Question about Many Worlds branching in Quantum Mechanics

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Supposing the Many Worlds interpretation of QM is true... If a branching occurs during what we perceive is a wave function collapse, why would this be perceptible to us as probabilties? Wouldn't we just branch, leaving it just as imperceviable as the passage of time? That is, it just happens. By way of analogy, there is no intermediate process in the passage of time. And this is how I envision the branching of many worlds.

In other words, why would we have any evidence of our own branching?
 

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  • #2
Demystifier
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Supposing the Many Worlds interpretation of QM is true... If a branching occurs during what we perceive is a wave function collapse, why would this be perceptible to us as probabilties? Wouldn't we just branch, leaving it just as imperceviable as the passage of time? That is, it just happens. By way of analogy, there is no intermediate process in the passage of time. And this is how I envision the branching of many worlds.

In other words, why would we have any evidence of our own branching?
Why do you think that passage of time is not perceivable? What do you mean by "intermediate process in the passage of time"?
 
  • #3
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Why do you think that passage of time is not perceivable? What do you mean by "intermediate process in the passage of time"?
Point is, the supposed branching process is impercievable in the macroscopic world. I know decoherence explains part of that, but it isn't scientifically accounted for why there is a manifestation of the branching process in the microscopic world, when measuring/observing. It is unaccounted for as far as I can tell
 
  • #4
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the supposed branching process is impercievable in the macroscopic world.
Why?

I know decoherence explains part of that, but it isn't scientifically accounted for why there is a manifestation of the branching process in the microscopic world, when measuring/observing. It is unaccounted for as far as I can tell
It is one thing to claim that it is not clear why the branching has a manifestation, and another to claim that it does not have a manifestation. Which of the two do you actually claim?
 
  • #5
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It is one thing to claim that it is not clear why the branching has a manifestation, and another to claim that it does not have a manifestation. Which of the two do you actually claim?
The first one. We are assuming for arguments sake that some version of the many worlds is true, that is alternate histories are constantly taking place. There is no accounting for why there is a visible branching in the subatomic world when measuring, instead of just branching right away and no knowledge that it took place.
 
  • #6
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Perhaps you are asking this: If the wave function branches, then why do we see only one branch and not all of them? Is that your question?
 
  • #7
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Perhaps you are asking this: If the wave function branches, then why do we see only one branch and not all of them? Is that your question?
I am asking why we see any branching at all, and probabilities assigned, supposing Many Worlds is true. I don't believe a Many Worlds universe would look like the universe we live in. If it was proposed prior to findings of QM, I would be far more receptive to the theory.
 
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I don't believe a Many Worlds universe would look like the universe we live in.
So how do you believe that a many worlds universe would look like?
 
  • #9
DrChinese
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I am asking why we see any branching at all, and probabilities assigned, supposing Many Worlds is true. I don't believe a Many Worlds universe would look like the universe we live in. If it was proposed prior to findings of QM, I would be far more receptive to the theory.
No, it was proposed about 30 years later, essentially with the intent to explain elements of probabilistic outcomes. If you throw a die repeatedly, and there is branching, you still see the expected statistical outcomes. Except in perhaps a very small number of branches. And even those will eventually evidence the normal patterns.
 
  • #10
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For instance, a many worlds theory can account for why the value of the universe is largely arbitrary. As you know, there a far more theoretically functional universes than just the one we live in, and this is driving physicists nuts. One is prone to thinking that the universe somehow exists out a mathematical neccesity, but modern physics debunks this old notion.
Many worlds can explain these arbitrary values due to the other universes already existing parallel to ours.
 
  • #11
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No, it was proposed about 30 years later, essentially with the intent to explain elements of probabilistic outcomes. If you throw a die repeatedly, and there is branching, you still see the expected statistical outcomes. Except in perhaps a very small number of branches. And even those will eventually evidence the normal patterns.
I wrote "if" it was proposed before rather than after QM
 
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So how do you believe that a many worlds universe would look like?
A subatomic world identical to the macroscopic, driven by Newtonian principles.
 
  • #13
DrChinese
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I wrote "if" it was proposed before rather than after QM
I saw that. What I meant is that MWI was proposed to resolve the some of the collapse issue.

I personally don't see it as much of a solution, but that's me. After all, some collapse is reversible. :smile:
 
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I saw that. What I meant is that MWI was proposed to resolve the some of the collapse issue.

I personally don't see it as much of a solution, but that's me. After all, some collapse is reversible. :smile:
It is not a bad theory and exemplifies "thinking out of the box". I don't think there was much thought given to multiverses and many worlds prior to Everett.
 
  • #15
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I am asking why we see any branching at all, and probabilities assigned, supposing Many Worlds is true.
Perhaps you think that first there are many worlds and then branching somehow happens? If that's what you think, that's completely wrong and probably the main source of your confusion. We first have one world, then a branching (more precisely - decoherence) occurs, and then we have many branches which can be thought of as "many worlds".

A subatomic world identical to the macroscopic, driven by Newtonian principles.
I have no idea why do you think so. :wideeyed:
 
  • #16
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So in my opinion, Many Worlds leads to a

Reductio ad absurdum



"In logic, reductio ad absurdum (Latin for "reduction to absurdity"; also argumentum ad absurdum, "argument to absurdity") is a form of argument which attempts either to disprove a statement by showing it inevitably leads to a ridiculous, absurd, or impractical conclusion, "
 
  • #17
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Perhaps you think that first there are many worlds and then branching somehow happens? If that's what you think, that's completely wrong and probably the main source of your confusion.
Not really. It is equally unaccounted for why we are privy to witnessing the branching.
 
  • #18
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For instance, a many worlds theory can account for why the value of the universe is largely arbitrary. As you know, there a far more theoretically functional universes than just the one we live in, and this is driving physicists nuts. One is prone to thinking that the universe somehow exists out a mathematical neccesity, but modern physics debunks this old notion.
Many worlds can explain these arbitrary values due to the other universes already existing parallel to ours.
Aaaa, I think I finally see the source of your confusion. You are confusing multiverse with many worlds. Those are different things!!!!
 
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The source cited in this post is not acceptable under the Physics Forums rules
I have no idea why do you think so. :wideeyed:
Hehe, well... My contention is that the citizens of a many worlds reality would NOT be privy the manifestation of the branching at any scales of observation. The reason I believe that is because it is an unneccesary component of the theory, and one which is unnaccounted for. You could say that I am applying Ockhams Razor.
 
  • #21
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Depends on who you ask.
Multiverse = Many Worlds, Say Physicists
Two of the most bizarre ideas in modern physics are different sides of the same coin, say string theorists

https://www.technologyreview.com/s/424073/multiverse-many-worlds-say-physicists/
So are you actually trying to say that you disagree with this interpretation? I do too, as do most other physicists. Many worlds and multiverse are considered different by almost all physicists. Even the authors of the idea above did not take this idea seriously in their subsequent works.
 
  • #22
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So are you actually trying to say that you disagree with this interpretation? I do too, as do most other physicists. Many worlds and multiverse are considered different by almost all physicists. Even the authors of the idea above did not take this idea seriously in their subsequent works.
I am not suggesting that they are one and the same, but they are compatible models that could very well be the same thing.
 
  • #23
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So are you actually trying to say that you disagree with this interpretation?
Given what we know about quantum mechanics, yes.
 
  • #24
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So in my opinion, Many Worlds leads to a Reductio ad absurdum
I think you need to understand what it really is saying first.

Murray Gell-Mann explains it well:

What MW calls a world is almost certainly not what you think it is - it not specified that clearly.

Thanks
Bill
 
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I think you need to understand what it really is saying first.

Murray Gell-Mann explains it well:

What MW calls a world is almost certainly not what you think it is - it not specified that clearly.

Thanks
Bill
I'm not saying that the many worlds theory leads to reductio ad absurdum by default. The theory is consistent but probably not an accurate description of the universe. Quantum Mechanics casts serious doubt on the MW postulates, for the reason I gave.
 

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