But, according to Smolin, the downsides are even greater. The trouble with string theory is that consistency with special relativity and quantum mechanics requires extra spatial dimensions. The world we live in has only three directions - up, down and side to side. String theory seems to require an extra six.
The fact that we cannot see these extra directions is not necessarily a fatal flaw. If some of the nine directions are curled up small enough, we would not be able to perceive them after all. And the precise details of the ways in which six directions are squashed together offer a chance of pulling off the second half of the unification project, a chance to explain why it is that the particles and forces look so different even though they all come from strings.
A dizzying variety of theories now results, whose workings are so fiendishly difficult that thirty years of work and two major breakthroughs later, no one can say for sure that a consistent theory actually exists.
Smolin then spends the next sixty pages mapping out alternatives, focusing mainly on an intriguing suggestion he is working on for unifying gravity and quantum mechanics called loop quantum gravity, before returning to examine string theory's dominant position within theoretical physics. He describes an arrogant, cult-like sect imbued with a tremendous self-confidence, dominated by a few strong leaders, which values mathematical facility over original thought.
According to Smolin, string theorists show little interest in work going on outside string theory, a "cavalier" attitude to distinguishing between conjectures and results, and an avoidance of risk, though he offers no convincing account of how such a sinister cabal has managed to seize power. He tries repeatedly to depersonalize his attack, stressing that he admires and respects both individual string theorists and much of their work, but it would be naive to suppose that such assurances carry much weight with those whose professional lives are under assault.
A quick detour into the philosophy of science offers a just-so story which describes science as a community of sceptics, a story advanced with a cheerful optimism and unthinking realism that will hearten and dismay philosophers of science in equal measure. Smolin follows Thomas Kuhn in dividing science into "normal" and "revolutionary" phases, and suggests that different types of scientist are needed for each phase. Until consensus is established, "seers" are needed to come up with a wide range of approaches to outstanding problems.
When the evidence "forces consensus", "master craftspeople" can then rapidly achieve results with the agreed theoretical machinery. According to Smolin, the problems that confront twenty- first-century physics require a generation of seers, but physics departments are structured to produce a generation of craftspeople. He sketches a few proposals for reform that would be hard to disagree with - "young scientists should be hired and promoted based only on their ability, creativity and independence"; "people who invent and develop their own research programmes should be given priority"; "people should be penalized for doing superficial work that ignores hard problems" - and some that seem arbitrary or impractical: "when there is a recalcitrant but key problem, there should be a limit on the proportion of support given to any one research programme that aims to solve it - say, a third of total funding". He finishes with an appeal to scientists, department heads and the general public to think for themselves.
It is difficult for the non-specialist to come to an opinion about the merits of differing approaches to resolving the outstanding problems in theoretical physics, but that should not deter readers - it is difficult for theoretical physicists to decide themselves. One of the most attractive features of The Trouble with Physics are Smolin's descriptions of what it is like to do theoretical physics. His encounters with physicists who have other ideas give an inkling of the excitement of new insights; his decisions about which avenues he should pursue give an indication of the difficulties in being confronted with an intellectual choice that could determine the future course of your career. He compares working in string theory to "doing your income tax every day, all day, for a week, and still not getting the calculations to add up consistently". Theoretical physics is hard. The problems with string theory may be nothing more than a reflection of its difficulty - and there is no reason to suppose that the universe is constructed so that it is easy to work out how everything fits together - or they may be because of some fundamental flaw. At the moment there is no way of telling. Smolin's homespun account of how science works is no help to us now. String theory seems unlikely to produce a workable theory of everything any time soon, exerts an influence on the academy and on the popular imagination quite out of proportion to its questionable successes, and may well turn out to be nothing more than an interesting dead end. There are certainly other approaches worth exploring - I have a hunch Smolin's suggestion that time needs some attention has something in it - but it is worth remembering that nobody is forcing young scientists to become string theorists.
Smolin has little new to say about how the institutions of science are undermined by personal ambition, internal politics and bureaucratic overload - as he himself admits. Designing institutions that are transparent and robust is also hard. Finding and rewarding the candidates who can think in new ways that are not only radical but also useful is a problem that confronts even the software companies and music conglomerates of which he is so enamoured. The "seer" who comes up with the fundamental insights needed to resolve the unfinished business of twentieth-century physics is as likely to be found outside the academy as within it. The Trouble with Physics offers an engaging take on the state of fundamental theoretical physics, mercifully free of the thumbnail character sketches that dog much popular science, and is all the more readable for its unashamedly partisan nature. While talk of a "crisis" in physics is surely overblown - physics goes on peaceably in neighbouring fields after all - it is perhaps unsurprising that a guide who really knows the territory does not scruple to take sides when talking about a local dispute.
