Why the "Many-Worlds" Theory doesn't make sense...

Discussion in 'Physics & Math' started by stateofmind, Feb 12, 2015.

  1. stateofmind seeker of lies Valued Senior Member

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    ... to me.

    For the sake of argument let's say the many-worlds theory is true and that for every moment in time the universe branches off for every possibility. If that's the case then how can cause and effect ever exist? Either reality is an unbroken chain of domino-like moments which fall into one another or it's chaos. Either the universe is one entirely connected whole where every "thing" has an influence on every other "thing" or it's made up of separate, discrete pieces that have no effect or influence on one another. I don't see how it can be both. What am I missing?
     
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  3. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    I don't either, but the explanation sometimes given is that, why would we expect the universe to make sense. If we are a random result of chemical iterations in hospitable environments on a planet capable of generating and evolving life, then where in that equation is anything that says it should be possible for the human mind, or human logic to understand it?

    Of course that same question must be asked of those who advocate the various many-worlds theories; what makes them think their solution has any chance of being reality, when it is against logic and common sense? What do they have going for them? Nothing more that those who think there is a local reality have going for them, I don't think.
     
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  5. stateofmind seeker of lies Valued Senior Member

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    But how do quantum physicists even reconcile "chemical iterations" or any other repeatable phenomenon? I admit I'm not even an armchair quantum physicist, but this is the impression I get from what I've read: There's a steady and repeatable 50% chance that a quantum particle will exist or not exist - and this goes for all matter. Observing that, it makes no clear sense why any matter is one thing and not another. Is that the idea?
     
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  7. river

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    Very good observation
     
  8. Captain Kremmen All aboard, me Hearties! Valued Senior Member

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    It can't be called a theory because there is no evidence for it, and it can't be tested.
    Until then it will remain a hypothesis, or an interpretation.


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    Last edited: Feb 12, 2015
  9. Captain Kremmen All aboard, me Hearties! Valued Senior Member

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    Judging from this single poll, most physicists are undecided or agnostic about the nature of the universe.
    The Copenhagen interpretation comes in number two.
    (The Copenhagen interpretation states that a particle exists in all states at once until observed.)
    Many Worlds is surprisingly popular, at number three.

    See http://www.quora.com/Why-do-60-of-theoretical-physicists-believe-in-the-many-worlds-theory
     
  10. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    This is an area where science hasn't settled on what the implications are of wave-particle duality. When the Many-worlds interpretation of Quantum Mechanics was put forth, there was a scientific debate about the wave nature of particles, vs. their particle nature. Experiments supported both views.

    One interpretation of QM at the time, the Copenhagen interpretation, took the hard line that since we cannot know either the location or momentum of a particle unless we observe the particle, the reasoning evolved to conclude that the particle could be anywhere in the universe if we aren't observing it, and that got compounded into the interpretation that every possible location of the particle might represent its presence in another separate universe.

    The wave function expresses all of the possible locations of the particle. Many Worlds is consistent with the wave function.

    "Chemical iterations" resulting in a primordial DNA molecule by random chance is consistent with the "iterations" generation of life, in one place, on one planet at at time, in our one universe. It would be hard to reconcile that with Many Worlds though, because the particles involved in the formation of that DNA must have location and momentum in that one place in that one universe prior to the successful DNA combination, in order for the combination to occur, since the proximity of many particles is required.

    However, they can explain away any argument using an interpretation that the particle can not only be anywhere, but by saying that the particle can be everywhere, or nowhere until observed :shrug:.
     
  11. danshawen Valued Senior Member

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    It would violate conservation of energy, and that's just for starters.
     
  12. Captain Kremmen All aboard, me Hearties! Valued Senior Member

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    It is probably mathematically self-consistent.
     
  13. stateofmind seeker of lies Valued Senior Member

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    Maybe I'm naive but that seems like a huge leap of assumption. Wouldn't it be more conservative to assume the particle is more likely to be in or around the apparatus observing it than, say, somewhere in the Andromeda galaxy?

    I think I'm missing something about how quantum particles combine to form what we generally call "matter". If it's just as probable that a quantum particle will be present locally to form a DNA molecule, as it likely to be on the other side of the universe, then it would only make sense that the consistency and repeatable-ness of our normal, every day sensory experience of reality is an infinitely improbable illusion, like a monkey at a typewriter eventually writing all the works of Shakespeare, in sequence, given enough time. In which case, it's infinitely more likely that the whole universe will turn into chaos at any moment. Am I completely missing something here?
     
  14. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    Lol, no, I think you've got it, if your conclusion is the same as the thread's title.
     
  15. PhysBang Valued Senior Member

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    One of the serious problems that philosophers had for the many-world interpretation is that it was unable to generate the probabilities of QM. If every event happens, then what is to generate frequencies?

    Recently, schema were developed whereby different events could be assigned different weights, so that one was more likely to end up in certain worlds than others. (Essentially, one can imagine that there are more of certain worlds than there are of others.) I'm not sure that these schema has solved this problem entirely, but it has convinced many that the no-probabilities objection is not viable.
     
  16. stateofmind seeker of lies Valued Senior Member

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    I have to think more about all of this. TBH I don't know the landmark studies that give us our insight into QM so it would probably help if I knew what they were and read them.Maybe 2 months ago I read that some scientists had found evidence that the results of the double slit experiment were actually another manifestation of the uncertainty principle - something I had a nagging suspicion about for a while.

    PhysBang - I have to say that a Many-Worlds scenario w/ probability dictated worlds, proportioned according to their probability, really excites my imagination. Probably a more realistic interpretation of a many-worlds scenario. Still it all strikes me as a bit more complicated than it has to be. I mean, hypothetically, if the universe was (to use a programming term) "single-threaded" and there was only one reality existing at a time, if time were infinite and matter was not, then in all likelihood every single scenario will play out eventually, just on a time scale that's ridiculously unfathomable.
     
  17. RJBeery Natural Philosopher Valued Senior Member

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    The problem with MWI doesn't have anything to do with the math, it has to do with the subjective experience of reality. WHY do we only experience one value on all measurements? Proponents will say that the act of measurement causes the worlds to decohere...but then we're back to the measurement problem. If ANY form of measurement causes the worlds to decohere then it's basically happening continually, in all places, across all "worlds"...worlds that have decohered cannot superpose each other...but what good is the wavefunction if superposition is effectively eliminated?

    The other thing that MWI can't account for is the "thickness" of the branches. It's easy to see that Schrodinger's Cat is half-alive and half-dead but what about the 1-in-10^30000 chance that Schrodinger's Cat will spontaneously turn into a dog? It's only unlikely, not impossible. Why is it that we tend to experience "more probable" branches in proportion to their expected values?

    EDIT: I just read PhysBang's post and he also mentioned this problem of probabilities...
     
  18. Maxila Registered Senior Member

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    You might be interested to know a few years ago a scientific publication (I can't recall which one) polled Quantum Physicist asking which of the 5 major interpretations of QM they supported. The results showed they were equally split between the 5 major interpretations asked about, and their own pet ideas. I interpret that to mean, the only thing we know about QM for certain is that it can predict observable outcomes to a very high degree of accuracy.
     
  19. Layman Totally Internally Reflected Valued Senior Member

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    The MWI doesn't make sense just because it is a completely bogus theory. It can't be tested. It doesn't make any predictions. It doesn't even change the way people do physics. All it does is say that physicist can all look at the same equations, and then they can say that they mean whatever they want them to.
     
  20. Captain Kremmen All aboard, me Hearties! Valued Senior Member

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    Maybe the 16% see it as mathematically useful rather than true.
    Or just the best choice out of a bad bunch.
     
  21. Captain Kremmen All aboard, me Hearties! Valued Senior Member

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    In order for an emitted electron to be found light years away, you would have to have a detector there, and years would have to pass.
     
    Last edited: Feb 14, 2015
  22. brucep Valued Senior Member

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    It's an interpretation of quantum mechanics. There's a whole classroom full of them. They're equivalent because they all recover quantum mechanics and all it's theoretical predictions associated with quantum phenomena.
     
  23. brucep Valued Senior Member

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    It's an interpretation of quantum mechanics. Quantum mechanics is the theoretical model [theory]. Many worlds is an interpretation of a theory.
     

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