Explaining the universe - it's child's play

<i>Three Roads to Quantum Gravity</i> by Lee Smolin (Weidenfeld &amp; Nicolson, &pound;16.99)

Lee Smolin is best known for his book The Life of the Cosmos, which presented the startling speculation that our universe may be just one among a multitude and has literally evolved, by a Darwinian process of imperfect reproduction, from its forebears. Exciting and profound though these ideas are, they represent light relief from Smolin's day job: that is, his research into what many physicists see as the ultimate problem of their profession - the attempt to unify the general theory of relativity and quantum mechanics into one mathematical package known as "quantum gravity".

Lee Smolin is best known for his book The Life of the Cosmos, which presented the startling speculation that our universe may be just one among a multitude and has literally evolved, by a Darwinian process of imperfect reproduction, from its forebears. Exciting and profound though these ideas are, they represent light relief from Smolin's day job: that is, his research into what many physicists see as the ultimate problem of their profession - the attempt to unify the general theory of relativity and quantum mechanics into one mathematical package known as "quantum gravity".

Smolin has now attempted to explain this quest in general and his role in particular to a non-specialist audience. He has cautioned prospective readers of Three Roads to Quantum Gravity that they are likely to find it heavier going than The Life of the Cosmos; but to some extent, he has done himself an injustice. There are passages in this book that require concentration in order to follow the argument. But there are also sections that provide profound insight into the way physicists think and what that current quest is all about, at a level no harder to follow than the science stories that appear in this newspaper.

Some of the most delightful sections of the book are indeed those that focus on the people Smolin knows and has worked with. They go a long way towards counteracting the image of mathematicians portrayed so graphically recently by Essex schoolchildren. I also particularly enjoyed his debunking of the myth of Albert Einstein as a lone genius who needed no help from anybody in his own quest to unlock the secrets of the Universe.

Although the current search for a quantum theory of gravity is deeply mathematical, the philosophy behind the search is straightforward. It deals with the questions that every child asks at some time, but which most adults choose to ignore. Does space go on forever? How did time begin? How will the universe end?

The difference between the best physicists and ordinary adults is that the physicists have not lost this childlike sense of wonder at the universe we are living in and are still trying to answer questions like this. But they are also like children in other ways, and can become engrossed in one particular craze or fashion while ignoring equally valid schools of thought. The three roads that give Smolin his title are like that: three different approaches to quantum gravity that each have enthusiastic adherents who, in many cases, fail to understand, or deliberately ignore, the alternatives.

Smolin is rare in being a researcher at the cutting edge of this work who, although he has specialised in one particular approach, is aware of alternative approaches and realises that there is no one true path.

He is also aware of the real world of human and political relationships outside the ivory towers of science and makes an eloquent case for the need to encourage as many different approaches as possible to fundamental problems of science, rather than allowing available funds to be swallowed up in huge single-track projects.

For anyone who has followed the most way-out developments in physics in recent years, there is sure to be something here that will be familiar enough to be comforting. Perhaps it will be Julian Barbour's work on the nature of time, or the "many worlds" interpretation of quantum physics, or the idea of cosmic inflation, or string theory. But there is also sure to be something new for you to discover, and a great deal of pleasure to be gained from seeing how Smolin puts everything together to make a whole that is greater than the sum of its parts.

There are those difficult passages, and even some equations, but that makes it all the more satisfying when you penetrate to the nub of the argument. This is real 21st-century science, not some Mickey-Mouse popularisation of old ideas.

The reviewer is a visiting Fellow in astronomy at the University of Sussex; his latest book, 'Stardust', is published by Allen Lane