Does Decoherence Von Neumann Interpretationrefute

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Main Question or Discussion Point

Von Neumann wrote in a major physics book decades ago that consciousness was what collapse the wave function.. how could he stated this bizaare statement and the facts remain up to this day?

Is the interpretation been refuted already by the latest discovery of Decoherence? I can't find website which says it's refuted already.

What Von Neumann was like saying was that in the earth core where no-one observes it, the core is in a state of superposition where no position exists. Is this possible? Can dynamics still occur like producing the earth magnetic field even though the core is not in definite physical state but in superposition??

If the idea is absurd the earth core is in superposition, why did Neumann state it in the first place being a great mathematician and scientist he was? What went on in his mind when he proposed it?

It doesn't just work in the earth core, but any ocean area where no consicous human is nearby could be said to be in a state of superposition. However, if we leave a camera and record the area. We can get video of it fully existing. So how can Von Neuman mechanism work where only consciousness can supposedly collapse the wave function when it was already recorded in video?

Hope someone can clarify the basis of Von Neumann logic and why he stated it in the first place.
 

Answers and Replies

  • #2
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I guess both flavors of Copenhagen Interpretation, include the Von Neumann's one, are not taken seriously in 21 century as fundamental explanation - even they are still very useful as 'rule of thumb' on a practical level?

On the other hand, it appears that Von Neumann was right in some sense... because the world we see is a result of the decoherence of the ultimate reality using some pre-selected basis, called ‘consciousness’
 
  • #3
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I guess both flavors of Copenhagen Interpretation, include the Von Neumann's one, are not taken seriously in 21 century as fundamental explanation - even they are still very useful as 'rule of thumb' on a practical level?

On the other hand, it appears that Von Neumann was right in some sense... because the world we see is a result of the decoherence of the ultimate reality using some pre-selected basis, called ‘consciousness’
Isn't there any way to refute it? For example in volcanic vents hundred of miles underneath the oceans are many organisms. Since no human has seen them and they are in superposition, how can they evolve in the first place if there is no definite position???
 
  • #4
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Isn't it that by superposition is meant there is no position, meaning everything is in limbo? So how did the organisms underneath the ocean near underwater volcanos evolve if there is no position.. unless there is still position even during superposition if the phases are decohered??
 
  • #5
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Universe wavefunction is objective. For these organisms it is irrelevant if humans exist or not. Universe wavefunctions determines if such structures can exist nd if yes, then how often.
 
  • #6
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Universe wavefunction is objective. For these organisms it is irrelevant if humans exist or not. Universe wavefunctions determines if such structures can exist nd if yes, then how often.
After hours of researching in the net.. i still haven't found the answers I seek about von Neumann model and why nobody can refute it.

I think what von Neumann is saying is that without human consciousness, physical matter exists as some sort of limbo where there is no physical location. It is upon measurement with our consciousness that the limbo state turns into definite physicality. This means any unobserved area like below the world ocean, it is in limbo without definite particle position. Now my question is, how could dynamics exist (like fishes evolving) when there are no physical environment. Or did I misinterpret von Neumann model? What is he really saying that only consciousness can collapse the wave function? In what context does he meant? Let's just focus on what von Neumann meant and not what the latest model about Decoherence says which is more believable.
 
  • #7
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Ah, you mean the original Neumann's point of view?
Sorry for confusing you, I was replying thiking about some similarity between his view and MWI.
 
  • #8
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Ah, you mean the original Neumann's point of view?
Sorry for confusing you, I was replying thiking about some similarity between his view and MWI.
Yup. Bohr says before measurement, position doesn't exist. So when von Neumann stated consciousness can collapse the wave function, i wonder if he meant without consciousness, the wave function doesn't collapse, meaning there is no definite position in any of the particles say beneath the ocean. But then.. I just think now that what he meant was that in any system that can be measured, that is.. his example only work for a system with phase entanglement that can interfere. In macroscopic objects, phase are all decohered so no superposition is possible. But then at the time of von Neumann, Decoherence is not discovered, so what's his explanation for the macroscopic world why they are not in superposition??

I want to understand all this so I can debunk all works related to mind that mentioned about von Neumann and his model.
 
  • #9
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Please clarify, are you interested in it as studying the history of physics (which makes perfect sense) or as a theory which can explain measurement (which does not make any sense in 21 century)
 
  • #10
Please clarify, are you interested in it as studying the history of physics (which makes perfect sense) or as a theory which can explain measurement (which does not make any sense in 21 century)
First, thanks for some good information; you have a very brief and profound way of making your points that I admire.

Unfortunately, you're being led-on by a crackpot.

https://www.physicsforums.com/showpost.php?p=3078403&postcount=19

Here's where he wants to go...

Alfrez said:
<SNIP>I'm thinking that consciousness (via von Neumann modelling) can interact with the wave function and indeed transmit signal non-locally. Has experiment been done where this is tested or refuted??

If von Neumann mediated consciousness can indeed transmit signal non-locally, then we can say that Special Relativity is finished. Right??
I don't mean to be rude, and if I'm making an unfair assumption and derailing a good thread, then I apologize, and will take my lumps. I don't like seeing this kind of re-threading, when you're clearly trying to help someone.
 
  • #11
Fredrik
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Von Neumann wrote in a major physics book decades ago that consciousness was what collapse the wave function.. how could he stated this bizaare statement and the facts remain up to this day?
I haven't read that book, but I would be surprised if he presented as a fact. It was just his speculation, and there's nothing to support it.

Is the interpretation been refuted already by the latest discovery of Decoherence? I can't find website which says it's refuted already.
It doesn't need to be refuted, since wavefunction collapse is an unnecessary concept (not to mention the idea that consciousness is causing it).

Decoherence explains why superpositions are unobservable. Interactions with the environment moves most of the quantum weirdness into the microscopic degrees of freedom of the environment (but doesn't eliminate it completely). It makes a system (that isn't isolated from its environment) for all practical purposes indistinguishable from a classical system.

What Von Neumann was like saying was that in the earth core where no-one observes it, the core is in a state of superposition where no position exists. Is this possible? Can dynamics still occur like producing the earth magnetic field even though the core is not in definite physical state but in superposition??
Yes. This is a simple consequence of the linearity of the Schrödinger equation. But the core isn't going to be in a superposition of macroscopically distinguishable terms due to its interactions with its environment.

If the idea is absurd the earth core is in superposition, why did Neumann state it in the first place being a great mathematician and scientist he was? What went on in his mind when he proposed it?
Quantum mechanics is very hard to understand, and von Neumann was active in its infancy. No one understood it really well at the time, and even today, no one can tell you what "actually happens" to a system between state preparation and measurement.

It doesn't just work in the earth core, but any ocean area where no consicous human is nearby could be said to be in a state of superposition. However, if we leave a camera and record the area. We can get video of it fully existing. So how can Von Neuman mechanism work where only consciousness can supposedly collapse the wave function when it was already recorded in video?

Hope someone can clarify the basis of Von Neumann logic and why he stated it in the first place.
Before decoherence theory, it seemed plausible to some that a camera wouldn't collapse the superposition, but a mind would. Decoherence theory has told us that superpositions are (almost) destroyed very quickly, so in most scenarios, we don't even need a camera. Air, water or whatever surrounding the system will act as an observer by interacting with the system. In a system like the Earth's core, I'm sure parts of it will act as a part of the environment of the other parts. Almost all the quantum weirdness will end up in the microscopic degrees of freedom.
 
  • #12
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I haven't read that book, but I would be surprised if he presented as a fact. It was just his speculation, and there's nothing to support it.


It doesn't need to be refuted, since wavefunction collapse is an unnecessary concept (not to mention the idea that consciousness is causing it).

Decoherence explains why superpositions are unobservable. Interactions with the environment moves most of the quantum weirdness into the microscopic degrees of freedom of the environment (but doesn't eliminate it completely). It makes a system (that isn't isolated from its environment) for all practical purposes indistinguishable from a classical system.


Yes. This is a simple consequence of the linearity of the Schrödinger equation. But the core isn't going to be in a superposition of macroscopically distinguishable terms due to its interactions with its environment.


Quantum mechanics is very hard to understand, and von Neumann was active in its infancy. No one understood it really well at the time, and even today, no one can tell you what "actually happens" to a system between state preparation and measurement.


Before decoherence theory, it seemed plausible to some that a camera wouldn't collapse the superposition, but a mind would. Decoherence theory has told us that superpositions are (almost) destroyed very quickly, so in most scenarios, we don't even need a camera. Air, water or whatever surrounding the system will act as an observer by interacting with the system. In a system like the Earth's core, I'm sure parts of it will act as a part of the environment of the other parts. Almost all the quantum weirdness will end up in the microscopic degrees of freedom.
I'm familiar with Decoherence having an entire book about it. But what I wanted to know was what von Neumann thought why macroscopic superposition didn't occur. At that time, he may not have known about Decoherence. If he did, he could easily state that any interaction with the environment can disturb the phase and decohering the setup without consciousness having to do with it. So what was von Neumann reasoning why macroscopic superposition didn't occur (now we know it is most likely because of decoherence but what did von Neumann thought of at that time)??
 
  • #13
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First, thanks for some good information; you have a very brief and profound way of making your points that I admire.

Unfortunately, you're being led-on by a crackpot.

https://www.physicsforums.com/showpost.php?p=3078403&postcount=19

Here's where he wants to go...



I don't mean to be rude, and if I'm making an unfair assumption and derailing a good thread, then I apologize, and will take my lumps. I don't like seeing this kind of re-threading, when you're clearly trying to help someone.
No. I'm not a crackpot. A crackpot is someone who believes an idea and would defend it at all cost even when wrong. Well. I don't even know if von Neumann is correct. That's why I'm seeking critical and logical points that can refute it.

If you meant a crackpot as someone who shares strange idea. Don't you know that physicists really believe there are Many Worlds and every time the wave function splits, other worlds are created. This is ultimate strangeness and may seem crackpottry.

But we don't call it crackpottry because it is supported by mathematics.. although it is just a QM interpretation.

Now von Neumann interpretation is another one where he stated directly that consciousness has to do with it. Of course I don't say I believe it although if it were true, the natural consequence is to ask whether it has Bell-like consequences. But then I knew I was wrong now in the statements you quoted because there is nothing non-local about it because before measurement, position properties don't exist before measurement, so with no position there is nothing non-local about it because locality doesn't even exist.

And since Special Relativity is seeming infallible. Bohmian Mechanics is more likely incorrect. In Bohmian Mechanics, the wave function is sensitive to all configuration in all particles in the universe at once. Add von Neumann model to Bohmian Mechanics and the natural thought is to think consciousness can transmit signal non-locally. But then since SR is infallible without any possibility of being falsified as physicists believe. Then for Bohmian to be correct, it has to be united with SR, so non-equilibrium non-local signalling is impossible in this fashion to avoid violating casuality.

Bottom line is, I'm not crackpot. I listen to reason.

To Dmitry67, Yes, I'm partly interested in the history of physics as to von Neumann original formulation about macroscopic stuff. As you know. He didn't understand Decoherence at that time, so he couldn't have meant macroscopic superposition was not possible due to Decoherence. I wonder if it means he believed macroscopic superposition was possible since he believed consciousness can collapse the wave function, and in regions where there is no human like inside the moon, does it mean inside the moon material properties inside exist in superposition and in limbo with no definite particle positions??
 
  • #14
No. I'm not a crackpot. A crackpot is someone who believes an idea and would defend it at all cost even when wrong. Well. I don't even know if von Neumann is correct. That's why I'm seeking critical and logical points that can refute it.

If you meant a crackpot as someone who shares strange idea. Don't you know that physicists really believe there are Many Worlds and every time the wave function splits, other worlds are created. This is ultimate strangeness and may seem crackpottry.

But we don't call it crackpottry because it is supported by mathematics.. although it is just a QM interpretation.

Now von Neumann interpretation is another one where he stated directly that consciousness has to do with it. Of course I don't say I believe it although if it were true, the natural consequence is to ask whether it has Bell-like consequences. But then I knew I was wrong now in the statements you quoted because there is nothing non-local about it because before measurement, position properties don't exist before measurement, so with no position there is nothing non-local about it because locality doesn't even exist.

And since Special Relativity is seeming infallible. Bohmian Mechanics is more likely incorrect. In Bohmian Mechanics, the wave function is sensitive to all configuration in all particles in the universe at once. Add von Neumann model to Bohmian Mechanics and the natural thought is to think consciousness can transmit signal non-locally. But then since SR is infallible without any possibility of being falsified as physicists believe. Then for Bohmian to be correct, it has to be united with SR, so non-equilibrium non-local signalling is impossible in this fashion to avoid violating casuality.

Bottom line is, I'm not crackpot. I listen to reason.

To Dmitry67, Yes, I'm partly interested in the history of physics as to von Neumann original formulation about macroscopic stuff. As you know. He didn't understand Decoherence at that time, so he couldn't have meant macroscopic superposition was not possible due to Decoherence. I wonder if it means he believed macroscopic superposition was possible since he believed consciousness can collapse the wave function, and in regions where there is no human like inside the moon, does it mean inside the moon material properties inside exist in superposition and in limbo with no definite particle positions??
I meant crackpot according to forum rules.
 
  • #15
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I meant crackpot according to forum rules.

If crackpot in forum rules meant discussing stuff outside of convensional formalism. Hmm... but my level of discussion is within tolerable limit... it's simply the following facts.

At the time of von Neumann half a century ago. Bell's Theorem didn't exist. Had it existed. It would not be hard to tie up consciousness and Bell's Theorem. But I'm not interested in this now and I understand forum rules forbid discussing it and hence I won't discuss it anymore.

I simply want to know for now what von Neumann thought about macroscopic superposition. Since Decoherence concept didn't exist in his time. Did he actually mean that Schrodinger Cat in superposition is possible say inside a cave where no human consciousness is present? What perflex me a lot is how does the cat blood vessels pump blood when there is no position as it exists in pure limbo. Since we know it is absurd. Then what is von Neumann reasoning why he thought macroscopic superposition is never possible even if his consciousness collapsing the wave function factor is not present in a region without a human? If someone can answer this, then I got my answer and the thread is closed. Thanks.
 
  • #16
If crackpot in forum rules meant discussing stuff outside of convensional formalism. Hmm... but my level of discussion is within tolerable limit... it's simply the following facts.

At the time of von Neumann half a century ago. Bell's Theorem didn't exist. Had it existed. It would not be hard to tie up consciousness and Bell's Theorem. But I'm not interested in this now and I understand forum rules forbid discussing it and hence I won't discuss it anymore.

I simply want to know for now what von Neumann thought about macroscopic superposition. Since Decoherence concept didn't exist in his time. Did he actually mean that Schrodinger Cat in superposition is possible say inside a cave where no human consciousness is present? What perflex me a lot is how does the cat blood vessels pump blood when there is no position as it exists in pure limbo. Since we know it is absurd. Then what is von Neumann reasoning why he thought macroscopic superposition is never possible even if his consciousness collapsing the wave function factor is not present in a region without a human? If someone can answer this, then I got my answer and the thread is closed. Thanks.
Ahhh... so you'll talk all around it, flirt with it, and try to get others talking about it? BTW... threads?... you start 'em, but only mentors get to end them.
 
  • #17
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Ahhh... so you'll talk all around it, flirt with it, and try to get others talking about it? BTW... threads?... you start 'em, but only mentors get to end them.

When I wrote about von Neumann and Bell's theorem. I didn't know at that time that discussion outside of the mainstream view is forbidden. After I knew it. I won't discuss it anymore.

Hmm... I think what you are doing now is to provoke quarrel so this thread would be closed prematurely. But as I have said. I only want to know what is von Neumann original ideas about macroscopic superposition and why he didn't believe it is possible even without knowing about Decoherence. That's all. When someone answers it. Then I'd no longer bring up other points. Peace dude.
 
  • #18
Fredrik
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The linearity of the Schrödinger equation implies that if microscopic systems can be in superpositions, then so can macroscopic objects. This is the point of the Schrödinger's cat thought experiment. I'm guessing that von Neumann was just (like everyone else at the time) seeking an explanation for why macroscopic superpositions have never been observed, even though they (at first glance) seem to be predicted by the theory.

Did he actually say that he thought macroscopic superpositions don't exist? Then I would take that to indicate that he didn't believe in that consciousness nonsense either, because "consciousness causes collapse" is only needed if we believe that macroscopic superpositions exist until they're observed (and that a wavefunction represents all the properties of the system, and that there's only one world).
 
  • #19
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The linearity of the Schrödinger equation implies that if microscopic systems can be in superpositions, then so can macroscopic objects. This is the point of the Schrödinger's cat thought experiment. I'm guessing that von Neumann was just (like everyone else at the time) seeking an explanation for why macroscopic superpositions have never been observed, even though they (at first glance) seem to be predicted by the theory.

Did he actually say that he thought macroscopic superpositions don't exist? Then I would take that to indicate that he didn't believe in that consciousness nonsense either, because "consciousness causes collapse" is only needed if we believe that macroscopic superpositions exist until they're observed (and that a wavefunction represents all the properties of the system, and that there's only one world).

At that time von Neumann proposed it. It was not known that there are billions of galaxies in the universe. Had he known it. He could not have stated his theory. Because the implication was that an entire galaxy could exist in superposition in space without definite positions if there is no consciousness that has evolved yet.

Of course right now we hold on to Decoherence which may be a more logical idea. But then can't we debunk the von Neumann model by the macroscopic mechanism. You stated that
the linearity of the Schrödinger equation implies that if microscopic systems can be in superpositions, then so can macroscopic objects. But then can't one give an example where position is important and without position no evolution of any systems is possible??

Or in other words. Are you saying that the linearity of the Schrodinger equation means that (for sake of discussion) if supposed the earth suddenly exists in superposition without definite position, we can still use the internet and communicate? How? There are no keyboards to type the message and view the screen so how can one still communicate if the world suddenly exists in just pure superposition?? Note this is just for sake of illustration how stuff work inside superposition and we can use the example of organisms dynamics existing in underwater volcano miles beneath the ocean but typing keyboard is a more distinct example.

I just want to thoroughly understand this so I can completely debunk and forget von Neumann seemingly nonsense model.
 
  • #20
Fredrik
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You stated that
the linearity of the Schrödinger equation implies that if microscopic systems can be in superpositions, then so can macroscopic objects. But then can't one give an example where position is important and without position no evolution of any systems is possible??
I don't understand the question, but I'll add that I should probably have said "...then in principle, so can macroscopic systems". In real experiments, we will always fail to isolate macroscopic systems from their environments, and this will effectively destroy the superpositions.

Or in other words. Are you saying that the linearity of the Schrodinger equation means that (for sake of discussion) if supposed the earth suddenly exists in superposition without definite position, we can still use the internet and communicate? How? There are no keyboards to type the message and view the screen so how can one still communicate if the world suddenly exists in just pure superposition??
In principle, if the Earth could be isolated from its environment (this could probably only happen in a universe without gravity), then from the point of view of an external observer, it could exist in a superposition of very different eigenstates of the observable that the external observer would measure when he breaks the isolation. Before that "measurement", those eigenstates would evolve completely independently of each other. It's possible that one of them involves people communicating over the internet, and that another one involves an Earth where everyone's dead.

Considerations like these are the reason why many of us think that some sort of many-worlds interpretation is necessary if QM is to be thought of as a description of reality, i.e. if the wavefunction actually represents all the properties of the system at all times, and therefore tells us what "actually happens" to the system even at times between state preparation and measurement.

Of course, a much simpler solution is that QM isn't a description of reality at all, and is just a set of rules that tells us how to calculate probabilities of possibilities.
 
  • #21
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I don't understand the question, but I'll add that I should probably have said "...then in principle, so can macroscopic systems". In real experiments, we will always fail to isolate macroscopic systems from their environments, and this will effectively destroy the superpositions.


In principle, if the Earth could be isolated from its environment (this could probably only happen in a universe without gravity), then from the point of view of an external observer, it could exist in a superposition of very different eigenstates of the observable that the external observer would measure when he breaks the isolation. Before that "measurement", those eigenstates would evolve completely independently of each other. It's possible that one of them involves people communicating over the internet, and that another one involves an Earth where everyone's dead.

Considerations like these are the reason why many of us think that some sort of many-worlds interpretation is necessary if QM is to be thought of as a description of reality, i.e. if the wavefunction actually represents all the properties of the system at all times, and therefore tells us what "actually happens" to the system even at times between state preparation and measurement.

Of course, a much simpler solution is that QM isn't a description of reality at all, and is just a set of rules that tells us how to calculate probabilities of possibilities.


Many-worlds is as bizarre as macroscopic things existing in superposition.

Anyway. You didn't completely understand my questions. Maybe the following question is more clearer of the concept I intend to comprehend.

If the world now suddenly existed as superposition.. what would be the difference between the normal and superposition mode? For example. In the superposition, would I still see this keyboard and monitor I'm using? Or not?? How to tell the difference??

You described how an observer from outside would supposedly observe if the earth experience macroscopic superpostion, what I wanted to understand is how the person within the superposition would see himself. Can the insider tell? If no difference. Then you mean it's possible the earth now can be inside a superposition without our knowing it??

This discussion is ignoring Decoherence & Many Worlds for sake of understanding what goes on inside a macroscopic superposition.
 
  • #22
Fredrik
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I don't see any difference between a macroscopic superposition that actually describes reality, and many worlds existing at once. You wouldn't know if you're a part of a superposition or not, beause your states would be correlated with the keyboard's states.

Just QM: A wavefunction represents the statistical properties of an ensemble of identically prepared systems, not the properties of the system. (The latter means that QM simply doesn't tell us how things are perceived from the inside of the system).

Many-worlds interpretation (MWI): A wavefunction represents the properties of the system. If the wavefunction is expressed in terms of the members of a particularly nice basis, each term describes a "world".

Conciousness-causes-collapse (CCC): Like MWI, but the existence of many worlds is temporary. All but one of the worlds are destroyed when the system interacts with a consciousness. (This idea is so silly that I can barely make myself type it).
 
  • #23
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I don't see any difference between a macroscopic superposition that actually describes reality, and many worlds existing at once. You wouldn't know if you're a part of a superposition or not, beause your states would be correlated with the keyboard's states.

Just QM: A wavefunction represents the statistical properties of an ensemble of identically prepared systems, not the properties of the system. (The latter means that QM simply doesn't tell us how things are perceived from the inside of the system).

Many-worlds interpretation (MWI): A wavefunction represents the properties of the system. If the wavefunction is expressed in terms of the members of a particularly nice basis, each term describes a "world".

Conciousness-causes-collapse (CCC): Like MWI, but the existence of many worlds is temporary. All but one of the worlds are destroyed when the system interacts with a consciousness. (This idea is so silly that I can barely make myself type it).
Many thanks for the above clear distinctions. To make the understanding complete. Please share your definition and understanding of "Decoherence" in terms of:

1. Just QM
2. Many-worlds interpretation (MWI):
3. Conciousness-causes-collapse (CCC):
 
  • #24
Fredrik
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It would take too long to answer that thoroughly (especially decoherence in the context of a MWI). QM is defined by the axioms discussed here, and the interpretations by additional assumptions on top of those. The idea that QM is a description of what actually happens is a key part of any MWI (but not of QM itself).
 
  • #25
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if supposed the earth suddenly exists in superposition without definite position, we can still use the internet and communicate? How? There are no keyboards to type the message and view the screen so how can one still communicate if the world suddenly exists in just pure superposition??

You are mixing so called 'Birds view' (c) Max Tegmark where you see very complicated and fuzzy picture of the whole universe wavefunction where all options exist, and 'frog's view', inner observer's view, where observer is not even a 'tree' but a 'line'. When Birds' view is mapped into one's particular frog’s view, we observe all artifacts like ‘collapse’, ‘measurements’, ‘no superposition’ etc.

P.S.
I strongly believe that QM (except the high energy corrections + quantum gravity part) is accurate description of the Universe wavefunction, except the formulas, the ideology of it will be the same when TOE will be discovered, so TOE wont solve the measurement problem. After TOE there will be a tricky part – to justify the choice of the basis of decoherence called ‘consiousness’. We will know all the formulas but we won't be able to say why the world behaves this way :)
 

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