# QM Many Worlds Interpretation

Discussion in 'Physics & Math' started by RJBeery, Mar 10, 2009.

1. ### BenTheManDr. of Physics, Prof. of LoveValued Senior Member

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You haven't told me how you'd measure an infinite amount of energy. You've only told me how you'd measure the amount of energy in the observable universe. To demonstrate an inconsistency, you actually have to measure something that is inconsistent. This is, after all, how experiments work. Instead, you're using Bushy logic:

0.) Assume that the Many Worlds Interpretation is correct.
1.) Assume that the Many Worlds Interpretation implies infinite energy.
2.) Measure a finite amount of energy in the universe.
3.) By 1.), I have measured an infinite amount of energy.
4.) Therefore, MWI is wrong.

Hopefully you can see the gap in the logic here. Everything after `0' is wrong.

And note: you don't need gravity or fancy arguments by famous people to show that your objection has no merit.

3. ### RJBeeryNatural PhilosopherValued Senior Member

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This sounds like a God argument to me, unfalsifiable because any objection based upon known Physics could be dismissed with a "Physics as we know it doesn't apply to MWI".

This doesn't represent my logic flow; regardless, are you refuting that each universe requires a non-zero amount of energy? Are you refuting that MWI produces an infinite number of universes?

My logical flow goes like this:
1) Assume that a valid Physics interpretation cannot require an infinite amount of energy
2) Calculate that our Universe (or "world") requires a small but non-zero amount of energy to come into existence, even if this energy is returned at a point in time labeled A
3) Interpret MWI as having a characteristic such that an infinite number of "worlds" would be created after any arbitrary point in time
4) Conclude that MWI would require the creation of an infinite number of worlds, each of which would require a non-zero amount of energy to exist which would not be returned, resulting in a net energy requirement of infinity for the Multiverse
5) Conclude that MWI is not a valid Physics interpretation

I'm not saying this is fact; I'm offering my thought progression and I welcome debate that is inside the realm of logic. Why don't you print out this single post and provide a copy to your Physicist friends for their thoughts?

Last edited: Mar 17, 2009

5. ### BenTheManDr. of Physics, Prof. of LoveValued Senior Member

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Where does the infinite amount of energy exist?

What observer can measure an infinite amount of energy?

7. ### quadraphonicsBloodthirsty BarbarianValued Senior Member

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Interpretations, by definition, do not differ in their physical implications. If you think that one implies an infinite amount of energy, either you are wrong, or it's not an interpretation at all, but some new theory.

Contrary to MWI, as far as I understand. There is no energy cost associated with the world branching itself. If there were, MWI would not be an interpretation, but a new theory, since it would imply observeable differences from standard QM. Wavefunction collapse is likewise held to be "free," in the interpretations that employ it.

Also not a standard part of MWI. It is possible that the number of worlds is finite, just very very large.

8. ### PandaemoniValued Senior Member

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Sort of...there are two points to note.

First, you can't apply a science outside of its element. Classical physics works well in our universe on a large scale, but if you try to apply it to understand quantum phenomena, or branes moving in multiple dimensions outside of our comfortable spacetime, it falls flat and leads to wrong answers. If an aquatic race were to develop a theory of the mechanics of swimming, they'd be stunned to learn that it does not apply outside of the water. It works brilliantly in the medium it was designed for, but you can't assume the same model will work outside of the context for which it was developed. All you can do, if you are a scientist, is test your model in the new medium and see if it is still predictive. (Even if it is, your model is not necessarily a description of "reality," all you can say is that the model predictive, or not.)

Second, the many worlds interpretation is not science, it's metaphysics. The same goes for the Copenhagen interpretation or consistent histories, David Bohm's deterministic and non-random hidden variables interpretation, the transactional interpretation, the relational interpretation, etc. All of these are ways of describing "what happens" in the quantum world, but they all make exactly the same predictions about how the model will behave. None can be falsified under their own terms because they all lead you to the same moidel for quantum mechanics. Which interpretation you or I prefer is a matter of aesthetics, not science.

9. ### RJBeeryNatural PhilosopherValued Senior Member

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In the MWI-proposed Multiverse.
No observer that exists within a given "world", but that should not matter. If one makes a postulate that requires an infinite amount of energy, one does not need to measure the existence of that energy in order to evaluate the plausibility of the postulate based upon the infinite-energy requirement.

Agreed. My argument is that MWI is a new theory which would require an infinite source of energy.
I'm not claiming that the branching requires energy. I'm claiming that the original Big Bang expansion requires an infintesimal, yet non-zero, amount of energy as mentioned in the linked article in post #58. The branching, if it is indeed replicating a world that possesses a non-zero amount of energy required to exist, would then by extension multiply the net-energy needed to represent the multiple "worlds". Please read post 58 and beyond.

Two points here. The first is that, as pointed out in post #22, the random decay process would apparently necessitate an infinite number of "worlds" because of the continuous nature of the possible wavefunction collapse as a function of T. The second is that, even if MWI required an arbitrarily LARGE amount of unanswered energy I feel it is prudent to consider the interpretation (or theory) a violation of the general conservation of energy prevalent in current Physics theory.

I can tell from your post that you possess intelligence, Pandaemoni, similar to Pete. My response is that MWI is not an interpretation, but a new theory which would require a minimum of an astronomically large (if not in fact infinite!) amount of energy to represent the proposed Multiverse.

I also take issue with your neutral stance on interpretations. I could say that all of Physics is determined by the whims of magical leprechaun who happened to decide that reality should match the results of the Copenhagen Interpretation, and the "metaphysical" defense would serve as a validation. I feel that when evaluating interpretations, one SHOULD consider aesthetics as well as general principles such as beauty and Occam's Razor.

10. ### quadraphonicsBloodthirsty BarbarianValued Senior Member

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It matters a great deal what observers can and cannot observe. If that's not of interest, there is no physics to interpret in the first place.

The only implausible postulate I see in this thread is your "infinite energy requirement."

Yeah, you are unambiguously mistaken on that count.

Who is "representing" the "worlds" here, and why should we care about whether he can do with with finite energy or not? I can't even represent one world with finite energy, and so I don't tend to bother trying to. Fortunately, nature operates quite independently of any such concerns.

But how can you ever prove that the space of outcomes is truly continuous, rather than just quantized very, very finely?

You can't, in any finite amount of time.

"Unanswered?" More like "undefined." There is no "representation," and so no energy that must be answered for, in MWI.

11. ### RJBeeryNatural PhilosopherValued Senior Member

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If you believe that things which are unobservable are not "Physics to be interpreted in the first place", then you must believe that MWI is not Physics since it clearly cannot be observed, even in theory. Note that I am arguing against MWI despite its unobservable characteristics.

You make a bold statement about an unresolved issue. Be careful.

The energy required to begin the expansion of the Universe is not undefined. It is hypothesized to be zero plus a very small amount of energy in order to initiate the Big Bang expansion as referenced in post #58. If this energy is not "given back" to the Multiverse in some form then an infinite number of worlds would require an infinite source of energy.

12. ### PandaemoniValued Senior Member

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The truth is no one could refute the magical lephechaun interpretation either, and its primary "flaw" is that it lacks the sophistication of other models. Again, it all comes down to aesthetics because none of the interpretations has proposed any means of testing their validity.

Left to my own devices, I'd probably prefer Bohm's interpretation because quantum mechanical objects and events are entirely deterministic, rather than left to truly random chance. That said, the reason I don't favor it is that what I learned I learned under what amounts to a "consistent histories" approach, and so that is how I tend to conceptualize it.

Until someone devises a test to narrow the field, the only real criticism of the magic leprechaun interpretation is it's lack of a mathematical underpinning and the fact that you just made it up. Those two facts do not, logically, render it necessarily incorrect. though. If anyone chose to defend it, my only cogent response boils down to "But I don't like it."

It is true that MWI posits a very different reality than what is needed for Copenhagen. And Copenhagen is very different in its description of "reality" than the transactional interpretation, with it's time traveling waves. In a sense, the various interpretations are mostly mutually exclusive descriptions of reality...but the processes and things they describe are always fundamentally unknowable. Each gives a way of conceptualizing quantum events, but most if not all of them must be "wrong" on some deeper level.

Perhaps someday someone will discover a test to falsify them, but not yet to my knowledge. As for MWI and energy, since our best theory is that the energy in the universe just appeared one moment in the Big Bang and started expanding (along with time and space), I can completely see that the law of conservation might not apply to "extra-universal" events.

13. ### BenTheManDr. of Physics, Prof. of LoveValued Senior Member

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If there exists no observer who can measure an infinite amount of energy, this clearly invalidates your experiment, then.

Do you disagree?

14. ### RJBeeryNatural PhilosopherValued Senior Member

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I appreciate your input, thank-you. In the Astro Society article I referred to it is speculated that any modicum of energy required to start the Big Bang expansion could be given back almost immediately, yet the expansion would continue because of the net-zero energy nature of mass-energy and gravity. With my "rock in a pond" analogy in post #59 my point was that, if worlds were created under MWI after this initial energy was given back then the Multiverse would not be net-zero in terms of energy. Another analogy would be that an entrepreneur takes out a small loan to start a store, and pays back the bank almost immediately; now he multiplies the store many times over at no cost using MWI. To me, each new store represents the product of an initial investment repayment that never happened.

That isn't my only problem with MWI, though. Another one was hinted at in post #19 (although got no response) which is this -

Describe the mechanism which would make one world "more likely to be experienced" than another.

A third objection I have with MWI was beat to death in another thread which I would nevertheless not mind your response to if you ever get the time: QM vs SR. My QM vs SR objection would be -

Simply, when do the worlds split?

Yes, Ben, I disagree. I think you are confused between the observer's role in quantum mechanics and the observer's role in logically evaluating a theory/interpretation.

15. ### quadraphonicsBloodthirsty BarbarianValued Senior Member

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Yes, exactly. MWI is metaphysics.

This doesn't make sense: there is no energy (or anything else) "outside" of the multiverse, and so no concerns about its "source" or "giving back." You are clearly laboring under some very serious, fundametnal misunderstandings of how MWI works, and you should clear these up before attempting to square it (or any other interpretation of QM) with cosmology and gravity, which is an area we don't even understand the physics of in the first place.

16. ### RJBeeryNatural PhilosopherValued Senior Member

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quadraphonics: Speaking specifically about a single "world" (Universe), quantum fluctuations do produce energy over short periods of time, but this energy is "returned" in the form of an antiparticle for every particle in a "virtual pair" whereby the net energy gain remains zero and the conservation of energy appears to hold. When I use terms like "giving back" what I am referring to is making sure that the conservation of energy holds in each world on its own. It may be sufficient to show that conservation of energy does not hold under MWI in a single world but I feel that emphasizing that this violation of conservation happening many times, possibly an infinite number of times, accentuates the point. Does that makes more sense?

17. ### BenTheManDr. of Physics, Prof. of LoveValued Senior Member

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Heh...confused. Sure man.

By your own admission, there is no observer which can observe an infinite amount of energy, yet you continue to claim that somehow this invalidates the interpretation?

18. ### RJBeeryNatural PhilosopherValued Senior Member

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Ben, you've made it clear that in your view an infinite-energy requirement does not invalidate a QM interpretation. I understand that the reason you feel this way is because the "infinite energy" is spread across an infinite number of "worlds" which cannot be observed. I get it. We're going to have to agree to disagree on the point because I feel that if an interpretation (or theory) required infinite energy in any form, in any realm, whether observable or not, it deserves a jaundiced eye.

19. ### quadraphonicsBloodthirsty BarbarianValued Senior Member

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No, it doesn't. If you accept that conservation of energy holds (at least on the average) under QM, then it follows that it any interpretation of QM inherits this property. If there's an issue with energy conservation, then it's an issue with QM, not with MWI per se.

20. ### RJBeeryNatural PhilosopherValued Senior Member

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Agreed completely, which is why in post #66 I said
If it is true that MWI violates the conservation of energy, while we are all in agreement that QM does not, then MWI is not an interpretation but rather a new theory.

21. ### RJBeeryNatural PhilosopherValued Senior Member

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To this point I have given three objections to MWI. They are:

1) What is the mechanism which makes a given world "more likely" than another to be experienced such that the laws of probability are observed in the outcomes of quantum measurements?

2) It is said that potential worlds diverge "upon measurement of the quantum particle" which avoids the wavefunction collapse. Considering the SR implications of "now" having no absolute definition, "what" exactly splits, and "when" does it do this? This problem is more clearly seen in the context of the wavefunction collapse of a pair of entangled yet space-like separated particles.

3) [Reworded from my infinite energy objection but based upon the same principle] Does a newly created world carry over any "unpaid energy debt" from the world which spawned it? This debt can exist, for example, between the creation of an energy particle and the creation of its complementary anti-particle which comprise the "virtual pair" that preserve a net energy gain of zero over time.

We've discussed #3 at length (although as you can see I've changed the wording again to attempt to make it as simple as possible). If Ben, quad, Pandaemoni or anyone else would like to discuss the less nuanced objections I would welcome it.

22. ### PandaemoniValued Senior Member

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Just to be clear on terminology, I take it you are using "theory" here to mean either "hypothesis" or even an "untestable hypothesis" rather than a "theory" in the normal scientific sense. I think of MWI as a untestable hypothesis regarding some supposed "real" inner workings of quantum mechanics. In that regard it is no different than any other interpretation.

It seems clear to me that we have boiled this down to a merely semantic debate, but in my view even requiring increasing amounts of "created" energy does not render it any different than the other interpretations, because any differences there are are fundamentally untestable. All of the interpretations have these fundamentally untestable elements and one could easily reject; it's just with no experience or data regarding the what happens "outside" the universe we live in, there's no way to really absolutely reject these features.

Is Schroedinger's Cat really in a superposition of the states of "alive" and "dead"? Copenhagen tends to say yes. The relational interpretation says that you could say that it is, I could see that the cat is alive and well, and we could both be "right." Bohm's interpretation says the cat is always either alive or dead. My gut tells me that cats do not get stuck in superpositions, but I know that the only way to be sure of that is to figure out what a cat does when no one is observing it, which can never be done.

In the same way, I have sympathy for your positions, but putting them to any sort of test requires that we separate ourselves fronm this universe. Were MWI correct, all of its universes are conveniently orthogonal to the one I am presently in, and entirely undetectable as a result.

23. ### quadraphonicsBloodthirsty BarbarianValued Senior Member

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Okay, but such is not the case. MWI is not able to disagree with QM in any way, because it doesn't have any physical content apart from QM.