. Einstein saw the null results of the ether-drift experiments as support for the
relativity principle, not (as is sometimes assumed) support for the postulate that light always moves at a constant velocity. John Stachel, “Einstein and Michelson: The Context of Discovery and Context of Justification,” 1982, in Stachel 2002a.
26
. Professor Robert Rynasiewicz of Johns Hopkins is among those who emphasize Einstein’s reliance on inductive methods. Even though Einstein in his later career wrote often that he relied more on deduction than on induction, Rynasiewicz calls this “highly contentious.” He argues instead, “My view of the annus mirabilis is that it is a triumph of what can be secured inductively in the way of fixed points from which to carry on despite the lack of a fundamental theory.” Rynasiewicz e-mail to me, commenting on an earlier draft of this section, June 29, 2006.
27
. Miller 1984, 117; Sonnert, 289.
28
. Holton 1973, 167.
29
. Einstein, “Induction and Deduction in Physics,”
, Dec. 25, 1919, CPAE 7: 28.
30
. Einstein to T. McCormack, Dec. 9, 1952, AEA 36-549. McCormack was a Brown University undergraduate who had written Einstein a fan letter.
31
. Einstein 1949b, 89.
32
. The following analysis draws from Miller 1981 and from the work of John Stachel, John Norton, and Robert Rynasiewicz cited in the bibliography. Miller, Norton, and Rynasiewicz kindly read drafts of my work and suggested corrections.
33
. Miller 1981, 311, describes a connection between Einstein’s papers on light quanta and special relativity. In section 8 of his special relativity paper, Einstein discusses light pulses and declares, “It is remarkable that the energy and the frequency of a light complex vary with the state of motion of the observer in accordance with the same law.”
34
. Norton 2006a.
35
. Einstein to Albert Rippenbein, Aug. 25, 1952, AEA 20-46. See also Einstein to Mario Viscardini, Apr. 28, 1922, AEA 25-301: “I rejected this hypothesis at that time, because it leads to tremendous theoretical difficulties (e.g., the explanation of shadow formation by a screen that moves relative to the light source).”
36
. Mermin, 23. This was finally proven conclusively by Willem de Sitter’s study of double stars that rotate around each other at great speeds, which was published in 1913. But even before then, scientists had noted that no evidence could be found for the theory that the velocity of light from moving stars, or any other source, varied.
37
. Einstein to Paul Ehrenfest, Apr. 25, June 20, 1912. By taking this approach, Einstein was continuing to lay the foundation for a quandary about quantum theory that would bedevil him for the rest of his life. In his light quanta paper, he had praised the wave theory of light while at the same time proposing that light could also be regarded as particles. An emission theory of light could have fit nicely with that approach. But both facts and intuition made him abandon
that approach to relativity, just at the same moment he was finishing his light quanta paper. “To me, it is virtually inconceivable that he would have put forward two papers in the same year which depended upon hypothetical views of Nature that he felt were in contradiction with each other,” says physicist Sir Roger Penrose. “Instead, he must have felt (correctly, as it turned out) that ‘deep down’ there was no real contradiction between the accuracy—indeed ‘truth’—of Maxwell’s wave theory and the alternative ‘quantum’ particle view that he put forward in the quantum paper. One is reminded of Isaac Newton’s struggles with basically the same problem—some 300 years earlier—in which he proposed a curious hybrid of a wave and particle viewpoint in order to explain conflicting aspects of the behavior of light.” Roger Penrose, foreword to
(Princeton: Princeton University Press, 2005), xi. See also Miller 1981, 311.
38
. Einstein, “On the Electrodynamics of Moving Bodies,” June 30, 1905, CPAE 2: 23, second paragraph. Einstein originally used
for the constant velocity of light, but seven years later began using the term now in common use,
