We live in a world to which we are uniquely suited. The Earth is the right type of planet, moving round the right type of star in the right type of galaxy. Were this not so, we would not be here. But is our universe the only one - or can there be others, existing in different dimensions, that we cannot see and with which we have no contact? This idea of "parallel universes" is only one of the many concepts discussed by astronomer royal Sir Martin Rees in this fascinating book.
The text is divided into three main sections. The first of these, "From big bang to biospheres", describes the universe as we see it today. Certainly our opinions have changed beyond all recognition over the past few decades. For example, we now know that other stars are indeed the centres of planetary systems, and Rees is by no means sceptical about the chances of life elsewhere, though he feels that the answers may come from biology rather than astronomy.
We are exploring the solar system: "During the first decade of the 21st century, probes will trundle across the surface of Mars and even fly over it, they will land on Titan, Saturn's largest moon, and samples of Martian soil will be collected and brought back to Earth." Within 20 years, we may well have direct views of planets of other stars.
Beyond the solar system, this section deals with topics such as stellar evolution, black holes, new ideas about gravity and the nature of the mysterious dark matter that seems to pervade the entire universe as we know it.
We then turn to "The beginning and the end", devoted mainly to the evolution of the universe. There are speculations about the big bang (a term first used by the late Fred Hoyle, who did not believe in it) and about the universe's eventual fate. There can be no doubt that the groups of galaxies are receding from each other, so that the universe is expanding, but Rees is suitably cautious about recent claims that the rate of expansion is accelerating. As he points out, the evidence for acceleration is strong, but it is not conclusive, so further research is needed. Moreover, what exactly is "quintessence", the force in space that drives the expansion? We have to admit that we do not know.
The book's last section, "Fundamentals and conjectures", is the most rivetting. Can it be true that our universe is only one of many, and that others exist in different dimensions completely inaccessible to us? If so, our universe has been designed on a "special recipe", and most of the other universes may be hostile to life of our kind. Rees is sympathetic to ideas of this type: "The multiverse concept is already part of empirical science, and we may already have indications of other universes." One comment he makes is particularly telling: "Our universe is a fertile oasis within the multiverse."
The book is well produced, and I have found only two misprints: on page ten the star 51 Persei should be 51 Pegasi; and the cover picture is not a star cluster, as stated on page 78, but a display of aurora. The illustrations are adequate, and there is a useful index.
Rees is one of the great astronomers royal; he is a leading cosmologist, and his skill in writing what may be termed popular science is probably unequalled today. I know of no other author who could present such difficult concepts in so lucid a manner. This is a brilliant book, to be read and enjoyed by all.
Sir Patrick Moore is the author of more than 60 books, mainly on astronomy.
Our Cosmic Habitat
Author - Martin Rees
ISBN - 0 297 82901 7
Publisher - Weidenfeld and Nicolson
Price - £14.99
Pages - 205