Creationists will usually dismiss the overwhelming weight of scientific evidence by asking what came before the Big Bang? Which to my mind is a bit like asking what came before God? Funnily enough the answer to both questions is surprisingly similarity.
For creationists the bible is the equivalent of the Hitch-Hikers Guide to the Universe, an infallible guide to life the universe and everything. They will argue the answer to the question can be found in Genesis 1:1 “In the beginning, God created the heavens and the earth.” Therefore God sits outside space and time, neither of which existed until he created the universe. He created time, along with all the other dimensions of our universe. A pretty neat answer to a question that might other wise threaten ones faith.
According to Einstein's theory of relativity, time only came into being as the primordial singularity (roughly a million billion billion times smaller than a single atom) began expanding into the universe we know and inhabit today. As Stephen Hawkins once put it “since events before the Big Bang have no observational consequences, one may as well cut them out of the theory, and say that time began at the Big Bang.”
That of course hasn't stopped scientists theorising what came before the Big Bang or what the eventual fate of our universe might be with the two often being interlinked.
The Big Crunch theory holds that gravity will eventually become the strongest force in the universe. The rate that which the universe expands will gradually decrease until its starts to collapse back in on itself, ultimately ending as a black hole singularity or causing a reformation of the universe starting with another Big Bang (Often referred to as the Big Bounce). The good news for us is that this won't happen for at least another 20 billion years. And given that our small, insignificant Solar System will be consumed by our own dying sun in around 4.5 billion years we have more immediate concerns. Still that didn't stop the Japanese asking Stephen Hawking not to mention the possible re-collapse of the universe at a lecture in Japan, because it might affect the stock market.
The Big Rip holds that the forces driving the universe's expansion will eventually overpower gravity. When we reach this point galaxies will tear themselves apart apart, followed by black holes, planets and stars. Until everything disintegrates into unbound elementary particles and radiation. The end state of the universe being a singularity, as the dark energy density and expansion rate becomes infinite.
The Big Freeze or Heat Death suggests that the universe will gracefully decay as it continues to expand. In this scenario the gases used to form stars will be exhausted in approximately 100 trillion years from now and the atoms making up the remaining matter would start to degrade and disintegrate. As the stars dissolve, the universe becomes darker and black holes come to dominate. Eventually these black holes will evaporate and finally even light particles themselves will vanish.
The Multiverse theory suggests that there is no complete end. In this theory our observable universe is merely one among an infinite number of expanding regions of "normal" space within a larger volume of inflationary space. These regions of normal space cannot contact each other, so can be considered separate universes. Thus while any given universe eventually reaches heat death, there are always other regions that haven't, and new universes being produced within the inflationary volume, so the multiverse as a whole never ends.
It's even been suggested that our entire universe exists with in a black hole. That, as matter is sucked into a black hole, the torsional forces exerted on the matter that forms the singularity at its heart can suddenly be released triggering a Big Bang or Bounce creating a new universe.
In the final analysis the big difference is that for religion the universe is a closed book in which all the chapters have been written and all the answer given by the deity that created it all. There are no unanswered questions. Whereas for science the book is never finished. The next chapter is always waiting to be written and any of the previous chapters can be completely rewritten in the light of new evidence that redefines our understanding of the world around us.