Lee Smolin

THE TROUBLE WITH PHYSICS

The rise of string theory, the fall of a science, and what comes next

The book has four parts. Part 1 is an overview of modern physics, in which Smolin identifies five main questions which are still unresolved in the aftermath of the revolutions brought about earlier by quantum theory and general relativity. Here he has a very interesting chapter called "The Beauty Myth", in which he shows that some very appealing theories which intuitively look as if they ought to be right have nevertheless failed. He suspects that string theory may prove to be one such.

This is the subject of Part 2. String theory has experienced a remarkable reversal of fortune. When it was first put forward, in the 1970s, its originators encountered strong opposition and their academic careers suffered. Only a handful of researchers were working on it. Then, in the 1990s, there occurred what Smolin has no hesitation in calling a revolution and soon almost everyone was working on string theory. "It appeared to offer, in one bold and beautiful stroke, a solution to at least three of the five great problems of theoretical physics." Smolin explains the reasons for its appeal clearly for the non-specialist reader.

Two decades later, over a thousand of the world's most talented and highly trained scientists have worked on string theory, but Smolin finds that the original promises are still unfulfilled. It is not a fundamental theory. There may be a fundamental theory—so-called M-theory—but it has not yet been invented and may not exist. In the meantime we have a truly enormous number of possible versions of string theory and no good evidence for which of them, if any, really describes nature.

Are there any alternatives to string theory? Plenty, Smolin thinks, and in Part 3 he describes some of them. He believes that we may need to question fundamental assumptions, including, for example, Newton's law of gravity or the speed of light at earlier times in the universe. There is also quantum gravity, on which he has worked himself. He does not say that string theory is a waste of time or should be abandoned, but he deplores its dominance in physics today and also is repelled by what he finds is the near-religious attidude to it adopted by some of its practitioners.

Part 4 is different in tone from the rest of the book being concerned less with the nature of physical theories and more with the politics of university physics in the USA. It is therefore aimed mainly at Smolin's fellow-academics and especially at university administrators, though some of the points he makes certainly have wider relevance.

Smolin finds that there are at least two kinds of scientist, whom he describes as seers and craftpeople. Science has need of both at different times, but at present we need seers. Physics is in crisis. "It can break down, and I believe it is doing so now … We need real seers, and badly."

Seers have difficulty in getting academic appointments because their ideas are different from those of the majority. This is not a new problem: the prime example of a seer is Albert Einstein, who had to work outside the mainstream as a young man, but things are worse today. Smolin lists a number of modern seers, including Julian Barbour, who has chosen to work entirely outside conventional academia but whose ideas have been influential among physicists working on quantum gravity.

Smolin concludes with a plea for critical independent thought. "If you cannot give a precise defense of your belief and commitments, consistent with the evidence, if you let other people do your thinking for you (even if they are senior and powerful), then you are not living up to your obligations as a member of a scientific community." I should say that this admonishment has wider application even outside science.

16 May 2008