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An embarrassing question: what were the boundaries of the universe

  1. Nov 17, 2011 #1
    I say always that the universe has expanded, from an initially-hot and dense state, until it get its current forme...
    But it will be very natural to ask the question: at the first instances of its expansion, what were the boundaries of this universe, and what were the exterior of this boundaries..?
    Can someone explain me this?
  2. jcsd
  3. Nov 17, 2011 #2
    Last edited by a moderator: Apr 26, 2017
  4. Nov 17, 2011 #3
    We're actually not sure if it's infinite or not (according to Marcus, and the FAQ, the current data fits both infinite and finite models, pretty much equally well), but:

    -If the universe is infinite, then it was already infinite at the point of the Big Bang; there was never a time that it was finite.

    -If the universe is finite, it still does not (and never did) have boundaries. What happens when you reach the edge of the universe? Well, you never reach an edge; try this and you'll only end up back where you started (rather like as if you tried to sail to the edge of the earth).

    -In either case, it is expanding. One may wonder: if the infinite universe is true, how would an already infinite space expand further? Well, all the things in it just keep getting further away from each other.
  5. Nov 21, 2011 #4
    Thank you narrator and cephron, I think the idea is now somewhat more clear.
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