The atomic bomb brought nuclear physicists not only fame at large and fortune in government grants, but also parts in a tragic epic. Disinterested investigators of nature became allies or clients of the military or industry; according to their wartime leader, J. Robert Oppenheimer, nuclear physicists came to know sin. Abraham Pais, a distinguished theoretical physicist now at Rockefeller University, was not among them: He spent the war years hiding in an attic in Holland, working his way into the remote reaches of quantum electrodynamics.
"Inward Bound" is, in its author's opinion, an epic of the acquisition by physicists of their current knowledge about the fundamental structure of matter. His story begins with the great discoveries of the 1890s--X-rays, radioactivity, and the electron--and ends yesterday with the detection of particles that mediate sub-nuclear decays. He presents the story with very little reference to war or other external events. The forced emigration of physicists from Europe in the 1930s, which brought the leadership of theoretical physics to the United States, the demands and opportunities of industry, the contribution of the wartime projects to postwar work, all this has left as little trace in Pais' epic as if it had taken place in an attic.
About two-thirds of "Inward Bound" is a history of the subject from 1895 to 1945; the remaining third is a memoir about subsequent developments. The division at 1945 agrees only coincidentally with the end of World War II. With the liberation of the Netherlands, Pais entered the international community of physicists. His memoir of the postwar years is informed and enlivened by his direct participation in the construction of modern theories of elementary particles.
All aspects of atomic, nuclear, and elementary-particle physics would seem to be candidates for inclusion in "Inward Bound." Pais' criteria for admission are not easy to discern. With the important exceptions of the discoveries of the 1890s, the unraveling of beta decay, the checkered history of quantum electrodynamics, and postwar particle physics, the book is more episodic than epic. It is punctuated by what Pais calls "interludes," "interruptions," and "postscripts." It contains many interesting irrelevances, flashbacks to points as far distant as the 18th Century, odd inversions of chronology, and well-told if inappropriate anecdotes ("Apropos of nothing, I recount one more Rutherford story").
The jumping back and forth is not the least difficulty placed in the path of the general reader. The demand for special knowledge, minimal at the outset ("electron volt" is defined on the first page), rapidly escalates; the account of Pauli's exclusion principle, encountered a third of the way through, will exclude many; and anyone who reaches the last third is advised by the author to bring along an advanced text of quantum mechanics. There are no diagrams, even of experimental apparatus, to assist comprehension or indicate the appeal to visual imagery common among physicists.
Readers prepared to put up the required ante will find much to reward their effort: long quotations, for example, from the discoverers of the 1890s; uncommon information about Dutch physicists; a good outline of the contributions of Oppenheimer's school during the 1930s; appreciations of the work of J. J. Thomson and C. D. Ellis; Pais' memoir of postwar particle physics; and his asides about people he knew and knows. Pais has a great store of information gathered from wide reading and long experience. Although his identifications of the best or most useful histories are questionable, especially for the older periods, his references to sources are a notable and useful part of his book.
Physicists have not only made, but written most of the history of 20th-Century physics. About 25 years ago, however, historians started to assemble archives, publish correspondence, establish bibliographies, and write accounts of the branches of physics with which Pais was concerned in "Inward Bound" and in his well-received study of Einstein, "Subtle Is the Lord" (Oxford, 1982). Pais has examined much of the historians' work, and used some of their results, which is not typical of physicists writing about the recent past of their discipline. Not that Pais approaches his subject as a historian would: His epic is the inevitable acquisition of "correct" theory in the face of prejudice, ignorance, and misinterpretation.
Whence the inevitable? Pais faces up to the problem: Things happen when the time is ripe. What ripens it? Something teleological, even mystical: "A new generation was preparing," he and it somehow discerned, "for what was to come." An advanced potential, or influence of the future on the present, is not as acceptable in history as it is in physics.
Why did relativity and quantum theory develop on the Continent, the theory of atomic structure at first in Britain? Why do Italian, Japanese, and Soviet physicists make no appearance in Pais' story until the 1920s, and then figure prominently in it? Why has the subject of "Inward Bound," reductionist physics, dominated the discipline in our century? Does the shift in physicists' vocabulary from solemn neologisms grafted onto Latin and Greek roots to jocularisms like "quark" and "gluon" have any significance? How have the Americanization of high-energy physics, the use of computers, the imperatives of particle accelerators and detectors influenced the choice of problems attacked and answers accepted?
Pais does not address these sorts of questions. They are historians' questions. Their answers nonetheless belong as much to the epic of modern physics as Pais' large and valuable inventory of conceptual advances.