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Consequences of parallel universes

  1. Aug 25, 2013 #1
    Hi, I have some questions that came up while thinking of this idea of parallel universes, I'm glad if someone could help answer these.

    1. Assume we somehow discover another universe, does this discovery then imply that OUR universe is finite in size? Or is it still possible to have an infinite universe?

    2. I've read that one POSSIBLE way to discover other universes is the way they MAY interact on each other with gravitational forces. However, assume we have 2 universes affecting one another with their own gravitational force, these forces, do they propagate through something in between these galaxies? Maybe this question doesn't even matter, neither the answer to it. But think of it like general relativity, mass bends space-time. But does a universe as a whole also bend some kind of "space-time outside the universe", this "thing" the universes exist in. Maybe this whole idea is totally wrong since I imagine space-time to be something that exists IN our universe. This question might be very nonsense, if so I'm sorry, it's just imagination playing in my head. Maybe the concept of time is not needed "outside the universe", or in this "thing" the universes exist in. However, it's fascinating.

    Thanks in advance, please keep in mind I have no knowledge at all of this theory of parallel universes.
    Robin Andersson
  2. jcsd
  3. Aug 25, 2013 #2


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    Parallel universes is a very iffy concept. There are two or three variations.
    1) Quantum theory basis. All possible outcomes occur in parallel universes.
    2) Big bang created a bubble (our universe) in a multiverse.
    3) M theory. Brane collision led to the big bang.

    As far as I can tell there is no way to communicate with another universe, athough for 2 and 3, it was supposed to explain why gravity is so weak compared to other forces.

    This is all very speculative.
  4. Aug 25, 2013 #3
    It's still possible to have an infinite universe, being that the other universe would have it's own space. It doesn't share the space of our universe. If it did, they'd be a single universe.
  5. Aug 26, 2013 #4
    Can you explain how our infinite universe could "share" it's space with another universe?
  6. Aug 26, 2013 #5


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    How can an infinite universe have a finite 'age'?
  7. Aug 26, 2013 #6
    Chronos -Good question.

    I've always assumed assumed that the BB took place in an infinite universe. Any thoughts?
  8. Aug 26, 2013 #7
    It doesn't. The other universe has it's own space. It doesn't share space with any other universes. If two "universes" shared the same space, they'd be a single universe. You can still have an infinite universe with the existence of other universes, being that each universe has it's own space.
  9. Aug 26, 2013 #8


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    In the quantum multiverse, the different "universes" are just different branches of the wavefunction that cannot communicate with one another. They all occupy the same space, but can't interact.

    That said, though we really don't know for sure if our universe were infinite or not, I think a finite universe is a better bet overall. Though in this case, the size may be very very large indeed. Especially if it turns out that eternal inflation occurs.
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