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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

#91

Post by lisper »

jbay808 wrote: post #59
lisper wrote: post #53

Earlier quoted context omitted.

No it isn't. Copenhagenists insist that the wave function "collapses" upon "measurement" and so measurements only have one outcome in point of metaphyisical fact. Many-worlders insist that the wave function does not collapse, and hence measurements have many outcomes in point of metaphyiscal fact. You may consider this a distinction without a difference, but the fact of the matter is that people do argue about this.…

I agree that it's an important difference! And it matters a lot. I am just saying that the concept of "copies" is no more mysterious than the concept of "superposition", and if you can accept the latter then I don't see why you complain about the former. As for collapse, Copenhagenists can't seem to explain why an interaction between a photon and electrons in a polarizing filter does not collapse the wave function, b…

The reason I can accept superposition is that I have first-hand access to experimental evidence of it. I can see interference fringes with my own eyes. By way of contrast, not only do I not have any direct evidence of the existence of copies of me, I cannot possibly have such evidence. And this is not a technological limitation. This is a limit predicted by the theory itself.

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

#92

Post by lisper »

jbay808 wrote: post #58
lisper wrote: post #49

Earlier quoted context omitted.

Here's a quote from David Deutsch's "The Fabric of Reality": "When I introduced tangible and shadow photons I apparently distinguished them by saying that we can see the former, but not the latter. But who are ‘we’? While I was writing that, hosts of shadow Davids were writing it too. They too drew a distinction between tangible and shadow photons; but the photons they called ‘shadow’ include the ones I called ‘tangi…

I think Deutsch is doing a very good job of explaining exactly the concept I'm trying to explain. But you still have to peel back the words to think about what kind of mechanism they are describing, which Deutsch is trying to communicate. You can't just complain that he says "reality contains parallel universes" without accepting that he's taken the time to map "parallel universes" to a well-defined concept.

I'm not complaining about anything. I'm simply observing that Deutsch and other prominent advocates of the MWI do not consider multiple worlds to be metaphorical. They insist in no uncertain terms that they are real, and go to great lengths to justify this position. There is absolutely no ambiguity with respect to what they believe.

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

#93

Post by platz »

kgwgk wrote: post #88

"Let me address another issue with many-worlds. It is a deterministic theory, even a hyper-deterministic theory, i.e. determinism applies to everything in the entire universe. Indeed, since there can’t be any influences coming from outside and since the Schroedinger equation - the only dynamical equation of the theory - is deterministic, everything that happens today, e.g. what I am writing, the way each reader react…

I don't think we know enough to presume what was going on in the "initial state" of the universe, except perhaps that it was very low entropy.

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

#94

Post by asfarley »

TheOtherHobbes wrote: post #73
lmm wrote: post #17

Earlier quoted context omitted.

Conversely, Copenhagen-like explanations need to explain (or postulate) a decoherence/collapse operation that violates all the usual rules of QM: it would be non-time-symmetric, non-unitary, likely non-local (propagating faster than light), ...

Non-locality is practically axiomatic if you understand Bell's Inequalities, and doesn't require true FTL signalling. MWI doesn't really solve either the locality or the FTL problem. If you're going to believe in MWI you have to explain how an entire universe appears instantaneously, identical in every way to another universe, except for one almost insignificant difference in exactly one quantum interaction. That's a…

I don't think MWI claims, exactly, that an entire universe 'appears instantaneously'.

Couldn't MWI represented with a probability cloud? Maybe the many-worlds exists as a fixed-volume probability on all states in the universe.

From this perspective, MWI would be similar to a multi-universal annealing system, where different quantum outcomes result in fractures within the probability cloud (as opposed to an expansion of the tree-graph).

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

#95

Post by lisper »

ridewinter wrote: post #60
lisper wrote: post #49

Earlier quoted context omitted.

Here's a quote from David Deutsch's "The Fabric of Reality": "When I introduced tangible and shadow photons I apparently distinguished them by saying that we can see the former, but not the latter. But who are ‘we’? While I was writing that, hosts of shadow Davids were writing it too. They too drew a distinction between tangible and shadow photons; but the photons they called ‘shadow’ include the ones I called ‘tangi…

MWI provides a clear, comprehensive explanation for all of the “weird” quantum phenomenon. Beyond that, this quote from FoR [1] convinced me: “To those who still cling to a single-universe world-view, I issue this challenge: explain how Shor’s algorithm works. I do not merely mean predict that it will work, which is merely a matter of solving a few uncontroversial equations. I mean provide an explanation. When Shor’s…

This is a stupid argument, comparable to "if humans evolved from apes why are there still apes?"

An analogous question: when three objects are orbiting each other in space, where is the computation being performed that provides the solution to the three-body problem that represents their motions?

Well, obviously, the computation in the latter case is being "performed" by the three bodies themselves, and the Shor computation is being performed inside a quantum computer that exists in our universe. It's just that the stuff that is performing the computation isn't atoms, it's entangled qbits. There's no need to bring entire parallel universes into it.

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

#96

Post by faissaloo »

yters wrote: post #68
faissaloo wrote: post #66

Earlier quoted context omitted.

Depends who you ask, I'd say God, others might say the computer we exist in and others might say The Universe

But in a quantum universe everything is an uncollapsed wave. It doesn't seem anything can cause the collapse to happen.

Observation causes collapse, so perhaps because the effect it has is negligible to the system of the universe there's simply no point 'rendering'/wave collapsing. Perhaps there is some other collapse mechanism to explain life before conscious observers, or perhaps quantum behavior emerged as time went on after the big bang, or perhaps there exists some kind of proto-conciousness.

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

#97

Post by excalibur »

lordnacho wrote: post #2

I'm not sure if the Aeon article explains what Everett really meant, at least I still have questions. Suppose we're eternally branching, as in the example about the up/down spin. If there's no way to visit other branches, how will we ever confirm this? Second, what is the benefit of the branching interpretation? It seems to simply be a way to think about probabilities?

As scld touched on, this "article" is really an excerpt from Sean Carroll's new book, Something Deeply Hidden: Quantum Worlds and the Emergence of Spacetime.

https://www.amazon.com/Something-Deeply-Hidden-Emergence-Spa...

If you wish to read further, you may want to consider picking up a copy. Mine is waiting for me at home, I'm looking forward to it!

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

#98

Post by vilhelm_s »

kgwgk wrote: post #90
vilhelm_s wrote: post #89

Earlier quoted context omitted.

This seems wrong to me? A lot of "things that happen" seem to be created by randomness generated along the way, from only observing subsystems. I.e., suppose I create a random bit generator by shining photons on a half-silvered mirror and then measuring which way they go. I might then decide what to write depending what the bit is---if it's 0 I will write a HN comment, if it's 1 I will reply to an email. In this case…

There is no "randomness generated along the way" in the MWI. Schroedinger's equation is deterministic and according to many-worlders is the only thing that "makes things happen". Everything that happens in every "world" was bound to happen since the beginning of the evolution of the "multiverse".

Right, but my point is that this doesn't mean that the initial state contains very much information.

Maybe a different example makes this clearer. Suppose you use a quantum random number generator to choose letters from A to Z, and write out a full book this way. If you consider the entire (multiple) world, it's basically Borges' Library of Babel: it has non-zero amplitudes for every possible book. So one possible "thing that can happen" is that Shakespeare's Hamlet gets written.

But that doesn't mean that the initial state of the universe somehow encodes the text of Hamlet. The initial state of the universe doesn't have any information at all, in quantum fluctuations or otherwise. You only see Hamlet emerge if you restrict your attention to some particular branches of the world. It was "bound to happen" that Hamlet would get written, but only because every book would get written.

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

#99

Post by platz »

asfarley wrote: post #94
TheOtherHobbes wrote: post #73

Earlier quoted context omitted.

Non-locality is practically axiomatic if you understand Bell's Inequalities, and doesn't require true FTL signalling. MWI doesn't really solve either the locality or the FTL problem. If you're going to believe in MWI you have to explain how an entire universe appears instantaneously, identical in every way to another universe, except for one almost insignificant difference in exactly one quantum interaction. That's a…

I don't think MWI claims, exactly, that an entire universe 'appears instantaneously'. Couldn't MWI represented with a probability cloud? Maybe the many-worlds exists as a fixed-volume probability on all states in the universe. From this perspective, MWI would be similar to a multi-universal annealing system, where different quantum outcomes result in fractures within the probability cloud (as opposed to an expansion…

Carroll postulates that all the necessary degrees of freedom are already just sitting there in hilbert space - it's only when the states become orthogonal to each other (e.g. "branching") that we no longer have access to them. https://www.youtube.com/watch?v=jHLfMXvQqX8

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

#100

Post by yters »

faissaloo wrote: post #96
yters wrote: post #68

Earlier quoted context omitted.

But in a quantum universe everything is an uncollapsed wave. It doesn't seem anything can cause the collapse to happen.

Observation causes collapse, so perhaps because the effect it has is negligible to the system of the universe there's simply no point 'rendering'/wave collapsing. Perhaps there is some other collapse mechanism to explain life before conscious observers, or perhaps quantum behavior emerged as time went on after the big bang, or perhaps there exists some kind of proto-conciousness.

I guess my question is if the conscious observers are themselves part of the universe, what caused their waveform to collapse? And what is the special 'observation' part of their material properties such that it can cause collapse? Why don't other material configurations cause collapse?
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