>>4043493There are two theories that i'm aware of.
The one you listed is known as the Big Crunch.
Everything is pulled back together under the force of gravity.
Possibly forming a superdense black hole.
This theory goes on to suggest that , once the Big Crunch has gotten to it's smallest possible point , it will explode again , in a big bang.
Thereby we have a lot of following bangs and crunches.
A second theory is called the Big Drift [iirc]
Basically , everything keeps moving apart , galaxies move away from each other , within those galaxies the planetary systems move apart , the worlds drift away , until everything moves away from everything else , right down to the molecular level.
There is more evidence to support the Big Drift , b/c everything ~is~ moving apart [we can see this by the red-light shift , look it up.]
But further more , things are drifting apart faster.
Wiki should answer most of your questions adequately.
Hope that helps.
- Anon.