3 9 0 D O C . 2 5 6 D O U B T S A B O U T B O H R - K R A M E R S published in English in Bohr, Kramers, and Slater 1924a, which was submitted to Philosophical Mag- azine in January and published in May. A German translation was submitted to Zeitschrift für Physik on 22 February 1924 and published in May-June (Bohr, Kramers, and Slater 1924b). See also Doc. 240 for another critical comment by Einstein on the theory. Rudolf Ladenburg, who was present at the colloquium, reported on Einstein’s lecture in a letter to Hendrik A. Kramers: “About Einstein’s opinion of your new conception of radiation, I can inform you rather accurately since I attended his lecture of May 28 at the Berlin colloquium. His opinion was definitely not unfavorable he described the new conception as perfectly complete and consistent in itself and not in direct contradiction to any facts the mechanism of the wave theory should in his opin- ion be upheld in any case. Nevertheless, he strongly emphasized the conceptual logical difficulties of the new theory, of the ‘pre-established harmony’ which the fundamental introduction of probability in place of causality entails” (“Was Einsteins Meinung über Ihre neue Auffassung der Strahlung be- trifft, so kann ich Ihnen darüber recht genau berichten, da ich seinen Vortrag am 28. Mai im Berliner Kolloquium mitangehört habe. Seine Meinung war entschieden nicht ungünstig er erklärte die neue Auffassung als in sich völlig geschlossen und konsequent und nicht in direktem Widerspruch mit ir- gend welchen Tatsachen der Mechanismus der Undulationstheorie müsse nach seiner Ansicht auf je- den Fall aufrecht erhalten werden. Jedoch betonte er nachdrücklich die gedanklichen logischen Schwierigkeiten der neuen Theorie, der ‘praestabilisierten Harmonie’, die die grundsätzliche Einfüh- rung der Wahrscheinlichkeit an Stelle der Kausalität mit sich bringe” Ladenburg to Kramers, 8 June 1924, Bohr 1984, pp. 401–403). According to Doc. 250, Einstein had been asked to report on the Bohr-Kramers-Slater theory by Max von Laue. A few days after the colloquium, on 7 June 1924, Wal- ther Bothe and Hans Geiger submitted a short paper containing a proposal for an experimental test that would decide between the Bohr-Kramers-Slater theory and the light quantum conception (Bothe and Geiger 1924) see Doc. 398, note 7, for more details on the experiment. [3]This objection is made more explicit in Doc. 259. [4]In his letter to Kramers cited in note 2, Ladenburg comments on this point: “Individual objec- tions that he raised seemed to me to arise from an as yet incomplete knowledge of all your reasonings for example, he emphasized it as an asymmetric aspect that the production of virtual radiation is con- nected with a definite atomic state. In the discussion I pointed out in response that the virtual oscilla- tors possess the frequencies of the possible transitions—whereupon he retracted this objection immediately” (“Einzelne Einwände, die er geltend machte, schienen mir auf noch nicht völliger Kenntnis all Ihrer Gedankengänge zu beruhen so hob er als das Asymmetrische hervor, dass die Erzeugung der virtuellen Strahlung mit einem bestimmten Atomzustand verknüpft sei. Ich wies dem- gegenüber in der Diskussion daraufhin, dass ja die virtuellen Oszillatoren die Schwingungszahlen der möglichen Übergänge besitzen—worauf er dies Bedenken sofort fallen liess”). In the Bohr-Kramers-Slater theory, atoms can communicate with each other through virtual radi- ation fields, generated by sets of virtual oscillators that vibrate with the frequencies of all possible transitions within the atoms. See also objection 4 in Doc. 259. [5]At the GDNÄ meeting in Innsbruck in September 1924, Einstein discussed the Bohr-Kramers- Slater theory at length with Wolfgang Pauli. In a letter to Bohr of 2 October 1924 (Hermann et al. 1979, No. 66), Pauli reports on this conversation and lists four major objections made by Einstein. Two correspond to (1) and (4) above the other two can be summarized as follows: 1. Ever since one had given up the idea that the orbital frequencies of bound electrons should be related to the frequen- cies of spectral lines, for Einstein the undulatory properties of light had become secondary in charac- ter 2. Einstein disagreed with the theory’s explanation of the natural width of spectral lines, because it assumes a connection between the lengths of the radiation wave-trains produced in the transitions producing the lines, and the sharpness of the atomic stationary states in question, which is unnatural, according to Einstein. For a discussion of this document in the context of Einstein’s broader concerns with the quantum theory of radiation, see Klein, M. 1964, especially pp. 25–26. See also Darrigol 1992, pp. 246–247.