SPRINGER BRIEFS IN HISTORY OF SCIENCE AND TECHNOLOGY Alexei Kojevnikov The Copenhagen Network The Birth of Quantum Mechanics from a Postdoctoral Perspective SpringerBriefs in History of Science and Technology Series Editors Gerard Alberts, University of Amsterdam, Amsterdam, The Netherlands Theodore Arabatzis, University of Athens, Athens, Greece Bretislav Friedrich, Fritz Haber Institut der Max Planck Gesellschaft, Berlin, Germany Ulf Hashagen, Deutsches Museum, Munich, Germany DieterHoffmann,Max-Planck-InstitutefortheHistoryofScience,Berlin,Germany Simon Mitton, University of Cambridge, Cambridge, UK David Pantalony, University of Ottawa, Ottawa, ON, Canada Matteo Valleriani, Max-Planck-Institute for the History of Science, Berlin, Germany More information about this series at http://www.springer.com/series/10085 Alexei Kojevnikov The Copenhagen Network The Birth of Quantum Mechanics from a Postdoctoral Perspective 123 AlexeiKojevnikov Department ofHistory University of British Columbia Vancouver, BC,Canada ISSN 2211-4564 ISSN 2211-4572 (electronic) SpringerBriefs inHistory ofScience andTechnology ISBN978-3-030-59187-8 ISBN978-3-030-59188-5 (eBook) https://doi.org/10.1007/978-3-030-59188-5 ©TheAuthor(s),underexclusivelicensetoSpringerNatureSwitzerlandAG2020 Thisworkissubjecttocopyright.AllrightsaresolelyandexclusivelylicensedbythePublisher,whether thewholeorpartofthematerialisconcerned,specificallytherightsoftranslation,reprinting,reuseof illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmissionorinformationstorageandretrieval,electronicadaptation,computersoftware,orbysimilar ordissimilarmethodologynowknownorhereafterdeveloped. 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ThisSpringerimprintispublishedbytheregisteredcompanySpringerNatureSwitzerlandAG Theregisteredcompanyaddressis:Gewerbestrasse11,6330Cham,Switzerland In memory of my teacher, Igor Serafimovich Alekseev (1935–1988), philosopher and Marxist interpreter of Bohr’s complementarity Acknowledgements ThisprojectwassupportedbytheMax-Planck-InstitutfürWissenschaftsgeschichte, Berlin,andbytheSSHRCgrant410-2011-0936.Iwishtothankallmembersofthe quantum history group at the institute, in particular Jürgen Renn, Giuseppe Castagnetti,HubertGoenner,DieterHoffmann,EdwardJurkowitz,HorstKant,and Arne Schirrmacher, for many productive discussions. My special gratitude goes to FinnAaserud,ChristianJoas,FelicityPors,andthestaffoftheNielsBohrArchive in Copenhagen for their hospitality and invaluable advice. For further comments andsuggestions,IamthankfultoRichardBeyler,CathrynCarson,OlivierDarrigol, Paul Forman, Olival Freire Jr., John L. Heilbron, Anja Skaar Jacobsen, Diana Kormos Barkan, Helge Kragh, Dorinda Outram, Ted Porter, Helmut Rechenberg, Eric Scerri, Skuli Sigurdsson, and participants at the colloquia at Deutsches Museum, Munich; Institute for History of Science and Technology, Moscow; Harvard University; University of California Los Angeles; and Universidade Federal da Bahia. I am grateful to Lindy Divarci and Stefanie Ickert for editorial assistance. An earlier version of Chap. 6 was published in (Kojevnikov 2011). vii Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 KnabenPhysik . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2 “Mecca of Theoretical Physics”. . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 Scandinavian Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.1 Experiment Under Theory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.2 New Blood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.3 Meanings of Internationalism . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3 International Networking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.1 The Manchester Link . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.2 First German Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 3.3 New Partners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 3.4 The Value of Neutrality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 4 A “Kuhnian” Crisis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 4.1 The Field in Disarray . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 4.2 American Voyage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 4.3 The Copenhagen Putsch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 5 Revolt of the Postdoc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 5.1 Marginal Intruders and the Light Quantum. . . . . . . . . . . . . . . . . . 61 5.2 Inflation and Quasi-Free Postdocs . . . . . . . . . . . . . . . . . . . . . . . . 64 5.3 Werner Heisenberg’s Wanderjahre . . . . . . . . . . . . . . . . . . . . . . . 70 5.4 Quantum Mechanics Community. . . . . . . . . . . . . . . . . . . . . . . . . 74 6 Philosophical Wrangling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 6.1 The Problem with Quantum Philosophy. . . . . . . . . . . . . . . . . . . . 81 6.2 Matrix Mechanics (Fall 1925) . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 6.3 Wave Mechanics (Spring 1926). . . . . . . . . . . . . . . . . . . . . . . . . . 88 6.4 Quantum Mechanics (Fall 1926) . . . . . . . . . . . . . . . . . . . . . . . . . 91 ix x Contents 6.5 Philosophies of Compromise (1927) . . . . . . . . . . . . . . . . . . . . . . 93 6.6 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 7 Conclusions: The Precarious Copenhagen Network and the Forman Thesis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Appendix A. Visitors at Bohr’s Institute in Copenhagen (Chronological Order, up to 1927)... .... .... ..... .... 107 AppendixB.InformationConcerningFellowshipsinScienceAwarded by the International Education Board (1925) .. ..... .... 111 Appendix C. IEB: Excerpts from Applications and Correspondence Regarding Individual Fellows... .... .... .... ..... .... 113 References.... .... .... .... ..... .... .... .... .... .... ..... .... 117 Index .... .... .... .... .... ..... .... .... .... .... .... ..... .... 123 Abbreviations and Archives AHQP Archive for the History of Quantum Physics, APS and many other depositories AP Annalen der Physik APS American Philosophical Society Library, Philadelphia BCW Bohr Collected Works (Bohr 1972–2008) BGC Bohr General Correspondence, NBA BKS Bohr–Kramers–Slater theory BSC Bohr Scientific Correspondence, NBA DM Deutsches Museum Archive, Munich ETH ETH Library, Zurich HDQT The Historical Development of Quantum Theory (Mehra and Rechenberg 1982–2001) HSP(B)S Historical Studies in the Physical (and Biological) Sciences IEB International Education Board IMN Intellectual Mastery of Nature (Jungnickel and McCormmach 1986) NBA Niels Bohr Archive, Copenhagen NW Die Naturwissenschaften PWB Pauli Wissenschaftlicher Briefwechsel (Pauli 1979) PZ Physikalische Zeitschrift RAC Rockefeller Archive Center, Sleepy Hollow, NY SWB SommerfeldWissenschaftlicherBriefwechsel(Sommerfeld2000–2004) ZP Zeitschrift für Physik Unless otherwise stated, cited archival documents and letters are microfilm copies from AHQP; Bohr’s correspondence from BSC. xi