Double Slit Experiment.
Any physics experts here? I was wondering how many versions of this experiment have been run? What counts as an observer? Can they use an electronic eye to see and record where the photon actually goes, and half the time delete the results before a human becomes aware of it and half the time let it known to a human? I want to know if the electronic eye is interfering with the experiment and collapsing the wave function, or if it is awareness by a conscious human being.
Comments (159)
Wigner and Wigner's friend have also classically a different view. For Wigner's friend the cat is either alive or dead, for Wigner it is in a "probability cloud".
Even if it's irrefutable, that doesn't mean it's true.
How's about we bring a Raven into it? What does he/she say?
It is even more irrefutable that wave function collapse does not require consciousness. It seems that others are pointing this out. Wigner himself abandoned this interpretation when it was shown to logically lead to solipsism. Solipsism is another irrefutable thing.
Almost all quantum experiments take place without a human observer, except to gather the data afterwards.
Quoting TiredThinkerMetaphysically, it is one system interacting with another, in any way.
Epistemologically, it seems to be a function of awareness, be it human or otherwise.
You can't watch a photon. If you measure its path, any interference disappears.
Human awareness does not play a metaphysical role (except in the Wigner interpretation). A result can be kept in superposition, but I know of no way to 'delete' a measured result.
The E-eye is not necessary either. Any interaction (the photon hitting the far wall in a room with no people or sensory devices) is enough to collapse the wave function, in interpretations with wave function collapse.
SO true!
It's possible to mark which slit a photon goes through and then later erase that mark. With a stream of marked and then unmarked photons, an interference pattern will be formed as per the original double-slit experiment. See the quantum eraser experiment. However, apart from that kind of carefully controlled experiment, once information leaks out into the environment (say, to an electronic eye) there is no practical way of erasing it and no interference pattern would form. That's the case even if no human ever learns which slits the photons went through.
I doubt matter underlying the wave function ever fully collapses, as if an absolute demarcation between coherence and decoherence exists, but rather morphs into different shapes and formations depending on context, and can be composed of multiple states simultaneously, wavelike, particlelike, entangled, superpositioned, etc. all at once. Trillions of interacting atoms become comparatively particlelike (localized), but still participate in weird relativistic or nonlocal dynamics, for instance infused with EM radiation and further field phenomena that stretch or transgress the boundaries of classical physics. Much of this hasn't been adequately theorized so far, why quantum physics is so fascinating, truly a pioneering science.
I haven't read about this electronic eye deal, but is it somehow designed to avoid causing decoherence?
Are you speaking of a matter wave or a probability wave in QM? Kenosha Kid is probably out making millions with his guitar rather than really important work like clarifying physics on this forum. :sad:
The probability wave is the wave function, the quantized matter wave is the substance that the wave function probabilistically models.
It was performed ages ago using crystals to diffract the electrons, and more recently in a way more similar to how the experiment is actually described.
Quoting TiredThinker
Putting a light source close to the slits destroys the interference effect: the more powerful the light source, the less interference occurs. Basically the more powerful the light source, the more likely the electron will interact with one or more photons en route to the screen. So whether you look at the electronic eye's recordings or not, the photons would kill the quantum behaviour that the experiment interrogates.
I'll try, but...
Quoting jgill
I wish!
Quoting SolarWind
This first sentence is the only thing that made sense to me, and it's not right. It's certainly refutable that consciousness collapses the wavefunction. I'd say the greatest consensus is now around non-collapse interpretations of QM (e.g. MWI). Even among collapse adherents, I don't think it's common or even sensible to make collapse dependent on consciousness. I've never met a quantum theorist who believed this, but they do, or did, exist. Personally I think that's a symptom of humans insisting on the specialness of humans though.
I think the rest of your comment assumes your own particularly esoteric beliefs.
Quoting Enrique
Not sure what this means either. The material properties of, say, an electron (mass, charge, lepton number, etc.) certainly do transcend whatever's going on with the wavefunction if that's what you mean. Or maybe you mean the particle field. A particle is a quantised excitement of that particle field according to QFT, that is: whatever the excitation, it is constrained to have certain properties, that aforementioned material properties that are fixed, independent of the actual wavefunction.
As I understand it, the "collapse of the wave function" essentially models matter insofar as large quantities of interacting particles give rise to contexts of decoherence, resulting in definite statistical distributions relating initial and final states, beyond which the probabilities are effectively negligible.
What I was saying is that these probability distributions the wave function models when it collapses into a definite state are relative to a specific perspective on large wavicle quantities, where these wavicles tend to act like particles. The picture of matter as in an absolutely decoherent, "collapsed" state works for many practical purposes, but quantum nonlocality shows that this is an illusion, a degree of coherence always remains.
Perhaps you can explain to us how this "coherence" or quantum entanglement amongst wavicles is modeled. Local hidden variables were ruled out by experiment, so where is theory currently at in accounting for nonlocality?
In order to make any observation you need to crash bosons and fermions...not the most typical observation out there.
Well the classical limit ensures that, for the most part, material properties of large many-particle systems themselves are well defined. This doesn't mean that the particles within them have collapsed. Conducting electrons in metals, for instance, could be spread throughout the entire metal, but the metal itself still has well-defined material properties. On the other hand, as I said above, a single photon is sufficient to collapse an electron wavefunction. So it's not like there's a one-to-one correspondence between system size and collapse.
Quoting Enrique
Properly by the many-particle wavefunction (the solution to the many-particle Schroedinger equation). However that is difficult to interrogate. Usually by other approximate methods then, such as quasiparticle methods in which those correlations and the "wavicle" are treated as one independent thing, or by density- or density-matrix methods where they are replicated by exchange and correlation forces. These forces are intrinsically nonlocal, but not really there, rather they're just approximations to whatever is going on in the real wavefunction. Check out modular space-time too, in which locality is pretty much redefined to not be spatial.
Either it is possible, then also huge objects can be non-collapsed or the mathematics of the Schrödinger equation is wrong.
So if we sent 1 photon at a time at the slits and try to detect which slit they go through it would collapse the wave function whether or not a person checks the hard drive of results to compare against the background pattern?
A consciousness can "think away" the empty wave functions.
I don't think any physicist or neurologist or psychologist believe that our thoughts are random electrical signals (if that's any reassurance). In fact, "random" and "signal" contradict one another.
Quoting TiredThinker
Aye. The particle would collapse upon scattering with the photon and the pattern that would build up would be a classical double Gaussian rather than the stripes characteristic of interference.
One always has interactions with radio waves or neutrinos. How then can there ever be interference patterns?
Which frequencies of light a material can absorb depend on the properties of that material. In the simplest case, an atom, this is determined by the energy levels of that atom. Some of those energy levels are filled, some are empty. Which depends on the state of the atom, but generally the gap between two energy levels diminishes with increasing energy, until you hit the ionisation energy of the atom.
As such, unless an atom is in a highly excited state, you green generally need higher energy EM radiation to interact with it. Most atoms are going to be transparent to radio waves simply because, whatever energy levels the electrons are at, jumping to the next one up will require more energy.
Collections of atoms such as molecules and crystals have lower energy band gaps. Water vapour appears white, for instance, because it can absorb and therefore re-emit radiation at pretty much any frequency in and around the visible range. Metals will absorb any radiation no problem because the density of available energy levels is so high.
It is not about atoms. Why can't a single free electron interact with radio waves or infrared radiation in the apparatus?
Cool.
"This concept embodies the standard tenets of quantum theory and implements in a precise way a notion of relative locality. The usual string backgrounds (non-compact space-time along with some toroidally compactified spatial directions) are obtained from modular space-time"
and
"the principle of relative locality, a proposed generalization of the principle of relativity in which different observers see different notions of spacetimes."
I can interact. Why shouldn't it?
If the wavelength is large though, there will be more free electrons (if there are more than one). If the wavefunction of the electron extends over the whole material in question, you will make a better chance with large wavelengths.
Strictly following the axioms of QM, no. Only when an observer measures the one photon, be it directly or via memory disks, the wave function collapses. As hard to digest this might sound, a proponent of observer induced collapse can always keep this up. Strange stuff like the many worlds interpretation (to preserve unitarity of the evolution of the wave function, relocating non-unitarity merely to the branching points where the wave function splits in the states that were superimposed before a measurement, although it looks as if unitarity is maintained), and decoherence (which only seems to solve the problem of wave function collapse) are invented to solve the measurement (collapse) problem.
But even the friend of Wigner's friend who observes a person looking at Schrödingers can, can always say that it is him or her that causes collapse, no matter what the guy observing the cat directly, or the guy that observes this guy feels or thinks. Only in a theory with non-local hidden variables, the situation can be interpreted as a real, physical collapse, independent of observers. So let's hope they are discovered.
Isn't that equivalent to trying to explain away the physically central subjective role of all possible observation? I.e., the observer is not at the center of the Universe but the Universe is always centered on any possible observer? Perhaps that is why C is a constant, if O then c?
Maybe the physicists are studying an elaborate optical illusion they are mistaking for actual reality.
Many wanna-be ‘particles’ don’t reach the stable quantum energy level and so they come and go rather quickly, arising and returning back into the zero-point energy that isn’t zero, at the rest energy of the field or near to, they being known as the virtual ‘particles’. They do not come from ‘Nothing’ nor do they return to ‘Nothing’; so they can only be said to pop in and out of ‘existence’ in their ‘particle’ type nature as a so-called ‘particle’.
The entire universe is temporary, presumably because everything leaks, probably because infinite precision cannot be; however the Permanent quantum vacuum with its overall quantum field ever remains to someday make another universe of temporaries.
All paradoxes dissolve, if each observer has his own wave function. Of course, all are compatible with each other.
2. Closed-circuit television (CCTV)
3. Weeping Angels (Dr. Who).
Ergo,
4. There's something immoral/bad about waves.
The electron, which is negatively charged, in a sense, knows it's being watched/observed and behaves/acts accordingly. In my experience, only conscious entities do this. Are electrons, by extension everything, conscious? Panpsychism?
:joke:
One speaks also of the temperature inside the sun, although nobody will ever bring a themometer there.
Max Born wowed everyone with statistics. State is probabilistic:
Schroedinger insisted on an equation. It's got a "wavefunction" in it, whatever that is.
Einstein is having none of it:
Heisenberg:
Bohm thought that it is actually all deterministic and we just don't have enough information. And there's definitely others I've missed. At the bottom of the wikipedia page for "Copenhagen interpretation" there are some comments about alternatives, which could be of interest.
That's all to say, as far as I know, we're not much closer to putting the finger on any of this. As for the measurement problem, there are some people who dispute the idea of "wavefunction collapse" at all. [1] [2]
Other people still worry about consciousness though: [3] [4]
If you're interested in the consciousness aspect, I think the "delayed choice quantum eraser" experiment could be more useful as a search term than "double slit", which has many variations. Not just a thought experiment either, there are lab experiments of it, e.g. [5]
The third ref is paywall locked, but there could be preprints floating around. I'd love to give my opinion instead of just dumping references, but I'm severely underqualified. Hopefully this can at least motivate people less lazy than myself to look at this stuff.
When the river freezes the flow disappears by magic.
https://www.chemistryworld.com/news/quantum-double-slit-experiment-done-with-molecules-for-the-first-time/4014819.article
The first interpretation sticks to the most to the axioms of QM. The second assigns an objective existence to a mathematical entity (the wavefunction), which is absurd. I won't mention the third option again...
What's left is assigning a physical reality of what the wavefunction describes. And only such an interpretation can make all nonsense disappear like a bad dream.
:up:
Do you know of any theory in physics or other sufficiently mathematized science that doesn't do exactly that?
Quoting Cartuna
So... MWI then?
All of them. Math is just a way to describe physical stuff.
Quoting SophistiCat
No. My point is that the the MWI is caused by the wavefunction being seen as a mathematical entity. Giving rise to the problem of a non-unitary collapse. And according to the rules of QM this wavefunction has to evolve unitarian which it doesn't when measured. This is also mathematically done by a unitary time operator, which is of course only done by people, as there truly is no time propagating operator in nature.
As was decided in Copenhagen once. And eversince has been pushed in the minds of students, inc?uding mine. But who says that Nature is inherently probabilistic? How can this be? How can there be a mathematical distribution of chance, without a deterministic substrate, as it was decided back then? And also Einstein had this thought though he bases it on the understandable chances as seen in the throwing of a dice, after which Gòd lets a particle take position, so to speak.
If it was decided back then to start a search for a deeper theory, which de Broglie proposed more or less (by means of physical pilot waves), who knows what the theory would have looked like these days? But people were satisfied to shut up and calculate, leaving room for dozens interpretations. Among which hidden variables. Now these variables might seem just as obscure as pure, undetermined chance, but they somehow feel more satisfactory. Local hidden variables are ruled out by experiment, but the ones needed are obviously the non-local ones. But exactly what is hidden then? The mystery...
That's not right. The wavefunction is a mathematical entity. MWI came from taking that entity as a literal description of the universe.
Quoting Cartuna
It would look like Bohmian mechanics.
That's exactly what I mean. But it is no literal description.
Quoting Kenosha Kid
Yes. Like. The point is that it came too late. Giving birth to weird paradoxes like Schrödingers cat or Wigners friend. Or even weirder, the MWI. It gave Eels though...
That's just a fundamental belief. For all we know it's spot on. (I don't believe so either, but I don't claim to know things that haven't yet been determined.)
Quoting Cartuna
It would look like Bohmian mechanics because it is Bohmian mechanics, developed by Bohm and Dirac.
I don't say it is not spot on. It's indeed my fundamental belief that the wavefunction as a mathematical entity is a kind of Platonic view on reality, the metaphysical world of math being the world itself. How can a particle be at several places at the same time and how can it be pure chance (whatever that means without a deterministic substrate) that determines?
The fundamental belief here being that a particle cannot be in more than one place. Remove the belief and the question vanishes. All that remains is to falsify or verify that belief.
MWI doesn't say it's pure chance. Chance plays a role only in QM interpretations with collapse mechanisms.
A partìcle can be in all places it likes. But not at the same time. Call it a fundamental belief. If you think this all weird stuff of QM vanishes. You might ask yourself if that wouldn't generate, in the case of an electron, EM radiation, the electron hopping around weirdly like a Brownian particle. But a smeared out electron is just as weird.
But it still assigns probabilities to branching points.
I did, because it is. You're not making an argument here, you're just reasserting outdated beliefs. There's nothing more here than someone insisting that evolution is untrue because God made everything.
Science is driven by observation, and observations (such as the double slit experiment) do not favour your beliefs. Bohmian mechanics doesn't solve your problem either, since Bohm was obliged to move particle properties from the particle to the pilot wave to explain experimental outcomes (such as the zero electric moment of ground state hydrogen), and because the pilot wave itself is a field, i.e. a thing that's already in multiple places at once.
What we learned from Bohm was not that particles are points, but that we should keep an open mind.
Quoting Cartuna
It assigns branch widths according to the Born rule.
Why should I make an argument? I just belief it. Juat like you belief your stuff about the wavefunction. I don't see where God and evolution enter here. My view is just unorthodox.
So still a probability distribution. If one state has 0.1 (squared) weight and another 0.9, what does this entail for the corresponding two parallel universes? That the connecting branches have different widths? But what does that mean for the two univeres after the branching?
You don't see where God and evolution enter into the realm of fundamental beliefs that conflict with scientific evidence? Curious...
What scientific evidence you are talking about? The Copenhagen view is a belief all the same. And why should you take scientific evidence seriously in the first place? If you do science yes. And there is no scientific evidence in the case of QM.
Check the title of this thread ;)
I'm talking about the interpretation.
You just asked about evidence. Try and at least follow your _own_ end of the discussion.
I'm not sure what you mean by this. It feels you are throwing in a bucket of red or blue herrings. Do you mean I have to stop questioning the orthodoxy? Where in history have we seen that before, when science questioned the orthodoxy of the church? I have the inkling feeling you are the one defending God and rejecting evolution.There is no scientific evidence for the orthodoxy. I defend a hidden variables view.
That's excatly what I do. By questioning the other ends. What does a a unitary evolution of the wavefunction in the MWI entail for me as an observer? I know there is conservation of energy or mass, but what does it mean in that context? That I have a chance of ending up in following parallel worlds? Which makes it still hard to believe though that mass is conserved, but you can distribute it nicely. The MWI can ensure energy conservation by assigning the right weights. Still, the concept is ridiculous. The split might be unitary, but it makes me feel totally non-unitary, kind of a split personality, the ultimate schizoid.
No, you're not scientifically unorthodox, you're ascientific: your beliefs concerning nature are not impinged by scientific facts.
Quoting Cartuna
I've already given an example: the electric moment of ground state hydrogen.
Quoting Cartuna
I'm not sure you quite grasp MWI, or superposed states generally. Even if no branching occurs, and a particle's superposition of being here or there remains coherent, it still has a mass. You don't need branching or collapse to encounter issues like superposition.
In Bohmian mechanics, in the ground state of hydrogen, the electron is at rest relative to the proton. However, the electric dipole is not measurable, since any approach of an electric charge immediately sets the electron in motion. The guiding equation always results in no difference to quantum mechanics.
Then the orthodox view is non-scientific just the same. There is just no scientific evidence the orthodox view is the correct one.
All physical examples thus far contain no evidence whatsoever regarding the nature of the wavefunction, or more generally, quantum fields, a cross section of which delivers the wavefunction. If you have scientific evidence that the wavefunction is a probability measure without further explanation, it would be in the headlines. All explanations of the wavefunction and its behaviors, be it in the context of decoherence (offering only an apparent solution to the measurement problem), the MWI, or hidden variables, have no experimental backup yet. Clinging to one of them is just a matter of belief so far.
Quoting Kenosha Kid
The ground state of hydrogen has no electric moment (maybe if you could shake the proton, which would imply that the state is not a groundstate anymore though, like shaking the electron), but even if it had this would not constitute evidence.
Like I said, any evidence would be hot as hell. Which brings to my mind a Gedanken Experiment (involving arrival times) to discern if pure chance governs particles or something deeper.
To bring the experiment outside the realm of thought is very difficult though, and it's a pity I can't find it online. I saw it mentioned on a forum for physics. It is already shown that hidden variables are non-local, which is no surprise as they are introduced to explain non-local features like collapse.
Quoting Kenosha Kid
The MWI or superpositions generally are not that difficult to grasp. Of course a particle still has a mass when being in an isolated coherent state of superposition, but solving the measurement problem by decoherence is simply inconsistent with the Copenhagen interpretation, because that asserts an objective macrostate in which the isolated coherent state is embedded, giving rise to decoherence upon interaction, which makes the solution circular.
The embedding of an isolated coherent system in a universal wavefunction makes collapse superfluous altogether, but introduces parallel universes to achieve this. Giving rise to understandable questions like the question how energy can be conserved when the wavefunction unitarily breaks up in two disconnected wavefunctions after a measurement by an observer Energy or mass are simply conserved, just like mass and energy are conserved in any superposition. A superposition of two electron states doesn't mean there are suddenly two electron masses involved.
The observer and the coherent state he measures are just considered part of an all-encompassing state in which just one observer is distributed in disconnected states over the total state after a measurement, while before the measurement the coherent superposition is a still connected small part of the whole. Hawking, RIP, even used this universal wavefunction to account for the initial condìtions of the big bang, which obviously had to be such to give rise to the universe as we see it (I'm talking about different initial configurations and initial parameters like interaction strengths or particle masses). And there are quite a lot initial conditions, which all can be accommodated by a universal wavefunction and thus retroactively and trivially collapse the wavefunction to the state as we perceive today, while the MWI denies the collapse but conjectures a state in which all possible sub-states live happily side by side. You can even consider this in a timeless fashion, like I already wrote, in a block universal mode, which leaves open the question though of how the evolution in time "happens". If there are just branches of a universal wavefunction, then how one progresses from a coherent still superimposed state to non-coherent, disconnected states after a measurement? The same could be asked in a block universe where all worldlines are part of a static universe. How can one move in such a timeless universe?
The point of the initial fine-tuning doesn't need a universal wavefunction. If we keep that wavefunction within the domain of of the physics in our part of the universe, it suffices to conjecture that life is bound to emerge.
There is no reason to introduce a universal wavefunction, or parallel worlds to save unitary development, or a seemingly resolution of the measurement problem by decoherence if you don't accept the orthodoxy. Wigner's friend watching Schrödinger's cat, while the universe retroactively collapses, will become part of an evil fairytale.
That's untrue even in Bohmian mechanics. The electron is still moving, the relevant point is there should be a time-dependent electric dipole from the two separated charges.
Quoting SolarWind
You don't need to displace anything. Emitted radiation, for instance, tells you what the dipole moment is. Anyway, Bohm himself conceded that the charge distribution would have to belong to the pilot wave, not the particle, which is tantamount to giving up on the idea of point particles (charge being the most important particle property of electrons).
And there you make a false assumption. I already mentioned this. If an electron hops erratically like a Brownian particle, you would expect an EM field to come out of the wavefunction. But there ia no continuous flow of current. Just an electron being here and then there, smoothening out the virtual photon condensate around it. That's why there is no overall dipole moment.
An electron in the s-state is not a smeared out electron, as the probabilistic interpretation suggests.
Obviously there is, since consensus in science is built around evidence. Where there is no evidence, there is no orthodoxy. The correct interpretation of QM is still up for grabs, but that doesn't mean that any theory is as good as any other. One example is that God selects outcomes of quantum events.
Quoting Cartuna
That is the evidence, since in hidden variables theories like Bohmian mechanics, it _should_ have a dipole moment: two charges separated by space makes a dipole.
Quoting Cartuna
An EM field exists whether it's static or moving. That's what charge ensures. Where do you get this stuff? Hearing Brownian motion come up makes me think you're just grabbing at physics concepts at random in order to keep speaking for the sake of speaking.
Quoting Cartuna
Orbital angular momentum? Spin?
Once again, if there was evidence, you would make it to the headlines. The only evidence so far is the evidence for the non-existence of local hidden variables. And these are exactly the ones not needed for hidden variables. God may even select outcomes by means of hidden variables. Would explain nicely weird coincidences, though more down-to-Earth explanations could do just as well.
Quoting Kenosha Kid
That's why Bohmian mechanics isn't adequate. An adequate formulation doesn't predict an observable dipole moment. A smeared out electron, as suggested by the standard interpretation, implies an expanding negatively charged structure which can't collapse. A negatively charged extended structure only expands (in empty space). A measurement causes collapse though.
This should cause EM radiation, which isn't observed in a double slit experiment with electrons, like there is no electric moment observed for s-orbitals in atoms.
This shows that both in your example (there has to be a time-dependent electric moment), as well as in mine (there should be an EM field), QFT hasn't been taken into consideration, which for bound systems is rather complicated.
Quoting Kenosha Kid
At random? If you can't see the connection with hidden variables then I can only conclude you don't understand hidden variables. The medium in which the particle flows represents the wavefunction which litterally makes the Brownian move erratically and seemingly randomly. But the motion is determined by the medium. Metaphors, my dear... Don't take it literally. And certainly not randomly, which you only use here to belittle my argument. If you would see the connection it's not random, but if you don't see it than it looks random indeed. I'm not sure what's the tenth red herring about speaking for the sake of speaking is about.
Quoting Kenosha Kid
I'm not speaking here about the electron in a hydrogen atom. I'm saying that for a time varying EM field to appear, a continuous flow of charge is needed. An electron in an s-orbital has no angular momentum, and to associate spin with a continuous flow of current flies in the face of all modern conceptions of spin. The spin of an electron isn't related to a continuous flow of current (which only goes to show that the concept of a point particle isn't sufficient). An electron hopping around in the s-orbital will not produce a measurable electric dipole. If the hopping is fast enough. It would be a great test though to see if hidden variables are really there. :smile:
In collapse interpretations only.
Quoting Cartuna
No, it shouldn't cause EM radiation. Collapse simply changes the state amplitudes. You're back to thinking that physical properties themselves are somehow split. When collapse takes you from a*E1 + b*E2, for instance, there's no transition from E2 to E1. That wouldn't be collapse, that would be a process.
Quoting Cartuna
There's no randomness in Bohm, that's the point. There's _chaotic_ behaviour: which trajectory the pilot wave forces the particle is extremely sensitive to small, hidden differences in initial state, but is deterministic.
Quoting Cartuna
That's precisely where the magnetic moment of a charged particle comes from.
That's the one I'm talking about. Bohmian mechanics.
Quoting Kenosha Kid
If you envision the electron as being smeared out, than a change in this smearing out should cause a change in the associated smeared out electric field. This is not observed. I do indeed think that the electron and wavefunction are split. In this view the collapse is a process.
Quoting Kenosha Kid
I said there is a seemingly random motion of the BP determined by the medium.
Quoting Kenosha Kid
That's exactly where it doesn't come from. At least, not in the point particle view.
Bohmian mechanics is not a collapse interpretation.
Quoting Cartuna
I think the only thing to be learned here is that you parrot stuff you've heard of without any comprehension. I'll revert to my usual mode of just pointing out for the sake of others when you're bullshitting.
No need to get upset! Jesus man! For the sake of others you point out that I am bullshiting? How noble! Even Feynman didn't understand electron spin and you pretend you know? Explain me please.
I'm not either. Your spade is a different one than mine, that's all. I'm not sure what poker has got to do with this discussion though. I played a hidden variables card and you can't use it for your set. That makes you angry. Hidden variable wavefunctions collapse literally. And you still not made it clear how electron spin is caused by electric current. You keep on throwing in red herrings to diverge attention. Not very constructive.
Quoting Kenosha Kid
The analogy is with continuing to engage with someone long after you've realised they're not bound by normal debate conventions, like knowing or caring wtf they're talking about.
In that case I should indeed stop debating. Red herrings are not part of a normal debate, nor terms like bs, wtf, etc.
Quoting Kenosha Kid
You stated that the electron's magnetic moment is caused by a continuous current. I asked to explain how this happens then. Instead a new red herring. And a wtf, while you are the one who is bs... oops, while you are the one who shows he doesn't know what he is talking about. Don't take it all too seriously. Physics is just a nice game. But I understand that you feel endangered in your position of the hoarder of the herd. I'm just a newbie (not to be trusted), after all... :smile:
Haha! Wtf is Banno? Did he lay under a bull's hole?
True. Detection only requires the particle to collide with a physical system. All this 'observer determines outcome' is bunkum.
Interference has also been demonstrated for molecules. Inside the molecule, however, the atoms interact with each other and would collapse the wave function.
Is the wave function collapsed or not?
I think the collapse of the wave function is only a manner of speaking. Nothing collapses in real terms. The wave function is only an abstract way of grasping the mystery. Suppose you have 50 possible destinations that you can go to. This is the abstract space that you contemplate. You make a decision on one destination so the other 49 possibilities 'vanish'. But nothing collapses in real terms. Possibilities vanish, that is all.
The difference between classical probability and quantum mechanics is interference and this refutes the concept of a pure notion of the wave function. Back to the origin => double slit.
It's more and less than that. It used to be called "wavefunction reduction", and simply meant that, before measurement, we don't know if the system is in state A, B, C, etc. (or some mixture), but after measurement we know it's A so we "reduce" the description to that. It was purely epistemological: we revise what we know as we know it.
Some, including Bohr (I learned from Cat or Mww or another one of the great contributors here), came to think it was an actual physical process that occurred, likely non-deterministic.
It's probably going to go the way of the ether though, just an idea dead people once believed in out of ignorance.
Indeed. It's a shame that Copenhagen set the metric for evaluating the wave function. All QM courses are based on it. Shutting up and calculate was made the norm. Leaving those longing to relieve their ignorance in the dark. Giving way to strange distractions like the measurement problem, observer induced collapse, the MWI, Schrödinger's cat, and Wignerfriend. If only de Broglie was taken seriously and more would have been supportive. Powerplay...
Sean Carrol talks about that. Why don't scientists want to get to the bottom of it?
Another complication involves the word 'where'. Where is the particle? Particles exist in quantum spacetime which is mathematically different from ordinary 4D spacetime. So what do we mean by 'where'? What location in what spacetime are we talking about? Bohr said it is meaningless to say where a particle is outside detection. Maybe he means it is nowhere. Nowhere in 4D spacetime that is. It lives in its own quantum spacetime. A 'location' arises when a particle collides with our 4D spacetime (ie a physical detection apparatus). The particle must appear to be located in our 4D spacetime because the detection apparatus is in our spacetime. But 'where' was the particle prior to detection? Nowhere!
Careers at stake, satisfaction with the status quo, no imagination, calculations (and shutting up) done within the classical framework usually do the trick of delivering, etc. Physicists really trying to go all the way down are rare, and circumstances can impede. Some simply don't have the time to think about it. Universities have policies. Etcetera. Diverging from the norm can get one in trouble. Powerplay, competition (which can be a good thing though), and simple indifference (the most common attitude: don't even try to understand the quantum apple, once bitten, though I never understood the innocence lost after the bite. Which innocence? No need for explanation?
I'm quite sympathetic to the idea that, say, photons don't exist in space-time between their creation and destruction. Makes a lot of sense to me. I'm not sure how it would work for massive particles...
In the double-slit experiment, the electron is interacting with the Higgs the whole time. If we consider the electron 'not in space-time', then the Higgs field would also have to be 'not in space-time'. And if there are other electrons in the beam that it can repel, those other electrons would have to be 'not in space-time', along with the virtual photons they're exchanging to repel one another. End result being that everything is in this other realm, and our space-time starts looking rather empty (except for observations).
That's the question. There are more theories accounting for mass. The Higgs particle has been found. The Higgs mechanism has never been seen.
I thought the speed of light was a measure of the impedance due to space-time. If it's not going through space then it shouldn't be limited to the rate of motion a thing can travel through space. No?
If they don't exist within space-time, then in what sense do they exist? There's an idea in Heisenberg that they exist as potentia - that they have a different kind or degree of existence per this article:
In classical electrodynamics, yes. But bear in mind that, from the photon's point of view, not distance is traversed or time elapsed between creation and destruction. There's no physical reference frame in which the photon is at rest, but if you take the limit of the distance and time between events as velocity tends toward the speed of light for a frame parallel to the photon's trajectory, that distance and time period vanish. It ends up simply being a transfer of electromagnetic energy from one system to another. Nothing empirical can be said about a photon's transit.
Does that ^ cover it?
But taking a derivative is a mathematical change, the "vanishing" isn't a measure of reality anymore than rounding. It's just a product of calculus when there is a large number(speed) and relatively small numbers. Correct? It isn't known to literally vanish.
There is no photon's POV. The photon works instantaneously. But it looks to us as if it traverse space and time. Which is more or less what you stated. You can compare it with instantaneous interaction in Newtonian space. But since mass and energy must be interchangeable, c is finite.
As in has it been measured to do so? No, like I said, you can't transfer between frames of reference by the speed of light. But you can keep going faster and faster and watch the distance between events shrink. "Vanish" here is as it's used in mathematics and physics, e.g. "the wavefunction if the atom must vanish infinitely far from the nucleus."
So - what do you make of it? Genuine question, not trying to trip you up or anything.
Quoting Kenosha Kid
But for photons, yes, I can see how the above would work. The paths explored by the photon after creation would exist in this real realm of possibility, and only in our realm of actuality upon its destruction (by the effect it has on whatever destroyed it).
It's not quite how I picture it (my view was described at length in this thread: https://thephilosophyforum.com/discussion/9391/determinism-reversibility-decoherence-and-transaction ). As I said, I am sympathetic to it.
This is a recurrent theme in many discussions arising from just this experiment such as the discussion of Wheeler's views in Does the Universe Exist if we're Not Looking?
//ps// Also see physics in boxes
That's what you think. It could be just as well that the wavefunction is made out of non-local stuff and as such, space itself could be that stuff. What is more non-local than space? Nothing.
Pretty sure the suffix "function" denotes a mathematical model in play. Now, if you wanted to say something about the wave itself you could. Such as the wave doesn't change as a result of our calculations. Nor, do seemingly trivial parts of reality. Just because you can ignore distance and get the right answer doesn't imply distance was actually eliminated in reality. Like the centrifugal force from the earth spinning isn't factored into my luggage weight at the airport(yet); but it is still there. Are we understanding each other?
Considering the function yes. Though the wave can have the functional form (the square of it). Considering the centrifugal force and distance, yes. I fail to see why the wavefunction is connected with the two examples. What do we leave out of reality with the wavefunction?
I think I took a wrong turn near this intersection.
Can't you drive back?
In all of those cases you're surmising what might happen in the absence of there being an observer. But of course, we will never know that without observing at some point. In my view, 'observation' is an activity of a subject, and in the broadest sense, the subject is inextricable from what is being observed. Experiments and observations always concern some delineated object or set of objects or interaction (hence the link to the 'physics in a box' article). But at back of that, 'the observer' provides the framework within which any observation is made or conclusion is drawn. Realism wants to say that what is being observed would exist regardless whether observed or not - and in one sense that is true. But it's not true in any ultimate sense. And that is what is thrown into sharp relief by physics - the scientists dealing with quantum physics were obliged to ackowledge that they were more than simply observers, but also participants. Which is precisely the meaning of Wheeler's 'participatory universe'.
Rather: what might count as an observer.
Quoting Wayfarer
That seems to be going too far imo. There is no physical theory afaik in which results depend on conclusion, which sniffs of sneaking human importance for the running of the universe in through the back door. In collapse and branching interpretations, observation is the catalyst. In Wigner, nothing is, except personally.
Quoting Wayfarer
I don't think it's true that observations are independent of being observed. If there's one thing we can definitely conclude from QM, it's that observing things affects the observed thing, at least on the elementary scale. Traditional sciences are likely unaffected by this paradigm shift because they're generally dealing with statistical ensembles, even if we didn't used to think of them that way (the classical limit).
I like Wheeler. His one-electron universe was a big influence on Feynman's representation of antimatter being matter moving in the opposite direction in time, a big influence in turn on me (and the aforementioned thread), and his it-from-bit weighs heavily on your "Is information physical?" thread. I think all of his ideas are interesting, including the PAP, without necessarily being true. I find that he and others like him blur the line between ontology and epistemology: we are not just building up a history of the universe, but actually creating that history via the same process. Fascinating, but unjustifiable.
As I understand it there are two spacetimes (from a geometric point of view that is.) If the mathematics of ordinary physical spacetime is different to the mathematics of the quantum world then we are dealing with two geometries and two spacetimes. Chairs and tables live in physical spacetime, 'particles' live in quantum spacetime.
BOTH spacetimes are here in this ontological space because space is two things. It is a geometry and it is also a positive existence. It has being. Within this positive being we call space there are two geometries (at least): quantum geometry and ordinary physical geometry or spacetime. Both of them are HERE but are geometrically distinct. When a 'particle' collides with a physical object it leaves a trace effect in physical spacetime (eg a spot on a photographic plate). We don't observe particles, we observe trace effects. These trace effects are necessarily in ordinary physical spacetime because they are physical objects. This trace effect marks a location in physical spacetime and we say the 'particle' was 'there'. But what is 'there' is really a trace effect. The particle is nowhere in physical spacetime.
Then what about the screen with the spot?
The effect of measuring on a particle as Heisenberg exemplified, is a literal disturbance. This is not the kind of influence measuring the wavefunction has though. The wavefunction collapses during measurement, in both position and momentum space. The more precise you measure position the less precise momentum will be. This increased insecurity of momentum is not caused by the measuring particle adding momentum to the measured particle though. After measuring the position the wavefunction's momentum will have changed, and you don't know the momentum it had before the measurement, unless you prepare it in an ensemble of pure states. Measuring the wavefunction will change it's mean momentum through space. That's why two simultaneous measurements of position can never be made at the same time (contrary to the conjectured uncertainty relations, radiating from equal time commutation relations) which claims position and momentum cannot be measured simultaneously precisely. The relation holds for ensembles, but on a single wavefunction no two conjugate observables, like position and momentum can be made at the same time and momentum or energy need two time-separate measurements.
Also a physical object consists of particles, thus the distinction makes no sense.
I have already presented the solution. Every particle and also every group of particles sees another wave function, a section of the universal wave function.
It is comparable with mankind. Every group thinks it would be the most intelligent, but universally seen all are only part of the big stupidity. :)
Quoting Kenosha Kid
The spot is in this physical universe. That is, its location is in terms of 4d spacetime. The thing that made the spot/trace effect, is no longer observable and not in our 4d universe in the sense that it cannot be located here. Outside detection (ie interaction with a physical device) nothing can be said about its location.
And the screen itself? As we see it in the other world too?
So the particles in it are in the other realm?
Interesting! I'm not sure why it shouldn't always leave a trace though. Or potentially at least. After a particle has left a trace in a cloud chamber, can't it just continue in empty spacetime? In empty space, the particle's wavefunction will waver out, because it's not constantly measured. More and more possible paths will develop, while not interacting, while in the cloud chamber it seems to take one. Actually, this one path consists of many condensed paths following each other up serially, thus creating a seemingly stable path. Between two follow up interactions with the cloud, the small bundle of paths wavers a bit, then upon interacting reduces again to a narrow bundle, then wavers out again, then narrows again, etc, untill the end of the cloud is met, the particle doesn't interact anymore and the paths waver out freely into space. Ready to meat new cloud chambers, like a cosmic particle entering the atmosphere, while before entering ìt traveled on many paths at the same time (or in the hidden variables approach, they change constantly from path to path. You seem to place non-interacting particles in a quantum space.
That's the question. After interacting, particle trajectories still evolve in 4d spacetime. Wavering out into space and running towards one momentum, but still. There is no inherent reason to assume that non-interacting particle fields don't exist here. Of course there is a difference with interacting fields. You could relay the difference to an extra domain though, say a non-interacting domain showing if particles interact or not. This is in fact done in QFT. Non interacting particles are placed outside the domain of the scattering matrix. Though you could include them, giving rise to disconnected Feynman diagrams.
Have physicists ever tried this: One experimenter (x) observes the slits and another ( y ) observes x observing the double slit experiment? You know, a god's-eye-view!
Just slipping in here. This was considered as a thought experiment in Everett's paper "The Theory of the Universal Wavefunction"; in particular the introduction. There, "the slits" abstracts into any experiment and is S. Your x is A. Your y is B.
Wigner's friend! I remember that!
They have never been able to track a single photon infact we have never seen a photon the photon remains a hypothesis not a fact and so the entire experiment is a BS story
That's because photons don't emit photons themselves. So you can't see them. You can see them indirectly by letting them interact with the double slit equipment, look at the screen on which means looking at the screen. The screen emits invisible photons interacting with your eye (ou might even use your retina as the screen. You would see the interference directly), so you can see where they were when they interacted. When a photon has interacted with the screen, there will be a spots visible, by means of other photons reaching your eyes. The spots build up a complete interference pattern. The process of photons traveling in spacetime is not visible by itself (you can't enlighten them to make them visible), and in a sense all photons are virtual (so not only the ones between electrically charged particles, being the means for interaction).
So not being able to see them doesn't mean you can't imagine them to fly in space. The photons can't be seen but they still are there. Like a hidden force of nature.
It has been very well demonstrated that light energy transmits through space, from one place to another, as a wave motion. The idea that there are photonic particles which move through space from one place to another, is a theory which is completely unsupported by empirical evidence.
But waves include particles. All particles in the universe are physically described by point particles and wavefunctions can be seen as cross sections of all paths these particles are on simultaneously. Or jumping from one path to another. The jury still hasn't decided on that one yet.
Quoting Metaphysician Undercover
How has this transfer been seen seen then? Light moving through a bottle with liquid?
Particles are a product of our imagination, although useful at times as a model when there are little perturbations about. The photon shown in a Fenyman diagram between pairs of electrons is virtual, not to be confused with virtual particles in fields. This virtual photon is actually a disturbance in the photon field caused by the electron fields. All interactions involve quantum fields at heart, not particles but as sometimes for short. Photons and electrons go through two slits to form an interference pattern because they are directly field quanta.
That light transmits as waves is evident from the visual observation of refraction.
Quoting Metaphysician Undercover
But how do you visual observe this?
Maybe it's particles all the way down. Maybe we are ignorant about the nature of space and the wavefunction. What if there are only particles and space is a structure that surrounds the particles, and this space is interacting non-locally with the particle?
A rainbow, a prism. This phenomena is explained with reference to waves.
So the waves are imaginary too. You can't see the shape of wavefunction, just as you can't see the particles inside of it. A gravity wave on the water is a material wave. You can observe the shape of the matter waving. Waterwaves and and slits:
The water wave is observable. And so is a "water particle" making up the wave. But this doesn't hold for a wave function and the particle that makes it up. In a water wave, the particles making it up are water particles (small volumes of water, or maybe even H2O particles, though these are not directly observable). But the relation between quantum wave functions and particles is a different one than between water waves and constituent water particles. The constituent particles of the quantum wave are not the particles inside it. The two water waves will enhance each other at fixed locations, while canceling at other points. At the constructive interference regions the water particles show an increased amount of motion, while at the destructive interference regions the water shows no motion at all. The water wave is a periodic motion of the constituting water particles and waves, in the double slit case, can be superimposed linearly (which can't be done in the linear case). It is the water itself that waves, but in the quantum wave what is waving, if not constituting particles? The probability of finding a photon? But then why photons are not real but the waves are? The situation can be resolved by looking at the wave function realistically. Considering it to be made up of waving stuff pushing the particle along within its confines. So both the particle and the wave are real. The particle finds itself at a well defined position and has a well defined momentum at the same time, and collapse is no problem anymore but just a non-local happening when the particle interacts with the screen (for example).
I don't think this would work. The "waving stuff" would be transmitting energy from A to B, and also the moving particle would transmit energy from A to B, so way too much energy would be moving between A and B, violating the conservation of energy law.
If you assume the non local wave to contain energy yes. If not not.
How could the wave push the particle if it didn't have energy?
I don't think the wave is a wave consisting of other particles which push the particle. The stuff the wave is made of non-local stuff that dictates the particle where to be without exchanging energy with it. If you consider a Gaussian wave packet as you wave function, the particle is hopping around in the packet. Sometimes it's on the edges and sometimes in the middle. It's most of the times in the middle as the density of the wave stuff is highest there. The packet travels with a global velocity, and the particle "dances around" in it. It has a well-defined position at all times, though it changes continuously, instantaneously jumping from one position to another. The velocity is dependent on the packet's main velocity, and dances around like position, but the more position is confined by the shape of the wave function, the less the velocity is confined. You need two measurements of position and the more confined the particle is in space the faster the wavepacket spreads, which is an indication of the spread in velocities you measure (the momentum operator is associated with the derivative of the position, which is again based on momentum being the generator of translations in space, so maybe the stuff of the wave function is space itself, as I can't think of anything more non-local than space...).
If "the wave" is a theory which is intended to determine the probabilities of where a particle may be found, then it is not really active in causing the particle to be anywhere. And we cannot say that it is the wave that causes the particle to be where it is, because the wave is theory only. What we need to consider is what is causing the particle to be where it is. If the wave is the cause, then the energy is the property of the wave.
But if there is a wave which is active in causing the particle to be where it is, and the energy must be attributed to the wave, this leaves the particle as having no energy proper to it. Therefore the particle is non-existent during that time period when the wave is causing it to move from here to there, and it is not an acceptable representation to propose a particle being pushed by a wave.
The particle in the wave is not pushed in the way it pushed other particles, by means of mediating particles. If the particle interacts with other particles, the wave collapses physically. The wave as a mathematical function is theory also.
The particle is present always. Why can't it hop from one place to another instantaneously? As is can move continuously, why not discontinuously?
Exactly! That's why they hide beneath the wave function.
It are exactly the BS stories that are the nicest in physics! What you said about glowing unicorns is actually very to the point. If the experiment is done with electrons even more (no one has seen them either). Electrons can be considered as triplets of massless charges, Various kinds of them. And it are exactly charges that give rise to mass and consciousness. As they don't like being watched they hide under the comforting wave function, giving them shelter and direction while longing for other charges.
Serious! I seriously think physical charges are the base for consciousness. And I seriously believe quarks and leptons are composite particles. Two massless base fields can explain all elementary particle interactions. Just give me one such reaction.
So are you... Can you prove yourself?
You see? The particles are real!
This is a serious topic to me and a truly troubling one because so many people don't realize just how much of science is built upon imaginary ideas despite the motto being one of "if it ain't real it ain't real" and blind to anything related to the spiritual side of life
So yeah I've got better things to do with my time like make a sandwich so ??