The remarkable developments in atomic, nuclear, and quantum physics in the early 20th century before the outbreak of World War II have been the subject of so many books and articles that one might think that there is little more to be said about them. Any such notion will be soundly dispelled by this new treatment by Roger Stuewer. Stuewer, a distinguished historian of science, will be familiar to many AJP readers. Being the Founder of the Program in the History of Science and Technology at the University of Minnesota, he has published extensively on the history of nuclear physics, particularly in the areas of George Gamow's theories of alpha decay and the liquid-drop model of the nucleus, and the discovery and interpretation of nuclear fission. Awarded the Abraham Pais Prize for History of Physics in 2013, Stuewer is now formally retired but is still active; this volume can be regarded as a worthy capstone to his career.
The Age of Innocence covers developments in nuclear physics over the 20-year span from the time of Rutherford's discovery of artificial disintegration of nuclei in 1919 to the discovery of and early efforts at understanding nuclear fission in late 1938 and early 1939. The litany of discoveries and inventions during this time is astonishing. In addition to artificial disintegration and fission, there was the development of quantum mechanics and its application in modeling alpha-decay, the discoveries of the deuteron, positron, and neutron (all in 1932), alpha-particle-induced artificial radioactivity, the Cockcroft-Walton accelerator, cloud chambers, Ernest Lawrence's cyclotron, Dirac's theory of the electron, Fermi's theory of beta-decay, Bohr's concept of compound nuclei being formed as an intermediate step in reactions, and Fermi's discovery of the efficacy of slow neutrons in inducing radioactivity. Stuewer covers all of these topics and more in great detail.
The title of this volume reflects the fact that researchers had in mind no practical application for nuclear energy; their motivation was pure science. In 15 chapters that proceed largely chronologically, Stuewer explores the work of researchers in Cambridge, Paris, Copenhagen, Berlin, Rome, Berkeley, Vienna, Leningrad, and other locations, examining how institutions were shaped by powerful individual personalities and the political, cultural, and national environments within which they operated. Each was distinct, but they did not exist in isolation: Researchers kept each other apprised of their work and discoveries through preprints, journal papers, personal visits, student migrations, and meetings such as the famous Solvay conferences. In all, this gave rise to a remarkable cadre of experimental and theoretical researchers, some extremely young, who revolutionized the concepts of the atomic structure in a single generation.
Competition between research groups was mutually respectful but vigorous and occasionally punctuated by episodes of controversy and strong disagreement. A particularly notable example of this was a challenge to Ernest Rutherford and his group in Cambridge by a group at the Vienna Institute for Radium Research concerning what elements exhibited proton emission under alpha-bombardment. The Vienna group claimed that they could detect proton emission by many elements, particularly heavy ones, from which Rutherford and James Chadwick could detect no activity. The claims were regarded as suspect on the basis that the bombarding alphas should be unable to surmount the Coulomb repulsion of the target nuclei. The controversy became extremely heated, with publications of claims and counter-claims bordering on personal attacks. The issue was not resolved until Chadwick visited Vienna personally in late 1927 to witness experimental techniques used at the Institute. He found that the claimed detections were a product of psychological biases on the parts of a cadre of female scintillation counters who had been told in advance what was expected of various experiments, a protocol strictly avoided in Cambridge. Magnanimously, the British chose not to embarrass the Vienna group by demanding a retraction; the latter just ceased publishing on the matter. The Cambridge group emerged victorious, and the affair emphasized the need to develop electrical counting methods in order to remove the human equation from measurements.
While I was familiar with much of the history that Stuewer relates, I did learn some things which I did not previously fully appreciate, such as how Frederick and Irène Joliot-Curie's discovery of artificial radioactivity might have been triggered by a suggestion made by Francis Perrin, why Fermi began his search for neutron-induced radioactivity by bombarding heavy elements, and some of the nuances surrounding Niels Bohr's revelations regarding the physical understanding of nuclear fission that occurred to him in early 1939. A feature of this volume I particularly enjoyed is its numerous biographical vignettes, not only of the major players but also many of the less-famous ones as well. These can occasionally be repetitive but help make each chapter more self-contained and give the story great humanity. The book is well-illustrated with photos and drawings from the original literature; readers will enjoy following the evolution of ideas. Unlike what is often implied in textbooks, readers are continually reminded that breakthrough ideas rarely emerge fully formed from the minds of their originators: There is often a lengthy gestation period of conflicting experimental results, misinterpretations, and partially correct theoretical hunches before a fog of confusion lifts to reveal a clarity that always looks so obvious in hindsight.
The early history of nuclear physics cannot be disentangled from the turbulence of the times in which it occurred. As nuclei were being disintegrated with ever more powerful machines, the political situation in Europe disintegrated in parallel. The golden age began to end with Hitler's accession to the Chancellorship of Germany in 1933 and the exile of Jewish scientists to Britain and America. The fascist plague soon spread to Austria and Italy, and Stuewer chronicles the efforts of organizations such as the Academic Assistance Council (Britain) and the Emergency Committee for Aid to Displaced Foreign Scholars (America) in supporting displaced academics. Some exiles such as Enrico Fermi and Hans Bethe went on to distinguished careers in America, while others such as Lise Meitner managed to escape but had their careers essentially ruined. Meitner's case remains particularly poignant in that Otto Hahn later actively disavowed her role in the discovery of fission even though he had met with her in Copenhagen as late as November, 1938, to discuss the struggles he and Fritz Strassmann were having in trying to understand the results obtained in their uranium-bombardment experiments. Many others, of course, suffered infinitely worse fates. In reading Stuewer's descriptions of the “intellectual decapitation” of Germany, this reviewer could not help but think about current events in America.
I take issue with a part of one of Stuewer's capsule biographies. He describes Fermi's family life as warm and close-knit (p. 289), but this characterization is at odds with other recent biographies such as Gino Segrè and Bettina Hoerlin's The Pope of Physics (Henry Holt, 2016) which indicate that he was in fact somewhat remote from his children. But this is a minor quibble; to his credit, Stuewer should be lauded for not falling into the temptation of trying to psychoanalyze the thoughts and motivations of his subjects long after they are gone. Overall, he has produced a masterful single-volume history and exhaustive reference of inter-war nuclear physics, a testament to his decades of work in this area. This volume will especially be a keeper reference even for readers closely familiar with its subject matter. Notes for each chapter contain copious references to the original literature, the Bibliography runs to nearly 40 pages, and there are extensive Name and Subject Indexes. This book should be read by any serious student of the history of physics.
Cameron Reed is the Charles A. Dana Professor of Physics at Alma College, emeritus. He served as the editor of the American Physical Society's “Physics & Society” newsletter from 2009 to 2013 and is currently the Secretary-Treasurer of the APS's Forum on the History of Physics. His interests lie in the physics and history of nuclear weapons; his text “The History and Science of the Manhattan Project” was published by Springer in late 2013.
