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Math Science

A Mathematical Answer To the Parallel Universe Question 566

diewlasing writes to mention that Oxford scientists have proffered a mathematical answer to the parallel universe question that is gaining some support in the scientific community. "According to quantum mechanics, unobserved particles are described by 'wave functions' representing a set of multiple 'probable' states. When an observer makes a measurement, the particle then settles down into one of these multiple options. The Oxford team, led by Dr. David Deutsch, showed mathematically that the bush-like branching structure created by the universe splitting into parallel versions of itself can explain the probabilistic nature of quantum outcomes."
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A Mathematical Answer To the Parallel Universe Question

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  • Ummm . . . (Score:5, Insightful)

    by Orange Crush ( 934731 ) on Monday September 24, 2007 @02:39PM (#20732419)
    . . . so it "can" explain (mathematically) the outcome of quantum level observations using the many worlds theory. But is it falsifiable?
  • by dsanfte ( 443781 ) on Monday September 24, 2007 @02:41PM (#20732465) Journal
    If there are an infinite number of parallel universes for each possible quantum outcome, why do we only experience -this- one?
  • by Kristoph ( 242780 ) on Monday September 24, 2007 @02:45PM (#20732555)
    Well, I am not a physicist, perhaps you are ...

      Commenting in New Scientist magazine, Dr Andy Albrecht, a physicist at the University of California at Davis, said: "This work will go down as one of the most important developments in the history of science."

    I would image something that is 'one of the most important developments in the history of science' might qualify as news. Don't you think? Even if proven not to be 'one of the most important' it certainly qualifies for recognition based on that possibility, IMHO.

  • Re:Publication? (Score:4, Insightful)

    by ZombieWomble ( 893157 ) on Monday September 24, 2007 @02:47PM (#20732593)
    You honestly think they waited for this to be peer-reviewed and published before they belted out the press releases? That would mean they may be expected to provide some detail, which would be madness!

    Seriously though, there's no sign of a citation from any of the people running the story (most of which are nearly identical, so they're probably just copying from the same press release), and there's no sign of it on arXiv or from a quick trawl of journal feeds, so it's a very good chance that it's either unpublished work, or a conference paper somewhere. Not surprising, given how many "most significant discoveries in the history of science" turn out to be much less dramatic under the cold hard light of review than when they're first reported.

  • by Teresita ( 982888 ) <badinage1&netzero dot net> on Monday September 24, 2007 @02:48PM (#20732613) Homepage
    Because in all of the others, you are not posing this question.

    You got it 180 degrees out. The answer is the equivalent, but the reverse, of the Anthropic Principle. Every parallel universe also has copies of him asking that same question.
  • by u19925 ( 613350 ) on Monday September 24, 2007 @02:49PM (#20732635)
    There is a circular dependency here. The author assumes that the parallel universe interpretation is correct and then argues that if this interpretation is correct, then we can derive probabilistic nature of quantum of mechanics. All this means is that the parallel universe is a self-consistent theory. Nobody has argued against this for the last 50+ years.

    The problem with quantum mechanics interpretation is that as of now, no interpretation exists which is not bizarre in our traditional world view. Parallel universe is just one of them.
  • by MontyApollo ( 849862 ) on Monday September 24, 2007 @02:51PM (#20732673)
    The problem is that the brief news story was more focused on explaining what the Many Worlds hypothesis is to a lay audience and not really pointing out what the new breakthrough is really all about to a geek audience. Someone needs to link to science site and not a general news site.
  • by Hoi Polloi ( 522990 ) on Monday September 24, 2007 @02:53PM (#20732703) Journal
    How would you compare universes to be able to differentiate between them? How can you say which one you are experiencing? There is no "control universe" you can step back into.
  • by ZombieWomble ( 893157 ) on Monday September 24, 2007 @02:57PM (#20732777)
    As described in this article, the factor they claim to have "proved" does indeed make no sense - I was under the impression that the many worlds theory was defined so that this branching tree structure could describe the probabilistic nature, such that this result is a direct consequence of the theory. But I must admit, I'm more of a practical physicist, the minutiae of the underlying explanations for quantum mechanical processes don't really affect me much - is there any kindly passing mathematician who can explain what might be interesting about this result?
  • 1 = 2? (Score:4, Insightful)

    by Quiet_Desperation ( 858215 ) on Monday September 24, 2007 @02:58PM (#20732799)
    Where does the energy come from to give existence to this second universe? This whole splitting of the universe thing seems common in physics, so I'm sure I'm not interpreting this correctly. It seems like there's entire universes being created because of the uncertainty of a single particle.
  • by Anonymous Coward on Monday September 24, 2007 @03:00PM (#20732831)
    dear researchers (read: ill-informed mathematicians & faux-losophers):

    many worlds is the answer to a question that didn't need asking. why assume that superposition means that each state is uniquely there and existing, like a huge OR statement?

    look. we get it, it's weird. a particle can't "spin" both ways. the cat can't be alive or dead. it makes your brain hurt, and keeps you up at night.

    but you know what? i don't care. neither does reality. it's going to just keep on being whatever it is. and as far as we can tell, that is: things behave like waves. then we observe them, and they behave like particles.

    why are you worried about the other possible states? you're just making a philosophical assumption, that they were there to begin with. just accept the fact that things can behave according to probabilistic models, and we can all get on with our lives.
  • Re:Occam's razor (Score:3, Insightful)

    by Surt ( 22457 ) on Monday September 24, 2007 @03:14PM (#20733029) Homepage Journal
    Occam's razor proves nothing (and is often wrong!). Phrase the question differently, which is simpler:

    We're in the only universe, which just happens to be perfectly suited and tuned to our existence.
    There's an infinite number of universes, and we're in one where we're possible.

  • by frovingslosh ( 582462 ) on Monday September 24, 2007 @03:22PM (#20733177)
    ....showed mathematically that the bush-like branching structure created by the universe splitting into parallel versions of itself can explain the probabilistic nature of quantum outcomes

    Or in other words, this science fiction nonsense about parallel worlds, unscientific because it can never be tested or proven, and which was inspired by observations of quantum mechanics, is now supposedly able to explain, guess what, ... quantum mechanics, the very concept that the nonsense was built on in the first place.

    The absurd number of parallel universes that would have to be created is mind boggling, since, at the very least, an entire universe would have to be created every single time any atom decayed (one for the universe where that atom happened to decay at that instant, another for the case where that atom didn't happen to decay). Strange that none of the wackos who advocate this, and I use the term very loosely, "theory", bother to expain where all of the mass and energy is coming from for all of these extra universes. Note that we are talking about far more universes than atoms in our own universe. Absolute hogwash.

  • by Attila Dimedici ( 1036002 ) on Monday September 24, 2007 @03:28PM (#20733293)
    Besides being "a physicist at the University of California at Davis", who is Dr Andy Albrecht? and why should I think that he is any more likely than Jack Thompson to recognize one of the most important developments in the history of science? If we are talking Nobel Prize in Physics (or some other prestigious award in the field of physics) winner, maybe there is reason to believe that he is right, otherwise he is just "some dude from California who knows enough to understand the math".
  • Re:Occam's razor (Score:2, Insightful)

    by kylben ( 1008989 ) on Monday September 24, 2007 @03:47PM (#20733535) Homepage
    Or how about: There's only one universe, and we are what happened to be possible in it. The odds of winning the lottery are tens of millions to one. The chance that someone will win the lottery is 100%.
  • by aminorex ( 141494 ) on Monday September 24, 2007 @04:10PM (#20733921) Homepage Journal
    > if anyone would like to propose a repeatable and verifiable experiment for finding the universe where George W. Bush lost in 2000

    Just look out of your window.
  • by Jane Q. Public ( 1010737 ) on Monday September 24, 2007 @04:18PM (#20734065)
    I do not see anything new here at all. The "many worlds" hypothesis has always depended on a hypothetical "probability tree" to describe the odds of quantum occurrences. This idea was new to me, oh, about maybe 30 years ago, and was not actually new then.

    Are they trying to claim that their mathematical probability tree corresponds to a "real" probability tree? If so, on what basis do they make that claim?

    To them, I say: "Show me evidence, and I will believe. Until then, stop bothering me with old ideas."
  • Re:Ummm . . . (Score:3, Insightful)

    by kebes ( 861706 ) on Monday September 24, 2007 @04:36PM (#20734321) Journal

    That the laws of physics are invariant (first explicitly stated in geology as uniformitarianism [wikipedia.org]) is not a prediction, but rather an axiom of science.
    Agreed. It is an axiom of science as we do it.

    With this understanding the status of many worlds and the absurdly large number of parallel universes it entails is quite different from uniformity of natural laws. One (spatiotemporally uniform natural laws) is an assumption necessary for the scientific enterprise to function at all. The other (laughably large numbers of entire freakin' universes) is a clear and moreover, literal violation of occams razor
    Here I think you've misunderstood me. The point is that Many-Worlds is not an assumption: it is a prediction of certain theories (namely, modern unitary quantum mechanics).

    So, given two axioms:
    1. Laws of physics are invariant
    2. Unitary quantum mechanics describes the universe

    We obtain a wide variety of predictions, from transistors to molecules, and so on. One of the predictions is "the universe exists in a global superposition." The proliferation of branches is consequence of the theory, not an axiom.

    We may find the prediction uncomfortable, but without a logical (or empirical) reason to discard it (but retain all the other predictions, which we like better), how can we ignore it? (Honest question... I'm not an expert in philosophy so perhaps I'm committing a fallacy.)

    Positing even a single additional universe constitutes multiplying a nearly uncountable number of entities.
    To emphasize, nothing is being posited (beyond the axioms mentioned; I'm assuming no one is disputing that science and quantum mechanics can say something meaningful about the universe).

    Besides, the point is that unitary quantum mechanics is actually reductionist. It does away with a (superfluous?) ad-hoc assumption (about 'collapse of the wavefunction'). The resulting theory predicts a single object: a global wavefunction. That you or I call its various branches 'universes' doesn't mean anything is actually proliferating.

    We now return you to parallel universes' proper place in our culture as the home of a bearded, agonizer wielding Commander Spock.
    It's important to emphasize that the "Many Worlds" predicted by modern unitary quantum mechanics are not really the "wacky possibilities" seen on shows like Sliders. They represent the branches of superpositions of a global wavefunction. If you branch from a current position, the possibilities are deterministic and mostly uninteresting (e.g. an atom decays a moment later in one branch than another).

    Yes, the global wavefunction would include many variations (maybe even variants where historical events played out differently because millions of quantum branches biased events a certain way instead of another way), but all of these variations are ruled by the same deterministic physics. And, importantly, it's not a matter of "whatever universe you can imagine is out there somewhere!"--the possibilities are strictly limited by deterministic evolution of the wavefunction and the initial conditions of the universe.
  • by db32 ( 862117 ) on Monday September 24, 2007 @05:04PM (#20734699) Journal
    Yeah and the time difference between "I think it works like this" and "See we can prove it now" grows increasingly large the more complex the subject matter. You realize that our understanding of things is still limited by our vantage point in the universe and that we DON'T actually understand all the workings many claim to. Quantum anything is a pretty good example of one of those monkey wrenches of "AHA bitches, and you thought you understood how this works!, Gotcha" The part that is Science is the "Damnit...lets try again a different way".
  • Re:Occam's razor (Score:3, Insightful)

    by Xtifr ( 1323 ) on Monday September 24, 2007 @05:10PM (#20734771) Homepage
    The probability of the existence of other universes is unrelated to the probability of the existence of parallell universes. There could easily be $BIGNUM universes without any of them being parallel in the Many-Worlds-Interpretation of QM sense.

    Of course, it is worth pointing out that speculation about a creator merely pushes the question of origins back a level: where did this hypothetical creator and his/her/their universe come from?
  • Re:Occam's razor (Score:2, Insightful)

    by maxwell demon ( 590494 ) on Monday September 24, 2007 @05:31PM (#20735047) Journal
    Well, actually the MWI says the shit (i.e. wave function collapse) does not happen. The "split" is not a creation of new universes, but a change in our view of the universe. At the objective level, no split happens, and no wave function collapses. Instead, we ourselves get entangled with the observed objects (which is a normal result of any interaction in quantum mechanics). That interaction causes a "split" in the observed world, due to the fact that we ourselves, as observers, are part of it. We observe "shit happening", where no shit actually happens. Since in reality there's no collapse happening, all possibilities are still there, and therefore in a "parallel world" (which is just another projection of the same reality) a "parallel I" must have observed the other result.

    Now, which theory is simpler:

    Theory 1: As long as we don't look, everything follows law A, but as soon as we look, shit happens, and we have to apply law B.
    Theory 2: Everything follows law A, all of the time. The true reason why law B seems to apply is that law A also applies to us.

    Theory 1 is the standard Copenhagen interpretation. Theory 2 is the MWI.
  • by argent ( 18001 ) <peter.slashdot@2006@taronga@com> on Monday September 24, 2007 @06:48PM (#20736065) Homepage Journal
    Strange that none of the wackos who advocate this, and I use the term very loosely, "theory", bother to expain where all of the mass and energy is coming from for all of these extra universes.

    The mass and energy isn't coming from anywhere, because there's no new particles being created. The particles are the same ones, in all universes, their state is just getting more complex, and each "parallel universe" is just a description of one consistent state of all the particles of the universe over all histories. We only observe the particles as as having measurable (subject to Heisenberg) positions and velocities because we're using other particles to measure what those positions are.

    A better question might be "where is the information needed to describe the state of the particle stored". Or to put it another way "how many bits does God's Computer have, and can we hack it?"
  • Re:Ummm . . . (Score:3, Insightful)

    by kebes ( 861706 ) on Monday September 24, 2007 @07:15PM (#20736341) Journal

    If we can accept that there are many universes, with new ones sprouting all the time, is there some constraint on how those universes are? That there might be an infinite set within a certain limit?
    Short answer: there are constraints and limits.

    Long answer:
    First off, some of the discussion here is getting confused because people are equating the "many universes" of the Many-Worlds Interpretation with the "parallel realities" espoused by other theories (but, most prominently displayed in sci-fi), where "anything goes" or any possible arrangement of atoms (or even laws of physics) is possible, or even exists.

    I'm talking about Many-Worlds, which is an untested prediction of modern quantum theory. I'm not talking about parallel realities (for which there is currently no proof and which no mainstream theory predict). In Many-Worlds, the branches evolve deterministically from the current state (according to the equations of quantum mechanics). This means that along each branch (each "universe" if you prefer), the laws of physics are invariant, and are exactly what we are used to (quantum mechanics + relativity). Moreover, because the universe is evolving from a specific initial state, there are constraints on what the branches will look like. You won't get "every wild thing you can imagine": only those branches which can evolve from a current state will be represented in the global superposition.

    So the various branches of Many-Worlds look pretty much exactly like the universe you are comfortable with (planets, stars, galaxies). Along one branch an atom might decay and along the other branch it might not decay (yet)... In principle some branches may have quantum choices such that normally improbably things occur, but that's balanced out by the vast majority of branches which are, basically, boring.
  • Re:Occam's razor (Score:3, Insightful)

    by David Gould ( 4938 ) <david@dgould.org> on Monday September 24, 2007 @10:43PM (#20737877) Homepage

    Occam's razor is useless in situations like this. Basically Occam's razor comes down to a judgment call.
    Right. Besides which, it's not a "Law Of Nature" anyway -- it's more a rule of thumb. Occam's Razor never "proves" anything. It just lets you make an educated guess as to which avenue of inquiry is, all else being equal (that part's important), more likely to be fruitful. (And thus, which one you'd be wiser to spend the effort to explore.)

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