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What does the geometry of the Universe have to say about the Hartle-Hawking model?

  1. Aug 13, 2011 #1
    Hi there! I'm new here and am currently looking into the Hartle-Hawking and Hawking-Turok Quantum creation models.

    What I've read about the Hartle-Hawking model is that it predicted a Closed Universe. But isn't that the opposite of what we have learned? The WMAP sattelite has confirmed the Universe to be flat with only a 0.5% margin of error. If it is the case that the Universe is flat, doesn't that falsify the Hartle-Hawking model which predicted a closed Universe? On one site from the University of Victoria it says this:

    "The problem with Hartle and Hawking's theory is that it predicted the universe is "closed." Consider a closed universe to be the surface of an inflating balloon. Objects such as galaxies on the surface of the balloon would move away in one direction as the balloon inflates, and eventually end up at their initial positions. In addition, the concept of a closed universe implies that the universe will one day stop expanding, and collapse under the force of its own gravity.

    Observations suggest that there is insufficient matter in the universe to create enough gravity to recollapse it. In fact, there is evidence predicting the universe to be expanding at a faster rate than the inflationary theory predicts. Thus, observations favor the idea of an "open" universe, a universe that will continue to expand. One way of picturing an open universe is thinking of it as a horse's saddle, which curves up on one side and curves down on the other." ( http://web.uvic.ca/~jtwong/Hartle-Hawking.htm )

    It seems like that was written before the WMAP sattelite confirmed a flat Universe to some degree of certainty. But then, I read that Hawking and Turok made a similar model that predicted a Open Universe, the so called "Hawking-Turok Instanton Theory" because the data seemed to predict a Non-Closed Universe. But their model predicts a Open Universe. And the latest data leans more towards a Flat Universe, so, if the Universe is confirmed to be flat to a very high degree of precision, doesn't that falsify the Hartle-Hawking and Hawking-Turok models?

    Thanks!
     
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  3. Aug 14, 2011 #2

    Chalnoth

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    Re: What does the geometry of the Universe have to say about the Hartle-Hawking model

    These aren't opposites. It may predict a closed universe, but our universe can be extremely flat and still slightly closed, because flat is the boundary between open and closed. Additionally, depending upon how much curvature there is, it is conceivable that we could measure a slightly open universe while the universe remains topologically closed. How is this possible?

    Well, imagine two scenarios. First, imagine a balloon. A balloon is a closed surface, and its tension keeps it roughly spherical. This makes it so that every local area on the baloon is closed.

    But what if our universe isn't that smooth? What if, instead of a balloon, it's a much more irregular surface, like one of these giant soap bubbles:


    Most of the surface of those soap bubbles is closed, because the overall topology is closed. But different little sections of the bubbles can be open. Our observable universe might, in the end, turn out to be like that: a small section where we measure open curvature, even though the whole is closed. It all depends, really, upon the details: how much curvature is predicted?
     
    Last edited by a moderator: Sep 25, 2014
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