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posted by LaminatorX on Thursday September 03 2015, @06:59PM   Printer-friendly
from the Two-Roads-Diverged-in-a-Yellow-Wood dept.

The existence of parallel universes may seem like something cooked up by science fiction writers, with little relevance to modern theoretical physics. But the idea that we live in a “multiverse” made up of an infinite number of parallel universes has long been considered a scientific possibility – although it is still a matter of vigorous debate among physicists. The race is now on to find a way to test the theory, including searching the sky for signs of collisions with other universes.

It is important to keep in mind that the multiverse view is not actually a theory, it is rather a consequence of our current understanding of theoretical physics. This distinction is crucial. We have not waved our hands and said: “Let there be a multiverse”. Instead the idea that the universe is perhaps one of infinitely many is derived from current theories like quantum mechanics and string theory.

The universes predicted by string theory and inflation live in the same physical space (unlike the many universes of quantum mechanics which live in a mathematical space), they can overlap or collide. Indeed, they inevitably must collide, leaving possible signatures in the cosmic sky which we can try to search for.

Whether we will ever be able to prove their existence is hard to predict. But given the massive implications of such a finding it should definitely be worth the search.

http://theconversation.com/the-theory-of-parallel-universes-is-not-just-maths-it-is-science-that-can-be-tested-46497


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  • (Score: 3, Informative) by HiThere on Thursday September 03 2015, @09:31PM

    by HiThere (866) on Thursday September 03 2015, @09:31PM (#231979) Journal

    It's important to remember that there are several quite distinct multiworld theories, and most of them are not affected one way or the other by the truth of the others. It sounds like the one they are talking about is m-brane theory, when they talk about looking for the evidence, but when describing the origin of the theory it sounds more like they are talking about the EGW multi-world theory. Those are completely distinct theories. Either could be true without affecting the truth of the other. Either could also be false without affecting the truth of the other. And those are only two out of several. (E.g., one of the theories involves the inflaction not having any theoretical grounds for stopping at any particular time, which implies that somewhere beyond our light cone there are indefinitely large numbers of universes just about like the one we live in. So many, in fact, that there are instances that are identical down to the smallest atomic position (which implies that the universe from within their light cone looks just like this one, and that they speak English, Russian, Turkish, etc.)

    There MAY be some sound science behind this article, but you couldn't prove it from reading the summary.

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  • (Score: 2) by wonkey_monkey on Thursday September 03 2015, @10:35PM

    by wonkey_monkey (279) on Thursday September 03 2015, @10:35PM (#232010) Homepage

    So many, in fact, that there are instances that are identical down to the smallest atomic position (which implies that the universe from within their light cone looks just like this one, and that they speak English, Russian, Turkish, etc.)

    What boggled my mind was that you can even calculate how far you'd have to travel to stand a particular chance of finding one. I think it was something like a radius of 1082 light years within which there's a high probability of there being another region of space identical to our observable universe.

    Could be misremembering that number completely, though. And it probably goes up a lot if you have to start worrying about the laws of physics changing through space.

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    • (Score: 2) by HiThere on Friday September 04 2015, @10:04PM

      by HiThere (866) on Friday September 04 2015, @10:04PM (#232440) Journal

      Well, if the laws of physics change through space then I don't think you will get identical sections. Not unless they change randomly or oscillate or some such. So that would be a different multiworld theory yet.

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  • (Score: 2) by c0lo on Friday September 04 2015, @12:17AM

    by c0lo (156) Subscriber Badge on Friday September 04 2015, @12:17AM (#232046) Journal

    which implies that the universe from within their light cone looks just like this one, and that they speak English, Russian, Turkish, etc.

    Or not... you'll never know until you hear them, but suddenly you won't understand then. Or maybe you'd understand them, but you may never hear them.

    Alive or not, that cat be damn'd.

    (grin)

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    • (Score: 2) by HiThere on Friday September 04 2015, @10:02PM

      by HiThere (866) on Friday September 04 2015, @10:02PM (#232439) Journal

      You're misunderstanding. *If* the "eternal inflation" model is correct, what it's saying is that the universe is so large that sections of it large enough to form a light cone must be identical. Identical, as in indistinguishable by any test, were it possible to make such tests. (There will, of course, also be extremely many more sections that are different.) And that's why it's called a multiworld theory. They exist in separated regions that originated with the same "big bang" that started off the part that we live in. The quantum indeterminacy multiworld (i.e. the Everett-Graham-Wheeler one) is the one that depends on the cat being dead or alive. And, neither of those is the m-brane multiworld theory which is what it sounds as if this is searching for evidence of.

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      • (Score: 2) by c0lo on Monday September 07 2015, @01:04AM

        by c0lo (156) Subscriber Badge on Monday September 07 2015, @01:04AM (#233094) Journal

        (grin) [soylentnews.org]

        And no, I didn't misunderstood.
        First, what you say implies that the many universes would have the same number of (multidimensional) states - (e.g. necessary the same number of particles/energy); which isn't necessary true - see the Hilbert's Grand Hotel [wikipedia.org]
        Second: this is a pure academic exercise (and, for the moment, so is string theory); in practical sense, there's nothing to be gained if a second identical universe exists: if these universes are identical, any attempt to contact them would look like a monologue in the mirror. If the symmetry is broken and you'd actually have a dialogue with your counterpart, they will cease to be identical and they'll diverge exponentially (or faster) - therefore my play on the Schroedinger’s cat, the very act of the contact will kill the "identity cat"

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