Spin Foam

Michael Redhead

• Three Roads to Quantum Gravity: A New Understanding of Space, Time and the Universe by Lee Smolin
  Phoenix, 231 pp, £6.99, August 2001, ISBN 0 7538 1261 4

The old notions of space and time are currently being turned upside down by theoretical physicists in their attempt to reconcile the two great pillars of 20th-century physics: quantum theory and Einstein’s general theory of relativity. Lee Smolin, a major contributor to the subject, brings us right up to date with it in this book. It’s written for general readers, but is more than just another work of popular science: it is a serious attempt at clarifying the author’s own thoughts about the significance and interpretation of the highly mathematical theories he is discussing. The book belongs to a new genre of science writing, in which the author also tells the story of his own involvement in the research, so giving it a striking freshness. It’s reminiscent in this way of Brian Greene’s very successful The Elegant Universe, a book which covers some, but by no means all, of the same ground as Smolin. Indeed, the two complement each other nicely, for anyone who wants to understand, in more than a superficial way, what is currently happening to the deep conceptual foundations of physics.