Tim Attwood <tim### [at] comcastnet> wrote:
> Einstein postulated a finite universe as part of his formulation of
> relativity. He said that, since space-time can curve, eventually if
> you travel in a straight line far enough you will come back to your
> starting point. This would mean that there is no well defined edge.

  I understand how GR describes the curvature of space-time in relation
to masses, and given the enormous amount of experimental evidence which
corroborates this, I see no reason to doubt it.

  However, I don't understand why GR would predict a curved universe
where each geodesic line is closed. What would cause it? Certainly not
the mass in the universe. I don't think it would be even nearly enough.
(Because if it was caused by mass, it would mean that the entire universe
is actually inside its own Schwarzschild radius, which is clearly not the
case.)

> Modern astronomers can find no evidence of such a large scale
> warping of space-time. This is part of why the theories of parallel
> universes are in vogue, if the universe is infinite, then if you
> travel in a straight line far enough you might reach a region
> that is very similar to earth, but isn't quite. It would be "parallel".

  I don't find any kind of logic in that. Why would there be a "similar",
"parallel" version of anything if you travel far enough? It doesn't make
any logical sense.

-- 
                                                          - Warp

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