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How Deep Does the Multiverse Go?

Posted by samzenpus on from the beyond-the-beyond dept.

StartsWithABang writes Our observable Universe is a pretty impressive entity: extending 46 billion light-years in all directions, filled with hundreds of billions of galaxies and having been around for nearly 14 billion years since the Big Bang. But what lies beyond it? Sure, there's probably more Universe just like ours that's unobservable, but what about the multiverse? Finally, a treatment that delineates the difference between the ideas that are thrown around and explains what's accepted as valid, what's treated as speculative, and what's completely unrelated to anything that could conceivably ever be observed from within our Universe.

7 of 202 comments (clear)

  1. It's turtles all the way down by Anonymous Coward · · Score: 5, Interesting

    It's turtles all the way down.

  2. Many worlds by Livius · · Score: 5, Funny

    In one version of reality, this is a first post!

  3. Math? by meerling · · Score: 5, Insightful

    "Our observable Universe is a pretty impressive entity: extending 46 billion light-years in all directions, filled with hundreds of billions of galaxies and having been around for nearly 14 billion years since the Big Bang."

    The observable universe is observable because there has been time for the light to travel that far, which can not exceed the age of the universe. Therefor, if the universe is 14 billion years old, then the furthest we could see in any direction is only 14 billion light years, giving a maximum, diameter of 28 billion light years.
    So why does the summary say it's 46 billion L.Y. across and only 14 billion Y. old?

    1. Re:Math? by NEDHead · · Score: 5, Informative

      Because the expansion of space is independent of the light traveling through it, and the light that has just arrived came to us in some cased from objects that are now much further away than 14B lightyears

  4. Re:I don't understand... by vux984 · · Score: 5, Interesting

    The speed of light through space is distinct from the rate at which the universe itself expands. Weird fun things ensue. :p

  5. Speculative. by Oligonicella · · Score: 5, Insightful

    Anything dealing with multiverse is speculative. Math does not constitute evidence.

  6. Re:Wait a minute... by Anonymous Coward · · Score: 5, Informative

    For fuck's sake. How many times must similar questions be asked?

    http://science.slashdot.org/co...

    These are all basically the same question, which reduces to "I'm going to assume that the people who spend their lives working on this can't do elementary arithmetic". Instead, they're working within the strongest theoretical framework they can encounter. In this case, that framework is general relativity and, specifically, Friedman-Lemaitre-Robertson-Walker spacetimes. A subset of the FLRW spacetimes are the de Sitter and anti-de Sitter spaces. These have exponential expansion or exponential collapse, and as one might imagine, this means that if you somehow attached little radar transceivers to fixed points in (anti-)de Sitter space then the distance between them will change far greater than the speed of light would imply. There is no contradiction here, because in general relativity, the "speed of light" means something propagating along null geodesics, paths along which the observed travel time is zero. Null geodesics basically map out spacetime. This is then entirely and totally distinct from any conception of "space expanding faster than light" - the question becomes meaningless.