After reading Fabric of Reality, the idea of an infinite cycle of expansion and contraction of the universe, punctuated with Big Crunches and immediately thereafter Big Bangs, made the most sense to me out of all the theories about the nature of the universe.
David Deutsch proposes the idea at the end of his book that if highly-evolved, sentient life is around when the universe becomes in danger of collapsing upon itself (again), it will expend all of its energy and resources on re-arranging matter in space and therefore its gravitational pull. This could theoretically delay the Big Crunch, at least for a while, though the whole "Big Crunch" theory has fallen out of style over the last decade or so.
I've read up on competing theories and sure, I can believe that shit could just keep floating out into space and get stretched out so thin that it becomes nothing and then somehow the universe begins anew.
I believe that once quantum computing becomes a real thing, it will help answer questions about the nature of dark matter and so forth, which I believe is what comprises matter in parallel universes that are "close" to us. It will also lend credence to the model of the universe that David Deutsch uses to arrive at his conclusions about the multiverse.
Anyway, read the article. Its awesome.