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Re: Creation



From the point of cosmology *THIS* Universe (there may be many others) was
"created" ex nihilo ~15billion years ago -- at a *point* of zero volume.
Since then, this Universe has been expanding BUT it is not expanding into
some extant space -- it is creating its OWN space ie space is expanding as
well and the stuff of this Universe is expanding into this expanding space.
At first this space expanded faster [could one say >c? and have that be
understood?] than the stuff of the Universe (there were yet no galaxies or
even nebulae at this time). The rate of expansion of space is decreasing.
There is a debate as to whether the things (galaxies, etc) of the Universe
will catch up or not OR if the things of the Universe will collapse in
several billion years OR if space will collapse back to a point.

Jim,

I much prefer to stick to concepts that can be operationally defined and
to statements that can be empirically tested. When we say that the
universe is expanding or that space is expanding, what we really mean
is that the galaxies (or rather, clusters of galaxies) throughout the
observable universe are getting farther apart. Extrapolating backward
(with large uncertainties due to the uncertainties in current distances
and the unknown deceleration rate) leads us to believe that everything
in the observable universe was much closer together, more or less in
the same place, about 10-15 billion years ago. From the observed present
ratio of photons (background radiation) to nuclear particles of about
a billion to one, we can calculate what happened during the first few
minutes of time as we know it: the universe expanded and cooled and
by the time the temperature was low enough for nucleons to stick together
to make helium, the proton/neutron ratio was about 87/13, which agrees
with the observed H/He mass ratio of 74/26. This agreement between theory
and observation makes us pretty confident of our picture of what happened
during the first few minutes, but there's no similar observational
confirmation of theoretical extrapolations into the first 1/100 second
of time (as we know it). Even if there were, I don't think anybody
knows how to talk about the first 10^43 second, much less what happened
"before" that, if this concept has any meaning at all. Your phrase
"ex nihilo" seems to imply a time before the beginning when there was
nothing, and this bothers me.

By "observable universe", I mean everything we can see. The observable
universe is limited in size not by the size of our telescopes, but by
the finite amount of available lookback time: if the universe as we
know it is only 10 billion years old, we can't look out farther than
10 billion light years. (The practical limit is very slightly less
because at high temperatures the universe was opaque to light.) Hence
we have no idea what lies beyond our 10-15 billion-light-year horizon.
It's possible that space goes on forever in all directions, or that it
curves back on itself to make a finite total volume. Or something
much more complicated and bizarre.

If you haven't read Weinberg's The First Three Minutes, I highly
recommend it.

-dan