Book contents
- Frontmatter
- Contents
- Preface
- Dedication
- Note on some conventions
- 1 Introduction
- 2 Our Galaxy
- 3 The large-scale structure of the universe
- 4 Elementary particles – a preliminary look
- 5 Is the universe open or closed?
- 6 Three ways for a star to die
- 7 Black holes and quasars
- 8 Galactic and supergalactic black holes
- 9 A black hole is not forever
- 10 Slow and subtle changes
- 11 Future of life and civilization
- 12 A collapsing universe
- 13 The steady state theory
- 14 The stability of the proton
- 15 Epilogue
- Glossary
- Selected bibliography
- Index
12 - A collapsing universe
Published online by Cambridge University Press: 06 July 2010
- Frontmatter
- Contents
- Preface
- Dedication
- Note on some conventions
- 1 Introduction
- 2 Our Galaxy
- 3 The large-scale structure of the universe
- 4 Elementary particles – a preliminary look
- 5 Is the universe open or closed?
- 6 Three ways for a star to die
- 7 Black holes and quasars
- 8 Galactic and supergalactic black holes
- 9 A black hole is not forever
- 10 Slow and subtle changes
- 11 Future of life and civilization
- 12 A collapsing universe
- 13 The steady state theory
- 14 The stability of the proton
- 15 Epilogue
- Glossary
- Selected bibliography
- Index
Summary
In the previous chapters we have been concerned with the future of the universe if it is open, that is, if it will expand forever. The ultimate fate of the universe is dramatically different if the universe is closed, that is, if it will stop expanding at some future time and start to contract. If indeed the universe is closed, what is the time scale in which it will stop expanding and start to contract? This depends on the present average density of the universe. Models of closed universes can be constructed with arbitrarily long time scales for contraction by taking the present density to be above, but close enough to, the critical density mentioned in Chapter 5. Thus, in principle, it is possible to have a closed universe to expand for 10100 years before it starts to contract, so that most of the processes mentioned in the previous chapters will take place and then many of these processes will be reversed. If the universe is closed, however, it is extremely unlikely that its life-time will be as long as 10100 years.
Suppose for the sake of argument that the present average density of the universe is twice the critical density. Recall that in the simpler (Friedmann) models the closed universe has a finite radius. The universe will then expand until its radius is about twice its present value.
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- Information
- The Ultimate Fate of the Universe , pp. 112 - 114Publisher: Cambridge University PressPrint publication year: 1983