From what I understand, space itself is expanding at an accelerating rate. Galaxies and stars are moving further apart, faster and faster. This would seem to indicate that the universe will end with a whimper rather than a crunch.
Robert the Bruce, at one time the thinking was that the force of gravity would stop the expansion of the universe and even pull everything back into a singularity eventually- a big crunch! Now, observations seem to show that this will not happen.