Guide to the galaxies has universal appeal

To give an account of the history of the universe in a book fewer than 250 pages long is no easy task, but Joseph Silk has approached it with skill and obvious enthusiasm. As Savilian professor of astronomy at Oxford University, he is well qualified to act as a guide.

How much do we really know about the story of the universe, and how much of what we believe is based on firm evidence? It is generally thought that everything - space, time, matter - came into existence at one moment, about 13.7 billion years ago. This is always referred to as the big bang - a term coined scornfully by Sir Fred Hoyle, who never believed in it, and kept to the steady-state theory, in which it is argued the universe has always been in existence and will never die.

By now, ideas of this sort have been rejected, but we are still in the dark about the actual creation. Scientific analysis can take us back to the tiniest fraction of a second after the big bang, but for the earliest stages all analyses fail us. And what happened before the big bang, even if a "before" is admitted? These are some of the many questions that this book sets out to discuss.

Certainly there is so much that we do not know; for example, we are still unclear about the nature of the mysterious dark energy that seems to pervade the entire universe. We have to agree with what Silk says at the end of his book: "This is a time of wonder and awe and, like a child stepping into the darkness, we make our tentative gropings towards the ultimate theory of the cosmos."

Wisely, he begins by introducing the reader to the components of the universe, the general expansion, and the cosmic microwave background (weak radiation believed to be the last detectable manifestation of the big bang). He goes on to trace the sequence of events, from the earliest period that can be discussed scientifically (10-43 seconds after the big bang) through to what we see today.

He shows how it is feasible to construct theories of the birth, evolution and even the future of the universe, and to speculate about what will happen eventually: will the expansion continue until the groups of galaxies have lost touch with each other, and will matter itself disintegrate, thereby bringing the universe to its end? As yet, we cannot answer these questions, but we have made great progress in recent years.

Silk's book is not for the newcomer to astronomy, who will probably give up after the first few chapters. But this is not the author's fault: he is, after all, dealing with a demanding subject. However, the reader with a reasonable scientific background may struggle with some of the chapters but will, in the end, form a clearer picture of what cosmology is all about.

The reader who will benefit most is the serious inquirer, to whom the book will be invaluable. It is a mine of information, and it provides a bridge between the semi-technical and the really technical, filling a notable gap in the available literature.

The book is well presented; the plates are good, and the line drawings fully adequate. There is, however, one notable omission: a glossary. Not everyone will have heard of, say, the Higgs field, the quantum vacuum and Planck time. While all terms are explained in the text, many readers would welcome a list for quick reference.

This short history has been well worth writing. Readers who know little about astronomy would be advised to read some introductory texts before tackling it, but the serious inquirer should make haste to add it to his or her library.

Sir Patrick Moore is the author of more than 60 books, mainly on astronomy.