Time is real -honest

Like most popularisers of science, Lee Smolin reacts to this challenge by just leaving out the maths. "There are no equations," he says in the preface, "and everything you need to know to follow my arguments is explained." But, as Smolin must surely know, without the equations it is impossible to convey everything one needs to know to follow his arguments. This is especially true in his case, because he is not popularising accepted theories of physics; he is putting forward a speculative new foundation for the whole of theoretical physics that challenges much accepted wisdom.

In order to assess the cogency of his ideas, or even to follow the gist of what he is saying, a lot of difficult stuff needs to have been mastered. One needs, for example, to understand the currently accepted "standard model" of particle physics (bosons, hadrons, fermions and all that). One also needs to have some grasp of quantum mechanics and relativity theory and why it has proved so difficult to bring them together to form a unified theory - the formidable problems, for example, of trying to understand the force of gravity (one of the four fundamental forces of the standard model) in a quantum mechanical way. One needs to understand all this, because Smolin's contributions to physics lie at the cutting edge of the discipline; one cannot understand them without understanding the questions that contemporary physicists are wrestling with. Among physicists, Smolin is best known for his work on "loop quantum gravity", a theory that cannot easily be made accessible to a non-specialist audience.

This has not stopped Smolin from trying. His three previous books -Life of the Cosmos (1997), Three Roads to Quantum Gravity (2001) andThe Trouble with Physics (2006) - were, ostensibly at least, aimed at non-specialists. Like them, Time Reborn tries not only to convey an understanding of the difficulties faced by contemporary physicists, but also to advance novel solutions to those problems. As it turns out, however, at the heart of Smolin's proposed solutions to what he calls the "crisis of physics" is a philosophical view that should, in principle, be easier to grasp.

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