MAX-PLANCK-INSTITUT FÜR WISSENSCHAFTSGESCHICHTE Max Planck Institute for the History of Science 2008 PREPRINT 350 Christian Joas, Christoph Lehner, and Jürgen Renn (eds.) HQ-1: Conference on the History of Quantum Physics Max-Planck-Institut f¨urWissenschaftsgeschichte Max Planck Institute for the History of Science Christian Joas, Christoph Lehner, and J¨urgenRenn (eds.) HQ-1: Conference on the History of Quantum Physics Preprint 350 2008 This preprint volume is a collection of papers presented at HQ-1. The editors wish to thank Carmen Hammer, Nina Ruge, Judith Levy and Alexander Riemer for their substantial help in preparing the manuscript. c Max Planck Institute for the History of Science, 2008 No reproduction allowed. Copyright remains with the authors of the individual articles. Front page illustrations: copyright Laurent Taudin. Preface The present volume contains a selection of papers presented at the HQ-1 Conference on the History of Quantum Physics. This conference, held at the Max Planck Institute for the History of Science (July 2{6, 2007), has been sponsored by the Max Planck Society in honor of Max Planck on the occasion of the sixtieth anniversary of his passing. It is the first in a new series of conferences devoted to the history of quantum physics, to be organized by member institutions of the recently established International Project on the History and Foundations of Quantum Physics (Quantum History Project). The second meeting, HQ-2, takes place in Utrecht (July 14{17, 2008). The Quantum History Project is an international cooperation of researchers interested in the history and foundations of quantum physics. It has been initiated jointly by the Fritz Haber Institute of the Max Planck Society (FHI) and the Max Planck Institute for the History of Science (MPIWG) and is being funded from the Strategic Innovation Fund of the President of the Max Planck Society. In addition to the FHI and the MPIWG, the primary institutions of the project are the Johns Hopkins University, the University of Notre Dame, the University of Minnesota, the University of Pittsburgh, the University of Rostock, and the Universidade Federal de Bahia, Brazil. The aim of the Quantum History Project is to arrive at a deeper understanding of the genesis and development of quantum physics. While the main focus is on the birth of quantum mechanics in the period around 1925, the project also addresses further devel- opments up to the present time, including the theoretical and experimental practices of quantum physics as well as debates about its foundations. The project is conceived as a close collaboration of a large and varied international group of historians and philoso- phers of science as well as working physicists. Few scientific revolutions have drawn as much attention as the quantum revolution. We are fortunate that efforts in several places have built extensive archival records for historians to draw upon; and that some of the extant historical writings are models of scholarship. Parts of the existing literature, however, fail to meet the particular chal- lenges of writing the history of quantum physics. Unlike the relativity revolution, the development of quantum physics was a communal effort whose nature cannot be easily captured by a biographical approach that focuses on a few central figures. Careful at- tention must be paid to the broader community of researchers and to how they could achieve together what no single researcher could do alone. Another problem is that not much of the existing literature is reliable when it comes to explaining crucial mathe- matical arguments in the primary source material. Finally, a sound understanding of the advent of quantum physics cannot be achieved without a subtle appreciation of the radical conceptual changes that it brought. Much of the conceptual analysis in histor- ical writing on the quantum revolution uncritically presumes an unhistorical view of a unified Copenhagen interpretation. In fact, the history of the interpretation of quantum mechanics is, itself, a topic in need of more thorough and dispassionate historical inves- tigation, all the more so because debates about interpretation played and continue to play an unusually prominent role in the development of quantum physics. In view of these challenges, the Quantum History Project is conceived as a close col- laboration of a large and varied international group of historians and philosophers of science and working physicists, reflected by the contributors to the present preprint vol- Preface ume. Thus, the project takes advantage of the scientific expertise of the physicists and at the same time intends to reflect modern historiographical and philosophical approaches. It is based on the careful analysis of sources (published papers as well as correspondence, research manuscripts, and laboratory notebooks) and, where possible, instruments. At- tention is also paid to the institutional and socio-cultural dimensions of the development of quantum physics. The Quantum History Project aims at creating and fostering a collaborative climate and an infrastructure for scholarly research into the birth and development of quantum physics. We are actively establishing a network of scholars exchanging ideas and view- points through frequent and regular meetings (symposia, workshops, summer schools). In particular, we want to facilitate exchanges between physicists, historians, and philoso- phers interested in the history or the foundations of quantum physics. In addition, we make a special effort to draw young scholars into the project through graduate fellow- ships and postdoc positions. In support of these activities, we develop and maintain an easily accessible electronic resource base of both primary source material, published books and articles as well as archival material, and results of ongoing research by mem- bers of the network. We will likewise create an electronic educational resource for the dissemination of the history of quantum physics, creating and collecting materials ac- cessible to a wide range of audiences, from the general public to graduate students in (history of) physics. The aim of HQ-1 was to bring together scholars from different disciplines and countries who are experts in the conceptual and theoretical development of quantum physics, its experimental practice, and its institutional, philosophical and cultural context. Three areas were the main focus of the HQ-1 conference • The old quantum theory: Its emergence of an array of seemingly unrelated prob- lems in diverse areas such as statistical physics, radiation theory, and spectroscopy; how it was applied to an increasing number of problems; and how the physics com- munity came to recognize its limitations. • The genesis of modern quantum mechanics in the period around 1925, its con- ceptual development, the interplay with experiment, its socio-cultural and institu- tional context, as well as the debates about the different mathematical formula- tions of the theory (matrix and wave mechanics, transformation theory) and their physical interpretation (statistical interpretation, uncertainty principle). • The acceptance of quantum mechanics as a new basis for physics (atomic, mo- lecular, nuclear, and solid-state) and parts of chemistry; the elaboration of its mathematical formalism; the establishment of the dominant Copenhagen interpre- tation and the emergence of critical responses; and subsequent developments up to the present, including the ability to produce and control phenomena that until recently existed only as theoretical speculation. Not all contributions to the HQ-1 conference are included in this two-volume preprint. The selection has not been based on a peer-review process but it rather was left open to each participant individually whether to submit a paper. The editors wish to stress the fact that the aim of the present preprint is not to assemble former or future publications of the participants but instead to provide a glimpse on recent developments in the ii Preface field via papers of preprint nature that reflect the status of research at the time of the conference. The copyright for the papers remains with the original authors who have to be contacted for permission of reproduction or any further use. All papers have been carefully edited to conform a common LATEXstyle. The editors aplogize for any mistakes generated during this process and wish to thank Carmen Hammer, Nina Ruge, Judith Levy and Alexander Riemer for the considerable amount of time they invested into the completion of this two-volume preprint. We also wish to thank the other members of the Program Committee (Don Howard, Michel Janssen, John Norton, Robert Rynasiewicz) and all participants of HQ-1 for a fruitful conference. The editors would like to dedicate this volume to the memory of J¨urgenEhlers (1929{ 2008). We felt very lucky and honored that a physicist of his importance took such an enthusiastic interest in our project. J¨urgenEhlers participated from the beginning of the project regularly in our meetings. He contributed not only with his scientific acumen, but also with his thoughtful sense of history and his wonderful personality to our group. We will miss him sorely. Berlin, in June 2008, Christian Joas Christoph Lehner J¨urgenRenn iii Preface iv Preface v Preface vi Contents Volume 1 1 Einstein's Revolutionary Light-Quantum Hypothesis Roger H. Stuewer 1 2 The Odd Couple: Boltzmann, Planck and the Application of Statistics to Physics (1900{1913) Massimiliano Badino 17 3 Poincar´e'sElectromagnetic