BOOK REVIEW / A brief collision with the beginning of time: Dreams of a final theory - Steven Weinberg: Hutchinson Radius, pounds 20

ACCORDING to the grapevine on Capitol Hill, the dollars 8bn Super Collider atom- smasher is likely to emerge from the imminent budgetary carnage wounded rather than dead. The American physicist Steven Weinberg will be crossing his fingers: as he explains in this provocative book, the collider is desperately needed to provide clues towards the final theory of nature which is now on the cards.

The theory would form the irreducible core of our knowledge of the physical universe. Everything from the structure of a snowflake to the arrangement of stars in the Milky Way would ultimately be comprehensible in terms of the theory's underlying principles, although phenomena such as consciousness would probably remain outside its scope. Yet many sceptics dismiss the hope as unrealistic and - lowering their voices to murmur a dirty word - reductionist.

Weinberg tells us in trenchant terms why he believes physicists are within an ace of a final theory, and he outlines - using not a single equation or diagram - its expected shape and essential features (God's presence is not among them). He devotes considerable space to fierce rebuttals of armchair critics of the physicists' venture. The contributions of most philosophers, including Wittgenstein, are dismissed as unimportant (except in so far as the work of some of them 'helps us to avoid the errors of other philosophers'), as are the unfavourable observations of some sociologists.

While Weinberg may be accused of having a somewhat narrow understanding of the critics of modern science, no one will deny the authority of his views on physics. Among his many key contributions to the subject was a unified description of two of nature's fundamental forces, which later received strong experimental support and won him a share of a Nobel prize in 1979. He is what Americans call a 'big hitter'.

His belief that a final theory is more than a pipe dream seems to be based on his aesthetic intuition. As fundamental theories have encompassed more of nature's symmetries, their structures have become increasingly inevitable and rigid, qualities that Weinberg associates with beauty. Just as a perfect sonnet might be destroyed by altering a single word, so a beautiful theory is not readily susceptible to tinkering. Weinberg tries to describe the importance of beauty in assessing the value of theories, but I fear that for most of his readers he may as well be playing this particular tune on a dog whistle. The austere beauty of mathematical physics transcends even the most lucid words.

Having rhapsodised about its theories, Weinberg laments that particle physics is in a rut. While he and his fellow theorists have leapt ahead, the experimenters no longer have the means to test key predictions. They need to arrange collisions of uniquely high energy between sub-atomic particles so that they can examine the debris for clues about the final theory. Without the constraining results of these experiments, theory is in danger of becoming a branch of science fiction.

This is where the Super Collider comes in. Due to be built near Dallas, Texas, it would steer particles around a 53-mile tunnel at almost the speed of light, creating conditions that momentarily existed a fraction of a second after the creation of the universe in the Big Bang.

But Dreams of a Final Theory is much more than an apology for the Super Collider. It is a remarkably clear account of the scope and ambitions of modern physics. Majestically written, subtly yet powerfully argued, it is one of the best popular books on the subject. The sheer conceptual density of parts of it may daunt the nonspecialist, but I thought the same of Stephen Hawking's A Brief History of Time and look what happened to that.

Of course, the most interesting outcome of switching on the Super Collider would be experimental results indicating that the latest theories were wrong. The theorists might then be tempted to take consolation from a remark attributed to the late British astronomer Arthur Eddington: 'One should never believe any experiment until it has been confirmed by theory.'