Martin Rees


This is the latest in the impressive series of books by Martin Rees that look at the present state of cosmology. It is based on a series of lectures given by Rees at Princeton University for a general audience, and the tone is therefore popular rather than technical. It covers a wide range of topics, but it is given an underlying unity by Rees's fascination with Einstein's question: "Could God have made the universe any differently?" In other words, is our universe the only one that could exist? This leads quickly to another question: if this is the only possible universe, why is it so finely tuned for life? As readers of Rees's earlier books will know, he favours the view that our universe is only one of an enormous multitude of other universes, most of which are unsuitable for life. Hence he speaks of the multiverse, in which the physical laws governing our universe are no more than local bylaws: the outcome of historical accidents during the initial instants of our particular Big Bang. "Our entire universe is a fertile oasis within the multiverse." Such ideas might seem to border on metaphysics, but Rees argues that they are within the bounds of empirical science.

The book is in three parts. The first part, "From Big Bang to Biospheres", starts with planets and stars and moves on through galaxies and pregalactic history to end with black holes and the possibilities for time travel. Part Two, "The Beginning and the End", considers what we know about the origin and ultimate fate of our universe. An important issue here is the mysterious dark matter, the unknown stuff that makes up most of the universe. Depending how much of this there is, the universe will either expand for ever or collapse back into a fireball like that from which it emerged. Rees thinks that we shall know the answer by the year 2010.

The final part, "Cosmos and Microworld", is the most speculative. This is where Rees discusses the multiverse idea and confronts the criticism that it is too speculative to count as science. The physics of the future, he suggests, may make the existence of multiple universes appear a necessity, but even with present-day physics it may be possible to test the hypothesis to some extent. Rees suggests that there are certain physical constants, such as lambda (the energy latent in empty space that causes a repulsion), whose values could be used to test whether our universe is typical of the habitable subset that could harbour complex life. In other words, is our universe a representative member of the subset that permits life, or is it a freak? If it is a freak, this would disprove the multiverse hypothesis.

Rees is a clear and elegant writer who does an excellent job of presenting the quite extraordinary ideas of modern cosmology for the non-mathematical reader.

%T Our Cosmic Habitat
%A Rees, Martin
%I Weidenfeld and Nicolson
%C London
%D 2001
%G ISBN 0-297-82901-7
%P xvii + 205 pp
Titles | Authors | Subjects