by Howard Baer and Alexander Belyaev (eds), World Scientific. Hardback ISBN 981238412X, $77 (£57).
Sitting in an undergraduate lecture, being introduced to the Dirac equation for the first time, I found myself wondering “How on earth did he come up with that?” My hope for this book was that it might provide some insight into what made Paul Dirac such a great physicist. I think that it was satisfied to some extent.
2002 was the 100th anniversary of Dirac’s birth and this book constitutes the proceedings of a symposium held at Florida State University, where Dirac held a faculty position during his last 14 years. There are 13 contributions from the speakers, more-or-less centred around areas of Dirac’s interest. The anecdotes sprinkled throughout are particularly entertaining to read, especially for younger readers who may not have heard many of them.
Dirac’s daughter, Monica, writes an endearing account of her father, the family man, with obvious warmth and affection. Memories such as Dirac measuring the length of the cat’s whiskers to make sure he’d fit through the cat-flap warm the heart. His love of walking, swimming outdoors and classical music also shines through.
Despite not being able to attend due to a snow storm, Frank Wilczek contributed an outstanding essay (contrary to some speakers who are named and shamed for not contributing). It starts with a discussion of the Dirac equation and leads in sometimes surprising directions: considerations of the possibility of artificial intelligence, for instance. Wilczek’s views on what one may learn from Dirac’s approach to physics is interesting, and we see from various contradictory quotations that Dirac sometimes changed his mind. In particular, there are several quotes about Dirac apparently not worrying too much about experimental results, but Wilczek exposes Dirac’s delight when the prediction of his equation that the ratio of the magnetic moment of the electron to its spin equals two was supported by data. William Marciano follows with a nice and succinct review of this latter topic. Later, Dirac also lost faith in “his” monopole due to the lack of experimental evidence.
There are good introductions to time variations of fundamental “constants” by Paul Langacker and neutrino physics by Vernon Barger, which will appeal to those of a more phenomenological bent. Some of the M-theory/brane and string-oriented contributions by Pierre Ramond, Roman Jackiw and Joe Polchinski will probably appeal to the more mathematical physicist. The contribution of Leopold Halpbern is frankly annoying, however, after he starts discussing his own work in general relativity, and I found Maurice Goldhaber’s resolution of the fermion mass problem bizarre and too heuristic.
So how did Dirac contribute so much important work? It seems by doggedly hanging on to an elegant idea that solves a difficult problem, then frequently changing methodology; certainly by looking for mathematical beauty but also by taking note of other theorists’ work and experimental data. Oh, and plenty of long walks.
