Maxwell's Demon: Why Warmth Disperses and Time Passes

  • Hans Christian von Baeyer
Random House: 1998. Pp.185 $25

Adolf von Baeyer won a Nobel prize for chemistry in 1905 for his work on organic dyes and hydroaromatic compounds. His name, this book tells us, appears alongside those of other luminaries of science on a plaque outside the headquarters of the German Physical Society in the former East Berlin.

His great-grandson, Hans Christian von Baeyer, spends his summers in Paris engaged in the “vulgarisation de la science ”. Here he has written for the general reader a popularized introduction to thermodynamics, the second half of which gives the life history, so far, of a ‘demon’. This amusing creature was introduced by James Clerk Maxwell but was named by Lord Kelvin. They thought it could help to violate the second law of thermo-dynamics, by sorting out the fast molecules in a gas from the slow ones to produce a temperature difference in a gas that was previously at a uniform temperature.

Von Baeyer discusses the ups and downs of the demon's life, pointing out that it was thought to have been ‘killed’ (on paper only, of course) several times, only to emerge again with a new trick up its sleeve. Perhaps it might have been emphasized more that the second law is in fact valid in the domain of macroscopic physics, whatever manipulations one imagines to be carried out with atoms. In the course of the story, entropy and probability theory are also discussed.

This is an enjoyable book that is easy to read. Much of the history of thermodynamics related by von Baeyer is familiar, and one would not expect much novelty in this area. But the story is skilfully put together: von Baeyer has read widely, and discusses very fully Richard Feynman's ratchet-and-pawl device for possibly breaking the second law. Perhaps he misses the odd trick by not mentioning that the demon has also entered recent discussions on quantum computing. Occasionally one may question his judgement, for example when he introduces a parable in chapter 8 that does not seem to add much to the story.

The law of conservation of energy is “as close to an absolute truth as our uncertain age will permit”. Well put! But readers may recall the uncertainty principle, which allows energy to be ‘borrowed’, breaking conservation, if this is done for a short enough time.