Boltzmann's Atom: The Great Debate That Launched a Revolution in Physics

  • David Lindley
Free Press: 2000. 256 pp. $24
Atomic force: Boltzmann linked thermodynamics to the concept of atoms and molecules. Credit: CORBIS

The Zentralfriedhof on the edge of Vienna is a place of pilgrimage for many tourists. The city's largest burial ground, it has a special section, the Ehrengrüber, where Beethoven, Schubert, Brahms, Strauss and various Viennese Bürgermeister are buried. Among these luminaries lies one of the great heroes of modern-day physics, Ludwig Boltzmann. His tombstone is inscribed with the simple equation, S=klog W, which may bemuse visiting music lovers but is a fitting tribute to the man who linked the phenomenological science of thermodynamics to the concept of atoms and molecules.

The true Boltzmann enthusiast (which it must be admitted includes the reviewers) would probably also visit the city of Graz, where Boltzmann spent his most productive years.There they could view the magnificent display of physical instruments he and his colleagues built for instructional purposes. Few, if any, university lecturers today would put such enormous effort into teaching — after all, it is research that brings in the money.

Unfortunately, there are no definitive biographies of Boltzmann because of the scarcity of personal records about his life outside science. There is, however, a wealth of information about his scientific activities and his interactions with the worldwide scientific community. David Lindley has drawn on these latter sources to produce, not a biography of the man, but rather a biography of an idea — the debate about the existence of atoms that raged in Europe in the latter years of the nineteenth century. All the familiar characters — Mach, Ostwald, Planck, Stefan, Maxwell, Einstein, Gibbs to name only a few — come alive for the reader through entertaining explanations of their work and ideas coupled to insightful glimpses of their personalities.

But the real core of this book is atomic theory as viewed by the great and the good from about 1865 to 1906, when the unfortunate (and certainly unstable) Boltzmann committed suicide. By this time, all but the most diehard of the “energeticists” had accepted the reality of atoms. The philosophical differences between those who believed in the unseen atoms and those who didn't are an important part of the story, as are the cultural differences among the adversaries. In England there was little or no resistance to atomic theory other than from the then aged and crotchety Lord Kelvin, who in 1900 is described in a letter from Josef Nabl to Stefan Meyer in Cambridge as “a silly old idiot”. But in the rest of Europe, many scientists were still in thrall to a Germanic philosophy opposed to theorizing about the 'unseeable'. They believed that all physics should deal only in the realm of the observable, with ultimate truth lying in empirical laws that described such phenomena. Had Boltzmann lived in England rather than Austria, he would certainly have had an easier time.

Lindley gives a superb account of the protracted attempt to explain the second law of thermodynamics in statistical terms, first by James Maxwell and then by Boltzmann. Both men envisaged matter as consisting of atoms obeying classical Newtonian laws. The confusion engendered by Boltzmann's H-theorem, and his attempts to explain away the anomalies in its implications that others discovered, is one of the best exposés of the subject we have read (albeit somewhat repetitious at times). The only slight flaw in Lindley's rendering of the debate is his failure to point out that those who opposed the statistical approach did have one reasonable objection — that classical statistical mechanics (as it came to be called by J. Willard Gibbs in 1901) could not explain the specific heats of gases. This problem had to await the advent of quantum theory in the early 1900s.

Another strange omission is from the early part of the book, in which the history of the idea of atoms is described in great detail. How can one go from the early Greeks to Maxwell's kinetic theory of gases and ignore the “father of the atom”, John Dalton? Perhaps the explanation lies in the age-old antagonism between physici- sts and chemists: Lindley was trained in the former discipline whereas Dalton, of course, is claimed by the chemists as one of their own.

It is a great temptation to shower superlatives on a delightful account of one's favourite topic, and here we plead some personal bias. But, with that caveat, we enthusiastically recommend this book, not only to chemists and physicists, but to any scientist with an interest in the history of the subject. Perhaps that category should include us all, since we have grown up in a world firmly founded on the certainty of the chemical/physical atom.