Re: expansion of the universe

[Gary Turner <turner@MORNINGSIDE.EDU>]

> Current measurements indicate that the universe is probably not
> closed.  Rather, it is "critical" or "open".  In either of these
> cases, the universe has an infinite amount of space AND ALWAYS HAS
> HAD AN INFINTE AMOUNT OF SPACE, no?

No, not really.  The universe is expanding at a finite rate and has been
doing so for a finite time.  It is finitely big.  After it has been
expanding for an infinite amount of time, it will be infinitely big.

If you fire a particle away from the Earth at greater than escape speed, it
will continue to separate from the Earth forever - but in 10 years, it will
not be an infinite distance away.

Cosmologically, it is a little harder than this example because parts of
the universe may be beyond our horizon.  They are so far away that light
cannot have reached us, so cannot be observed.  For all intents and
purposes, they may as well be an infinite distance away because they cannot
possibly affect us at the moment.  However, they are not.  It is just the
constraint of finite transmission speeds over extremely large (but finite)
distances.

So what is the universe expanding into?  Nothing!  Not empty space, but
nothing.  By definition, the universe is everything.  If there was
something for a universe to expand into, then that would have to be a part
of the universe - but then you just go around in circular reasoning.

> Here's the question:  HOW IS A UNIVERSE WITH AN INFINITE AMOUNT OF
> SPACE CONSISTENT WITH A BIG BANG?  I.e., can we possibly envision how
> an infinite amount of space undergoes creation?  I can certainly
> envision the expansion of a cylindrical universe from zero initial
> volume.  But I'm having real trouble(!) envisioning the expansion of
> a true "saddle" universe -- or any other open universe -- from zero
> initial volume.
>
> Can anyone help?  ... Or is my question itself flawed?
>
> - Tucker
> --
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> Tucker Hiatt, Director
> Wonderfest
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