Re: OT, and religeous

Taking this offlist ...

Well, the spherical universe is the 3D equivalent to the 2D surface of a regular
sphere. The hyperbolic is the corresponding 3D equivalent to a 2D saddle surface
(one that turns upwards along one axis and downwards along the other). Is that
of any help?

If not, I can only recommend an introductory text to non-Euclidean geometry. I
find it very difficult to explain geometrical concepts in a text-only medium.

                                            Andreas

> Andreas Johansson wrote:
>
> >Quoting Joe <joe@...>:
> >
> >
> >
> >>Andreas Johansson wrote:
> >>
> >>
> >>
> >>>Quoting Chris Bates <chris.maths_student@...>:
> >>>
> >>>
> >>>
> >>>>Since the concensus seems to
> >>>>be that the universe is finite,
> >>>>
> >>>>
> >
> >
> >
> >>>Really? All popular cosmology works from recent years I've read have said
> >>>
> >>>
> >>it's
> >>
> >>
> >>>probably not.
> >>>
> >>>
> >>>
> >>Really?  I find that very surprising.  All the stuff I've read suggest
> >>that it's boundless, but finite.  Like the surface of a sphere.
> >>
> >>
> >
> >Very briefly, an expanding general relativistic universe can have three
> overall
> >shapes; spherical, flat, hyperbolic. In the first case, it's boundless but
> >finite, in the two later, both boundless and infinite. The parameter
> >determining which is the mean matter density; if high, spherical, if low,
> >hyperbolic, with flat at the critical value. It's used to be thought that
> the
> >spherical version was the most likely, but observations in recent years seem
> to
> >have established that we're well with the hyperbolic regime.
> >
> >
>
> Interesting.  Can you explain to me what exactly the hyperbolic shape
> implies - I do, I'm afraid, have a very limited grasp of non-Euclidean
> geometry (especially in three dimensions).
>