einstein

elativity 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 Einstein’s Miraculous Year (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 V for the
constant velocity of light, but seven years later began using the term now in common use, c.
39. In section 2 of the paper, he defines the light postulate more carefully: “Every light ray moves in the ‘rest’ coordinate system with a fixed
velocity V, independently of whether this ray of light is emitted by a body at rest or in motion.” In other words, the postulate says that the
speed of light is the same no matter how fast the light source is moving. Many writers, when defining the light postulate, confuse this with
the stronger assertion that light always moves in any inertial frame at the same velocity no matter how fast the light source or the observer
is moving toward or away from each other. That statement is also true, but it comes only by combining the relativity principle with the light
postulate.
40. Einstein 1922c. In his popular 1916 book Relativity: The Special and General Theory, Einstein explains this in chapter 7, “The Apparent
Incompatibility of the Law of Propagation of Light with the Principle of Relativity.”
41. Einstein 1916, chapter 7.
42. Einstein 1922c; Reiser, 68.
43. Einstein 1916, chapter 9.
44. Einstein 1922c; Heisenberg 1958, 114.
45. Sir Isaac Newton, Philosophiae Naturalis Principia Mathematica (1689), books 1 and 2; Einstein, “The Methods of Theoretical Physics,”
Herbert Spencer lecture, Oxford, June 10, 1933, in Einstein 1954, 273.
46. Fölsing, 174–175.
47. Poincaré went on to reference himself, saying that he had discussed this idea in an article called “The Measurement of Time.” Arthur I.
Miller notes that Einstein’s friend Maurice Solovine may have read this paper, in French, and discussed it with Einstein. Einstein would
later cite it, and his analysis of the synchronizations of clocks reflects some of Poincaré’s thinking. Miller 2001, 201–202.
48. Fölsing, 155: “He was observed gesticulating to friends and colleagues as he pointed to one of Bern’s bell towers and then to one in the
neighboring village of Muri.” Galison, 253, picks up this tale. Both cite as their source Max Flück iger, Einstein in Bern (Bern: Paul Haupt,
1974), 95. In fact, Flückiger merely quotes a colleague saying that Einstein referred to these clocks as a hypothetical example. See
Alberto Martinez, “Material History and Imaginary Clocks,” Physics in Perspective 6 (2004): 229. Martinez does concede, however, that it
is indeed interesting that there was a steeple clock in Muri not synchronized with the clocks in Bern and that Einstein referred to this in
explaining the theory to friends.
49. Galison, 222, 248, 253; Dyson. Galison’s thesis is based on his original research into the patent applications.
50. Norton 2006a, 3, 43: “Another oversimplification pays too much attention to the one part of Einstein’s paper that especially fascinates us
now: his ingenious use of light signals and clocks to mount his conceptual analysis of simultaneity. This approach gives far too much
importance to notions that entered briefly only at the end of years of investigation . . . They are not necessary to special relativity or to the
relativity of simultaneity.” See also Alberto Martinez, “Material History and Imaginary Clocks,”Physics in Perspective 6 (2004): 224–240;
Alberto Martinez, “Railways and the Roots of Relativity,”Physics World ,Nov. 2003; Norton 2004. For a good assessment, which gives
more credit to Galison’s research and insights, see Dyson. Also see Miller 2001.
51. Einstein interview, Bucky, 28; Einstein 1956, 12.
52. Moszkowski, 227.
53. Overbye, 135.
54. Miller 1984, 109, 114. Miller 1981, chapter 3, explains the influence of Faraday’s experiments with rotating magnets on Einstein’s special
theory.
55. Einstein, “On the Electrodynamics of Moving Bodies,” Annalen der Physik 17 (Sept. 26, 1905). There are many available editions. For a
web version, see www.fourmilab.ch/etexts/einstein/specrel/www/. Useful annotated versions include Stachel 1998; Stephen Hawking, ed.,
Selections from the Principle of Relativity (Philadelphia: Running Press, 2002); Richard Muller, ed., Centennial Edition of The Theory of
Relativity (San Francisco: Arion Press, 2005).
56. Einstein, unused addendum to 1916 book Relativity, CPAE 6: 44a.
57. Einstein 1916.
58. Bernstein 2006, 71.
59. This example is lucidly described in Miller 1999, 82–83; Panek, 31–32.
60. James Hartle, lecture at the Aspen Center for Physics, June 29, 2005; British National Measurement Laboratory, report on time dilation
experiments, spring 2005, www.npl.co.uk/publications/metromnia/issue18/.