|MadSci Network: Astronomy|
Good insight! In the 60's and 70's, so-called 'oscillating universe' models were popular. The basic idea was that after the big crunch, there may be another big bang, and the big bang/big crunch cycle might go on forever. One of the most difficult challenges this model has faced has to do with entropy, a subject which is discussed in great detail here, along with references to several more books you can check out from the library to learn more.
Many people like the oscillating universe theory on a philosophical basis, but it fails one important test -- most observations indicate that the universe is open. If the universe is indeed open, it will expand forever; the big crunch would never happen. The observational tests vary from the brightnesses of distant supernovae to the exact shape of ripples in the cosmic microwave background.
Try the links in the MadSci Library for more information on Astronomy.