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arXiv:0709.3099 · Historical Studies in the Physical and Biological Sciences

Emil Rupp, Albert Einstein, and the canal ray experiments on wave-particle duality: Scientific fraud and theoretical bias

Jeroen van Dongen

Published Mar 1, 2007• 54 citations
arXivHTMLPDF

Abstract

In 1926 Emil Rupp published a number of papers on the interference properties of light emitted by canal ray sources. These articles, particularly one paper that came into being in collaboration with Albert Einstein, drew quite some attention as they probed the wave versus particle nature of light. They also significantly propelled Rupp's career, even though that from the outset they were highly controversial. This article will review this episode, and in particular Rupp's collaboration with Einstein. Evidence that Rupp forged his results is presented and their critical reception in the socially and politically divided German physics community is discussed. These divisions fail to explain the full dynamic; the latter is attempted by turning to the role that theoretical bias on occasion has in assessing experiment. Einstein's responses in particular are analyzed in this context.

DOI
10.1525/hsps.2007.37.s.73

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In 1926 Emil Rupp published a number of papers on the interference properties of light emitted by canal ray sources. These articles, particularly one paper that came into being in collaboration with Albert Einstein, drew quite some attention as they probed the wave versus particle nature of light. They also significantly propelled Rupp's career, even though that from the outset they were highly controversial. This article will review this episode, and in particular Rupp's collaboration with Einstein. Evidence that Rupp forged his results is presented and their critical reception in the socially and politically divided German physics community is discussed. These divisions fail to explain the full dynamic; the latter is attempted by turning to the role that theoretical bias on occasion has in assessing experiment. Einstein's responses in particular are analyzed in this context.
The Einstein-Rupp experiments were proposed in 1926 by Albert Einstein to study the wave versus particle nature of light. Einstein presented a theoretical analysis of these experiments to the Berlin Academy together with results of Emil Rupp, who claimed to have successfully carried them out. However, as the preceding paper has claimed (HSPS 37 Suppl. (2007), 73-121), Rupp's success was the result of scientific fraud. This paper will argue, after exploring their interpretation, that the experiments were a relevant part of the background to such celebrated contributions to quantum mechanics as Born's statistical interpretation of the wave function and Heisenberg's uncertainty principle. Yet, the Einstein-Rupp experiments have hardly received attention in the history of quantum mechanics literature. In part, this is a consequence of self-censorship in the physics community, enforced in the wake of the Rupp affair. Self-censorship among historians of physics may however also have played a role.
The Einstein-Rupp experiments have been unduly neglected in the history of quantum mechanics. While this is to be explained by the fact that Emil Rupp was later exposed as a fraud and had fabricated the results, it is not justified, due to the importance attached to the experiments at the time. This paper discusses Rupp's fraud, the relation between Albert Einstein and Rupp, and the Einstein-Rupp experiments, and argues that these experiments were an influence on Niels Bohr's development of complementarity and Werner Heisenberg's formulation of the uncertainty relations.
Abstract Einstein receive a letter from Bose and developed his idea into Bose–Einstein statistics. He also used De Broglie’s idea to clarify wave-particle duality. De Broglie also inspired Schrödinger to develop his equation in quantum mechanics. Bothe and Geiger ruled out Bohr’s BKS theory experimentally. Heisenberg came up with wave mechanics on the island of Heligoland. Born and Jordan realised that matrices were the mathematical key to quantum mechanics. Schrödinger developed an equivalent formalism. Heisenberg formulated his uncertainty principle. The Solvay Conference in Brussels in October 1927 was the scene for the famous Einstein–Bohr showdown, in which Bohr refuted Einstein’s thought experiment calculated to show that quantum mechanics was incomplete, a subject to which Einstein would return years later in the EPR paper. In Brussels, Einstein met Elisabeth Queen of the Belgians, a violinist with whom he would play chamber music many times. Einstein collaborated with Emil Rupp on experiments to explore quantum effects. Rupp turned out to be a charlatan who duped Einstein with fabricated results. Einstein became involved with the academic politics of the Hebrew University of Jerusalem, and clashed with its head, Judah Magnes.
This chapter details not only the prehistory of EPR but also examines the structure and logic of the EPR paper – including Einstein’s own preferred version of the argument for incompleteness. We here attempt a seamless interweaving of the excellent extant literature with additional details that have emerged from our work and the recent work of others. Some examples of new aspects in this prehistory of EPR include evidence of a ‘proto’ photon-box thought experiment Einstein had developed in connection with his ill-starred collaboration with Emil Rupp in 1926. We also describe the potential importance to this prehistory of Einstein’s paper with Tolman and Podolsky and of Einstein’s seminar and discussions with Schrödinger in Berlin in the early 1930s.
As has become evident from historical studies, science does not proceed in the coherent and predictable way that basic science texts would have us believe. I will argue that an excellent counter-example is an episode from the historical development of quantum mechanics in which the incompatibility of the particle and the wave representations of the electron and light were destined to be encompassed by two mathematically equivalent, but conceptually quite different theories. I shall argue that the appearance of two such different, yet equivalent, quantum theories was not surprising at all and I claim even predictable. As Einstein himself wrote in 1909: ‘It is my opinion that the next phase in the development of theoretical physics will bring us a theory of light that can be interpreted as a kind of fusion of the wave and the [particle] theory.’ Certainly, the interpretative content of Werner Heisenberg's and Erwin Schrödinger's theories could not have been more different. By mid-1926, the theoretical foundations had been laid for a scientific and emotional battleground between the particle and the wave. I suggest that an important element in the debate was not the incompatibility itself but actually coming to terms with ambiguity in science. For, in the end, ambiguous and vague interpretations of the same phenomena became part of science, where science was supposed to give a clear and unambiguous description of nature.
The wave-particle dual nature of light was discovered from experimental observations and from theoretical works of Max Planck and Albert Einstein during the beginning of the twentieth century. This paper reveals that wave-particle duality is just one aspect of the all dual nature of light (electromagnetic waves) and electromagnetic fields and that light and electromagnetic fields manifest dual natures in other ways also. For example, light is not only a local phenomenon as conventionally viewed, but also a non-local phenomenon. Light behaves both according to ether theory and emission theory. The speed of light is both constant (c) and variable ( c ± V). The phase velocity of light is independent of source and observer velocity and is always constant c, while the group velocity of light varies with observer velocity but is independent of source velocity. Light acts as if it travels both in a straight line and in curved path, at the same time! Electrostatic lines of force behave as if they are both straight and curved lines. Electrostatic fields behave as if they ‘propagate’ both at the speed of light and with infinite speed, at the same time! This paper is a summary of the findings reported in previous papers published by this author. An extensive theoretical research carried out by this author in an attempt to explain the Michelson-Morley experiment, the Sagnac effect and other light speed experiments led to uncovering of the broader and more fundamental nature of duality in electromagnetism.