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Thread: The Universe didn't arise from a single point?

  1. #1
    Join Date
    Oct 2008
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    The Universe didn't arise from a single point?

    There's been comments back to questions in this forum which critique the notion that the Universe expanded from a single point and that this just a misconception popularized by lazy science communicators. Fair enough, I'm not aware of observational evidence that would unequivocally confirm the single point origin concept. But what then is the alternate hypothesis? Did the Universe begin at time equals zero as a moderately large entity which then expanded further? How big was that initial proto-Universe? And why is this hypothesis more acceptable than the single point hypothesis? I'm not being at all sarcastic here - I am interested to know the answer, or to otherwise have my misinterpretation/s corrected. Thanks, Steve

  2. #2
    Join Date
    Mar 2010
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    Short answer is we have no idea because none of our theories work that far back. Even when T=0 is an extrapolation beyond the domains of applicability of our current theories.

    All the current big bang theory actually says is that the observable universe expanded from a hot, dense state that existed a finite time ago. There have been a number of speculations about what could have happened before - but honestly most of them are not much better than watching a kitten growing up and hypothesising that many years ago the early kitten was smaller than an atom.

    Current physics really only goes back to the quark epoch, which is post inflation. By that point the observable universe was somewhere of the order the size of our solar system. We have some clues about what happened before (although there are a lot of gaps) in the electroweak epoch when the universe was a few centimetres across. Before that we are mostly dealing with speculation, which is why there isn't really a good answer to the question "how did the universe begin?"

    And note that all of this is about the observable universe - we don't have a theory that really captures how the wider universe behaves. We just assume that we are not special so it should be similar to what we see in our neighbourhood.

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