, Everett's being an egregious example. A dose of humility and a sense of the limitations of science might be preferable.
The branching is an artifact of quantum mechanics still being formulated using classical mathematics when all the evidence, including macroscopic evidence, indicates nature is fundamentally analog and what is required, at the very least, is some sort of fuzzy logic variation on the excluded middle. That includes modern quantum mechanics which are formulated as wave mechanics according to the Schrodinger Equation.
My own belief, is the law of identity is going down the nearest convenient rabbit hole or toilet of your personal preference. Hence, the reason quantum mechanics are formulated in infinite Hilbert spaces, yet, the same mathematics display no preference for the arrow of time and the last hold-out for the arrow of time, the second law of thermodynamics, has proven to be violated experimentally the smaller anything becomes. Time is running backwards on smaller scales indicating that the contents of the past are synergistically producing contents in their own future which, in turn, is normalizing the contents of the past with the overall effect sometimes resembling infinite universes merging into one and, at other times, resembling the future determining its own past.
We simply don't see broken eggs reassembling themselves because the human mind doesn't work backwards.
Yep. But then MWI seems to be an example of applying fuzzy logic interpretations to those successful mathematical formalisms. Which would be ironic.
So the maths can't provide an actual (ie: real) wavefunction collapse. Your interpretive choice then is whether (1) to affirm that there must be a collapse to one-world classicality that so far has escaped out mathematical models, or (2) argue for a no-collapse reality and ride that to wherever it logically leads, like MWI, or (3) argue for strong agnosticism about the true nature of reality as with an instrumentalist version of Copenhagen.
And we are seeing MWI being defended in very fuzzy terms with talk of interactions, correlations, interferences, branches, and other such stuff happening causally across world lines. So concrete sounding mechanisms are being invoked, while at the same time the latest decoherence versions of MWI seem to get squirrely about what any of this talk means in a definite physical sense. The other worlds "don't really exist", just as the collapse "doesn't really happen".
So the charitable view is that MWI is part of the exercise of giving up fairly completely on our classical expectations about how reality works. In some way, the whole of existence is a thermal ensemble of evolving possibility with an emergently classical character. But nothing can be completely pinned down or localised.
So in some sense the very notion of "to exist" has to reflect that reality is fundamentally contextual and can feel the shadowy presence of all its alternatives - all its possible worlds - even as it hovers fitfully around some general emergent equilbrium balance of that ocean of possibility.
In that light, both hard and definite collapse scenarios, and hard and definite no-collapse/many real worlds scenarios, are too strong as interpretations. Existence is to be found somewhere between the bounds of the one and the many.
An approach to MWI I find appealing is Chad Orzel's - http://scienceblogs.com/principles/2008/11/20/manyworlds-and-decoherence/
He emphasises that in a twin slit experiment, every photon has a slightly different thermal history or context as it passes through the array.
So at a deep level, every photon has a spooky "completely entangled' connection. Yet at the emergent quasi-classical level, the world is varying enough to wash away the effect of these entanglements. Although you can arrange your experiment to also stop the entanglements being washed away and - now tilting the statistical ensemble the other way - present an accumulation of photon events that have the spooky connected pattern.
So the warring interpretations want to have it clean cut as being one or the other. Either there is one world spun of definite collapses, or many worlds spawned because of no-collapse. But a thermal realism says no world is perfect for any actual photon. It is always either relatively strongly entangled or relatively weakly entangled, depending on the amount of "perfect control" there is over the identicality of real world conditions.
That is, the context itself is varying or fuzzy at all times. Only an impossibly perfect and regular context could "manufacture" the kind of pure spookiness that hard-line approaches to MWI would demand. The "world" is itself never certain enough to justify the ontic demands of the no-collapse camp, just as much as an actual collapse view yielding a single classical world is also out of the question.
A parallel in thermodynamics might be the opposing notions of absolute thermal order that would be represented by the two possible minimum entropy organisations of a perfect gas. A highest state of order would be all the particles collected in the one corner of the jar - from where they would spread out randomly. But then the opposite perfect bound would be to start with every particle having an exact grid-like spacing - spread out as regularly as possible. Again, as soon as released, randomness would scramble that initial state very quickly (and much more quickly in fact that if the gas has to diffuse from one corner).
So that is an example of how real thermodynamics is about equilibrium states that are some thermal balance which is measured relative to two opposing perfect bounds. And with MWI, the collapse vs the no-collapse positions on quantum maths represent the single perfectly classical world and the unlimited perfectly entangled quantum world-lines of which our own world is the messy actual reality that exists between two impossible states of perfection.
There is huge uncertainty/contextuality at the local particle event level. But also that context has an always present residual uncertainty itself.
So as Orzel argues, we have to both accept spookiness as fundamental, but then not jump to treating it as itself something that has absolutely definite existence. Even the spookiness is relative to what emergently exists. The world in effect exists by suppressing the spookiness. It is not the spookiness that rules in a way that produces some unlimited number of actually branching world-lines, with their then fundamentally mysterious multiple "observers" experiencing different "collapses".
Orzel again...
You aren't thinking of yourself as a CI proponent in the "consciousness causes collapse" sense? - https://en.wikipedia.org/wiki/Von_Neumann%E2%80%93Wigner_interpretation
As for that article - I am dubious about the proposition of consciousness 'causing' anything. I interpret the wave function as being an intellectual construction which is predictive. But I don't think that the sub-atomic particles really exist anywhere until the measurement is taken - it is more like they 'manifest' at the point of measurement; to observe it is to 'make it manifest'. I think Heidegger thought something like that also. What bugged Einstein is his native faith that reality was 'there anyway', whereas the Copenhagen advocates all said that in this matter, the line between observer and observed was no longer clear-cut and that sub-atomic particles have no 'observer-independent reality' or at any rate not one we can know. And I'm with them on that, as far as I can understand it.
(I am having the mischeivous thought, though, that perhaps there aren't any fundamental particles, or that physics itself will turn out not to be fundamental, but only one aspect of the phenomenal.)
Really? Where?
Where is MW being "defended" by use of fuzzy terms?
I'm hardly ignoring the quantum zeno effect. Remember that that too requires "perfect watching" to stop the particle ever decaying. So it is both remarkable that we could slow down a decay, impossible that we could create the energy-demanding experimental conditions that would stop a decay.
Quoting wuliheron
I'm all for some version of retrocausality. But you are invoking a globally general version that again betrays perfect world thinking and not the fuzzy logic approach that I would take.
So our bulk model of time and causality is best described by this kind of thinking I would say - http://discovermagazine.com/2015/june/18-tomorrow-never-was
This thermal view of time says the past is pretty much solid and decohered, the future is a bunch of open quantum possibilities. And then quantum retrocausality would be about very local and individual events which are criss-crossing this bulk picture.
The bulk seems definitely sorted in having a sharp split between past context and future events. But on the fine grain, past and future are connected because - as with quantum eraser experiments - the context can take a "long time" to become fixed in a way that then determines the actual shape of the wavefunction. It is only in retrospect that we can see all that went into its formation.
So again, rather than time/causality being either absolute in a uni-directional classical sense, or instead absolute in a quantum non-local or "both ways" sense, the real world dangles somewhere between these two perfect limits. It emerges as the equilbrated bulk behaviour.
Quoting wuliheron
The trouble with Asian metaphors is that culturally they lack mathematical development. So they are inherently fuzzy in being verbal descriptions. At best, using proto-logical arguments, they are proto-mathematical.
So yes, it is my own argument that all early civilisations shared a fairly organic, symmetry-breaking, perspective on metaphysics. There are strong parallels between Anaximander and Tao.
But you can't claim quantum physics to be the triumph of the Eastern way over the Western way. It was Zeno who crystalise the mathematical paradoxes of a way of thinking, and thus made possible their equally sharp counter-reaction. You couldn't develop calculus unless you knew there was some sharp problem when it came to differentiating a curve. And you couldn't develop quantum mechanics if Lagrangian mechanics wasn't already a result of being able to do such differentiation.
So Zeno sparked something usefully concrete in Western thought. It allowed us to speak mathematically about the opposing limits on being. Asian philosophy just spoke about the fact that Yin and Yang gave you the I Ching - a proto-maths that was too fuzzy to ever go anywhere after that.
So I don't undervalue Eastern metaphysics. But there are reasons why Western metaphysics - in its built-in capacity to be "utterly wrong" via axiomatic mathematical claims - became the actually productive intellectual tradition.
Zeno made everyone's head spin for the next 2300 years. Asian metaphysics has since gone down the nearest toilet/rabbit hole even in Asia. Universities over there don't teach quantum theory any differently.
CI itself comes in a rainbow of variants. But the central idea in my view is that in the end what we can be sure of is that we don't know how to define what looks like a necessary division between observers and observables when it comes to quantum scale observations of observables. So we know there is an explanatory gap, but can see no watertight way to fill it.
So CI says there is a line for sure. We sit on its classical side. And where that line gets drawn to rule off the quantum side is something we can't answer.
And my response to that is that it is this notion of there being a definite line which is questionable. Instead, I see the classical and the quantum as complementary models of the two perfect limits on existence. So CI gets it wrong in persisting in believing in a dividing line. Although, as I say, CI comes in so many varieties that it can be seen as a "shrug of a shoulders" intrumentalism even about hard line vs fuzzy line ontologies. Who cares because we can use the maths to deal with the world and built great machinery?
Then Peirce comes in here because he was already dealing with this precise problem - the nature of observers. And he extended that epistemological question to make it a ontological answer. His semiosis is a way of defining soft dividing lines in worlds where observers and observables are fundamentally entangled, but can - thermally - develop robust habitual divisions.
So you keep claiming Peirce to be an idealist - someone somehow arguing that divine mind conjures the world into being. And at stages in his life, he may have well wanted to believe that.
But if you look at his actual metaphysics - his semiotic approach - then he was talking about signs rather than minds. Observers weren't localised experiencers but contextual habits of interpretance. The difference might be subtle, but it is also huge.
These are just my impressions though, and impressions from memory at that. We always differentiated between instrumental interp from CI, though.
(EDIT: Not really challenging you, just asking for a comment)
As you say, even if you go back to Bohr and Heisenberg, you can't recover some pure CI position. And perhaps I should have said pragmatist or logical positivist rather than instrumentalist initially - even though instrumentalism is only Dewey and Popper trying to strip down Peircean pragmatism of its "unfortunate" metaphysical leanings.
So I find that when I talk to modern proponents of CI, they are essentially arguing pragmatism - all we can know is that the maths sure works. And then the metaphysics that lingers at the back of this is the idea that the mind of the observer works on the classical side of the equation, so something that sure looks like a definite collapse of quantum weirdness must be the case in that we manage to extract classically understood measurements from the world (within the bounds of uncertainty).
So even the instrumentalism relies on a background metaphyics which I would say should be troubling. And it certainly was for Peirce who was working on a "fuzzy logic" view of metaphysics for just that reason.
Generally, I struggle to draw sharp lines between interpretations. But when given some central issue - like wavefunction collapse - people are going to divide quite logically into the three camps of (1) it must do, (2) no, it can't, and (3) can't know so learning not to care.
CI as people currently use it seems more 3 than 1 these days.
I'm reading Quantum: Einstein, Bohr, and the Great Debate about the Nature of Reality, Manjit Kumar, on this topic.
Kumar quotes Bohr as saying:
(p262)
Heisenberg, meanwhile, said:
These ideas were considerably elaborated by Heisenberg in his later philosophical essays, such as The Debate between Plato and Democritus, where he comes down on the side of Plato. He also compares the nature of the existence of electrons to Aristotle's potentia, which makes sense to me; I've read elsewhere that electrons don't exist, they only have a tendency to exist.
But as I have often noted, when Heisenberg says that electrons are 'not as real', this poses an ontic challenge; surely, you will say, something is either real (exists, =1) or not (doesn't exist, =0). Notice that this is precisely what is being called into question here. And that is what bugs Einstein.
(p262)
Now, I've realised what I think is wrong about this view. This is that science views reality through theories and hypotheses. And what I think Einstein is forgetting (and, hey, he's Einstein, so I know I'm saying a lot!) is that the kinds of purported facts that he is arguing about are only disclosed by a rational intelligence who is capable of interpreting the facts. So 'the facts' - and by extension, even the moon - don't exist irrespective of whether one is looking or not. 'Looking' is inextricably intertwined with what is being observed. That has always been the case, but it took 'the observer problem' for it to more or less come up and punch us in the nose!
There's an interesting article called When Einstein Met Tagore, which helps make this point.
But the point that I want to make, is that the Pythagorean theorem can only by known by a mind. So it's not mind-dependent, in the sense of being reliant or this or that mind, but in the sense of only being perceptible by a mind. So, what is, includes or implies a mind capable of grasping the truth! But that is what had been bracketed out of the scientific method by Galileo and his successors; this is where the idea of 'mind-independent' came from. So I think Einstein's conception of realism is at fault. Essentially, it doesn't want to recognize the limitations of science; saying that science sees 'things as they truly are' is a conceit.
Perhaps I fell into an odd camp, then. Though I learned it more from the Chem side than the physics side, though physics was part of it, so that might be why.
We went along with collapse was real, and it was the "observation" which made it real. But we didn't attach much significance to "observation", hence why I tend to go back to both H and B -- they both had different takes on it.
I note you are unable to defend your baseless claims.
Orzel's understanding of Many Worlds has improved over the years:
http://scienceblogs.com/principles/2015/02/20/the-philosophical-incoherence-of-too-many-worlds/
Yes, it's not merely statistical, it has a causal basis. My main point is that there is nothing mysterious about entangled particles under MW - it just means that they are on the same world branch. And if the observer becomes entangled with them, then they will also be on that world branch.
By all means keep an open mind. Nonetheless, Everett's is the only theory that explains why we see quantum interference effects. So it is the theory to beat.
And as a result of MW being the ONLY explanatory theory that can reproduce all the results of QM, it is also the only testable theory.
https://arxiv.org/abs/1508.02048
No, it's a testable theory:
https://arxiv.org/abs/1508.02048
It is different from standard treatments of QM in that does not have the Born rule as an axiom. The Born rule is derived.
It has also made far reaching predictions - quantum computing, and predictions regarding conscious agents running on reversible quantum computers.
A rudimentary quantum computer is capable of performing vastly more calculations in parallel than if all the matter in the visible universe was made into a classical computer. In fact, that is an understatement. Where these parallel calculations occur, is not a metaphysical question.
Also metaphysics. Assumes that 'conscious agents' are something that can be engineered. But it's probably beyond debate in your mind.
The realism is required by the epistemology of science.
But what does it mean for the collapse to be real (and the wavefunction not real) in Heisenberg's Kantian view? He talks about an epistemic collapse - a change in your state of knowledge. So the emphasis is on pragmatic modelling. We can only have knowledge about reality via our conceptions.
Our models encourage us to create certain measuring devices and experimental set-ups with which to probe. But whatever we learn is always in terms of those familiar conceptions. We don't get outside our own self-created observer bubble to grasp the thing-in-itself. All we have is a system of signs that seems well behaved. We can stick our thermometer into the bath and read off some numbers. We understand that combination of events as evidence there exists "a temperature". Likewise we can probe the quantum realm with quantum set-ups and read off observations in terms of the behaviour of a particle. Or of a wave. Depending on the choices made as the observer.
So you set up questions in a certain way - a human way and not necessarily nature's way. That will result in a reading, a sign, that "collapses" your ignorance. But what went on "out there" is another mystery.
So yes. CI is often considered to claim collapse realism. But Heisenberg appears to aim at a sophisticated epistemic position that instead takes as primary the Kantian impossibility of naked realism in any form.
And the mystery unsolved is then why the quantum mode of inquiry works so "objectively". The collapse of our ignorance when we conduct our probes is so reliable that it tempts us make a stronger causal connection than our epistemological limitations would warrant. We want to say we ourselves collapsed the wavefunction by touching reality with our minds. Or that collapse really is objective and caused by the physical aspect of our probing - the way we jarred the wavefunction with our material devices.
Thermal decoherence seems to offer now a fairly natural view of how macroscale observers can act as the decohering contexts that "collapse" quantum-scale possibilities. But unfortunately decoherence is quite tied up with MWI fundamentalism about wavefunction realism and no collapses.
Nice summary. I never understood all the confusion around CI, surely it's obvious that what will be observed is a facet determined by the capacities of the instrument being used to do the observing. The fact that those facets appear inconsistent is only due to it being a random snapshot of the facets.
To jump from there to a waveform collapse etc etc is assumption upon assumption while wearing blinkers. None of it follows.
I think you are agreeing with me on pragmatism. And as I say, that is what comes through from Heisenberg. But also Einstein got it in that he said (in a co-authored book) that scientific concepts are free creations of the human mind. So his issue was more one of metaphysical principle. He was loathe to sacrifice a concept that had worked as well as the principle of locality.
Glad you think so. But I note you are avoiding saying whether you agree with his essential point. Whereas many MWI proponents get quite fundamentalist about universal wavefunction realism, Orzel is treating it more as a matter of pragmatic limits. It is pretty much impossible in practice to repeat measurements in the exact fashion that would give you a single crystaline mass of sharply branched world-lines. That version of MWI - which is pretty widespread - is a misunderstanding.
And note how he ends for good measure....
So he is trying to challenge the more conventional MWI interpretations.
My book is an attempt to bring that kind of mathematical formalism to Asian philosophy. Essentially, it assumes the law of identity goes down the nearest rabbit hole or toilet of your personal preference allowing even the mathematics to always remain context dependent. Rather than a metaphysical approach that builds from the ground up, it takes the top down approach of merely sorting all the metaphors for any humble and elegant simplicity to make both more and less sense out of observations without requiring any assumptions other than that the law of identity must vanish into indeterminacy.
From what I read his vision of time is merely begging the question and splitting semantic hairs. Calling something random is like saying it has no properties and does not exist. He is circling the drain, so to speak, and attempting to do much the same thing that I am doing with my own writing using a more western metaphysical approach. The problem is he is mixing metaphysics and metaphors leading to a contradiction. Without a demonstrable definition for what random means he is essentially using metaphors in an attempt to describe everything metaphysically.
Again, the second law of thermodynamics has proven to be violated on micron scales and smaller meaning that entropy can decrease. A scrambled and fried quantum egg will reassemble itself and there's just no way metaphysics can explain the inexplicable any better than mysticism can. God may be able to see the back of their own head without a mirror, but the rest of us don't have that luxury. The implication is that all of fuzzy logic implies a yin-yang systems logic is required that can express both causal and acausal perspectives with a common shadow being an example of the acausal.
Whether we see a shadow as the absence of light just depends upon the context and, for example, in a dark room what was a shadow can become a faint blob of light because it isn't so much an effect of scale as it is how humble the specific context and its contents are relative to the observer and each other. Mathematically speaking, photons experience isomorphic space-time meaning they don't distinguish between forward or backwards in either space or time just as we might say that shadows don't distinguish between space or time. Photons are also instantly absorbed and emitted and appear to have no independent identity of their own merely conveying any energy and information with perfect fidelity just as a shadow can be said to merely convey the lack of energy and information instantaneously with perfect fidelity. The opposite is also true and in a dark shielded vacuum chamber virtual particles will appear out of nowhere because a context without any significant content is both physically and conceptually gibberish. Mother nature's mindless sense of beauty and humor can resemble that of a toddler, yet, the human eye is sensitive enough to detect a single photon ensuring that nobody is ever left completely in the dark.
Shadows express the same principle that can be applied to everything that a context without significant content and vice versa is simply physically and conceptually impossible. It would mean that thermodynamics need to be reformulated along the lines of Adrian Bejan's Constructal Theory, but as a systems logic that expresses retro-causality. The past merely represents more of the geometry of the universe that we can perceive and the future more of the time, but the two can exchange identities. In order to prevent the past from dominating the future its own synergy leads to the future normalizing any individual contributions of its contents.
Synergy itself becomes context dependent because it can be perceived as normalization.
I notice from the Orzel blog, 'The fundamental problem with Many-Worlds is that every argument about it devolves very quickly into stoner dorm-room bull session nonsense about parallel worlds and identity and morality. But none of that is physics.'
'The physics' can be understood solely in terms of mathematics, without delving into what it means in philosophical terms - whether there are many worlds, or how to think about what that means. But insofar as physics is purported to be about what is real, then dorm-room bull is inevitable, as far as I am concerned. I noticed in an earlier post about this, the Worlds were spelled with a capital W. So I think that 'many worlds' is actually morphing into a form of popular or science-fiction metaphysics (with David Deutsch as it's cult hero and the Quantum Computer as the cult object. Sure that's dorm-room bull, but that can be said of a lot of 'cultural artefacts').
As quantum physics developed, it undermined common-sense realism or even scientific realism. Einstein wanted to see a fundamental material unit, not all of this wave-particle ambiguity and now-you-see-it now-you-don't magic tricks. It offended his sense of propriety.
All the MWI advocates seem to be ignoring this point.
Sure, Many World advocates ignore that point.
http://www.cheapuniverses.com/
Orzel is also wrong. by the way.
Many Worlds is realist.
I'm guessing by 'weak' mwi, you mean instrumentalism. An instrumentalist would say that they don't know what summing over paths really means or, more strongly, that it doesn't mean anything. But it works extremely well for predicting phenomena, so we should use it.
But why does the math work? The straightforward realist explanation is that the world really is as the math describes it. There are paths that split off and interfere.
BTW, MW doesn't imply parallel universes, but instead paths (branches) within the universe. And these paths are observed in quantum interference experiments.
Tell me this, then - what does the "M" stand for in "MW"?
says you.
The old argument from consensus.
Only a minority of physicists advocate Everett. It's a scandal, which future historians will recognise as being an obstacle to progress. In fact Deutsch is on record, not only stating that Bohm could have anticipated Everett entirely, if only he had not equivocated about what is real and what is not in his theory, but that the quantum computer could easily have been invented in 1950s for the same reason. All the quantum mechanics was there, plus an extraordinary collection of towering geniuses.
Strange as it may seem, the nature of reality doesn't trouble most physicists, and few have any understanding of the importance of realism. Most shut-up-and-calculate, and whether they admit it or not, they do so as if they were dealing with reality. Methodological (or unconscious) realism works up to a point.
But, where it matters, i.e. where pretending QM is not about reality makes no sense whatsoever - particularly in the fields of quantum cosmology or quantum computation - then Everett may be consensus. Hawking is on record stating it is "trivially true".
Of those working on foundations, if Oxford U Philosophy of Physics dept. is anything to go by, then Everettians make up 25%. http://www.philosophy-of-physics.ox.ac.uk/
But physics can't claim to talk directly about what is real. All it can claim is to talk in a fashion that is systematically constrained by "the evidence". So it is ultimately a social practice. And its philosophy accepts that. But what a physicist can rightfully say is that s/he is better constrained by the evidence than most of the people who want to waffle on about metaphysical reality, employing half-baked traditional belief systems.
So the real issue here - as I believe Orzel illustrates - is that people take hardline positions on quantum interpretations because they are locked into either/or binary thinking. It must be the case either that wavefunctions are ontic or epistemic - a definite fact of the world, or a useful fiction of the mind. The same with wavefunction collapse. Or in a more general way, either classicality or quantumness is the illusion, the other the truth. Either everything is secretly hard and definite behind the scenes, or it is fuzzy and probabilistic - an eternal spawning confusion.
So there are two familiar alternatives when it comes to existence - actuality vs potentiality, being vs becoming. And a quantum interpretation must settle ultimately into one or other general category.
But why not instead see those two choices as the complementary limits on the notion of existing? Reality is never fully definite, nor fully probabilistic, always somewhere inbetween the static hardness of actuality and the soft fluidity of uncertainty.
So there are two ways of looking at quantum weirdness. Either you can take an internalist perspective - as I do - and see the classical world as a system that confines it and dissipates it. Or you can take an externalist view where quantum weirdness is essentially unconfined and spills out to take over everything. You get people saying the entirety of existence is not just a single giant superposition, but one that branches in unrestrained fashion, growing forever more byzantine.
Now the mathematics of quantum theory doesn't provide any machinery to collapse the wavefunction. So there is nothing in the bare formalism to constrain all the world branching, all the ever-expanding weirdness.
But as Orzel argues, properly speaking, this weirdness applies strictly only to isolated systems - parts of the world that are essentially disconnected from the thermal bulk. To get entanglement and quantum coherence, you have to be dealing with the very small and the very cold. And that takes special equipment. Generally the world is too hot and messy for quantum effects to manifest. The weirdness is always there, but classicality is about it becoming heavily suppressed.
So as I say, actual quantum weirdness can exist only at the very limit of the classical. The wavefunction defines that boundary where hot messy contexuality eventually peters out and all that is left - trapped inside a small and isolated spatiotemporal region - is your fundamental-level indeterminacy.
So yes, indeterminacy exists. We've manufactured it by very careful control over experimental set-ups that produce the level of thermal isolation that permit it to be the case. But to then do the MWI trick of claiming "unconfined isolation" would turn the whole universe into a giant unbroken and coherent superposition is to ignore how the world really is - so hot and messy that indeterminacy is always and everywhere in practice highly confined.
And the corollary is that the same applies to classical reality, the hot and messy bit. It doesn't have hard solid existence in the way that conventional materialist metaphysics imagines. It is everywhere and always that tiny bit quantum and indeterminate.
And the whole shebang has evolved. At the Big Bang, the Universe was basically in a generalised quantum state. It was 99.999% quantum, only fractionally classical. And now that the Universe is so cool and large, it has become 99.999% classical - at least at the scale we care about, the interactions between big and still warm lumps of mass. This is the era of the hot and messy.
Roll forward to the Heat Death and the balance shifts back to the quantum pole of existence. The contents of the Universe will only be describable in terms of a black-body quantum fizzle of ultra-cold photons being emitted by the cosmic information horizons.
From a MWI point of view, calling the Heat Death a multiplicity of worlds in superposition would be like comparing scrambled bags of sand. Technically you might claim every back to represent some unique possible state or arrangement of sand grains/quantum events. But in fact every bag is just another bag in a way that makes no useful difference. Every bag of sand world is unexcitingly similar due to the thermal inevitabilty imposed by the second law.
So my view is that this is the best metaphysical basis for interpretation - the real and possible are not two categories, one of which must be made to stick, but instead they represent the complementary bounds that form existence. The classical and the quantum mark the two ends of a spectrum. That means neither reality nor possibility are going to be 100% pure states.
And yet all interpretations try to force the issue and give an absolute categorisation in terms of various binaries. That is why all of the interpretations seem to be saying something right, yet none of them could ever get it all right because of the way they go about striving after a single definite metaphysical categorisation.
But now that quantum theory is being married to thermodynamics and information theory, now that it is importing a proper systems ontology in which you can model the kind of contextuality and scale effects that I'm talking about, things seem to be getting somewhere.
That is why I am a fan of decoherence even if I don't go along with the fanatical MWI view which wants to treat actual decoherence as a 100% illusion (resulting in completely unconfined superpositions), whereas I say that in our hot and messy classical reality, decoherence is pretty real in being only 0.0001% - or some sensible fraction - an ontic illusion.
So I would be an effective realist about both the collapse and wavefunction issue. Determinacy can approach 100% at one end of the scale, indeterminacy can approach 100% at the other. And neither in fact every completely rules. If we are going to construct a metaphysics of existence, then the fact that everything is always a messy mix, some balance on a spectrum, becomes the new foundation for interpretations.
Now, if it doesn't mean that, then there's nothing to debate. If the 'many' in 'many worlds' is simply an hypothetical mathematical construct or device, then it's back to 'shut up and calculate'. But the controversy is about the notion that it really does say there are many or parallel realms.
Right - decoherence, I get that. I think I'm more or less in agreement with your post, although I don't have the background to understand all of it.
And I think the first two points there are much nearer to Bohr and Heisenberg's attitude.
So it is clear Orzel indeed has you stumped because you can offer no analysis at all. But just saying "nope" is not going to get you out of the hole here. ;)
Nope, nowhere in MW is the claim made that measuring the spin of an electron means "you have to build an entire parallel universe around that one electron, identical in all respects except where the electron went". Definitely nope, Nope, thrice NOPE!
Sorry I misread and I've edited my earlier comment.
Quoting Wayfarer
People simply use different terminology to refer to the same phenomena. What is being referred to is the many paths, or branches, that can be in superposition.
And, yes, the realists say those branches are real.
Right, but by that he doesn't mean that it's referring to anything real. He's a positivist, i.e., doesn't matter whether there really are many worlds. From the Wiki article on Many Worlds:
My underline. So Hawking is saying, he doesn't know what is real (and the implication is, doesn't care.) So, it's all 'shut up and calculate'. MWI isn't about 'reality' at all. All you're doing is calculating possibilities - in which case there's nothing to debate.
I would have thought that the 'many paths' are not phenomena. They're inferences. But one cannot see 'the other paths', by definition - they're what's in the 'other worlds'. We only see one path - so that is the only 'phenomenon' being observed, the rest is inference.
Nope, it doesn't refer to that.
What Everett claimed is that the bare formalism of quantum mechanics may be treated in a straightforward realist way, without changing our general conception of science, or quantum mechanics.
So, here's the thing. According to text-book QM, when you have a macroscopic superposition, you declare indefiniteness. Under Everett, you accept multiplicity.
And how does that connect with what Orzel (or I) have argued?
The point is that even if you step back from many actual worlds - Tegmark's parallelism - MWI proponents still seem to believe in crisply real branches (and branching points). But it makes more ontological sense to treat that too as a mathematical idealisation.
So the argument is that the universe, as a whole, could never have the definiteness required to create itself as some entangled mass of matchingly definite world branches. You can get something like that occasionally - with a sufficiently isolated system. But even ordinary quantum experiments have a bit of jiggery-pokery going on in that they don't control for the fact that actual environmental isolation is physically impossible.
And physical reality ought to trump mathematical idealisation in this regard.
My apologies, I misread where Wayfarer's quote came from. It came from an article that Orzel did NOT like apparently.
Text-book QM claims that Schrödinger's cat is in a macroscopically indefinite state - a superposition of being alive and being dead.
Everett claims that the cat is in a superposition of macroscopically definite states - a superposition of an alive cat and a dead cat.
Text-book QM claims the act of observation transforms the indefinite cat into a definite cat, by a process indistinguishable from magic.
Everett (actually bare quantum formalism) claims that any environment that interacts with the cat in superposition will itself enter a superposed state, whose components correspond to entanglement with a macroscopically definite cat. Decoherence guarantees that very rapidly, the components of the environmental superposition cease to interfere with each other.
Here is an excerpt from the Phillip Ball essay:
So, for the umpteenth time, 'many worlds' means 'many worlds'? Yes or no?
Not sure why entering a macro superposition state is any less magical than exiting it.
The bare quantum formalism still requires its "observer", even if the tacking on of the further formalism of statistical mechanics - in the guise of the decohering environment - is certainly the way to deflate the notion of the "observer".
So collapse folk have the problem of getting rid of entanglement. No-collapse folk have the problem of initiating it. Sure the wavefunction evolves in the required fashion. But observers are then the necessary element to create the context that results in some actually specified wavefunction.
Meanwhile decoherence as a general machinery helps out both in making it clear that "observation" is not about conscious human experimenters but about the concrete existence of a thermalising environment. The Universe has the means to "observe itself" in that it has a definite past that acts as a general constraint on the indefiniteness of its future.
So I'm guessing you didn't even read that Orzel link you posted in rebuttal?
I actually asked a serious question. You might have had some worthwhile points to make about Orzel's angle.
Yes. In the Schrodinger's Cat thought experiment, there are two cats, both of them equally real. One is alive (and wondering why it is in a box) and one is dead.
I refer you to my post about macroscopically definite cats above.
Quoting Wayfarer
I reckon 'many worlds' must mean 'many worlds', what else could it mean?
Frankly, you can call decohered macroscopic superpositions whatever you like, it makes no difference.
Yes, there are parallel universes and we can find out about them.
The many worlds interpretation exists to preserve determinism.
Many experts hope this interpretation is true because it can be mathematically modeled.
If the universe is truly non-deterministic then that could mean there will never be a theory of everything that describes all of the universe's forces and natural laws.
Well, glad we got to the bottom of that, although it directly contradicts and answer you gave just above it.
If the universe is truly non-deterministic then that could mean there will never be a theory of everything that describes all of the universe's forces and natural laws.
The other explanation might be that physics only sees part of what is real, or that what is physical and what is real are not synonymous. It will be interesting to see how far people will go to avoid that.
That was another Tom in another world breaking through. By his own logic, his every possible state of belief is a real macrostate. So it hardly matters if he is contradictory. That's going to be the case no matter what. :)
Word is that the MWI is a religion. All hail the possible worlds that exist!
I challenge you to find anywhere in the formalism of Everettian Quantum Mechanics mention of parallel universes. Go ahead!
The axioms of quantum mechanics say NOTHING about parallel universes.
I challenge you to find anywhere in the formalism of Everettian Quantum mechanics mention of 'many worlds'. Go ahead!
The axioms of quantum mechanics say NOTHING about 'many worlds'.
And you have already agreed that MWI stands for Many Worlds Interpretation.
So, what incentive to I have to look for those particular terms in the 'formalism of Everettian QM'? I think the ideas of 'many worlds' or 'parallel universes' are generally associated with Everett.
If I was implying anything by the question, it was only that if anyone were to claim that most physicists buy MWI as an ontological commitment, the person making that claim about what most physicsts believe is probably mistaken in that. As you noted, and I agree with, " the nature of reality doesn't trouble most physicists . . . Most shut-up-and-calculate."
How does one "buy MWI instrumentally"? If you are a shut-up-and-calculate instrumentalist, then ostensibly at least you have no use for interpretations, MWI included.
Quoting tom
I am curious, Tom, seeing as you so stridently promote a position held by a small minority of physicists, if not by Deutsch alone - a minority among a minority of MWI proponents, most of whom, I believe, do not hold that MWI is the only [s]interpretation[/s] version of QM that can account for all known observations - I am curious, are you a physicist yourself? Do you have a thorough understanding of quantum physics? Is this position your own?
"With respect to MWI" doesn't imply "Using MWI in calculations."
MWI works as an instrumental interpretation of the calucations, as do other interpretations.
This is archaic thinking to say the least. A shadow is non-deterministic, yet we can still calculate its impact and origins. In fact, you can't have a perfect shadow because virtual particles will always appear out of nowhere. What it requires is a systems logic that can express everything both causally and acausally. A Theory of Everything and Nothing.
Using determinism as a yard stick for the value of non-deterministic theories is absurd.
(Just fyi, by the way, if you want a better chance of me seeing something and responding, use the "reply" function)
Interpretations can be instrumental or they can be taken as ontological commitments.
I'm using "interpretation" in a broader sense than something like the "Many Worlds Interpretation," where that's referring to a "story" being explicitly set forth, by the way. I'm using "interpretation" in the sense of any meaning and/or implicational assignment with respect to an explanation or account of how something works.
Instrumental interpretations don't care about ontological commitments. It's a matter of simply approaching the explanation or account as something that works for what it is, where it doesn't matter if it's a fiction or not.
Ontological commmitment interpretations are the opposite, obviously. One takes the explanation or account to be literally picking out things in the world, just as they are.
So, being an instrumentalist, you would class dinosaurs as just an 'interpretation' of fossils, rather than actually having existed? Perhaps you think fossils only come into existence when they are consciously observed?
I'm an instrumentalist on some things, and not on other things. I particularly tend to be an instrumentalist with respect to explanations/theories that are mathematical-only (or primarily), or that are more abstract in received view interpretations.
This is where the realist metaphysics kicks in. What explains the interference pattern in a double-slit experiment? What is actually interfering? What we are seeing is the interference of many paths. It is like we are standing on a road and seeing the road fork in front of us. But instead of the two roads being side-by-side, the roads are superimposed on each other like a superimposed photograph.
Consider the bent-stick illusion. We seem to see a bent stick when it is partly submerged in water. But we seem to see a straight stick when it is out of the water. Are we seeing a stick that has a mysterious straight-bentness nature that depends on how we observe it? Is the scientist's job just to record the observables and shut-up-and-calculate or do we expect that there is a natural causal explanation for why the stick appears differently under different circumstances?
Similarly, are we seeing phenomena that have a mysterious wave-particle nature that depends on how we observe it? The natural causal explanation is that we are seeing multiple phenomena that exhibit an interference pattern when they are in superposition.
But supposing that "there are multiple, branching universes" certainly doesn't strike me as a "natural causal explanation" that's more reasonable than "this stuff has some unusual characteristics that seems to behave like a wave at times and like a particle at times; we don't completely understand why yet, but these equations work for making predictions about it." Instead, it seems like incoherent fantasy.material.
What if probability waves are exactly what they seem - distributions of possibilities? So the patterns will appear along the lines of possibility, but when an object is measured, then they're no longer subject to probability, so the wave "collapses". But really nothing collapses because nothing was there in the first place other than a potentiality.
I think the issue with that, is that so-called 'realism' can't accomodate the notion of a 'real possibility'. It wants to assign existence in terms of a binary value - something either exists or it doesn't. But Heisenberg recognised that on the sub-atomic level, things 'kind of' exist. The parallel, in metaphysics, is the distinction between potential and actual existence - so the observation 'actualises' the potential existence of the object.
Which, I think, is far more like the general approach associated with the Copenhagen Interpretation. I think the issue is that it threatens the notion of 'a fundamental particle'. That is what the 'realist' approach is wanting to preserve - the fundamental separation of observer and observed. And they're prepared to accomodate the absurdities of the infinite branching universe in order to do it.
Take a look at this.
All material existence can be reduced to potential. The concept of energy does this. If this is reality, that all material existence is simply potential, then the appearance of an actual object is a creation of the mind. But I'd say that's a faulty premise, that all material existence is simply potential. If we assume this premise as faulty, we have to question what the reality of "an object" is based in..
If a single photon is fired in the double-slit experiment, the probability that it arrives at any particular position on the back screen is a function of the sum of the paths it could take.
There are really only two options available. Either the paths are real or they are not.
But possible (or potential) paths cannot create real interference patterns. Which leaves us with the first option, whether we like it or not.
(One other option is that QM is false, but I don't think anyone is arguing for that.)
Yes, the main issue is that the realist wants to keep things separate from our talk about those things. So modal language has an epistemic function and does not refer to (kinds-of) things that can exhibit interference patterns.
You forgot one important option. Is the photon real?
Quoting Andrew M
The option is not that QM is necessarily false, the option is that the interpretation of the photoelectric effect, which inclines people to describe light energy in terms of photons, is not a good interpretation.
That is how Einstein wanted to see it, but I think that is precisely what is at issue. Or - 'it depends on what you mean by "real" - because we're not dealing with particles at all, and it's mistaken to think of them as being that.
These 'particles' have no definite location until being measured; they're not in one place and don't have an actual trajectory. That is the 'fuzzy' nature of quantum particles. So the interference patterns might really represent the probabilities and nothing more than that; they're not really trails left by a particle, because there really aren't any particles until they're measured.
Heisenberg says that the tracks that appear in bubble chambers are not really paths. It seems like the vapour trail left by a jet, but it's not. 'Perhaps we merely saw a series of discrete and ill-defined spots through which the electron had passed. In fact, all we do see in a cloud chamber are individual water droplets which must be certainly much larger than the electron. There was no continuous, unbroken path.'
I think Einstein's view was actually presumptious - he believed that we could know the ultimate nature of things through science. Whereas I find Bohr's and Heisenberg's philosophy much more modest - they recognise the limitations of even the most exact descriptions. 'Heisenberg understood that Einstein...wanted to return to the reality concept of classical physics, or, to use the more general philosophical term, to the ontology of materialism: the believe in an objective real world whose smallest parts exist objectively in the same sense that stones or trees existk independently of whether we observe them or not.' This was, for Heisenberg, a throw-back to the simplistic materialist views that prevailed in the natural sciences of the nineteenth century.
Einstein and Bohr never came to terms over this matter, and they were, after all, two of the greatest scientists of the 20th Century, so it's obviously a really hard question. But insofar as I understand the so-called Copenhagen intepretation, which is probably not much, I'm in agreement with it.
All quotes from Kumar
In terms of talking about ontological commitments yes. But you can simply see it as an instrumental way of talking about what's going on, and assume that we don't really understand at all just what photons are like ontologically yet. What's really going on, what photons are really like, might be something that we can't really fathom yet. "Paths" are just a way to relate it to what we can conceive of, what we have experience with, etc.
I also see the idea that we're firing a single photon as an instrumental description, by the way. I don't think that we really know that we're firing single photons, a fortiori because we don't even really know what photons are yet--a "single one" might not even make any sense depending on what they turn out to be. Insofar as physics goes, they're primarily instrumental mathematical models.
Anyway, to understand my stances when it comes to this sort of stuff, just keep in mind that I'm basically a logical positivist in this realm. In my view, what we can say with any ontological commitment is that we're reading meters and computer screens and adjusting instruments and manipulating mathematical constructions and so on. That doesn't mean that I'm a logical positivst wholesale, and I certainly do not agree with them on the idea of meaning, etc., but I focus on what we are actually experiencing contra the stories we come up with via theorizing, via analogies to everyday experience, etc.
I am not sure there is a real distinction here, but anyway, I still don't see how MWI can be taken instrumentally in this sense. "The explanation or account as something that works for what it is" - that is the bare-bones QM. It gives us enough to perform measurements, relate them to other measurements, and make predictions. Interpretations, MWI included, go beyond that and make metaphysical commitments - which is what you seem to be shunning.
Quoting Terrapin Station
There are no mathematical-only explanations. Mathematics doesn't explain anything: in order for it to be an explanation, a physical theory, it needs to be related to the physical world. I don't understand the distinction that you are trying to make here.
But what if the wave function which describes the path really does represent the probable paths of any single particle? Then even if the particles were fired sequentially, they would always behave as though they were part of an ensemble. In other words, the addition of all of their paths would always end up forming an interference pattern. That is something like the 'pilot wave' theory, except the 'pilot wave' is really nothing other than the probability distribution.
Has anyone thought of that explanation? Does it make any sense?
//edit//So I suppose what is happening is, that when they're fired sequentially, they're still behaving as though they're an ensemble. It's as if Time has been taken out of the equation, so that the sequence of particles behaves as though they're being fired together instead of being chronologically separated.//end//
Yes - see What’s a Photon, and How Do We Know they Exist?
But even if you disagree, firing single electrons will also produce an interference pattern. In fact the double-slit experiment has been performed with molecules comprising 810 atoms.
The particles are real before they are measured. But they never have a precise position and momentum at the same time, either before or after measurement. A position measurement just picks out a more precise position at the expense of spreading out the momenta (or vice versa, for a momentum measurement).
This can be observed in the single-slit experiment where the slit is narrow enough that the position is precise when the particle goes through the slit, which means the momenta is spread out, thus resulting in a wide spread of photons (again in an interference pattern) on the back screen.
Note that the narrow slit constitutes a position measurement. We know that individually fired particles that reached the back screen all went through the slit, yet they still build up an interference pattern. So there is nothing special about measurement that changes the nature of the particle.
Not according to Neils Bohr; which is part of what is at issue, isn't it?
You don't need to know what photons are really like. QM applies to any quantum system whether it be photons, electrons, or more complex systems like 810-atom molecules and, conceivably, Schrodinger's Cat.
Scientific theories are meant to be ontological commitments, which means they can be tested (and potentially falsified).
Yes, but I'm pointing out that there is no need to question the reality of particles prior to measurement.
Do you know about the Bohr-Einstein debates?
Neils Bohr says there are no sub-atomic particles until an experiment is performed which elicits them as a response to that particular experimental set-up. This is an aspect of his famous 'wave-particle duality' argument. It is part of a set of theories, of which the uncertainty principle and 'entanglement' are other aspects.
The reason Einstein couldn't accept that quantum mechanics was complete, is because he believed that there simply must be objects that are not 'mind-dependent' in the way that Bohr was suggesting. They had many fierce debates, usually in the form of mind experiments which Einstein posed, which he hoped would show that QM must be incomplete in some sense. Every one of those challenges was met by Neils Bohr.
The EPR paper was one of these 'thought experiments' - it was that paper that led to the Bell's Inequality paper which was published in 1964 (many scientists will say that it is one of the greatest scientific papers in history). And it was that paper that formed the basis of the Alain Aspect experiments which in the early 1980's empirically demonstrated the entanglement of remote paired particles, thereby showing that the EPR paper was wrong. It was the final nail in the coffin of Einstein's realist philosophy, pending something world-shatteing coming along.
So the debate between Bohr and Einstein was very much between Einstein's classical scientific realism, and the interpretations of Bohr, Heisenberg, and others, which comprised the 'Copenhagen Interpretation'. But that is not anything like a philosophical school or principle, in fact Heisenberg, Bohr, Born, Pauli and Schrodinger, all had great differences of opinion between themselves. But Heisenberg and Bohr, in particular, were very critical of Einstein's realism (as per the quotes a few posts back). So the 'Copenhagen Interpretation' (a term not coined until the 1950's by the way) was just shorthand for 'the kinds of ideas Bohr and Heisenberg talked about.'
The upshot is, that so-called 'sub-atomic particles' aren't simply whizzing around, waiting to be measured. They're not 'out there somewhere'. Until they're measured, they can't be said to exist - as Heisenberg points out, words such as 'exist' have a certain set of meanings, which can't be unequivocally applied to photons and electrons. That is why QM is so perplexing - what were thought to be the 'ultimate building blocks' turn out to be more like mathematical ghosts.
Hence, this whole debate. I wouldn't think you would propose infinite branching universes unless you had a real need to do so.
That I certainly don't agree with. I agree with the tested/potentially falsified part, but that doesn't mean that theories etc. are not read instrumentally, and I neither agree that (a) something makes it the case that theories etc. are meant to be read as ontological commitments nor that (b) most scientists read theories etc. as ontological commitments rather than instrumentally.
To paraphrase... On making observations of fossils, paleontologists developed a theory of dinosaurs to explain fossils. They made an ontological commitment to dinosaurs - i.e. the theory *IS* that dinosaurs really existed, had real behaviour, and occasionally really died in such a way that their remains are preserved. The theory of fossils is actually a theory of dinosaurs, which no one will ever observe.
But there are alternative theories - how about that fossils only come into existence when consciously observed? Thus fossils aren't evidence of dinosaurs, but rather evidence of those particular acts of observation. Another theory is that dinosaurs are such strange animals that conventional logic does not apply to them. Or, how about the theory that it is meaningless to ask if dinosaurs were real or just a useful fiction?
None of those alternative theories are empirically distinguishable from the rational theory of fossils, yet we manage to reject them. Not so in QM unfortunately.
But in my post, I questioned the existence of all objects, so referring to molecules doesn't change anything. It is likely that the appearance of an object is something which is created by the mind. If this is the case, then we have to ask, what is it about the world which our minds interpret as objects. In the most simple, fundamental form, an object is the appearance of a temporal continuity of stability, something which stays the same, or can be described by laws of inertia, for a period of time.
The mind sees thing in terms of objects, which is a temporal continuity of the same, such that a change to the same, must be accounted for, by causation. The mind "chooses" aspects of reality which demonstrate a continuity of sameness, and produces the appearance of objects. We can challenge this, is it real this temporal continuity of the same, and if so, what are those aspects of reality which the mind chooses to seize upon, and create the appearance of objects.
If we remove this assumed temporal continuity of the same, then we have no support for the appearance of objects. In order to validate the existence of objects now, we must determine what produces the appearance of a temporal continuity of the same, what produces the appearance of stability in time. It is this appearance of stability which produces our conclusions that something should be like this, or should be like that. But if this is simply taken for granted, then we have no understanding of the reasons why it should be like that. Therefore it is necessary to determine what causes temporal continuity, the sameness from one moment to the next, in order to validate the real existence of any object.
Again, what tends to make the difference there is to what extent we're talking about observables rather than abstractions including strictly talking about mathematics. That's not binary consideration. There are degrees or levels of remove from direct observables.
You describe yourself as a Positivist, i.e. you hold the view that all statements apart from those describing or predicting measurements are meaningless. Why do you care if photons exist, if the question is strictly meaningless? I think I covered that particular dinosaur theory.
Your theory of meaninglessness, along with the theories of the inapplicability of reason, and the theory of consciousness-induced-creation, are all generic ways of denying anything. You can even use them to deny that quantum theory is true.
You complain about abstractions and mathematics. Given a simple experiment such as the photo-electric effect, what mathematics and abstractions particularly trouble you?
The analogy is not apt. The fossil history of life, whilst having some puzzles, is a story of pretty straight-forward linear development. The exploration of the sub-atomic realm is not at all like that. A more likely analogy would be, finding a fossil which had absolutely no explanation - like finding a raptor fossil with a rabbit fossil inside it. Then you would have some explaining to do.
Excellent analogies!
Per your comment Wayfarer, the issue is that realism serves us well in the straightforward cases and the alternatives obviously fail us - the scientific enterprise is built on that realization. So why, when the going gets tough, should we abandon what has proven to work and switch to the alternatives? It seems completely predictable that it will cause confusion.
OK, but then QM would not be applicable to anything since it only applies to things that exist.
While of course there are philosophical issues here, the fact is that most people reasonably do think that many things exist and also think that standard scientific explanations are applicable to those things. So that really needs to be the starting point for any meaningful discussion.
I agree that a theory can be used instrumentally, whether or not it is true, as is done with Newtonian gravity. But a theory provides an explanation of the world, which is why we consider it to be true or false (or reserve judgement if we're not sure).
Some might say that the world-shattering thing was Everett's relative state formulation which was published in 1957 - two years after Einstein's death. It preserves realism, locality and causality. EPR-style entanglement and Bell's Theorem are non-issues under this interpretation. (Bell's Theorem proves that local hidden-variable theories are not possible which is why pilot wave theories have to be non-local.)
Quoting Wayfarer
That's the irony. Many-Worlds does not propose infinite (or finite) branching universes. The branching is already integral to QM. The Copenhagen Interpretation has to add a postulate to QM to prune the branches it doesn't want, which is the famous wave function collapse. Here is an example to demonstrate how it works.
Suppose there is a particle in a superposition of spin-up and spin-down. Alice has a device that can measure the particle spin and display the result. Before she makes the measurement, there is a 50% probability of the device measuring spin-up and a 50% probability of it measuring spin-down. The wave function initially includes the particle in superposition, and also the external environment which includes Alice and the device.
Now Alice measures the particle spin. The wave function evolves to a superposition of (particle is spin-up and the device measures spin-up and Alice reads "spin-up" on the device) and (particle is spin-down and the device measures spin-down and Alice reads "spin-down" on the device).
That just is the relative state formulation, or Many-Worlds. The wave function does not collapse, it continues to evolve. Whereas Copenhagen prunes the branch of the superposition that doesn't match what Alice reads on the device, which is just one state in this example.
So Many-Worlds is just the straightforward meaning of QM. Whereas Copenhagen is QM plus a collapse postulate that otherwise appears nowhere in QM. Unfortunately, as well as failing to explain why Alice observes one definite spin, it also introduces various paradoxes, such as non-local EPR entanglement, that simply don't exist under Many-Worlds.
These are the kinds of considerations that motivate the Many-Worlds Interpretation.
I think the issues with QM, especially the MWI, indicate quite clearly that things do not exist in the same way "that most reasonable people" think that they exist. Therefore your claim that this "really needs to be the starting point for any meaningful discussion" is completely unjustified. In fact, that claim only demonstrates your ontological prejudice.
How can you take MWI seriously, yet at the same time, claim that the existence of things, as most reasonable people use "existence", needs to be the starting point for any meaningful discussion? The two are contradictory. Either we take QM, and MWI seriously, as a premise, to see what conclusions may be produced, and forget about the "existence" which most reasonable people refer to, or we take the "existence" which most reasonable people refer to, and forget about QM and MWI.
So, which do you choose? Do you want to discuss MWI, or do you want to adhere to the "existence" which most reasonable people refer to?
It's not an either-or. MW is just the ordinary language interpretation of QM.
That doesn't imply that things will therefore exist in the way that we might intuitively think. Who knew that things wouldn't have a precise position and momentum at the same time? They still exist, but we've learned new things about them.
Right. So it says the 'many worlds' are already there, it was up to Everett to see the implication.
The wave-function collapse is not a theoretical postulate. We're not discussing physics, we're discussing metaphysics.
The instrinsically grotesque nature of there being 'many worlds' is skipped over by the advocates; like, the strangeness of the idea that we're all part of an infinite 'hall of mirrors' is being skipped over, on account of the fact that it is 'mathematically convenient'. Don't you see how strange that is?
Neils Bohr was unmoved by it, and in my books his judgement counts.
We would hate confusion. Much better to be soothed than to be disturbed.
This has been an instructive debate. I have taken some of it over to Physics Forum.
This is a most enjoyable thread to read: thanks to all the participants. Sorry I've been too busy to contribute. Here is Nietszche (from another thread really!):
I have been fretting over the distinction between epistemology and ontology, surprised by its use in this thread. I don't think science in its practice deals with ontologies, and I don't think physicalists think so either. For example, I'm working on something about placebos. Scientific discourse about placebos uses 'beliefs' as data and refers to 'beliefs' in its hypotheses. But I don't think that commits physicalists to an ontology including mental terms like 'belief': they may perfectly well claim that such epistemic terms stand for an equivalent more fundamental physical term, or that the mental supervenes on the physical.
Conversely, there is nothing forcing someone who debates physics - while accepting the methods of science - into an ontology of one kind or another. There's a whole Stanford group of philosophers of science who would say this, including Dupre and...
I'm going to quibble with you here. The Copenhagen Interpretation does quite a bit more than postulating wavefunction collapse in order deny reality:
1. Copenhagen explicitly denies the reality it purports to be describing. i.e. wavefunctions do not exist.
2. Because wavefunctions don't exist, neither does wavefunction collapse.
3. The Complimentarity Principle - the Principle that particles either exist as particles or waves, never both.
4. The Correspondence Principle. The Principle that QM is a subsidiary theory to classical Mechanics.
5. Principle of Acausality. i.e. the Born Rule and its algorithm.
6. Principle of irreversibility.
(7. Consciousness causes collapse) - in brackets because it is so embarrassing.
Of course, as you know, Everett's theory doesn't make any of those assumptions let alone declare they are principles of reality.
Well, there is indeed "no inductive reason for counting these laws as true"- because there is no such thing as an inductive reason for any explanation, let alone for arriving at an explanatory scientific theory.
I must at your quote to my list of generic ways to deny reality - the direct appeal to fallacy.
It is an either-or, you're just in denial. You're claiming that the only possible starting point for meaningful discussion, is the premise that things exist in the intuitive, common sense notion of "things exist". And you want to maintain this premise, while introducing the QM premise that things do not "have a precise position and momentum at the same time". Do you not see that this QM premise contradicts the common sense notion of "exists"? When there is contradiction, we have an either-or situation.
If you want to proceed in understanding the quantum reality, you must drop this ancient, outdated, notion of existence, which is inherently contradictory to the quantum reality. When "matter" was superseded by "energy" as the principle of continuity in the physical world, "existence" in the common sense notion of the word, was lost. Berkeley demonstrated that there is no necessity to the assumption of matter, it's just a useful premise. Aristotle introduced it as a way to account for continuity in an ever changing world. The assumption that "matter" is real makes continuity real. That is what is at issue here, what assumptions will we make to account for continuity?
Aristotle posits matter as the principle of continuity, it's the continuous thing which is real. Newton adapts the principle of continuity, in his first law of motion, to allow that the continuous thing is moving. Notice that the formulation of Newton's first law is such that the motion of the thing is that which is continuous, not the "matter", which refers to the very existence of the thing. the very existence of the thing is no longer addressed, just the motion of the thing is said to be continuous. Now, the continuity of existence is assigned to a description of the object, a formula, which describes its motion. Here, the continuity of existence is attributed to a form of the object, its motion, rather than using the Aristotelian principle which assigns the continuity of existence to the object's matter. Matter and form are two completely distinct aspects of the object.
Are you ready to proceed into the realm of "energy", in which the continuity of existence is firmly established to be inherent within the formula, the description which applies to the movement of the object? If so, we cannot turn back and try to assign to the object itself a continuity, without some mathematical principles, because this is to relate one continuity to multiple continuities. We've given up the Aristotelian notion of individual continuities for each and every object (matter), in favour of one universal continuity, energy. This continuity is expressed now as a wave function, and to relate the wave function to individual continuities, of individual particles, requires field mathematics.
Do you AndrewM, recognize that there is a fundamental incompatibility between the premise that there is just one continuity, and the premise that there is multiple continuities? These two premises are incompatible, contradictory. So, when we progressed from Aristotle's principle of matter, which assumes a continuity for each individual object (multiple continuities), to modern physics' principle of "energy", which assumes just one universal continuity for all objects, we crossed a gap of incompatibility. There are principles of relativity which bridge this gap, but the fact remains that there is an inherent incompatibility, and the bridge is just an illusion. This illusion creates a misunderstanding in those people who believe that the gap has been bridged. Now, when we proceed back across the bridge, to relate the wave function, which represents the one single continuity, to the multiple continuities of individual particles, through the means of field mathematics, we have that very same incompatibility. There is no bridge there, the bridge is just an illusion created by relativity theory.
How do you explain quantum interference if the other path does not "exist"? How can things that don't exist be physically causal?
Why does the Elitzur-Vaidman bomb-tester work?
Sorry, I don't know what you mean.
From premisses via inductive reasoning we arrive at conclusions. Premiss 1: There are well-demonstrated laws X in the lab. Premiss 2: Lots of things that are lawful in the lab turn out to be lawful outside the lab. Premiss 3: Laws X are one of those sorts of thing. Conclusion: Laws X apply all over the place.
How do you think lab findings end up as (supposed) neutrinos passing through me and you outside labs?
If you read my posts, what I contest is the assumption that the particle, or any object in general exists. To talk about any paths of the object is pointless before we've established the existence of the object.
Quoting tomCausality is a description, and there is nothing which prevents us from making imaginary or fictitious descriptions.
Sure, but try making a fantasy or fictitious EXPLANATION.
Seriously, try it. If the bomb-tester is too complicated, then try constructing a fictitious EXPLANATION of the simple Mach-Zehnder interferometer.
This is a good example of something I was saying to Wayfarer in another thread. He was asking why I didn't give an example of/quote some other published philosopher whom I agree with on the mind/body issue. I said that one of the reasons was that people then take one to wholesale subscribe to that philosopher's views, at least in the realm in question, and that's the case even when you explicitly try to preempt that misunderstanding. In the post that you're responding to, i said this:
Quoting Terrapin Station
Unfortunately with this:
Quoting tom
I'm not even sure what you're talking about.Quoting tom
I'm not sure what you're referring to there, either. Any comments I made about that would have been by way of an explanation (specifically with respect to "what's really going on" in my view); I wouldn't have been complaining about anything.
A fictitious explanation is even easier than a fictitious description, because empirical evidence relates directly to the description, not the explanation. So I could provide a fictitious description of what I see out my window, suppose I describe a bicycle chained to a post. But this could be verified empirically, and determined to be fictitious. My explanation of why there is a bike chained to the post, a man put it there last night, or a woman put it there this morning, is an occurrence in the past, and therefore cannot be empirically verified. The explanation can be denied as fictitious only when it is determined that some elements of the description are fictitious. Either the description, "there is a bicycle chained to a post" is determined as fictitious, or the description of the man putting it there is determined as inconsistent with what is empirically determinable. The conclusion that the explanation is fictitious can only follow from empirical determination of fictitious elements in the description. Therefore any sort of fictitious explanation can pass as a possible truth, so long as consistency with the empirical evidence is maintained.
If you're trying to make a point, you should explain yourself more clearly, because what you have said so far appears as irrelevant nonsense.
So, you are defending the assertion that:
"
...by purporting that there is indeed an "inductive argument" for the opposite? Seriously?
"Virtually no inductive reason". What is that supposed to mean?
Your premises are a joke, surely?
Over to you. The Mach-Zehnder interferometer explained ...
No. I defend its coherence, I'm agnostic about whether it's true, it's obviously a radical opponent of metaphysical realism, but some realists go along with the sort of thing Dupre and Cartwright say about 'ontology'.
What I was doing was responding to you saying...
...by asking you what you meant. I'm not being sarcastic, jokey or offensive. I genuinely don't know what you mean by the sentence I'm quoting. I tried to posit a banal way of constructing an inductive argument in the hope you would then show me what you meant. How do you arrive at an explanatory scientific theory other than by inductive reasoning?
Thanks! I [URL="https://www.physicsforums.com/threads/propagation-of-de-broglie-waves.789751/#post-5624477"] took a question over to physics forum [/URL] and made what I consider an original discovery. This is that the interference pattern in the double-slit experiment is not rate-dependent. In other words, whether the protons are fired singly or as a beam, makes no difference to the interference pattern. So that means that the interference is not dependent on time and space. Which suggests to me that the so-called 'wave function' is not something in time or space either.
The interference is from the fact that the particle can take two possible paths through the twin slits. So it is about the particle and the apparatus, not the particle and all the other particles.
And the fact that you see a particle hitting the detector screen is the destruction of that wave function. The particle shows up at some place, and you can attach a probability to that place ranging from very low to very high.
So to "see" an interference pattern on the screen requires we collect some reasonable number of wavefunction collapses - the story of many individual particles trips through the probabilistic maze. But the point of the experiment is that even a single particle will behave like a wave - a superposition of a pair of probability waves.
Right! That is what I have been thinking about. The question seems to be: how can a particle 'interfere with itself'?
So is there any sense in which the probability distribution is causing the individual particle to behave as though it is part of a beam of particles? It seems as if the probability distribution is itself like the so-called 'pilot wave' - in other words, it determines all the possibilities, but only in the sense of constraining the possible paths that any particle takes, whether individually or as part of beam. But because it is simply probability, or possibility, it is not something that actually exists; it is on the borderline of potentiality and actuality. So it doesn't exert any force, it is not causal in that sense, but causal in the sense of being a constraint.
You know, he also said this:
Buddhism does not promise, it delivers, while Christianity promises everything and delivers nothing.” —F. Nietzsche, The Anti-Christ
Lol, you're right I did. I'll just relocate that then...
Quoting Metaphysician Undercover
The issue of course is that we have no good explanation in terms of concrete commonsense notions. So you are not going to get the kind of answer you are seeking in terms of things you think you understand.
But such caveats aside, there is no particle travelling through the apparatus. Instead there is an evolving wave of probability of detecting a particle that reflects the shape of the apparatus. If there are two slits that the wave has to pass through, then it "goes through both" and you get the resulting wave-like interference effect.
Remember that you get a wave-like defraction effect even if only a single slit is open. The slit causes particles to spray out across the detection screen. If the particles acted exactly like particles, they ought to just go straight through and burn a crisp hole in the one spot, not get smeared out across the screen.
So that is the wave~particle duality. We know that only one particle gets emitted, one particle gets detected. But on its travels, it acts like a classical wave and responds to the shape of the experimental apparatus accordingly.
Quoting Wayfarer
But don't forget the causal role being played by the apparatus here. There are some specific - classical - set of constraints being placed on the particle event. That may include experimenters making complicated delayed choice measurements with half silvered mirrors, or whatever.
So in the decoherence view, we can see this as being about the hierarchical nested constraint of quantum potential. The causality is contextual.
Start with a naked vacuum - the Universe in its most unconstrained state, without any kind of experimental apparatus. You still have some probability of an emission and absorption event. But it would be very random and patternless. The wavefunction would represent very little causal or contexual information beyond some probability of a patch of vacuum having an energetic fluctuation.
But now start to assemble an apparatus. You have a photon gun, or some other particle producing machine that heats up and is designed to produce quantum events at some controllable rate. Now you have a wavefunction that is becoming quite highly constrained by its "classical" context. It is like corralling pigs in a pen and then creating a small gate which you can open. Pigs will start to fly out in a predictable direction.
Then start adding in slits. This is like creating another pen with another gate. The pigs that happen to make a straight bee-line towards the next gate will fly through, but are then free to bend off once they are past. If there are two such gates, the pigs will form an interference pattern as they eventually smash into some distant wall set at an appropriate angle across their path of flight - a further act of constraint.
So the wavefunction itself is the product of some environmental arrangement, some set of constraints that give shape to a "process". And the collapse is then just taking that constraint a further step. It is placing an end-stop by insisting that absorption happens "right now" due to some overwhelming constraint, like a particle detector screen.
The quantum weirdness then comes in because no detector can ask every question of nature that you might expect of the one event.
In the classically-imagined world, the particle (or wave) would have some exact position and momentum at all times. But in the quantum reality, you can't answer both questions at the same time with complete certainty. So the weirdness lies in the fact that the environment can causally constrain events up to a point. But that ability to create exactness runs out before classicality believes it should.
And as I say, even a single slit results in quantum uncertainty. The narrowness makes it certain that any particle had to come through it. But at the detector, you have to pay for that certainty by losing certainty about the momentum.
There you are standing waiting for your pigs to come flying straight through your maze of gates. But while you now the pigs can only come through the gate, they are then free to veer off randomly once their path is not constrained. And so veer off they do.
I do get that. Note these quotes.
And is that the wave that is described by the Schrodinger equation?
But I'm thinking, it can't be a product.
The fact that 'rate is not important' strikes me as being an important point.
Consider this thought-experiment - set up two double-slit experiments. In one, fire the photons off sequentially, i.e. one at a time. In the other, send them as a beam.
Then send the results to a third person.
Would that person be able to tell which was which? According to what I am told on Physics Forum, the answer is 'no'.
So if the pattern is not rate-dependent, then by implication the cause of the pattern is not a function of time.
What do you think?
You mean the pattern isn't the function of other particle histories. The pattern is simply a function of the fact the same maze, the same apparatus, imposes its constraints on a sequence of highly identical events.
So it is the design of the system that makes it rate-independent. You could stick the equipment in a cupboard for a thousand years, pull it out, and the quantum statistics would be unchanged.
Perhaps you are confusing entanglement and superposition in your understanding of what is going on?
...http://backreaction.blogspot.co.nz/2016/03/dear-dr-b-what-is-difference-between.html
The pattern is dictated by the wave function. That will be so regardless of which apparatus or set-up you're using. The equation which describes the distribution is not dependent on the apparatus, although I imagine that the particulars of each set-up might produce variations because of the distances involved etc. But the underlying determinative cause is the wave equation itself - however the wave equation is not a material cause, as it is not something which exists, it's simply a pattern of probabilities, as the name says. The ontological status of the wave function is the outstanding issue in all of this, it is what lead to the 'relative state formulation' in the first place. So I think the real sticking point is, how can a probability be causally efficacious. Isn't that what the whole argument is about? That's what Einstein kept saying to Bohr - 'God doesn't play dice'. He made a slogan out of it.
The reason why the rate-independence is significant, is that the behaviour of individual 'particles' (not that they're actually particles) is described by the wave-function, whether they're together or separate. In other words, whatever is causing that, is independent of space/time, or, that duration and the proximity of 'particles' are not factors in determining the result. Or so it seems to me.
That's not confusing super-position and entanglement, although what I'm starting to think is that the 'rate-independence' of the pattern, and the so-called 'entangled states', are actually two aspects of the same underlying cause.
The wave-function is the Face of God, or the Greater Context of the Truth if you prefer, that which none may know in all its glory. It is where the context and content meet with their identities becoming conflated and indeterminate. That's why for all practical purposes photons express the same behavior as their own shadows being instantly absorbed and emitted and displaying no preference even mathematically for any direction in space or time. Its a question of how humble their contents and contexts are relative to the observer which is why both shadows and quanta can express apparently acausal behavior. It means they should be measurable for both bandwidth potentials using differentials and juxtapositions for integrals that, combined, form a self-organizing system.
...and you can't see how you just contradicted yourself?
In the real world, every set-up is particular, and so a particularisation of the wavefunction equation.
Quoting Wayfarer
The equation is the useful, in the limit, generalisation or abstraction which describes no actual world until some numbers are plugged into it, just like the laws of motion.
You are making the mistake of reifying it and then treating that reification as a mysterious further concrete part of nature. Platonism redux.
So it is not simply a pattern of probabilities until some actual numbers have been plugged into the equation.
Quoting Wayfarer
The sticking point is that probability is irreducible. The wavefunction is the tool that limits the extent of the weirdness in useful fashion. But in the end, it can't be eliminated by just an equation. The equation - even if total information is plugged into it - can only point its finger to roughly where to expect a particle to be. So the question is how does that residual uncertainty ever get eliminated by a "real collapse".
Quoting Wayfarer
Well you are wrong. It is an important point that the particle "goes both ways" even if it was a one-off, never to be repeated, experiment.
The problem is you can't see that just from observation of the one event.
Quoting Wayfarer
So with next to no demonstrable understanding of the theory, you have convinced yourself you have stumbled on the missing link which has eluded a century of physicists?
Isn't that the definition of crackpot?
Again, in what way does the event by event accumulation of a twin slit interference pattern (or even single slit diffraction pattern) depend on the rate at which one event follows another? Where does the formalism require such a dependence?
You seem to think that the interference pattern is caused by some kind of dependency of one outcome on all the others. It is the particles that are all physically interfering with each others statistics in some kind of spooky, nonlocal, time and space defying, fashion.
But that is wrong. It is about how each event is affected by its (observational) context. So it is about a single event and the exact set-up of the apparatus for that run. And it is the human experimenters who control the state of the emission source and the apparatus, so ensuring that the interference pattern will accumulate over multiple trials replicating "the same event".
What's annoying was that this is the issue that Orzel was highlighting - the impossibility of perfect repeatability in the real thermal world. Something is always slightly different about the world. And that to me is a promising angle from which to attack the absolutism of MWI.
The point is that a superposition constitutes many states and they are all necessary for the wave function to evolve.
Quoting Wayfarer
Yes it seems strange because we intuitively think we live in a classical world. But we don't, we live in a quantum world. So the key to resolving that strangeness is to think of things (like particles, trees, cats, humans) as quantum systems, not classical systems.
Quoting Wayfarer
Indeed - I've enjoyed the discussion.
Thanks Tom - great list!
It doesn't contradict it. This just comes down to Wittgenstein's private language argument which, as I recall, you reject.
The term "existence" has a public referent. We point to an apple and say that that is what we mean by something existing. Even though we update our knowledge about apples from time to time, we are still referring to the same ordinary, familiar, existing apples that we were before.
Quoting Metaphysician Undercover
My apple, at the moment, may have a well-defined position. So it therefore will be in a superposition of momenta. This just means it's not a classical object, it's a quantum object.
There is only a contradiction if I say there is both an apple and not an apple at the same time and in the same respect, which is not what I'm saying here.
Quantum tunnelling between threads. It happens...
Rather than telling me I must be a crackpot, please consider the point.
I didn't say anything of the kind. What I was told on Physics Forum, is whether the particles are fired one at at time, or whether they are fired altogether, the end result is the same. So I am saying, it can't really be a result of 'interference', can it? Because if the interference pattern is not dependent on time, then it is also not dependent on proximity, is it? We are, after all, talking about 'space-time', so 'proximity' and 'duration' are two aspects of the same thing. So it's not actually 'interference' in the sense that interference in water waves is; that is, at best, an analogy for what it is. That is the only point I am trying to fathom at the moment, and I think it is quite in keeping with the 'Copenhagen Interpretation'.
When one refers to "the apple", that individual is referring to a particular instance of temporal continuity in which the similitude of an apple is of the essence. In order that one can refer to 'the apple", it is necessary that this similitude appears for a duration of time. What constitutes the "existence" of that apple is that this similitude persists through a duration of time. If the similitude seemed to flash upon the scene for a simple yoctosecond of time, then was gone, we could hardly assign "existence" to the apple. "Existence" requires that the described thing has a temporal duration
Quoting Andrew M
There is no such thing as your apple at "the moment", because as soon as you mention this moment, it is then the next moment.. You only have "an apple", if the same identifiable thing persist through an extended period of time, so this "existence" is not defined by a moment of time, it is defined by an extended period of time.
.
Ok. so let's assume that there is no particle, I'm cool with that. Isn't that what you say here, "there is no particle"?
Quoting apokrisis
Wait a minute, I thought the assumption was that there is no particle. Where did the particle come from?
So are you saying the two paths of an individual quantum event don't interfere due to superposition?
And bear in mind that we are talking about the interference of probability waves. And also that interference is about the additive or cancelling effect of wave peaks and troughs arriving at a point of space and time - the detector screen.
Given that, in what sense is it not analogous to wave interference in classical mechanics?
And given that, why would you expect the rate of producing individual events to make some kind of difference to the accumulation of an interference pattern at the detector?
Here is the relevant exchange from the Physics Forum:
afcsimoes: "So, if we made a first double slit experiment using a beam and a second experiment firing the same amount of particles but on a one by one basis, then we wil finish with two concrete objective and real identical images of an interference pattern?"
bhobba (moderator): "Yes".
Wayfarer: "Thanks! So from this, can I presume that the interference pattern is not rate-dependent, i.e. the rate at which the photons are emitted doesn't affect the distribution?"
bhobba: "Yes".
('bhobba' is one of the science advisers on physics forum. I asked some other questions as well, to which the answer was (predictably) 'go and read these six books'. Fair enough, but I'm only addressing a single point, I'm really not trying to solve physics problems per se. It's a strictly philosophical question as far as I'm concerned.)
One of the well-known problems of the double-slit experiment is that particles fired singly seem to act as though interference is happening. But how can interference occur when there's only one particle? It's one of the notorious difficulties of quantum mechanics. So I'm not saying 'they don't interfere due to superposition'; I'm saying that what appears as 'an interference pattern' isn't really interference at all - where it would be exactly that is if it really were water waves or sound waves.
So, it is analogous to the interference of waves in a medium, but here there isn't a medium! So the reason it is perplexing is because, there are waves, but nothing for the waves to be 'in'. The 'waves', so called, really are probability distributions, not actual 'waves' at all. The equation models both them and material waves, but they're of a different nature to waves in water, because there's no medium. They're not really waves, in the same sense, and for the same reason, that electrons are not really particles.
Now the reason I say that is compatible with the Copenhagen Interpretation is that there are many statements along similar lines from them: 'What we observe is not nature itself, but nature exposed to our method of questioning', said Heisenberg. Whereas, Einstein wanted to insist that there were something objectively real and (crucially), 'mind-independent', of which QM was an incomplete description. So he wanted to see 'nature itself' and was annoyed when Bohr and Heisenberg said 'no can do'. So that is really a big argument. I don't claim to have solved or discovered anything, but I think what I'm saying is at least close to the heart of the 'dispute between Bohr and Einstein'.
But again, this isn't a physical interference of the kind we imagine with classical material waves. It is the analogous "interference" of probability waves. And it is the "interference" of all the possible paths a single particle could take. And it is the "interference" which is both constructive and destructive. So it builds up probability densities as well as knocks them down.
So there is little point trying to apply some simplistic and materialistic understanding of the word "interference" here.
Quoting Wayfarer
Right.
Quoting Wayfarer
But that's ancient history. Today we know for sure that you have to give up either localism or realism. And probably have to give up both (in some sense).
However your posts here were making some kind of deal out of interference patterns not being rate-dependent. And it is not clear why you think that is relevant to the interpretation issue in any form.
If you have a wave machine making an actual wave of water in the lab, and the wave passes through twin slits, the split wave produces an interference pattern. So it is not an issue that we are talking about individual trials.
But a quantum twin slit experiment results in only a single particle like event at the detector screen. And the interference pattern disappears if the path of the particle is observed. So that's the weirdness that realism would have to explain away, and the weirdness that a CI-style pragmatism simply gives up trying to explain in terms of real world mechanism.
Not being rate dependent is not part of the weirdness. It would instead be weirder still if the particle-event was affected also by every other event both before and after it. How could we even calculate any statistics if we had to take the entire past and future of the Universe into account?
The point that interests me about 'rate dependence' is this - what is varied if the same amount of energy is released one photon at a time versus being released all at once? The only difference between the two trials is duration (=time). So if there is no difference in the end result, then it shows time is not a factor in the formation of the pattern. Doesn't that strike you as being significant?
I don't think I did that. I am saying, to imagine probabllties as actual waves is to do that.
Again, who is saying time is a factor in the sense that multiple events need to accumulate for there to be quantum interference?
Complementarity applies to the attributes of an object. To say, as you did, 'there is no particle travelling through the apparatus" is to say that there is no object called "the particle" to which the complementarity principle may be applied. To then speak of the paths of the particle is simple contradiction. The object being referred to exists as a wave particle duality, so if there is no particle travelling through the apparatus it really doesn't make any sense at all to ask questions concerning which way the particle goes.
Quoting Wayfarer
This is the dilemma which special relativity gives us. The principles of this theory deny the possibility of a real medium for electromagnetic waves. It is impossible that there is a medium for light waves, or else the special theory of relativity would be an incorrect representation. Light must always maintain the same velocity relative to objects, so there cannot be a medium, or else the object would have its velocity relative to the medium, rather than relative to the waves.
But the physicists who interpret special relativity do not allow for the possibility that the medium may actually be attributed to the object, that the object might actually be the medium itself. This would allow that the object maintains a constant velocity relative to the light waves, and also that these waves have a medium. Instead, physicists produce an artificial medium, space-time, which is completely separate, conceptual, it is unreal, and this unreal medium is the only place where the waves can exist. I think that this is an unreal representation of reality which creates false models. Instead of understanding electromagnetic waves as a property of objects, they are understood as the property of a conceptual medium, space-time, and this produces a categorical separation between the waves and the objects. The object itself, the real mind-independent object, has no real position in this conceptual medium.
All David Wallace's work is first class, and this talk particularly accessible:
It is impossible to arrive at an explanatory scientific theory via induction. For details see "The Logic of Scientific Discovery" by Karl Popper, or, appropriately to this thread, this succinct exposition.
https://arxiv.org/abs/1508.02048
Unless you subscribe to Everettian QM, in which case you retain both.
I'm sure you spotted I was being deliberately tendentious in some of the points in the list. I did this because I have given up any hope that critics of Everett know enough about QM to notice.
Kinda a reductio ad absurdum if you may...
Quite the opposite! Everettian QM is observer-independent, furthermore, you only exist in an infinitesimal slice of the multiverse.
I find it solipsistic and incomprehensible to view every entity existing in a multiplicity of states in the multiverse. Doesn't one wavefunction entail another or do these wavefunctions exist/evolve independently?
The question is, what causes the interference? With actual waves, the interference is a consequence of kinetic energy which varies with proximity. But in this case, the patterns are not dependent on the proximity of the particles to one another. So what is causing the pattern is not physical energy but purely probability.
I'm gong to make a list of the arguments against Everettian QM that appear in this thread. The argument from personal incredulity is most of them.
There is only one wavefunction.
Sounds like something you say in a cult. Never mind me, I never got past understanding how one defines an or a ? 'observer' in QM.
It may seem a subtle point, but what I said was there was no (classically-imagined) particle. There was "an evolving wave of probability of detecting a (classically-imagined) particle that reflects the shape of the apparatus".
So I was trying to highlight the irreducible quantum contextuality of the existence of any "particle".
There is plenty of "physical energy" represented in the experimental apparatus set up to make the quantum observation. So - given my contextual view of causality - the pattern is produced by a narrowing of the space of quantum possibility so that just this particular set of probabilities, as described by the system's wavefunction, remains.
So you are thinking in conventional bottom-up terms of probability spaces having to be constructed from an ensemble of "paths". And that is indeed pretty mysterious.
But I am pointing out how the apparatus represents a further localised constraint on raw quantum probability. Naked space would still have some (vanishingly remote) possibility of fluctuating in a way to produce a hot particle that has to pass through some pair of slits to get to some absorbing surface. But the apparatus exists as something some experimenter has invested time and energy to build. And so some probability space has been given an enduring physical shape, creating an ensemble of paths, as described by a wavefunction.
So my approach is contextual and top down. It fits with the view that the particle isn't "really there". It is contextual probability in the fashion of a soliton or phonon - the trapped excitations of a field, as described by condensed matter physics.
And remember that the excitations of condensed matter physics, these "topological defects", act like quantum particles. The similarity is not analogous but literal.
So your concern is based on the mystery of how probability spaces might arise out of nothing. My contextual approach instead says that probability spaces arise out of the constraint of everythingness. You get crisply "quantum behaviour" after the vague or indeterminate world has become sufficiently constrained so that what is left is the most irreducible aspect of that indeterminacy.
You eventually get down to the point where observables are no longer commutable. You can no longer ask all the definite questions that realism supposes of an event at once.
So the approach I am taking is holistic. World features only have sharp existence due to some localised context of constraints. Existence does not inhere in atoms or substances. Instead, atoms and substances are the end product of a suppression of flux or unbound possibility.
I enjoy collecting these fallacies - this one I will call the attribution of religion.
Can things get any more pathetic on a philosophy forum ... probably.
There is no 'observer' under Everettian QM. All physical interactions are treated exactly the same.
I note that you failed to reply on Orzel's points.
You appear not to be able get beyond chanting Deutsch and MWI in monotonous cult-like fashion.
Regarding that. Is there any distinction between local events and supra-local events in Everettian QM?
Of course, but what determines the pattern is not the consequence of things being arranged by physical forces, but as a consequence of the emergence of patterns in accordance with the 'probability wave'. So here, probability is acting causally - which is the problem, as probability is not physical.
So what I would like to argue is that the 'probability wave' is 'real but not physical'.
In the blog post that Tom pointed to, David Wallace notes that:
Fair enough. If you read my earlier posts, I suggested we could question the existence of the "particle", just like we can question the existence of objects in general. Andrew M took exception to this.
Quoting Andrew M
As you describe, apokrisis, the particle exists only in the context of the apparatus. Now, we assign a larger context of "existence" in general to the apparatus, and this is supported by its relationship to other things, and in particular, the observer. So the existence of the particle is supported by the existence of the apparatus. If we remove this assumption, that the apparatus exists, then it follows that the particle no longer is assumed to exist. In order to understand the existence of the particle therefore, it is necessary to justify the "existence" of the apparatus, and this is to formulate an understanding of what it means to exist as an object.
Now, notice there that "real" and "physical" are assumed to be equivalent. This figures, because all the authors there are "physicalist" - i.e. "what is physical, is real". But this is precisely the point at issue! In what sense are probabilities causative? They're not materially efficient, all they represent is likelihoods (or potentialities) - but in a very concise and indeed mathematically-exact manner.
Heisenberg accepted this, and said on those grounds that his view was more Platonist than materialist. So too did some of the other European quantum physicists, who weren't physicalists. But I'm saying, the current physicists literally can't think like that. Because they're operating within a physicalist paradigm, they can't accomodate the idea that there are non-physical realities. And what is happening as a consequence is the proliferation of these vastly speculative labyrinths of parallel worlds and multiple universes.
That's fine. So what is it in a "real but non-physical" sense?
I've already explained my own view of that - which tallies broadly with modern information theoretic and condensed matter influenced thinking.
But I also generalise the notion of apparatus so that the Cosmos is "an apparatus". It does have a past history that acts as a constraint on quantum indeterminacy.
The result of cosmic evolution - its spreading and cooling - is primarily that it has transitioned from being a relativistically hot bath or radiation to largely a cool dust of massive particles. So you could say we now live in the era of "proper particles" - stably-persistent protons and elections and neutrinos.
The experimental set-up simply reveals the contextuality of all this - because experiments can relax the constraints in ways that systematically demonstrate their existence at the normal, thermally-decohered scale, of our being.
The "existence" of the particle is validated by its context, within the apparatus. The "existence" of the apparatus is validated by placing it within another context. If the "Cosmos" is the apparatus, then to validate its existence requires that it be positioned within a context. The past history of the Cosmos does not provide us with this context, because its history is actually part of the Cosmos. To put it into context is to relate it to something external to it.
2.Quoting tom
3.Quoting tom
The first quote gives me the impression that this one wavefunction is representative of all interactions between objects in space, which seems to go against quote 3.
Now, I'm having trouble understanding how quote 2 and 3 can coexist. All physical interactions are treated exactly the same relative to what?
I appreciate your responses and apologize if my questions are rudimentary.
I don't particularly defend the term "probability wave" as its sounds overly concrete. And yet also you have to respect that it is only really making an epistemic claim about how quantum probabilities are observed to evolve in a fashion that is best described by the familiar equations of wave mechanics.
So where things get stretched is trying to read some hard realism into the formalism that turns out to work.
And then again, the point of dispute was about the issue of "time dependence".
The formalism describes each quantum event riding its own personal probability wave. So - as usual for any mathematically tractable theory - it builds in an atomism that allows bottom-up construction. As with MWI, you can then entangle individual histories to construct a whole spawning, eternally branching, never collapsing physical mess.
So there is not much disputing that interference is a property of individual wavefunction histories in the formalism. That is the successful presumption of the model.
And yes there is then a deep problem in that we believe that beyond the wavefunction, there must be its physical collapse. That is a view which both accords with common experience of seeing particles hit detector screens at some particular place, and with the highly successful presumptions of classical physical models.
So there are two strong states of belief in tension.
Then what best so far resolves the tension is to question the whole orientation of notions about realism. I appeal to the tradition of organic holism and hierarchical organisation - contextuality.
So it is "mechanics" - either classical or quantum (or statistical) - that is wrong in presuming that reality has locally inherent counterfactuality rather than provisional, contextual, counterfactuality.
That means I take indeterminacy - and its constraint - as the basic complementary ontic dichotomy from which crisp existence evolves as an expression of limit states.
And such an interpretation is consistent with the mathematics as the maths is taken to encode limit states, not atomistic actualities.
It's a hard question. If it was an easy question, why do you think the two greatest scientists of the 20th Century could never come to terms over it!
I think the original observation I have come up with is that if the interference pattern in the double-slit experiment is not rate-dependent, then it is not time-dependent, as rate is a function of time. This can't be the same for physical waves. Therefore, what is causing the pattern is non-physical.
Now, I don't think this is a crackpot theory. There is an article on Cosmos and Culture, by Ruth E. Kastner, on the need for a new paradigm, where she states:
She then goes on to outline something called the 'transactional interpretation', which I can't say that I understand. But what I am saying seems to be quite compatible with the quoted paragraph.
But again, quantum mechanics is not claiming the situation to be (classically) physical. That is why it talks about probability waves and not classical waves.
So this is an argument against something not at issue.
And part of the incompleteness of quantum mechanics is that it has to presume a backdrop classical time dimension to do its thing. The wavefunction of a particle is the evolution of its probabilities in time. And then at some point in time there is - the collapse.
So the double slit experiment does depend on a rate in the sense that it depends on an event actually happening the once - a wavefunction collapsing to create a recorded flash on a screen.
The mystery - from the quantum view - is how anything happens even the once with counterfactual definiteness. That is why we get the eternalism of MWI where nothing ever actually collapses and as many worlds as you like get added.
But others believe that QM can make no sense until time is also seen as an emergent feature of a deeper theory. And those are the kind of current approaches that interest me.
Quoting Wayfarer
Yep. The transactional approach tries to allow for contextual retrocausality. But it is clunky in being still a mechanical paradigm that relies on a classical notion of time and not an emergent one.
Some people, being incapable of any deeper thought, put a lot of store by what something is called. The original name for Everettian QM was The Theory of the Universal Wavefunction. Since then, nothing has really change.
When realist claim the wavefunction is "real", what they are asserting is that the Reality has properties which are in one-to-one correspondence with the mathematical properties of the wavefunction and the configuration space upon which it exists.
So, this mathematical description must provide direct descriptions - e.g. atomic orbitals, and permit emergent quasi-classical physics. If it fails to do this, then QM fails. QM has been tested and analysed to destruction, and nothing has been found to render it problematic.
How the Universal Wavefunction manages to do this is down to a property of the (projective) Hilbert Space it inhabits - i.e. separability.
Just like real space, what happens in Andromeda does not affect what happens here at the same time. What happens in sectors of the Hilbert space don't affect each other immediately either.
Quoting Question
There is no special "observer" interaction, causing wavefunction collapse. All interactions are the same as each other.
But, at least some interpretations are claiming exactly that. What is the motivation for the Many-Worlds Interpretation? According to David Wallace, the expert blog poster that Tom referred to above:
'people who accept the “state-as-physical” view are generally led either to try to make sense of quantum theory without collapses (that leads you to something like Everett’s many-worlds theory) or to modify or augment quantum theory so as to replace it with something scientifically less problematic.'
'Less scientifically problematic' because 'not appealing to non-physical factors, such as observation.'
So please don't tell me that what I'm talking about is a 'dead issue' when it is directly connected with the OP.
As any science must, as Kant pointed out. Anyway, that's it from me, there are far more knowledgeable people than myself involved in all this, I really have to concentrate on something else for a while, thanks, it has been very stimulating.
Where does MWI require the interference to happen between particle histories rather than within particle histories?
Thank you, I think I understand now. One last question that is on my mind. Does Everettian QM obey causality? And if not what determines the evolution of the wavefunction?
This is the guts of it. The interpretive hang-ups arise because there is this feeling that physicalist ontology must make a sharp distinction between what is real and what is not real.
With classical physics, all the regular physicalist ontic commitments seem to be upheld and so there is not even an interpretive issue - except for stuff folk don't talk about, like where physical laws reside in the scheme of things, and how they actually affect the world causally.
But with quantum physics, we should have been shocked out of this kind of complacency. Instead we have people still trying to cling on in Bohmian or MW style desperation to something being "real" in a traditional comforting local realist sense.
The way out of this intellectual bind is give up on "physicalist reality", and thus also on the "others" that frame its particular dialectic. As Heisenberg suggests here, we should understand existence in terms of being in the middle of two complementary limits - like reality and possibility. Or classical counterfactuality vs quantum indeterminacy. We are bounded by two extremes and thus exist at neither of them.
And it is this essential "between-ness" which is the fundamental.
That is why I am a fan of decoherence but not MWI. Allying the formalisms of QM and statistical mechanics is a way of describing an in-between "critically poised" state. It allows the evolving history of the Cosmos to be separated from the local histories of its particles by sheer classical scale. Space and time make a real difference.
But then MWI is what you get when you still want to assign fundamental reality to the quantum formalism and pretend that the classical realm is some kind of epiphenomenal illusion.
Again, if you assign fundamental reality to the in-betweeness - the causal story of how things become separated in the first place - then the quantum and the classical become the complementary limits of that evolving process.
And this is the emergent view which physics is working towards with quantum gravity. It is why MWI itself has largely retreated from its more extreme claims about multiverse type realitiies. The Orzel's are more representative than the Tegmarks when it comes to ontological discussions in this field.
That's what I thought I had been arguing all along.
Which is all well and good, but then arises the question of "manifested from what"?
Even Platonism demanded its chora so that imperfect reality could be manifested in actually substantial form and not remain confined to a real of ideas.
There is one way to answer this pertinent question. If every physical law is computable, then we can recreate reality (on a much smaller scale) here on earth...
And Godel's Incompleteness Theorem certainly comes into play here. How? Still working on it...
Isn't that switching categories though? If we put a thing into a context of other things, to validate its existence, isn't it a category error to attempt to validate a thing's existence by putting it into a mathematical context? In other words, mathematics cannot validate a thing's existence, because it cannot give the thing context, because there is a categorical separation between physical things and mathematics.
Sometimes I wonder if this world exists, and is for real. And if it is real, what kind of reality does it have that isn't shifting faster than it can be seen, let alone understood.
(Well maybe not exactly... It's an exaggeration, but only slightly. Occasionally, i feel sympathy with the familiar quote from the Buddha, on how to view the world:
As a lamp, a cataract, a star in space / an illusion, a dewdrop, a bubble / a dream, a cloud, a flash of lightening / view all created things like this.)
Very interesting thread though. Thanks to all. Carry on!
If you want to defend this particular categorical separation, go right ahead.
My point is that you can only do it via some kind of dichotomistic "othering". You will only have a metaphysically strong argument if you can describe the situation in terms of some mutually exclusive/jointly exhaustive pairing.
And so it is the kind of separation that in fact encodes a co-dependency. Each needs the other as the negation which underpins its own affirmation. And thus really any categorical separation is merely towards complementary limits. It becomes the disunity of a symmetry breaking which reveals the existence of a unitary symmetry.
So in this case, the maths stands for the eternally abstract. Which in turn means that "physical things" get reduced to the most impermanent notion of materiality - dimensionless fluctuations.
The argument is familiar to you. The proper opposition is not between substances (actual physical things) and (immaterial) ideas, It is between (physically general) potential - prime matter or Apeiron - and (mathematically general) forms.
The categorical separation I actually make - using systems jargon - is between constraints and freedoms. And then that separation in fact gets triadic or hierarchical development. That is how we end up with the hylomorphic "sandwich" of possibility, actuality and necessity.
So in the beginning there is just vagueness - the perfect symmetry of the ultimately indeterminate.
Then this gets broken. Constraints are habits or regularities - historically developed information - that break the raw symmetry and start to organise it.
But then constraints themselves encounter limits. Eventually you end up with the simplest state - like the U1 spin symmetry of electromagnetism. The symmetry of a circle. And where you get crisp symmetry emerging in that fashion, you get the baked-in freedoms of reality. You get the inertial degrees of freedom due to conservation laws as described by Noether's theorem.
Newtonian mechanics are the result of the emergent irreducibility of the freedom to move inertially in terms of translational and rotational symmetries. Relativity arises because Lorentzian symmetry is baked in for boosts or changes in energy scale.
So we have a "mathematical physics" that already tells its own story in terms of a triadic evolution. It all begins with "naked quantum chaos" - a perfectly vague symmetry of unbounded fluctuation. This symmetry is then broken by the emergence of spacetime - a Big Bang universe where dimensionality is reduced to just three global spatial directions, and filled by a cooling/expanding bath of radiation that gives everything an irreversible, symmetry-broken, direction in time.
But then as time develops, further more crisp symmetries, and thus symmetry-breakings, can manifest. The Universe gets cold and large enough for "massive particles" like protons and electrons to condense out of the radiation. We finally start to get the substantial classical things that you want to take for granted. That kind of stuff starts to pop out of the maths too.
So we already know a lot about how our notions of "maths" and "physical things" have an underlying unity, and how a disunity can evolve as further phase transitions due to cooling/expanding. Eventually things get stably broken because a particle like an electron is the mathematically simplest possible speck of matter. And then in the even longer term, all this matter will get swept up into black holes and radiated away to the coldest possible version of nothingness - the black body quantum sizzle of cosmic event horizons.
I mention all this yet again because this is modern metaphysics. It makes MWI seem the most Micky Mouse kind of philosophical contrivances. MWI nicked some of the maths of thermodynamics, but incorporates none of its deep ontology.
MWI is such a scam in that regard. It wants you to pay attention to physical situations with the simplest binary branch structure - a particle that might freely be spin up or spin down until someone has looked. How neatly the world divides into two.
Yet most emission interactions are wildly open-ended. When a photon is absorbed at point x in spacetime, then that directly creates the vast number of spacetime locales where the event will never occur. At the very least, there is a light cone sized sphere of places - a vast surface - where the said event counterfactually didn't happen.
So rather than two worlds, the simplest (being far less environmentally constrained) emission event would spawn a truly galactic number of alternative world-lines. It is a good job that MWI now uses decoherence's thermal averaging trick to treat this raging variety as differences that don't really make a difference in the big scheme of things.
But there is a basic dishonesty in claiming both wavefunction realism and then finding ways to ignore its full consequences due to the fact that "the observer don't care" about stuff that can be epistemically averaged away as not mattering.
It doesn't matter if a particular light ray from a distant star is absorbed by your eye, or by an eye on Alpha Centauri. Your eye is going to pick up some kind of thermal event from that distant star as it produces so many of them. And yet if we are to believe MWI, every possible version of the events exists as a real superposition. There is almost infinite branching the whole time, but only a select few of these branches - like spin up vs spin down - are treated as "separable". The rest are allowed to blur into an unmentioned bulk on good old epistemic grounds - the principle of observer indifference.
I of course agree with this epistemic view - in reading it from the other side. It is the point that decoherence is about a blanding away of the quantum uncertainty to leave only classical counterfactuality standing proud. We see a world of sharp black and white because grey gets averaged away. And then ultimately - at the quantum scale - there is a limit to this counterfactuality. That is what we are seeing when we ask non-commutating questions of nature like "where exactly are you/how fast and in what direction are you heading?".
So where MWI claims global irresolvability (no collapse), I instead focus on local remnants of irresolvabilty (so all of existence is the product of a relative state of collapse, it is only absolute collapse that is impossible).
And decoherence is a statistical mechanics add-on that lets you calculate the shrinkage of quantum weirdness to it limiting minimum. Yet MWI wants to read the maths the other way round - as a tool for the endless magnification of "real possibilities in superposition".
I don't agree with this. A categorical separation is not a distinction of co-dependency or complementary limits. The opposing terms, which describe the limits, hot and cold, big and small, for example, are always within the same category. If we describe two distinct categories with two distinct words, these are not opposing terms of co-dependency or complimentary limits, as you suggest, because those necessarily fall within the same category.
Quoting apokrisis
So here we have a categorical separation, the distinction between matter and form. But notice it is not a "proper opposition", it is not an opposition at all, it is a categorical distinction. The opposition, of being and not-being is contained within the category of form.
Quoting apokrisis
But constraints and freedoms are just the two limits of form, they describe the two complimentary limits, and as such, are of the same category.
Quoting apokrisis
All right, now this is a different category, "vagueness". So we have one category which consists of constraints and freedoms, and another category which consists of vagueness. Have you any principles whereby you establish a relationship between these two categories? Is one prior to the other? It appears like your claim is that vagueness is prior, but how could constraints and freedoms emerge from pure vagueness? That doesn't make sense, there is a categorical separation between these two.
You are ignoring the fact that I said the category from which complementary distinctions originate is the third category of vagueness. All categorisation has this triadic (that is, semiotic) organisation in my book ... if not yours.
Quoting Metaphysician Undercover
I just said that a symmetry breaking must reveal that there was a symmetry to be broken.
And if the breaking produces crisp division, then the originating symmetry must be the "opposite" of that - ie: radical indeterminacy.
So the argument has been supplied.
I may have a take on what Wayfarer is considering, but my terminology might be unpalatable in philosophical terms.
The implication as I see it is that this "probability wave" is an emanation from a portion of reality beyond the recognised membrane of our spacetime manifold. This portion may well have holistic presence as you suggest, perhaps transcendent of space and time, or reflective of such a state.
Personally the way I see it(apologies for the weird language) is as a reality in which space and time as we understand them are constructs, projections, like the two dimensions on a sheet of drawing paper, these are projectedthrough a substrate(again a construct) let's say the pre-noumenon forming a self contained field or membrane, or drawing on the sheet of paper. This is our spacetime manifold, as a holistic whole it exhibits probabilistic points, correlating to the symmetrical patterning of symmetry breaking of the whole(this whole might have fractal tendencies). This could also be viewed as a field or membrane projected between two poles in a pre-electromagnetism.
So as I see it particle physicists are trying to discern the probabilistic points in the projection I refer to, unaware of the pre-noumenon, or the reality in which the projection was constructed. l say constructed because I consider that the projection is an artificial fabrication conceived in a real world in which multifarious forms or species of projection, even fabrication are discussed, generated, and then individually put into practice on ocassion in a fabricated world, our world.
By analogy we are puppets and we are examining the strings which animate us wondering how they come into existence, unaware of the real world in which there is an author, a puppet maker, a stage, a puppet master and an audience. Let's say Punch and Judy.
The apple sitting on the table is the same apple that I pick up and take a bite out of a few seconds later. That is what is meant by identity.
It doesn't matter that the apple's atoms may be replaced by other atoms of the same kind over time or that the apple's appearance changes. Those aspects are not what our ordinary notions of identity and existence refer to.
Everettian QM is better than that - it is fully deterministic. i.e. given the state of the system at any time, plus the laws of motion, the state at any other time is determined. This goes for the future, and the past.
The universal wavefunction is static. Here's some experimental evidence to support this view:
https://medium.com/the-physics-arxiv-blog/quantum-experiment-shows-how-time-emerges-from-entanglement-d5d3dc850933#.t4rlu8hvu
This is an amazingly beautiful and powerful idea - the multiverse is at rest, and because of this it is in an eigenstate of its Hamiltonian. Different times are just special cases of different worlds, related by the laws of physics.
We know that every physical law is computable, and that any future law will be too. This is called the Church-Turing-Deutsch Principle (not to be confused with the Church-Turing Thesis).
Even a fairly rudimentary quantum computer will have the sheer capacity to simulate billions of visible universes simultaneously. Programming it to do so, is another matter of course.
Quoting Question
Pretty sure it doesn't.
Now my point, Andrew M. Appeals to identity do not support the real existence of the apple. "Identity" claims, asserts, or presupposes existence, but what we need here is the principles by which such a claim of existence is justified. Then we can apply these principles in an attempt to justify the existence of the particle, as an identified existent.
For example, suppose that you eat the apple. We must agree that at some point, the apple no longer exists. What comprises this passage from existence to non-existence of the apple? What distinguishes, or separates its existence from its non-existence. If we claim that it is our ability to identify the apple, as "the apple", which validates the existence of the apple, then we have nothing real, nothing objective here to support our claims of existence, we have only a subjective principle, that if the apple can be identified, it exists. Therefore to support our claims that the identified object, the apple, has real objective existence, we need to look for something real, inherent within the apple, which we can refer to for justification of its claimed existence. That's what Aristotle called the matter.
As implied in my discussion with you already and in my discussion with apokrisis, in modern physics we have switched this principle out. It is no longer assumed that matter, which is inherent within the object, is the principle which justifies the existence of the object. The existence of the object is justified by its relationships to other objects (relativity). That's what I discussed with apokrisis as "context". But then each context itself must be justified so we get a wider and wider context until we end up with the largest context, what apokrisis called the Cosmos.
In simple terms, we have an assumed "world", or "universe", and if the identified object has a valid position within this world, it has context and therefore existence. But the existence of that object is only valid within the context of that assumed world. So I asked apokrisis, what validates the existence of the "Cosmos", or in this case the "world" and the answer was "mathematics".
So here's the problem. The logical system at work here is set up with the premise that the existence of the object is justified if, or, "the object exists if", it has contextual relations with other objects (relativity). So any mathematics used will produce conclusions from this premise. If we desire to assume a "Cosmos", "universe", or "world", to objectify such relationships, and validate the existence of any particular object, that very premise, will not allow that the assumed "world" has existence except in relation to other worlds.
Let me get this straight then, you have one mother category "vagueness", and any other category is assumed to exist as a subset of this category.
The main contenders are:
1. Everett got it wrong due to my personal inability to comprehend.
2. Everett got it wrong because of my personal incredulity.
3. Everett got it wrong because I personally deny anything in a generic way, including apples.
Do we have to go through Bell's and other associated theorems AGAIN?
Well yes and no, because vagueness would be the ground state - in being the state "beyond categorisation". And also, in the full semiotic view, categorisation is irreducibly triadic. So there is no ultimate monism - unless you want to talk about the "one thing" of the triadic semiotic relation.
In Peirce's scheme, you have the three categories of firstness, secondness and thirdness that would correspond to my "system" here of vagueness, dichotomisation and hierarchy. That is pure possibility "reacts" against itself and becomes divided towards its crisp polarities. Then having divided, the division can mix over all scales to form a hierarchically structured world.
If say discrete and continuous are the two ultimate ways things could be, then the more definite it becomes that things are categorisable as either discrete or continuous, then also you get all the various in-between states of connectedness, or disconectedness, that go along with that.
I realise that this triadic, three dimensional, approach to categorisation is difficult and unfamiliar. It allows "rotations" through an extra dimension that normal categorisation - based on strict dialectics - fails to see.
So what does that mean? It means you have to remember that the extra dimension is one of development or process that stands orthogonal to the dimension of existence or structure.
So your very words are: "...and any other category is assumed to exist as a subset of this category?". That is you are, for the moment, restricting yourself to a static structural view to the exclusion of the further possible developmental or processual view. And I would reply, yes, vagueness does kind of stand in relation to the crispness of dichotomous categories as "a mother". But then I would want to rotate the view to remind that vagueness is defined itself dichotomously as the dynamical other of crispness. And it is never left behind in the developmental trajectory as development consists of its increasing suppression.
So you are hooked on the need to make some pole of being the ground state - which then stays where it is so a (constructed) movement away from it becomes a possibility. That is how you understand prime matter, for example. You have to start with a concrete stuff that represents efficient cause.
But in my view, vagueness is itself only granted existence in terms of what develops. It is the context of any thing that happens - it is the potential. But then it is only that because something does happen. The results are the context which make vagueness "a thing".
The logic of this would be circular if it weren't in fact hierarchical or triadic. ;)
So the metaphor you want to use here is "the mother and her many possible children". That encodes a forwards in time, unidirectional, efficient causality, with an unrestricted future state. The general begets the particular. The one begets the many.
But that is a truth of a triadic metaphysics seen from just one angle. It is only one cross-section of the whole.
Switching away from the structural/static view to the developmental/dynamical view, we would say the vague begets the dichotomy of the general~particular, or the one~many, the whole~parts. And vagueness is itself - structurally - a subset of the greater relation which is the dichotomy of the vague~crisp. Vagueness is the particular child of that more general parent relationship.
As for me, I have realised that to say anything meaningful about physics, requires that one does physics! I have posted on physics forums from time to time, but I think I am going to stop doing that, or saying anything about the subject in future. Life is too short.
It is hard to make sense of your post. But in a general fashion, physics does make use of this kind of "projection from a higher dimension" thinking. For any dynamical system - like some dancing sea of particles - you can step back to a higher level view that sees it as a now frozen mass of vectors or trajectories.
This is the trick that quantum mechanics relies on in invoking an infinite dimensional Hilbert space. There is room enough in Hilbert space for every alternative history. And reality can then be a projection of that frozen realm. If you look through it, you see the average state, the least action sum, that becomes what is most likely to actually happen.
But the ontological issue is whether the mathematical trick is just a mathematical trick or - as MWI might want it - the higher reality is the true reality, and the projection is merely some kind of localised illusion.
You get exactly the same issue arising in frozen block universe notions of time, based on special relativity. Or now with the AdS/CFT correspondence in string theory (where the 3D quantum play of particles is treated as projection of a gravitational string theory that sits on the holographic boundary of this "reality").
My own view of course is that it is simply a mathematical trick. It is how modelling works. And to get carried away by it is mistaking the map for the territory.
But folk find it weird and seductive to believe our physical existence is some kind of projective illusion. It's been a popular point of view ever since Plato and his shadows on the cave wall.
Quoting Punshhh
And here you seem to be trying to introduce some mind behind the scenes and directing the action. So you are really stacking up theism on top of the mathematical Platonism. I'd call that doubling down on everything I would disagree with as a natural philosopher and systems thinker here. :)
It seems I must establish a sub-category:
1. Everett got it wrong due to my personal incapacity to comprehend.
1.1 Everett got it even more wrong due to the fact I have been humiliated on a public forum.
I have already covered.
4. Attribution of religion.
Thanks for reminding me though.
Thanks for the new devastating criticisms:
5. Capitalisation of Words. Devastating!
6. Mentioning David Deutsch. Maybe you don't care that I mentioned Wallace, Everett, Schrödinger, Hawking, and implicitly DWitt?
We officially have ad hominem as an argument against Everett!
7. You claim I have no interest in Philosophy. For real!
You must admit that you come across as having the one true interpretation of quantum physics when the interpretation issue is famously wide open. And also you fail to respond to specific challenges concerning the ontic commitments that one might reasonably have even under a broad church view of MWI.
Let me elaborate my reasoning. Let's say that some sufficiently complex computer of whatever origin is designed to simulate all the physical laws of the universe. Now, keeping Godels Incompleteness Theorem in mind we have a problem of affirming that every outcome of such a computer is determinate. How does a computer of such sort prove its own consistency in modeling deterministic behavior?
How does science prove anything? It doesn't!
Goldel showed that the overwhelming majority of mathematical truths can't be proved. Not sure why you think that truth is relevant to physics.
Thats all very well, but the blinkers of what we know in this world and the mathematical consistencies we find here, are still being worn. Or in other words we just project what we already know, because we don't know anything else.
Or that the true ontology is something else not thought about.
I agree, but we can't know if our world is a localised reflection, localised peculiarity, or the best of all possible worlds. Again we are blinkered.
.Well that depends on what I mean by mind* and a mathematical Platonism is an oversimplification. I know now your approach and I'm with you in the phrase, natural philosopher and I like these systems ideas. I'm with you all the way with the triadic approach, that's how I think, but I happen to have another world and philosophy of the "ghosts in the machine", which I overlay and integrate within the naturalism.
*for me mind is equivalent to being the way being is used around here. Or the living entity which is hosted, emerges from, the body. But mind is itself viewed as a material(subtle). So this mind you suggest I am introducing behind the scenes is nothing more than another material, operating in the same, in essence, way that the material of science operates. So I refer to a hierarchy of more subtle or higher minds, which are all materials in turn, embracing a hierarchical regression (eternal, not infinite) of materials which each appear as minds in the sphere below in the chain. The ghost in the machine is irrelevant other than in the introduction of agency and purpose into the system( sorry if this is meaningless).
Your understanding of categorical separation is incompatible with mine. To me, if things are separated categorically, there is no crossing over or in between states, they are separated. Crossing over occurs in differences within the category. This is how I distinguish a categorical separation from a separation of opposition. The separation of opposition occurs within the category, like hot and cold, such that there are degrees of crossing over, in between. If the separation of hot and cold was a categorical separation, they would refer to different types of things, like temperature and size for instance, so there would be no such in between or crossing over.
My question to you, is do you respect that there is such a thing as categorical boundaries? It appears like you do not. You allow vagueness to be the principal, such that it permeates all boundaries, then there is fuzziness, degrees of separation, or in-betweenness even at the boundaries of categorical separations. This entails that the categorical separation becomes a separation of opposites, with degrees in between. In other words, there are no categorical separations. This allows your claim that mathematics permeates all boundaries, because there are no qualitative boundaries, they have been reduced to separations of degree, and these principles allow you to mix apples and oranges.
So take the above quote for example. You mention the separation between discrete and continuous as if it is a categorical separation. But if it were a true categorical separation, it signifies two different types of things, a qualitative difference. There could be no crossing over, such that a particular property of reality is both discrete and continuous, though there might be things which if we failed to understand them well, we wouldn't know which category to place them in.
Now, by saying that there are "various in-between states" you seem to deny that this is really a categorical separation, reducing it to a separation of degree (denying the qualitative separation between apples and oranges to speak metaphorically), such that you can justify your claim that the entire Cosmos exists in a context of mathematics. You have reduced the categorical separation between discrete and continuous to a separation of degree by assuming that there are in between states.
Quoting apokrisis
There is no "extra dimension" in your triadic approach, all you have done is reduced the categorical separation which by definition separates two incompatible types of things, to a single category. You are left with two opposing terms, such as hot and cold, with a separation of degrees in between. By redefining the names which dialectically indicate separate categories, to indicate a dichotomy of two opposing terms, rather than a categorical separation, you reduce the two categories to a single category.
Quoting apokrisis
This indicates that you do this with all categorical separations. Even vagueness, which is the principle by which you dissolve the categorical separation into a separation of degree, itself has an opposing term, such that there is now a vagueness in the categorical separation between vagueness and crispness, then an infinite regress of vagueness is implied.
Quoting apokrisis
Actually, it's an infinite regress.
Well if physics is mathematics manifest in nature, then a computer modeling such a mathematical construct would have to face with Godel's Incompleteness Theorem also? That's at least how I understand the issue.
IF that were the case, then what has Godel have to do with it?
But it's not the case.
But, that is the case, because any formal system relies on mathematics and logic to rationalize it.
For the matter Tegmark's ultimate dimension of the multiverse is literally mathematics with the wavefunction existing in N dimensions of Hilbert space.
It doesn't require mathematics. But even IF it did, what implication does Godel hold for simulating reality, or any part of it?
For example that some events within a simulated universe can be unintelligible. Or maybe that there are emergent phenomena within a universe that can't be explained from within the system itself.
I'll have to skim Tegmark's philosophy on the matter and get back to you with some actual arguments or theories of his. His multiverse philosophy get's complicated; yet, intelligible fast.
What does "unintelligible" mean? The laws of physics are all computable - that means that any finite physical system may be simulated to arbitrary accuracy by a universal computer. For something to be "unintelligible" that means it is contra the laws of physics, which is impossible.
The REASON for Godel's theorems is that the laws of physics do not support non-computable functions, which almost always involve infinite processes. Godel states that the overwhelming majority of mathematic truths cannot be proved by a physical process.
All this does is put mathematics on the same footing as physics - nothing in physics can be proved!
If no physical law can be proven, then doesn't that mean that physics will always be incomplete? In other words, you can have a supposed infinite amount of degrees of freedom and never accurately model a phenomena due to that.
It means we can conjecture true laws, but just as in mathematics, they cannot be certified as true by any algorithmic process. Not sure why you think that significant.
Progress is never-ending, but guaranteed. All problems are soluble. How can we be expected to solve a problem if we don't know it exists.
What I say is that (metaphysical strength) categories are in fact boundaries. They are limit states. And they come in dialectical pairs. They are the opposing extremes of what could definitely be the case.
So if a metaphysical separation is possible - such as the discrete and the continuous - then the separation "exists" to the degree it is crisp ... or not-vague.
I'm not sure why you are struggling so much with the natural logic of this.
So it is the same metaphysical logic. The difference is that Aristotle was still talking about what sounds like an actuality - substance has primal existence - and I'm talking about a "state" of potential in talking instead of primal vagueness. So my emphasis is on the possibility of developing contrariety as opposed to receiving it.
And remember the classical importance of making the distinction between contradiction and contariety, as represented in the square of opposition for example -https://en.wikipedia.org/wiki/Square_of_opposition
So I think you are fixed on thinking about categories in terms of contradiction where to get down to primal being, you have to apply contrariety as the deeper principle.
Don't know how you can possibly believe that when there are so many conceptual gaps in theory of matter.
Incidentally, an article here about the fact that ''wave-particle duality' is simply the quantum 'uncertainty principle' in disguise, reducing two mysteries to one.
"The connection between uncertainty and wave-particle duality comes out very naturally when you consider them as questions about what information you can gain about a system. Our result highlights the power of thinking about physics from the perspective of information," says Wehner, who is now an Associate Professor at QuTech at the Delft University of Technology in the Netherlands.'
Read more at: http://phys.org/news/2014-12-quantum-physics-complicated.html#jCp
I disagree with this, in a number of ways. First and foremost, you haven't distinguished between the category itself, and the defining features of the category, such that the defining features, the limits, are the category for you. I believe this is a mistake. So for example, if the category is temperature, you haven't distinguished this from the limit states, the opposing extremes, hot and cold. Therefore you no longer have the category of temperature, you have hot and cold. If you want to allow that temperature exists as a category, you must accept that it is something other than hot and cold.
Quoting apokrisis
But your claim was that there are degrees of in-between, between discrete and continuous. How is this possible, if discrete and continuous are different categories? What would it mean to assign to a thing as a property, that it is in between discrete and continuous?
Quoting apokrisis
I don't see your argument. The contrarieties which Aristotle refers to are each of the same category, black and white, hot and cold, good and bad. Each pair of contrary terms represents the extremities of the category. When we assign to a substance, a property according to a category, we cannot say that the substance has contrary properties of that category, though it can at different times. The same substance can be at one time hot and at another time cold, but it cannot be both hot and cold at the same time.
Quoting apokrisis
It seems quite clear to me that you have this backwards. Categorization is the deeper principle. Contrariety exists within each category, but there is no contrariety between the categories, only a type of difference.
Look up fractal geometry - https://en.wikipedia.org/wiki/Hausdorff_dimension
The in-between spectra are now mathematically well defined.
Quoting Metaphysician Undercover
Huh? We say it is cold because it lacks heat, and hot because it lacks chill. So it is about "both things at once" - except it is about that as a broken symmetry or asymmetry. At any particular time or place, we have more of the one in terms of having less of the other.
Again the logic of this just seems really simple.
Quoting Metaphysician Undercover
Well, I've already said you can turn around and treat vagueness as the ur-category - the limit on contrariety. And that recreates Aristotle's argument for hylomorphic substance, but just recasts it in more suitably developmental or dynamic terms.
Asking for justification for the existence of the apple is misplaced here. The thing on the table that we can publicly point to is what we mean when we talk about apples. And part of what we mean is that they exist. (As opposed, say, to our talk about unicorns - we can only point to pictures of unicorns.)
This just is the Aristotelian approach that you mention. There really is an apple there and it has a particular form such that we can point to it and identify it. How the apple appears to us depends both on the apple and on the surrounding environment, including the body and brain of the observer and the interacting light particles.
Quoting Metaphysician Undercover
I agree that is the problem. A scientific theory such as QM is an explanation of the world, not a mere formalism. And it is testable on that basis. We can plug in particles (or, in principle, apples) and compare what the theory predicts with our subsequent observations.
But don't you agree that if you eat the apple, at some point it will no longer exist? And, don't you think that the apple came into existence at some time? Unless you can describe what marks the difference between the existence and the non-existence of the apple, why do you feel so confident that the apple exists? I mean, to me, it appears like you just take it for granted that the apple exists, without even knowing what it means to exist. If you knew what it means to exist you could probably tell me what constituted the apple coming into existence, and what constitutes the apple going out of existence.
Quoting Andrew M
OK, if we agree here, then let's go back and take a look at the Aristotelian principle, to see the difference. Instead of defining the existence of the object through its relations with other objects (relativity theory), or as I discussed with apokrisis, defining the object as being in a context, Aristotle defined a principle of existence (matter) which is inherent within the object.
Do you agree that these are two very distinct ways of defining existence? The way of modern physics is to define the object's existence through its relations to other objects. The way of Aristotelian physics is to assume that there is existence inherent within any object, regardless of its relationships with other objects, it has substance. Now let's consider the apple on the table. Which do you think is the truth concerning the existence of the apple? Do you think that the apple only has existence because it has relationships with other objects, the table etc., or do you think that there is something inherent within the apple itself, which constitutes its existence?
This is an issue because given any sufficiently sophisticated universal computing device there will be "truths" or what can be called manifest physical laws (through mathematics, e.g in Hilbert Space) that can't be proven to be true.
This is essentially putting a thorn via Godel's Incompleteness Theorems into the validity of the Church-Turing-Deutsch Principle. I don't know if you see the link there yet or if I haven't made the causal link sufficiently clear.
If you want to take this line of reasoning as far as possible, then this conundrum extends all the way to ANY physical law, in that we can never be certain of it being true in all circumstances. Even in a deterministic universe via Everttian QM, we could have a computer that will never be able to tell us that every Entscheidungsproblem will be able to be resolved in a deterministic manner.
Nothing in science can be proven true. This isn't news.
Quoting Question
Godel's theorem is irrelevant.
Quoting Question
It is logically impossible to certify a physical law as true. This isn't news.
No, you can't certify any scientific theory as true (for the nth time) and that has been known since at least 1936.
Now, what difference does that make?
At some point the apple grew on a tree and before that the tree grew from a seed. And in the other direction, at some point the apple will be eaten or decompose and perhaps its seeds will grow into into new trees. This is just matter changing form such that we can identify substances like apples. So the boundaries at the coming-into-existence and going-out-of-existence of an apple can be vague or ill-defined. But the apple is clearly identifiable when it is fully formed. And so we can develop language to talk about it.
Quoting Metaphysician Undercover
Right. The logical form of the apple is not sufficient for existence. Matter is also required.
Quoting Metaphysician Undercover
The latter. The way I would put this is to say that if the apple has form and matter then it is substantial. That is, it exists.
To relate this back to QM. The formalism is the Schrodinger equation. The primary dispute is whether the equation is substantial. That is, is the wave function real? If it is, then that explains why we see interference effects.
So, what I am getting at is what you can ask.
My main point is that how can we know for certain that the MWI is actual/real/valid/.../true if the only practical means of verifying it is via trying to simulate the laws of the universe via the Church-Turing-Deutsch Principle, which itself can't be known to be true?
What's even more damning is that Godel showed that even if the Church-Turing-Deutsch Principle is by some means true, then even if one were to create such a sophisticated logical Turing Machine, then even then we would not be able to know whether halting problems (physical phenomena taking place within such a machine) are deterministic (via computational means) or not.
It's kinda like standing on a rug and pulling at it at the same time.
I'm going to try and simplify my question to a more simple one pertaining as to whether Godel's Incompleteness Theorems negates the possibility of constructing a universal Turing machine that would be capable of computing all known physical laws. Or am I running in circles in trying to state that all physical laws can be proven to be true (computable or replicable?). I mean, the act of a computer able enough to simulate them, would be sufficient evidence despite not being able to verify them from within such a system.
If anyone want's to take a stab at it here, then by all means.
How can you possibly prove physical laws with a calculation? Being computable or otherwise neither proves nor disproves anything. Nor does this have anything to do with Incompleteness theorems, as far as I know.
Those sorts of machines already exist, and a theorem regarding proofs in mathematics didn't stop that happening!
Quantum computers and classical computers share the same set of computable functions. Given eternity, infinite power, infinite memory, then a classical computer can perform the same calculations that would take a rudementary quantum computer a few cycles.
In the case of the classical computer, we are happy to point to where the calculation is taking place - here's the cpu, here's the memory etc. Where does all this happen in a quantum computer?
To put this in a bit of perspective, the visible universe is thought to contain ~2^149 bits of information (from memory). A rudimentary quantum computer with a few hundred qubits outstrips that by an astronomical figure. Actually, "astronomical" doesn't even begin to express the magnitude of the difference.
As David Deutsch has said, when the first quantum computer is constructed, its major impact will be psychological.
Quoting Question
I think I have already mentioned that no scientific law can be "proven to be true". They can however, be tested.
Everett's is the only explanation of quantum mechanics known. It is also the only explanation that is testable and which agrees with quantum mechanics.
https://arxiv.org/abs/1508.02048
See:
https://www.physicsforums.com/threads/proving-the-church-turing-deutsch-principle.894529/
No, if something is computable (doesn't encounter the Halting problem), then it is real in some sense. If something can't be computed then that is indicative of a gap in understanding or that there are some things that are unintelligible.
I always had a problem with understanding the importance of physics, mathematics, and logic and which of them follows from the rest.
Best of luck with that.
Could you ask them to prove the Principle of the Conservation of Energy while you're at it?
The CTD Principle is proved under quantum mechanics. Otherwise, it is a conjecture about future unknown laws. It is a guide to what they must be like. Just as we expect any future law to be Unitary.
No aspect of physical reality in non-computable.
No, it means that physics is a subset of reason. Science is constrained by the fact that it only deals with physical reality. Reason is not constrained in any way.
Yet, that statement requires much-needed justification!
Is it all platonism in modeling logical relations between objects in logical space?
You need to study the scientific method. There is no justification, there are no "good reasons", such things are unobtainable and of no use.
I have yet to see proof that every physical law can be computed, which you (by the way) state as an absolute truth(?) Until then this is an unsubstantiated claim that you're throwing around here and there.
OK, I'm going to try to relate this to what you say about the apple, and about QM. I hope you understand, that to say the apple consists of matter and form, in the Aristotelian sense, is to invoke a type of dualism. You are saying that the apple consists of two distinct aspects, its matter and its form.
Under Aristotelian physics, the form of an object is what is active and changing, while there is an underlying matter which persists, and does not change.
Quoting Andrew M
Let's say that the apple is growing, ripening on the tree, so it is changing colours. It's form is changing. Do you believe that there is an underlying matter which is not changing? Of all the nutrients that the tree is putting into the apple, while it becomes sweeter and sweeter, is there really some underlying, "matter", which is not changing? If there is not some underlying "matter", which establishes continuity, the continued existence of the apple is not substantiated. We can call it "the apple" at one moment, but since it is changing, then unless we assume something underlying which is not changing, our claim that it is "the apple" at a later moment is unjustified.
When the molecular structure of the apple is changing over time, how can you say that 'this is just matter changing form"? Everything is changing, where is the "matter" which we assume is changing form? You can justify the claim that there is matter, by saying that there must be matter, because it remains "the same" apple. But the problem is that the existence of matter is just assumed in order to account for the apparent continuity of existence. So to now say that there must be such continuity, because there is matter, is circular reasoning. If we cannot validate the existence of matter, then we cannot justify that the apple continues to be the same apple despite changing, because we know that even the molecules and atoms are changing. When an apple tree comes into existence from a seed, and grows, how can this be matter changing form, if even the atoms and sub-atomic particles are changing?
Quoting Andrew M
Let me suggest to you that the concept of energy has replaced the concept of matter in most modern applications of physics, as the underlying thing which persists, and doesn't change, while the form which energy takes, actually changes. So we have the energy of the apple, rather than the matter, as the principle of continuity, this is firmly established by special relativity. Energy may come into the apple, and it may leave the apple, and as long as the amount is conserved, we have an underlying thing which doesn't change, the existence of that thing is substantiated through its energy.
I am not extremely familiar with the Schrodinger equation. I understand that it is closer to classical mechanics than it is to special relativity. Classical mechanics, being based in mass rather than energy, as the principle of continuity, is closer to the Aristotelian conception of matter, than the conception of energy in special relativity. Since substantial existence can be validated by any principle of continuity, whether it be mass (matter) or energy, then there should be no question as to whether or not the equation is "substantial". However, there may be inconsistencies between what is believed to constitute "substance".
What sense is that? Does it have anything to do with what I asked? ("How can you possibly prove physical laws with a calculation?")
Quoting Question
How do you figure that? Do you even know what it means for something to be computable?
Try this
http://www.daviddeutsch.org.uk/wp-content/deutsch85.pdf
or Google
If a physical law can't be certified as being true, how can it be computable?
https://www.physicsforums.com/threads/church-turing-deutsch-principle-and-incompleteness-halting.895072/
I'm considering contacting David Deutsch in regards to this question... I don't see any harm in doing that as this is quite an important question in my mind.
I'd at least try to read the paper I linked to though - the one where the CTD Principle is elucidated and the quantum computer invented. You are misrepresenting the CDT Principle, which makes you look like you don't begin to understand it.
I am reading it as we speak. I see no mention of the halting problem thus far...
Quoting Metaphysician Undercover
Aristotle doesn't claim that two kinds of substance exist or that two kinds of properties exist, which is the usual sense of dualism. Instead substance (i.e., a thing that exists such as an apple) is an integration of matter and form.
Quoting Metaphysician Undercover
The simple explanation is that the apple's identity doesn't depend on its molecules and atoms being the same. Instead object persistence is implied when we talk about particular apples. What would be relevant is if someone secretly took the apple from the table and replaced it with a different apple.
So the issue is really about meaning and use, not justification.
Talking about something does not cause the existence of the talked about thing.
Quoting Andrew M
So if such aspects of the apple are changing, then by what principle do we insist that the same apple continues to exist? We cannot just say "it is the same apple that it was yesterday", assuming that because we say that it is the same apple, therefore it is the same apple. We know that many things have changed, and therefore it really isn't the same apple. We need a principle to justify us saying that it is the same apple, so we can claim this to be the truth.
Quoting Andrew M
No, it's really a matter of justification. You can sit and watch the apple all day, and even see it change, without taking your eyes off it, so you know that no one has switched it. You know that it has changed, so you know that it is not the same apple. Yet we say that it is the same apple. Saying that it is the same apple does not cause it to be the same apple. So we need to justify this saying. What causes it to be the same apple, despite the fact that it has changed? We need to know this in order that we can be satisfied that what we are saying (it is the same apple) is the truth
Yes we do. That's because object persistence is part of the ordinary concept of an apple.
Quoting Metaphysician Undercover
That's correct, but the issue here is what is meant by the term "apple".
You're taking a particular time slice as constitutive of what it is to be an apple, like an individual frame in a film. But, in ordinary usage, the entire time line (or world line) is understood to constitute the apple.
To use the film analogy, it is the same film despite the fact that its frames are different. But there would be a legitimate issue if the second half of the film were replaced by frames from another film. This latter issue is where justification is relevant.
Saying that temporal continuity, "object persistence", is part of the concept of the object, does not justify the assumption. That's like saying that the reason why I believe it, is because I believe it. Conceptions can be wrong. And that is the whole point here, we assume temporal continuity, but on what basis?
Quoting Andrew M
No, that is not what is at issue here, you don't seem to get it. We know what is meant by "apple", or "object", temporal continuity is implied, but the question is whether or not this is a misconception. We know that the word "apple": is being used to refer to the appearance of a persistent similitude on the table. We know that the idea of temporal continuity is implicit with the concept of "apple", but the question is, is this temporal continuity real, or is it just an appearance. If it is just an appearance, then this is a misconception.
When I joined this discussion, what I questioned was the existence of the particle. I question the existence of the particle by the same principle that I question the existence of any object. If the assumed temporal continuity of the apple, or any object, is a misconception, then the same thing follows for the existence of the particle.
So help me out here. Do you think there is a causal basis for the apple on the table appearing as it does from moment to moment? Or do you think that, for all we know, it's just random coincidence?
Clearly it's causal, an object cannot be random. Random existence is unintelligible but an object's existence is intelligible.
World lines apply to objects, whether particles or apples. The world line for an apple is the convergence of particle world lines.
That's a causal explanation. But in everyday life, it is intelligible to talk about an apple as persisting because we know its continued appearance is not random coincidence, whether or not a causal explanation is readily available. Which is sufficient justification for the claim that the apple exists.
There is no such thing as the convergence of particle world lines, each is an individual. You could create an average, or a gravitational centre, but this requires another completely different assumption.
Quoting Andrew M
OK, I accept this, because you recognize that a cause may be needed. Let me put aside the question of whether or not you are actually convinced of the necessity to assume such a cause, and proceed under the assumption that it is necessary. We can take the traditional approach now, and assume that the cause is God. This is Newton's approach in the first law of motion. The continued existence of the object is simply assumed, guaranteed by the Grace of God, as the most divine Gift, existence. But don't you agree that the true philosophical approach, and consequently the scientific approach, would be to attempt to determine and understand the activities of this cause?
If we proceed, while holding the belief that there is necessarily a cause of temporal continuity, how could we integrate this cause into what we observe as the continued existence of the apple? Isn't it necessary to assume that at each moment of time, there is a cause which acts, to ensure that the apple will appear in a way similar to how it appeared in the last moment. Any change to the apple would be caused by an interference with this divine cause. This could be an interaction with other objects, each object having its own cause of temporal continuity, the will of God acting within each object individually.
But what constitutes a moment of time? This divine cause has been described above, as acting between moments of time, such that at each moment of time, the apple has continued existence. What happens when we divide the duration of time into shorter and shorter periods? At some point, we will reach a period of time which is so short, that this cause has not had time to act. What do you think we would observe in this short period of time, pure randomness? Perhaps you would expect to see that if you forgot about this cause. But if you believe in this cause, then you would expect to find it in action.
You can approximate the apple as a point, or treat it as an extended volume (which would be a world tube) or aggregate the segments of the individual particle world lines that converge.
Quoting Metaphysician Undercover
Sure, we should try to figure out what the cause is. My only point is that we don't need to doubt the existence of the apple just because we don't know what that specific cause is. We know there is a cause (because it's not random coincidence), but it may be that no-one can explain exactly what it is or perhaps our current best explanation will end up being overturned tomorrow. Regardless, we can continue to intelligibly identify apples as existents in everyday life just as we always have.
It's not that we must doubt the existence of objects if we do not know the cause. You know we can live without knowing the cause. But if we want to find out the cause, then we must doubt the existence of the object. By doubting it, we express recognition that its existence is contingent. The question which naturally follows is "contingent on what?". So we proceed to seek that cause. If we take the existence of the object for granted, then we assume that it's existence is necessary, so long as it exists according to the laws of nature, which are induced from its observe existence. We state the law to the best of our knowledge, and we circumvent the question of why does the object exist, by converting it to "why does the object act according to the law?". This is answered with "because it exists" (existence being taken for granted). Existence appears as a necessity because it is the premise for logical procedure. Therefore it is not doubted, it is not seen as contingent, and the cause is not sought.
I won't say, "I believe it's true." But, the concept does appear to have some usefulness.