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Finite Universe ?

  1. Feb 25, 2010 #1
    If the approximate time since the big band is correct at about 14 billions years, then the universe should have a limit as to how far it has expanded/inflated. Why then do people still postulate an infinite universe ?
  2. jcsd
  3. Feb 25, 2010 #2
    Our models predict that the observable universe started out from a dense state smaller than a proton. However, the same models do not rule out that the whole universe (the observed universe plus the still unobserved part) did not start out infinite in size.
  4. Feb 25, 2010 #3
    Thinking about this some more..cosmology and physics can take us back to a fraction of a second ATBB but says nothing about the BB itself. So though the physics takes us back 14 billion years that may be a fraction of the way back to the actual BB.

    Am i right in thinking that the BB could have occurred an infinitely long time ago in which case it would have had an infinite amount of time to expand and there would not be a singularity at the BB as there was in fact no beginning ?
  5. Feb 26, 2010 #4


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    The observable universe is temporally finite. That does not mean it is spatially finite.
    We cannot comment on the existence or extent of regions unobservable to us. The big bang 'singularity' is unbounded by physics as we know it.
  6. Feb 26, 2010 #5


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    1. We don't know how big our region of space-time started out as, as others have noted. Personally, I tend towards thinking that it is likely spatially finite.
    2. We don't know whether or not it stemmed from a larger space-time. So space may well be infinite even if our region is not.
    3. Extrapolating into the future, our universe will approach infinite size, so in a sense it is certainly infinite.
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