The Copernican Principle and the Waveform of Reality - A Copenhagen Bug

[IllyaKuryakin]

So, let's say that a star 50,000 light years distant does not exist until it is observed. One day I look up and see a bright star and it's waveform collapses into existence as we know it. Now suppose my pet kitty observes it, does the waveform collapse? What if a tiny bug saw the star? It has been observed, does it's waveform collapse? No. Because, there was no information created about the existence of the star. It's really the connection between information theory, and reality. For the waveform to collapse, the information must come into existence at the same moment as the observation is made, and the waveform of there probably being a star at that location is collapsed by the act of the information coming into existence. No information, no star.

So, what if a hermit sees the star, but never communicates that observation to anyone in any fashion, so the information dies with the hermit? Information cannot die, it lives on, perhaps in the remains of the hermit, but once created, it exists forever. And since the information about the observation of the star lives on forever, in some form or another, then the star is forever crystallized from only a probability of existence, into what we call reality.

This then places humans back at the center of existence. In a very real sense, it invalidates the Copernican principle that we are not in a special or favored place in the Universe. It seems we are very special indeed. The Universe would not exist without us.

 

[Matterwave]

When defining the Copenhagen interpretation of QM, one must be very careful in the word "measurement" or "observation". "Measurement" or "observation" collapses the wave-function. But it is not usually taken as necessary that these "measurements" or "observations" be conducted by a human.

In fact, if you set up a lamp inside of a 2-slit experiment, you make the interference go away even if you don't have a human checking which slit the electron moves through. The wave-function collapses as soon as it is possible to make such a measurement.

No such measurement has to be carried out, though (i.e. it doesn't matter that a human reads the output of the measuring device).

 

[Drakkith]

So, let's say that a star 50,000 light years distant does not exist until it is observed.

Of course it exists. Don't read too much into the philosophical stuff behind QM. It's all merely speculation and such. Stay with the facts and leave it at that I say.

 

[IllyaKuryakin]

When defining the Copenhagen interpretation of QM, one must be very careful in the word "measurement" or "observation". "Measurement" or "observation" collapses the wave-function. But it is not usually taken as necessary that these "measurements" or "observations" be conducted by a human.

In fact, if you set up a lamp inside of a 2-slit experiment, you make the interference go away even if you don't have a human checking which slit the electron moves through. The wave-function collapses as soon as it is possible to make such a measurement.

No such measurement has to be carried out, though (i.e. it doesn't matter that a human reads the output of the measuring device).

I see your point, but I'd look at it a little differently. If no human ever looks at the result of the experiment, then no information was ever created, and the waveform has not collapsed. The cat is neither alive nor dead.

My point is, there must be information generated to collapse the wave-function. I'm not sure how the information is generated in your example, but if you collapse the wave function, I'm sure it is. I'll have to think that one over.

 

[IllyaKuryakin]

Of course it exists. Don't read too much into the philosophical stuff behind QM. It's all merely speculation and such. Stay with the facts and leave it at that I say.

If a tree falls in the woods, and no one was there to hear it, does it make a sound? QM says no. There was only the probability of a sound but never the reality of one. In fact, there was only a probability of a tree, or a fall. Those are the facts. Unless, you chose to believe there is an infinite number of Universes, some in which the tree falls, and some in which it doesn't. Your choice, the math works equally well either way, but I like to stay as far away from infinities as possible.

 

[Matterwave]

I think you're putting too much stress on humans in Quantum Mechanics. Nowhere in QM does it mandate that measurements and observations can only be made by humans, or sentient beings...

 

[lfqm]

I think the problem behind this stuff is the lack of a precise definition of "information" (in quantum mechanics) and "reality".

 

[IllyaKuryakin]

I think you're putting too much stress on humans in Quantum Mechanics. Nowhere in QM does it mandate that measurements and observations can only be made by humans, or sentient beings...

Ah! That's where I started. We are back to the bug. It's bug eyes observe the photons from the distant star, but it's bug brain can't generate information about what it has observed. So the wave-function does not collapse. It is still just a probability of a star at that location.

Well, I could be wrong. Perhaps a tiny bug could collapse the wave-function of a star instantly 50,000 light years away without generating any information about what it has observed. That would be even more interesting, in my own humble opinion.

I'm just musing about the connection between the generation of information and the collapsing of the wave function. I didn't mean to disturb anyone. Carry on.

 

[Dmitry67]

I think you're putting too much stress on humans in Quantum Mechanics. Nowhere in QM does it mandate that measurements and observations can only be made by humans, or sentient beings...

Well, there are 2 'flavours', with realistic wavefunction and where 'wavefunction is just a knowledge of the system'. Negative experiments also partially collapse the wavefunction 'because we understand, that if particle haven't hit this target, then...'

So the existence of sentinent beings (able to posess the 'knowledge') is somehow assumed. The mixture of 2 flavours makes it even more confusing. As before, I believe that in modern era Copenhagen Int makes more harm than good.

 

[Q-reeus]

So, let's say that a star 50,000 light years distant does not exist until it is observed. One day I look up and see a bright star and it's waveform collapses into existence as we know it...

Am I the only one who considers this absurd for one blindingly obvious reason - how can there be starlight to be observed unless it has already (maybe tens of thousands of years ago) been generated by that star? Do you not see a clear logical contradiction? As an aside, I admired your acting role in 'The Man from U.N.C.L.E.'

 

[unusualname]

If you accept that nature is fundamentally probabilistic then there is no confusion, there is no need for a physical wave function collapse, observing the star simply confirms its existence, which can not be known otherwise (ie you can't do a calculation to confirm it exists, you can only ever calculate probabilities).

Probabilities evolve deterministically and unitarily in the universe, the act of observation doesn't need to have any effect on the evolution of probabilities apart from enabling us to know something about the past evolution of the universe (which we could not know without making observations). The universe evolves on and on in its merry deterministic fashion according to schrödinger evolution just as it did in the billions of years before we even existed.

But what is evolving deterministically are probabilities. Many people don't like this, they want a purely deterministic "real" universe, but as I tell my 5-year old "want want want" doesn't "get get get".

Nature ain't really real, deal with it.

ps. if a tree falls unobserved then that's what happened, it fell unobserved, but no-one will ever know this, just like trees that fell before we evolved on the planet (unless they left some fossil record)

 

[Demystifier]

Many people don't like this, they want a purely deterministic "real" universe ...

A deterministic universe is one thing, a real universe is something completely different. One may be without the other.

 

[unusualname]

A deterministic universe is one thing, a real universe is something completely different. One may be without the other.

Yes, that's what I mean by purely deterministic. If the universe can be reduced to purely deterministic rules then it is "real" in the epr sense, although (to explain modern experiments) it must have some non-classical feature like non-locality or information loss (essentially a many-to-one mapping in the deterministic laws cf 't Hooft).

I like the simple picture of deterministically evolving probability states, which seems to explain everything quite "naturally", the universe has deterministic and non-deterministic components.

 

[harrylin]

Am I the only one who considers this absurd for one blindingly obvious reason - how can there be starlight to be observed unless it has already (maybe tens of thousands of years ago) been generated by that star? [..]

I agree - a different interpretation can't be right.

 

[Q-reeus]

I agree - a different interpretation can't be right.

Right on Harry. Another important factor here imho is that the light our observer receives is not from 'the star' as such but some infinitesimal fraction of ionized gas in it's surface layers. Hence even if you believe in some mystical backward causation possibility here (not arguing with Quantum Erazer etc), it could at most effect those few actual source emitters of light. And I wonder how conservation of energy/momentum would survive our ability to 'realize' an entire star by observation?! I gained a lot from a (very long) thread on Schrodinger's cat here: https://www.physicsforums.com/showthread.php?t=468101&page=6, in particular #96 helped to clear up some of the misconceptions that abound. Just substitute 'star' for 'cat'.

 

[unusualname]

Right on Harry. Another important factor here imho is that the light our observer receives is not from 'the star' as such but some infinitesimal fraction of ionized gas in it's surface layers. Hence even if you believe in some mystical backward causation possibility here (not arguing with Quantum Erazer etc), it could at most effect those few actual source emitters of light. And I wonder how conservation of energy/momentum would survive our ability to 'realize' an entire star by observation?! I gained a lot from a (very long) thread on Schrodinger's cat here: https://www.physicsforums.com/showthread.php?t=468101&page=6, in particular #96 helped to clear up some of the misconceptions that abound. Just substitute 'star' for 'cat'.

All a bit complicated, easier to just accept the universe has evolved along a definite path, but that path is probabilistically defined so we can't know what it is without "looking".

The past has already happened, it cannot be changed.

 

[DrChinese]

The past has already happened, it cannot be changed.

After it is determined, it cannot be changed. However, it is not clear when that point is actually reached!

 

[unusualname]

After it is determined, it cannot be changed. However, it is not clear when that point is actually reached!

Yes, it's undetermined as far as conscious thinkers who haven't observed it yet are concerned, but I doubt if we destroy ourselves in some silly war this will change what the rest of the universe has done for 13 billion years!

Obviously I have no experimental proof of this, but it seems reasonable (note: I have left out the elephant in the room - human free-will, but that gets us into very speculative areas ;-) )

 

[Q-reeus]

All a bit complicated, easier to just accept the universe has evolved along a definite path, but that path is probabilistically defined so we can't know what it is without "looking"...

Admittedly even that entry was somewhat long, but a passage towards the end is relevant:
"To say a wave function is collapsed, you must have a wave function in the first place. A mixture is not a wave function, it is a mixture of wave functions. Classically, it is the mixture that matters, not the quantum mechanics of the wave functions-- the evolution of a mixture is a classical evolution, what the individual wave functions are doing gets lost (like a thermodynamic treatment of an ideal gas where we are not a whit for what any given particle is actually doing, only the generic possibilities for what they are allowed to do). When a cat is a super-complicated statistical average of a bunch of possible individual wavefunctions, then it is a classical object, not a quantum mechanical one."
How much more a star! May be wrong, but likely the OP got his que from that famous exchange between Einstein and Bohr where Einstein is quoted "I like to think that the moon is there even if I am not looking at it." An hyperbole, but combine that with the fact Bohr's Copenhagen viewpoint has almost unanimously considered to have won against the EPR argument, and hey presto - the Moon depends for it's existence on being observed. Or not.

The past has already happened, it cannot be changed.

There have been a few recent threads where 'backward causation' as apparently confirmed in delicate experiments was discussed, but I would agree it has no relevance to 'the world at large'.

 

[Rap]

I gained a lot from a (very long) thread on Schrodinger's cat here: https://www.physicsforums.com/showthread.php?t=468101&page=6, in particular #96 helped to clear up some of the misconceptions that abound. Just substitute 'star' for 'cat'.

Yes - a good thread, although not completely resolved. I am still scratching my head about some of those points.

The wave function is not a physical entity with totally objective existence. Its a mathematical tool. It's an encoding of what has been measured, and along with QM theory which allows us to predict probabilities of future observations. The wave function collapses when our knowledge (as the result of measurement) changes. 200 years ago there were no wave functions, because QM had not been developed. To a duck observing a star there is no wave function, because the duck does not understand things in terms of QM.

All of the apparent paradoxes are resolved by this interpretation, which is, I believe, the Copenhagen interpretation. But after the above thread, its clear that things are not this simple.

 

[unusualname]

The point is that our ability to observe might not be that big a deal, the moon is there but we can't show this by calculations on paper, these calculations can only predict probabilities (assuming a complete physical theory which includes quantum gravity) we have to "look" to see if the moon is there. If no one "looks" that doesn't mean the moon is not there it just means that there are (unlikely) probabilistic evolutionary states of the universe where the moon suddenly disappears, they are so unlikely that they have an average expectation time in excess of googleplexes of the order of the age of the universe, so we discount them for scientific purposes which involves what we can reasonably observe in this universe.

What we are doing physically when we "observe" the universe might be pretty mundane (literally!), especially if we take into account that what created us (evolution) couldn't even manage radio communication technology.

The modern interpretation relies on decoherence to explain away the macroscopic superpositions, but similar mathematics can explain why a "feynman path" might actually be the ontological evolution.

 

[Upisoft]

If a tree falls in the woods, and no one was there to hear it, does it make a sound? QM says no.

Actually it says yes. The woods is still there to make the observation/measurement.

 

[Q-reeus]

...The wave function is not a physical entity with totally objective existence...

I tend to agree Rap, but try telling that to a MWI advocate!

 

[Q-reeus]

..If no one "looks" that doesn't mean the moon is not there it just means that there are (unlikely) probabilistic evolutionary states of the universe where the moon suddenly disappears, they are so unlikely that they have an average expectation time in excess of googleplexes of the order of the age of the universe,...

Amazed that however tiny, there is a finite probability for such an event. Mind explaining what that implies re COEM (conservation of energy/momentum) - is it violated via an extremely unlikely HUP fluctuation, or do we expect some compensatory shuffling of matter elsewhere that maintains an exact overall COEM at all times? Some folks think COEM is only statistical in QM, others believe it is always obeyed.

 

[DrChinese]

The wave function is not a physical entity with totally objective existence. Its a mathematical tool.

Are you sure about that? You say that, but there is plenty of evidence that would say that it is objectively real. After all, you can manipulate probabilities through spacetime as if they are physically real in any sense of the word "real". In fact, I would say that the evidence supports the idea that the wave function is more "real" than the unmeasured properties of the same particle.

 

[unusualname]

Amazed that however tiny, there is a finite probability for such an event. Mind explaining what that implies re COEM (conservation of energy/momentum) - is it violated via an extremely unlikely HUP fluctuation, or do we expect some compensatory shuffling of matter elsewhere that maintains an exact overall COEM at all times? Some folks think COEM is only statistical in QM, others believe it is always obeyed.

I think COEM would not be violated, certainly not globally (ie in the entire universe). Just like COEM is not violated when a single atom quantum tunnels across a potential barrier, now imagine the probability of every single atom in the moon (or any macroscopic part of it) suddenly quantum tunnelling outside the solar system, this is vanishing small, and we ignore it in scientific models, just like we ignore the poincare recurrence theorem when doing usual statistical physics.

 

[dm4b]

Are you sure about that? You say that, but there is plenty of evidence that would say that it is objectively real.

You piqued my interest - what is some of that evidence you are thinking of? I guess I always leaned towards giving the wave function some "reality", but never really had a solid ground for doing so.

 

[Rap]

Are you sure about that? You say that, but there is plenty of evidence that would say that it is objectively real. After all, you can manipulate probabilities through spacetime as if they are physically real in any sense of the word "real". In fact, I would say that the evidence supports the idea that the wave function is more "real" than the unmeasured properties of the same particle.

There was a very good discussion on this at https://www.physicsforums.com/showthread.php?t=468101&page=6, but its a long thread.

I am, of course, not absolutely sure, its one viewpoint in the many attempts to deal with the interpretation of waveform collapse. I find it to be the best. It disposes of many of the problems of waveform collapse, wondering when and how the collapse occurs. In particular, referring to the above thread, it deals with the problem of "Wigner's friend". Wigner's friend is a scientist inside the box with the cat and dealing with what he observes, using wave functions to describe the state of the cat. How does the observer outside the box deal with this? Is Wigner's friend in a superposition of states, some of which involve calculations of the wave function for a dead cat, some of which involve QM calculations for a live cat?

What is it like for the scientist inside the box to be in a superposition of states? Once you realize that the wave function is a calculational tool, all of this makes sense. The wave function that Wigner's friend uses is different from the wave function that the outside observer uses, because they have access to different information. It is a good demonstration of the subjectivity of the wave function. Only when all observers have access to the same information will they agree on the wave function. This is always implicitly assumed, but is not necessary, as this example demonstrates.

 

[DrChinese]

...I am, of course, not absolutely sure, its one viewpoint in the many attempts to deal with the interpretation of waveform collapse. I find it to be the best. It disposes of many of the problems of waveform collapse, wondering when and how the collapse occurs. In particular, referring to the above thread, it deals with the problem of "Wigner's friend". Wigner's friend is a scientist inside the box with the cat and dealing with what he observes, using wave functions to describe the state of the cat. How does the observer outside the box deal with this? Is Wigner's friend in a superposition of states, some of which involve calculations of the wave function for a dead cat, some of which involve QM calculations for a live cat?

What is it like for the scientist inside the box to be in a superposition of states? Once you realize that the wave function is a calculational tool, all of this makes sense. The wave function that Wigner's friend uses is different from the wave function that the outside observer uses, because they have access to different information. It is a good demonstration of the subjectivity of the wave function. Only when all observers have access to the same information will they agree on the wave function. This is always implicitly assumed, but is not necessary, as this example demonstrates.

If the wave function were real, then you could manipulate it physically. And there is every evidence that you can. You can use a polarizing beam splitter to separate the H and V portions, then do tricks to them, and later recombine to restore the original beam. The recombined beam having attributes that the separate beam components would not have. That seems like more than a mathematical device. (However, this does little to explain the phenomenon of collapse itself.) See Eberly:

http://www.optics.rochester.edu/~stroud/cqi/rochester/UR19.pdf

 

[Q-reeus]

I think COEM would not be violated, certainly not globally (ie in the entire universe). Just like COEM is not violated when a single atom quantum tunnels across a potential barrier, now imagine the probability of every single atom in the moon (or any macroscopic part of it) suddenly quantum tunnelling outside the solar system, this is vanishing small, and we ignore it in scientific models, just like we ignore the poincare recurrence theorem when doing usual statistical physics.

Clearly in the context of 'massively moving Moon' this is purely an academic exercise, but my view of tunneling as per Schrodinger eq'n is that while say a bound atomic electron can have a finite probability of being found at any spatial location, it does so at the 'expense' of the rest of the atom's energy/momentum. In other words the overall system COEM places an absolute restraint on what is possible. This is not so - given enough time, anything is possible?

 

[unusualname]

Clearly in the context of 'massively moving Moon' this is purely an academic exercise, but my view of tunneling as per Schrodinger eq'n is that while say a bound atomic electron can have a finite probability of being found at any spatial location, it does so at the 'expense' of the rest of the atom's energy/momentum. In other words the overall system COEM places an absolute restraint on what is possible. This is not so - given enough time, anything is possible?

The "overall system" has to really extend to the entire universe, even if you're talking about a single atom, since it's not possible to isolate any single part of the universe for an idealised laboratory experiment. In practice we can get excellent approximations to isolated systems, but they are always approximations.

Eventually this discussion will lead to statements about supposed absolute laws and how applicable they are, but it will be fruitless since we do not really know the exact correct form of the absolute laws. We do not worry that the second law of thermodynamics contradicts poincare recurrence, since there is no conceivable macroscopic scenario where poincare recurrence can have more than the remotest possibility of being relevant. When the final laws are found it's posiible that we might see that the universe recurs eternally on huge timescales, but it's pointless to worry about those sort of questions before we have established the basic fundamental laws.

We're still struggling to accept the probabilistic nature of QM, over 80 years after it was discovered!

 

[Q-reeus]

...Eventually this discussion will lead to statements about supposed absolute laws and how applicable they are, but it will be fruitless since we do not really know the exact correct form of the absolute laws. We do not worry that the second law of thermodynamics contradicts poincare recurrence, since there is no conceivable macroscopic scenario where poincare recurrence can have more than the remotest possibility of being relevant. When the final laws are found it's posiible that we might see that the universe recurs eternally on huge timescales, but it's pointless to worry about those sort of questions before we have established the basic fundamental laws...

I take the point, but darn, was so hoping to lever this into a heated discussion about the 'Boltzmann Brains Crisis' some ivory tower academics worry so much about!

 

[Rap]

If the wave function were real, then you could manipulate it physically. And there is every evidence that you can. You can use a polarizing beam splitter to separate the H and V portions, then do tricks to them, and later recombine to restore the original beam. The recombined beam having attributes that the separate beam components would not have. That seems like more than a mathematical device. (However, this does little to explain the phenomenon of collapse itself.) See Eberly:

http://www.optics.rochester.edu/~stroud/cqi/rochester/UR19.pdf

When you say "If the wave function were real, then you could manipulate it physically", do you mean that if it were not you could not?. I don't see a problem with manipulating the wave function by performing certain measurements. The measurements alter your knowledge, which alters the encoding of that knowledge - i.e. it alters the wave function.

Also, how do you explain the Wigner's friend variation of the Schroedinger Cat paradox?

 

[alxm]

Also, how do you explain the Wigner's friend variation of the Schroedinger Cat paradox?

The same way Wigner did: They're not in superpositions because they're interacting with the environment and their wave functions have decohered.

"Wigner's friend" was a philosophical musing that Wigner published in a popular-scientific book of his. To whatever extent he took those ideas seriously himself, he later abandoned them.
Because he later not only embraced decoherence as the answer to how the wavefunction "collapse" occurs, but actively contributed to the research on it.

 

[DrChinese]

1. When you say "If the wave function were real, then you could manipulate it physically", do you mean that if it were not you could not?. I don't see a problem with manipulating the wave function by performing certain measurements. The measurements alter your knowledge, which alters the encoding of that knowledge - i.e. it alters the wave function.

2. Also, how do you explain the Wigner's friend variation of the Schroedinger Cat paradox?

1. I have 50% probability A and 50% probability B. As separate entities, they may have definite polarizations H (if A) or V (if B). But if I recombine them, I restore a superposition. Yet that state cannot be constructed from an H or V individually. So the thing I am manipulating in each portion is not a photon in and of itself. It is a wave state.

2. What's to explain? There is no experiment.

 

[Rap]

1. I have 50% probability A and 50% probability B. As separate entities, they may have definite polarizations H (if A) or V (if B). But if I recombine them, I restore a superposition. Yet that state cannot be constructed from an H or V individually. So the thing I am manipulating in each portion is not a photon in and of itself. It is a wave state.

When we all have access to the same information, we all agree on the wave function, and it appears to have an objective reality. Its only when two people have different information, and this is not the result of incomplete measurements by one or the other, that you need two different wave functions to encode knowledge. The only way I know to do this is to make one observer part of the system being observed by the second observer, as exemplified by Wigner's friend.

2. What's to explain? There is no experiment.

I don't understand - it is a thought experiment. Are you saying thought experiments are invalid? Are you saying that I did not explain it correctly or completely?

 

[DrChinese]

I don't understand - it is a thought experiment. Are you saying thought experiments are invalid? Are you saying that I did not explain it correctly or completely?

Well, it's a paradox so there is a faulty assumption. I wouldn't try to resolve that by reference to the reality of the wave function. And I don't pretend to be able to explain what collapse is. Is it physical and objective? I dunno, wish I did. All I can say is that the existence of interference effects, as well as the ability to reconstruct a superposition, leads me to conclude that the wave function has objective reality. And I would say that the experimental evidence supports this view.

 

[Rap]

Well, it's a paradox so there is a faulty assumption. I wouldn't try to resolve that by reference to the reality of the wave function.

I would - especially if it produced no further paradoxes, and every other attempt to resolve the paradox were unsatisfactory. It seems to me that almost every paradox in QM is resolved by rejecting the classical notion of objective reality, independent of measurement. And we can never measure the wave function, we can only infer it from measurements which involve the modulus of its amplitude.

 

[DrChinese]

It seems to me that almost every paradox in QM is resolved by rejecting the classical notion of objective reality, independent of measurement. ...

True enough, no argument from me on that. But to me the issue is: objective reality of what?

To me, the relationships of the HUP are objectively real while non-commuting particle observables are not. To me, conservation rules (and conserved quantities) are objectively real while their constituent components are not. So I tend to think of the wave function itself as physically real, and not just a tool. Of course, this may just be application of semantics to the phrase "objective physical reality" itself.

 

[Rap]

True enough, no argument from me on that. But to me the issue is: objective reality of what?

To me, the relationships of the HUP are objectively real while non-commuting particle observables are not. To me, conservation rules (and conserved quantities) are objectively real while their constituent components are not. So I tend to think of the wave function itself as physically real, and not just a tool. Of course, this may just be application of semantics to the phrase "objective physical reality" itself.

I would be interested in any thoughts you have on the resolution of the Wigner's friend paradox. An observer is put inside a box. Forget the cat, the observer is looking at a screen which registers a photon from a low-intensity source. When the box is closed, no photon has been observed. At time t>0 an outside observer now describes what is inside the box as an apparatus and observer in a superposition of photon-seen and photon-not-seen wave functions. To the observer inside, the wave function is either in a photon-seen state, or photon-not-seen state (collapsed).

 

[DrChinese]

I would be interested in any thoughts you have on the resolution of the Wigner's friend paradox. An observer is put inside a box. Forget the cat, the observer is looking at a screen which registers a photon from a low-intensity source. When the box is closed, no photon has been observed. At time t>0 an outside observer now describes what is inside the box as an apparatus and observer in a superposition of photon-seen and photon-not-seen wave functions. To the observer inside, the wave function is either in a photon-seen state, or photon-not-seen state (collapsed).

I doubt anything I say is going to answer much of anything on this. If Wigner's friend is in a superposition according to Wigner, then there cannot be a measurement by Wigner's friend that has now been collapsed. That's true no matter what the friend says.

Now I realize that the idea of the paradox is that the position of the observer leads each to report a different reality, and therefore reality cannot be objective. But I would still say that the result of an experiment should not contradict anything I said above.

 

[Mute]

Ah! That's where I started. We are back to the bug. It's bug eyes observe the photons from the distant star, but it's bug brain can't generate information about what it has observed. So the wave-function does not collapse. It is still just a probability of a star at that location.

Well, I could be wrong. Perhaps a tiny bug could collapse the wave-function of a star instantly 50,000 light years away without generating any information about what it has observed. That would be even more interesting, in my own humble opinion.

I'm just musing about the connection between the generation of information and the collapsing of the wave function. I didn't mean to disturb anyone. Carry on.

You seem to be confusing "information" with "meaning". Information, as discussed in a scientific context, is divorced from having "meaning". A binary sequence is a simple example - it's just ones and zeros, but it has information content that we can analyze. The "meaning" that the string has is something we impose on it; it is not a property of the string itself. When photons reach the bug's eyes information is generated: neurons are triggered to fire, spike pulses encoding more information are produced, etc. Whether or not the fly can attach any meaning to this information processing is a separate issue entirely. Quantum mechanics might have something to say about information, but it has nothing to say about the "meaning" of that information. The meaning is just what interpretation we decide to ascribe to the information that has been measured.

 

[Rap]

I doubt anything I say is going to answer much of anything on this. If Wigner's friend is in a superposition according to Wigner, then there cannot be a measurement by Wigner's friend that has now been collapsed. That's true no matter what the friend says.

I am having difficulty understanding what Wigner's friend experiences if your statement is true. If your statement is true, then Wigners friend is in an objectively real superposed state. What is that like?

 

[DrChinese]

I am having difficulty understanding what Wigner's friend experiences if your statement is true. If your statement is true, then Wigners friend is in an objectively real superposed state. What is that like?

Hmmm. I think it is very similar to the state in which it is approaching 5 o'clock.

 

[IllyaKuryakin]

I've carefully read and considered all the replies above and suggest the following resolution. We have very good experimental evidence that the Universe proceeds in a probabilistic fashion on the quantum scale of single particles. We also have excellent evidence that the Universe proceeds deterministically on the macro scale of anything we can see with the unaided eye. I offer GR as proof of this, as it has been experimentally tested to many decimal places in many ways, and no deviation of data indicates the probabilistic scattering we see in QM. So, let's accept that both are true, and the transition from QM behavior to deterministic occurs at some small level and we just don't know yet what physical laws govern that transition. There are many experimental physicists looking for that transition and the laws that govern it now, and just because we don't completely understand it now there is no reason to believe we never will. So, let's assume some day we will understand that transition, and all the physical laws that govern it. In that case, I have to reverse my earlier conclusion and say, I agree, if a tree falls in the woods, and no one observes it, it's just a tree that fell deterministically, and it made a sound whether anyone observed it or not. So, logic holds and all is well with the Universe, Yes? No, not yet.

We come to the strange action at a distance, and the odd observations that seem to indicate that a photon knows whether we are observing it or not. Perhaps, there is a logical explanation for these effects as well. Let's look at non-locality. It's predicted by the math of QM and has been verified experimentally. So how is this possible? One solution is to look at the Universe in a holistic fashion as a single quantum computer, running the math of QM and determinism and the transition from one to the other. Then, the seeming communication between particles at a distance is really just a math program running on a computer. One bit of code describes one particle, and another bit of code describes the other particle, and QM describes the relationship between the particles. There is then nothing mysterious about non-locality, since all the math is run on the same computer, distance between the particles isn't even a factor in the computation. Thus, the problem of non-locality is efficiently disposed of. No additional physics is required, other than the physical laws governing the transition from probabilistic to deterministic reality, as discussed previously. Of course, all of this is just my own humble opinion.

 

[IllyaKuryakin]

Well, it's a paradox so there is a faulty assumption. I wouldn't try to resolve that by reference to the reality of the wave function. And I don't pretend to be able to explain what collapse is. Is it physical and objective? I dunno, wish I did. All I can say is that the existence of interference effects, as well as the ability to reconstruct a superposition, leads me to conclude that the wave function has objective reality. And I would say that the experimental evidence supports this view.

If QM math does not just model objective reality, but is in fact a part of objective reality itself, basically running on the quantum computer of the Universe, then yes, the waveform is objectively real. Classical determinism is also objectively real, but it's a different set of equations running on the same computer. Decoherence is perhaps a mathematical link between the two, but we just haven't discovered all the math to that process yet. As odd a notion as it seems, I believe it completely agrees with experimental evidence. Of course, I must credit Seth Lloyd and his, "The computational Universe" for that concept.

To put a sharper point on it, our perception of objective reality is only that, a perception. It is not reality itself. Reality is only the math. Of course, for that to be true, the math must be processed somehow, and that's where the concept of the Universe being a quantum computer comes in.

Here's how Dr. Lloyd looks at it: http://www.edge.org/3rd_culture/lloyd2/lloyd2_print.html

 

[Rap]

So, let's accept that both are true, and the transition from QM behavior to deterministic occurs at some small level and we just don't know yet what physical laws govern that transition.

No, there is no transition, its just that the probabilistic aspects of QM become negligible (but not zero!) in the macroscopic realm. Ultimately, to form a complete theory, GR will have to incorporate quantum indeterminism.

In that case, I have to reverse my earlier conclusion and say, I agree, if a tree falls in the woods, and no one observes it, it's just a tree that fell deterministically, and it made a sound whether anyone observed it or not. So, logic holds and all is well with the Universe, Yes? No, not yet.

Science is about repeatable, measurable events. A single tree falling in the woods that no one observes, is unrepeatable and unmeasured, therefore it is not properly a subject for scientific inquiry.

 

[StevieTNZ]

'Quantum Enigma' by Bruce Rosenblum - consciousness collapses the wave function

'Quantum Reality: Theory and Philosophy' by Jonathan Allday - ability to infer or not infer information about which path the particle collapses determines whether interference is observed or not

'The Quantum Challenge' (2nd edition) by George Greenstein & Arthur G. Zajonc - pags 110-113 - mentions of having partial information and the resulting interference.

 

[jibblesmgee]

This is more like Confucius than Copenhagen. You have to keep in mind Schrodinger's Cat was more of a joke at probability than a proof for it. The reason the star doesn't exist to you as an observer if it's 50,000 lightyears away and was just created is that all the information we can observe from it doesn't reach us for at least 50,000 years. So this is the speed that time travels as well. This is a General Relativity idea. I think it's been fairly well proven that the energy density of space dictates the vector of the constant (curvature of spacetime)

Please correct me if I'm wrong (I'm a physics student, so I'm used to being wrong.)

 

[IllyaKuryakin]

No, there is no transition, its just that the probabilistic aspects of QM become negligible (but not zero!) in the macroscopic realm. Ultimately, to form a complete theory, GR will have to incorporate quantum indeterminism.

Experimental results show no probabilistic scattering of in GR test data at all, so I can't see how this can conform to those results. The results indicate that the transition, or decoherence if you like, from QM to GR is complete at larger scales.