MadSci Network: Astronomy |
Hi Michael,
Good questions! There is significant evidence from supernovae
and the cosmic microwave
background that the energy of the universe is dominated by a vacuum
energy or cosmological
constant.
Under the simplest models for vacuum energy, the universe will eventually
re-enter a phase of exponential expansion similar to the proposed
"inflationary" period immediately following the Big Bang.
As for our bodies being torn apart by the expansion of the universe, check
out this
link.
By the "observable universe", astronomers simply mean anything that can be
observed by us. Because light has a finite speed this means that we can't
see anything further away than the speed of light times the age of the
universe (roughly 10-15 billion years). If the universe is infinite (as
suggested by current observations), then there's more to the universe
beyond this limit, but it's too far away for us to have seen anything yet.
Patience can solve this: wait another 10 billion years and you can see
objects 10 billion light years further away than you can now. This is
different from dark
matter, which is matter within the observable universe which doesn't
emit light but shows itself through gravity.
Try the links in the MadSci Library for more information on Astronomy.