First, I want to quote wikipedia: "However, if the universe has a large amount of dark energy (as suggested by recent findings), then the expansion of the universe can continue forever – even if omega > 1" Wikipedia is not scientific, but I couldn't find a better source at the moment. M...

As far as I've heard, the "omega constant" is probably a little greater than 1, so the big crunch will never occur. All planets will separate from each other and the gravitation will not be able to hold everything together. Eventually the universe will cool down. But we don't have to worry...