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How the Many-Worlds Theory of Hugh Everett Split the Universe

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Re: How the Many-Worlds Theory of Hugh Everett Split the Universe

#31

Post by jbay808 »

lisper wrote: post #15
platz wrote: post #14

Earlier quoted context omitted.

> The main difference is that the MWI has trouble explaining the Born rule. To re-phrase, the claim in that article is that once MWI has done away with the Born rule, it has to deal with how the probabilities that we find in experiment are calculated under MWI. .. Which is not obvious at first glance, because MWI seems to suggest everything happens with probability = 1. Carroll acknowledges it is one of the challenge…

> OP's post was edited For the record, the original just said (as quoted in the above response) "The main difference is that the MWI has trouble explaining the Born rule." Upon reflection I decided that wasn't really the main difference, that the main difference is the difference in ontology. But the fact that the MWI has to recover the Born rule from the linear dynamics is a major consequence of this difference in o…

> Um, what do you think that the "MW" in "MWI" stands for?

Ok yes, it is named that, but what the theory postulates is really just that "when Schrodinger opens the box to check on his cat, he himself is in a superposition just like the cat was -- and what it feels like to be in a superposition is that you don't notice you're in a superposition, because your superposed states each only observe one cat."

Re: How the Many-Worlds Theory of Hugh Everett Split the Universe

#32

Post by ncallaway »

lisper wrote: post #15
platz wrote: post #14

Earlier quoted context omitted.

> The main difference is that the MWI has trouble explaining the Born rule. To re-phrase, the claim in that article is that once MWI has done away with the Born rule, it has to deal with how the probabilities that we find in experiment are calculated under MWI. .. Which is not obvious at first glance, because MWI seems to suggest everything happens with probability = 1. Carroll acknowledges it is one of the challenge…

> OP's post was edited For the record, the original just said (as quoted in the above response) "The main difference is that the MWI has trouble explaining the Born rule." Upon reflection I decided that wasn't really the main difference, that the main difference is the difference in ontology. But the fact that the MWI has to recover the Born rule from the linear dynamics is a major consequence of this difference in o…

The label "Many Worlds Interpretation" is a popular label for the theory, but it's not a particularly accurate one.

The original paper by Hugh Everett was titled '"Relative State" Formulation of Quantum Mechanics'.

The underlying principle of Many Worlds isn't actually that there are many worlds. Is that there is a singular wave function, which is the true reality. The things we refer to as "worlds" are massively-complicated entanglements and superpositions within that wave function, of which we—for some reason—can only observe one position of that superposition.

Re: How the Many-Worlds Theory of Hugh Everett Split the Universe

#33

Post by platz »

lisper wrote: post #26
platz wrote: post #25

Earlier quoted context omitted.

He didn't say to re-add it as an axiom . He's pointing out that the "born rule" (or something that gives you probabilities in the way that you need to agree with experiment) can potentially "emerge" i.e. be recovered (if they can find the right proof for it), without having had to assume that up front. It's like when GR can "recover" F=MA, despite not having assumed F=MA that as an axiom.

> He didn't say to re-add it as an axiom Yes, he did: > MWI is not incompatible with postulating the Born rule if you want to "Postulate" (as a noun) and "axiom" are synonyms.

Ok - well then he and I meant different things.

Re: How the Many-Worlds Theory of Hugh Everett Split the Universe

#34

Post by lisper »

jbay808 wrote: post #31
lisper wrote: post #15

Earlier quoted context omitted.

> OP's post was edited For the record, the original just said (as quoted in the above response) "The main difference is that the MWI has trouble explaining the Born rule." Upon reflection I decided that wasn't really the main difference, that the main difference is the difference in ontology. But the fact that the MWI has to recover the Born rule from the linear dynamics is a major consequence of this difference in o…

> Um, what do you think that the "MW" in "MWI" stands for? Ok yes, it is named that, but what the theory postulates is really just that "when Schrodinger opens the box to check on his cat, he himself is in a superposition just like the cat was -- and what it feels like to be in a superposition is that you don't notice you're in a superposition, because your superposed states each only observe one cat."

> your superposed states each only observe one cat

Again, I have to ask: what do you think "many worlds" means? Because what you've just described is exactly what the advocates of the MWI describe when they talk about "many worlds", which they absolutely do. The MWI literature is festooned with references to "copies" or "versions" of yourself, and "the branching structure of the multiverse".

Re: How the Many-Worlds Theory of Hugh Everett Split the Universe

#35

Post by lisper »

ncallaway wrote: post #32
lisper wrote: post #15

Earlier quoted context omitted.

> OP's post was edited For the record, the original just said (as quoted in the above response) "The main difference is that the MWI has trouble explaining the Born rule." Upon reflection I decided that wasn't really the main difference, that the main difference is the difference in ontology. But the fact that the MWI has to recover the Born rule from the linear dynamics is a major consequence of this difference in o…

The label "Many Worlds Interpretation" is a popular label for the theory, but it's not a particularly accurate one. The original paper by Hugh Everett was titled '"Relative State" Formulation of Quantum Mechanics'. The underlying principle of Many Worlds isn't actually that there are many worlds. Is that there is a singular wave function, which is the true reality. The things we refer to as "worlds" are massively-com…

Everything you say is true. Nonetheless, if you read papers written by self-identified advocates of Everett, they invariably refer to it as "many-worlds" and they talk about "the branching structure of the multiverse" and "copies" or "versions" of yourself. So regardless of what you or I think Everett meant, the present-day advocates of his theory are clearly trying to advance the idea that there are, in point of metaphysical fact, many worlds.

Re: How the Many-Worlds Theory of Hugh Everett Split the Universe

#36

Post by lmm »

lisper wrote: post #28
lmm wrote: post #24

Earlier quoted context omitted.

Yes and no. I'd argue that the Born rule as a rule for subjective probabilities in a MWI context is much cleaner than a full Copenhagen-style collapse operation.

You are, of course, free to argue that. But most advocates of the MWI will disagree with you. That's why they put so much effort into trying to derive the Born rule.

There's a significant gap between "cleaner than a Copenhagen-style collapse" and "clean enough to be a good part of our fundamental theory of nature" :).

Re: How the Many-Worlds Theory of Hugh Everett Split the Universe

#37

Post by platz »

lisper wrote: post #35
ncallaway wrote: post #32

Earlier quoted context omitted.

The label "Many Worlds Interpretation" is a popular label for the theory, but it's not a particularly accurate one. The original paper by Hugh Everett was titled '"Relative State" Formulation of Quantum Mechanics'. The underlying principle of Many Worlds isn't actually that there are many worlds. Is that there is a singular wave function, which is the true reality. The things we refer to as "worlds" are massively-com…

Everything you say is true. Nonetheless, if you read papers written by self-identified advocates of Everett, they invariably refer to it as "many-worlds" and they talk about "the branching structure of the multiverse" and "copies" or "versions" of yourself. So regardless of what you or I think Everett meant, the present-day advocates of his theory are clearly trying to advance the idea that there are, in point of met…

If you agree on that math/science then this point you're adamant about whether it is or is not a "world" reduces to a semantics/ontology/philosophy question, which we're not going to get further clarity on in a thread about trying to gain a proper or better understanding as laypeople of the scientific theories, unless you want to advance the conversation to the understanding of those scientific theories into a semantic/ontological/philosophic realm.

Re: How the Many-Worlds Theory of Hugh Everett Split the Universe

#38

Post by erdleerdle »

drcode wrote: post #30

Sean Carroll's new book on quantum physics that came out yesterday is the clearest laymen's exposition of quantum physics I have ever read: https://www.audible.com/pd/Something-Deeply-Hidden-Audiobook...

Started reading this and realized it was Sean... he gave a great talk on this last night at Symphony Space on the UWS. Believe he's doing a full book tour - worth checking out.

Re: How the Many-Worlds Theory of Hugh Everett Split the Universe

#39

Post by akvadrako »

lisper wrote: post #28
lmm wrote: post #24

Earlier quoted context omitted.

Yes and no. I'd argue that the Born rule as a rule for subjective probabilities in a MWI context is much cleaner than a full Copenhagen-style collapse operation.

You are, of course, free to argue that. But most advocates of the MWI will disagree with you. That's why they put so much effort into trying to derive the Born rule.

Not that it really matters but I disagree that MWI advocates like it because of the born rule derivations. Actually most born rule derivations apply equally to all interpretations.

I’m with Vaidman on this, who is one of the best known supporters of MW, which is that the clearest solution is just to postulate the connection between psi magnitude and subjective experience. It’s an empirical discovery that works.

Re: How the Many-Worlds Theory of Hugh Everett Split the Universe

#40

Post by jcims »

drcode wrote: post #30

Sean Carroll's new book on quantum physics that came out yesterday is the clearest laymen's exposition of quantum physics I have ever read: https://www.audible.com/pd/Something-Deeply-Hidden-Audiobook...

Halfway through his latest Mindscape podcast episode that drills down into this topic in a very approachable way.
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