Einstein: His Life and Universe

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

. Folsing, 174–175.

47

. Poincare 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 Poincare’s thinking. Miller 2001, 201–202.

48

. Folsing, 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 Fluck iger,

Einstein in Bern

(Bern: Paul Haupt, 1974), 95. In fact, Fluckiger 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