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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

#51

Post by jbay808 »

lisper wrote: post #34
jbay808 wrote: post #31

Earlier quoted context omitted.

> 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".

There seems to be some confusion here, based around the usage of words.

You seem annoyed by the terminology of words like "worlds" or "multiverse", but are you also thinking about what a MWI advocate is referring to by the usage of those words? They are shorthand for "the observable wave function" and "the global wave function".

There being "copies" of Schrodinger observing his cat is the most intuitive and expressive way to summarize Schrodinger being in a linear superposition of two states in a (cat alive, cat dead) basis. It's not any different from how a Copenhagenist would treat a photon passing through a polarizating beamsplitter as being in a superposition of having passed through and having been reflected; if the photon then goes and interacts with other things, they would keep track of what would have happened in each "branch" of the superposition.

If you have an issue with those, why don't you have an issue with the idea of superposition itself? It's exactly the same concept.

(UPDATE)

In particular, when MWI people say "multiverse", it's not a sleight of hand where we are being deceptive when we actually mean "observable and unobservable components of the wave function". The term "multiverse" had no prior meaning in physics; MWI is defining it to mean the global wave function, using that word to draw attention to the fact that it has unobservable components.

These words are being given rigorous definitions that align with their intuitive meaning. You seem to be arguing against that practice?

Should I complain that when a Copenhagenist says "collapse", nothing is actually falling down and so it's misleading?

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

#52

Post by faissaloo »

yters wrote: post #27
fallingfrog wrote: post #8

You can do a really simple thought experiment that provides a persuasive argument in favor of the many worlds theory. Or at least, it shows that wave function collapse is relative to an observer, not universal everywhere. Start with Schroedingers cat: the cat is in a box, it’s in a state of quantum superposition. It’s 50/50 alive or dead. Now a researcher opens the box: the cat is found to be either alive, or dead, a…

The problem with many worlds is why do I think I'm in a particular timeline? If many worlds is correct, there is no "I", there are many rapidly branching "I"s, which intuitively doesn't make sense. Of course, each "I" will have the perception of being the sole "I", but the overall view that there is no singular "I" is very counter to my self conception. I prefer to preserve intuitions over conjectures, so I count tha…

This whole idea of observers just brings to mind things like culling in graphics rendering, perhaps that's what's happening

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

#53

Post by lisper »

jbay808 wrote: post #51
lisper wrote: post #34

Earlier quoted context omitted.

> 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".

There seems to be some confusion here, based around the usage of words. You seem annoyed by the terminology of words like "worlds" or "multiverse", but are you also thinking about what a MWI advocate is referring to by the usage of those words? They are shorthand for "the observable wave function" and "the global wave function". There being "copies" of Schrodinger observing his cat is the most intuitive and expressiv…

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. A lot.

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

#54

Post by crankylinuxuser »

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…

> "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.

Is the collapse of the wave function related to consciousness? How would we construct a test to verify that?

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

#55

Post by platz »

lisper wrote: post #53
jbay808 wrote: post #51

Earlier quoted context omitted.

There seems to be some confusion here, based around the usage of words. You seem annoyed by the terminology of words like "worlds" or "multiverse", but are you also thinking about what a MWI advocate is referring to by the usage of those words? They are shorthand for "the observable wave function" and "the global wave function". There being "copies" of Schrodinger observing his cat is the most intuitive and expressiv…

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.…

Your usage of "many outcomes" is what may be causing contention/confusion for those looking for answers in what is described by the mathematical equations, and scientific theories. If you want to justify "many outcomes" on metaphysical grounds, that is not a scientific conversation.

Also "metaphysical fact" is a questionable term.

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

#56

Post by JoeAltmaier »

lisper wrote: post #53
jbay808 wrote: post #51

Earlier quoted context omitted.

There seems to be some confusion here, based around the usage of words. You seem annoyed by the terminology of words like "worlds" or "multiverse", but are you also thinking about what a MWI advocate is referring to by the usage of those words? They are shorthand for "the observable wave function" and "the global wave function". There being "copies" of Schrodinger observing his cat is the most intuitive and expressiv…

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.…

Confused. Consider a light beam with only one photon at a time (very dim) measured by a photoreceptor. Put a 2nd photoreceptor after the first - it detects no photons.

So detecting the first, definitely 'collapsed the wave function'. This is not an unknown result in physics.

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

#57

Post by lmm »

lisper wrote: post #49
lmm wrote: post #47

Earlier quoted context omitted.

> The MWI literature is festooned with references to "copies" or "versions" of yourself, and "the branching structure of the multiverse". Many MWI advocates will describe that physical wavefunction in those terms, but that's a metaphor/model/aid to understanding, not a "point of metaphysical fact". The only thing that MWI demands we take as metaphysically real is the wavefunction. Given a wavefunction like 1/sqrt2(|e…

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…

Deutsch may believe that. (Heck, I believe it). It's a natural interpretation of the MWI wavefunction. But it is an interpretation, a layer on top of the physical claims, a model - not a mandatory part of MWI. Deutsch may interpret a given wavefunction as describing a particular ensemble of 'tangible' and 'shadow' objects, but someone who interprets that same wavefunction a different way (but agrees on the same wavefunction, and expects it to evolve according to the same laws of quantum mechanics) will still generate the same experimental predictions and, more to the point, still be doing MWI.

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

#58

Post by jbay808 »

lisper wrote: post #49
lmm wrote: post #47

Earlier quoted context omitted.

> The MWI literature is festooned with references to "copies" or "versions" of yourself, and "the branching structure of the multiverse". Many MWI advocates will describe that physical wavefunction in those terms, but that's a metaphor/model/aid to understanding, not a "point of metaphysical fact". The only thing that MWI demands we take as metaphysically real is the wavefunction. Given a wavefunction like 1/sqrt2(|e…

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.

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

#59

Post by jbay808 »

lisper wrote: post #53
jbay808 wrote: post #51

Earlier quoted context omitted.

There seems to be some confusion here, based around the usage of words. You seem annoyed by the terminology of words like "worlds" or "multiverse", but are you also thinking about what a MWI advocate is referring to by the usage of those words? They are shorthand for "the observable wave function" and "the global wave function". There being "copies" of Schrodinger observing his cat is the most intuitive and expressiv…

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, but an interaction between a photon and electrons in my retina does. They're made of the same stuff and should be following the same quantum rules; why does one of them perform a unitary transformation and the other a lossy projection?

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

#60

Post by ridewinter »

lisper wrote: post #49
lmm wrote: post #47

Earlier quoted context omitted.

> The MWI literature is festooned with references to "copies" or "versions" of yourself, and "the branching structure of the multiverse". Many MWI advocates will describe that physical wavefunction in those terms, but that's a metaphor/model/aid to understanding, not a "point of metaphysical fact". The only thing that MWI demands we take as metaphysically real is the wavefunction. Given a wavefunction like 1/sqrt2(|e…

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 algorithm has factorized a number, using 10^500 or so times the computational resources than can be seen to be present, where was the number factorized? There are only about 10^80 atoms in the entire visible universe, an utterly minuscule number compared with 10^500. So if the visible universe were the extent of physical reality, physical reality would not even remotely contain the resources required to factorize such a large number. Who did factorize it, then? How, and where, was the computation performed?”

[1] https://www.newyorker.com/magazine/2011/05/02/dream-machine/...

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