| MadSci Network: Astronomy |
Hello As you may know there are 3 possibilities for how the universe evolves. These are 1. It can expand then collpase, 2. expand to a fixed size but the expansion keeps slowing down 3. the expansion keeps going forever. The thing that determines which scenario is the right depends on the average density of the Universe. Essentially the average density determines the overall gravitational pull of the Universe which stops or does not stop the expansion. The problem then is measuring the average density of the Universe. For many reasons this is quite hard to do and depending on what measuring system you use you get different answers. Most answers suggest that the universe has not enough density to stop expansion but there are strong theoretical reasons to suggest case 2 above is how the universe should behave. New evidence published recently suggests more strongly that the Universe may indeed keep expanding indefinitley but there are more too many variables at work for this one experiment to conclusively proove it has the right answer. In short, no one knows yet whether the universe will keep expanding or stop expanding in the future. This is one the biggest unanswered questions in Cosmology and many people are working on finding better ways to answer it. If you wish to know a bit more I would suggest reading one the many web pages hosted on university sites bout Cosmology. Some of the better ones are Ned Wrights home page or John Baezs' Pages. Ned Wright also has the FAQ for the Cosmology usenet groups. There are also some good general text books on this subject. Kip S. Thornes "Black holes and time warps, Einsteins outrageous legacy" is a good general book on cosmology and relativity though it does not cover the full details of the problems in measuring the average density. I just bought and started reading Alan H. Guths book "The Inflationary Universe", so far I am very impressed and it covers expansion of the Universe in some detail. There are plenty of other books by John Gribbins, Stephen Hawking and Paul Davies that cover this topic in partial detail. If you need more detail please mail me at my private e-mail account
Try the links in the MadSci Library for more information on Astronomy.