If you wonder what Big Chill or Big Rip are, read this article for detailed answers.
However, in short:
- Big Crunch = death of the universe by gravitational implosion; not likely to happen (based on recent discoveries);
- Big Chill = death of the universe by freezing to zero Kelvin temperature, meaning that molecules won’t move anymore (although they would still be normal matter); gravity doesn’t win and the universe expands forever;
- Big Rip = death of the universe by Big Chill + breaking all matter in elementary components, while the universe would still be expanding forever.
I’d bet on Big Rip.
Becuase I think that Big Crunch could generate a new universe by quantum effects near singularity level that would make particles to not actually all crunch and re-explode in a new Big Bang, Big Chill leaves some movement alive: electrons would still move inside atoms, although molecules won’t move themeselves (seems physically strange, too), and only the Big Rip actually destroys every possible interaction: I personally believe that God (or the nature) wants everything destroyed in the end: it’s nicer, cleaner, and in a way, looks more natural to me.
What do you think? What theory would you bet on?