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B How large might the Universe be

  1. Nov 6, 2017 #21

    phinds

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    @PeterDonis is this "periodic boundary" model viable? (start w/ post #13). It doesn't seem so to me but I never let a little thing like total ignorance get in the way of having an opinion.
     
  2. Nov 6, 2017 #22

    PeterDonis

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    It depends on what you mean by "viable". :wink:

    If you mean, is it mathematically consistent, yes, it is.

    If you mean, is it consistent with the data we have up to now, yes, it is, but only if the periodicity is very, very much larger than the size of our observable universe. (This is similar to the way that a model with positive spatial curvature is consistent with the data we have up to now, but only if the curvature is very, very small, so that the spatial volume of the 3-sphere universe now is very, very much larger than the size of our observable universe.)

    If you mean, is it likely to be true, that's a matter of opinion. I personally think it's unlikely; it seems to me like an ad hoc suggestion which, while mathematically consistent, doesn't have any real physical principle to back it up. But as I said, that's just an opinion. We don't anticipate having any way of testing the matter experimentally any time soon.
     
  3. Nov 6, 2017 #23

    phinds

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    Thanks.
     
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