Re: How would you prove the big-bang was not the result of a big-crunch?

Hi Alastair,

Thanks for your question and sorry for the long delay in responding.

The idea of a "bounce" universe has been tossed around for a while. This model runs into trouble with ent ropy. Could the universe have had a "near-miss" Big Crunch rather than a Big Bang? Possibly, but the universe had to become sufficiently hot and dense to destroy all the elements from the previous universe. This is because Big Bang nucleosynthesis models do an excellent job of predicting the observed ratios of light elements (hydrogen and helium). If the Universe was this hot and dense, any and all record of the previous universe would be destroyed, so it is very difficult if not impossible to distinguish this scenario from the conventional Big Bang picture.

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.