BOMB HISTORIOGRAPHIES, I: BY ANALOGYSeveral months after the dropping of atomic bombs on Hiroshima and Nagasaki, on 2 November 1945 J. Robert Oppenheimer gave an address to the scientists at Los Alamos that many remembered years later. To gain some understanding of their situation, Oppenheimer told his colleagues one naturally looked for analogy, first to the development of relativity, atomic theory and quantum mechanics in the early twentieth century, and second to the era in which science had disentangled itself from religion in the renaissance. In the early twentieth century science had forced a reconsideration of the nature of reality and the relations between science and common sense; and still earlier its very existence and value had been in question. Oppenheimer thought his analogy imperfect, because nothing in the experience of building the bombs had involved revolutionary ideas.1 Yet both the events he lit upon and the limits he saw to the analogy reveal widely shared assumptions, which have arguably shaped much historical writing on physics in the twentieth century. When academic historians of science first began publishing on the twentieth century, a decade or so after Oppenheimer spoke, they were preoccupied with the subjects of Oppenheimer's analogy, perhaps for similar reasons, and sometimes to teach similar lessons about the relations between science and the everyday. They also incorporated the terms of his description into their analyses of scientific change; yet they rarely dealt explicitly with atomic bombs. After considering the contexts in which histories of physics were written before 1945 in this introduction, the second section of this essay will examine the characteristics of this early concentration of academic historiographical thought. Tracing trajectories of historical concern with relativity and quantum theory will show that in fifty years of historical research, a focus on revolution and ideas has never been fully shaken off, but it has been met by the challenges of social causation, by the demand to pay due attention to experiment and the material dimensions of science, by an interrogation of the political dimensions of work in physics and a concern with the institutions of big science, and also by the rise of cultural histories, some of whose central characters are not scientists at all. From the 1980s, historians have increasingly focused attention on Oppenheimer's situation and the complex demands of physics in the cold war era, so much so that this may well form the present centre of gravity of research in history of physics. Exploring the consequences and limitations of our now explicit concern with bomb historiographies will occupy the third and fourth sections of this essay.First, consider how understandings of the history of physics were shaped in the early twentieth century. Oppenheimer's sense ofthat history is likely to have been formed from a range of sources, but most viscerally through his education and research. As a student at Harvard from 1922 his voracious reading of science texts was so improbably impressive that he was allowed to shift straight from chemistry into upper level courses in physics. After graduating in 1925 he moved through Cambridge, Gottingen, and other European centres before fellowships at the California Institute of Technology and Harvard, and beginning teaching at Berkeley in 1929. There his work in the new quantum mechanics helped found a school of theoretical physics side-by-side with the ever-expansive experimental work on accelerators being led by Ernest Lawrence.2 In 1932, Oppenheimer wrote his brother Frank to say his work was fine, not in fruits but in the doing: We are busy studying nuclei and neutrons and disintegrations; trying to make some place between the inadequate theory and the revolutionary experiments.3 Had he looked for histories of his subject, between his reading in Sanskrit, of Plato, and physics, Oppenheimer could have drawn on only a few professional histories of science, and most of those focused on earlier centuries. …