(Submitted July 09, 2001)
My question is, what would happen to the all the matter in the universe
when it turns into stars, which in turn turn into black-holes, which
would suck in more matter, would it just become an "empty space?"
First off, all the matter in the universe will not end up in black
holes. Most stars in the universe don't have enough mass to become black
holes at the end of their lives. Neutron stars and white dwarfs are much
more numerous; this is what most stars end up as.
Secondly, black holes are not cosmic vacuum cleaners, whatever you may
have heard. They will not suck up everything in the universe. They only
suck up what crosses their event horizons.
The universe, if it is "open" and keeps on expanding forever, will
probably end up as a cosmic graveyard, populated by things like black
holes, neutron stars, and white dwarfs.
This website has more on black holes:
And this one has info on cosmology:
Amy C. Fredericks and Mike Loewenstein
for Ask an Astrophysicist