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B Edge of the Universe

  1. Apr 1, 2017 #1
    So I'm sure you've all heard people talk about increasing expansion of the universe, the compact nature of the universe at the moment of the big bang, and other comments like this. The idea of an expanding universe immediately suggests to me an "edge" of the universe, which is something often referred to in pop-science (for the record, I know that expansion does not necessarily mean a movement of the boundary of the universe, it means an expansion of the internal volume. I just don't know if this is the only real implication of this).

    My question is, is the idea of an "edge of the universe" really valid, or is this just a erroneous view perpetuated by pop-sci sources? Is there a real edge of space, is it just like a bubble of energy and mass outside of which there is absolutely nothing, or is this totally incorrect? What do QFT and modern models have to say about this?
  2. jcsd
  3. Apr 1, 2017 #2
    As far as I'm concerned, that is nothing but pop-sci. If there was an edge to the universe, that would imply there is a center as well. According to Big Bang theory, this cannot be true because the Big Bang didn't occur at one point; it occurred everywhere and simultaneously.
  4. Apr 1, 2017 #3


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    Absolutely not
  5. Apr 1, 2017 #4
    Thanks, but could you explain a bit more? Is the universe infinitely large, or is it somehow circular so if you go far enough in one straight line you return to your starting point?
  6. Apr 1, 2017 #5


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    Yes, it's probably one or the other but we have no idea which. In any case, there is no edge and no center. I recommend the link in my signature.
  7. Apr 1, 2017 #6
    Okay, cool. I was in the process of asking why the universe couldn't be finite with a center and then I realized that that had already been answered. Thanks!
  8. Apr 2, 2017 #7


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    Same here - I have to make deliberate efforts to get past that notion. It helped me to change my internal articulation from 'the universe is expanding' to 'the universe is becoming less dense'. The universe was denser in the past than it is now. The extent of the universe being infinite or finite is not different now than it was in the past.

    I can say it, but my brain can only make a picture for me using an analogy like Phinds describes in his discussion of the balloon analogy. I struggle trying to mentally picture an infinite flat universe moving away from every part of itself; like you, I keep wanting an edge in that picture.
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