Einstein (129 page)

at times certainly felt impoverished, Einstein did try to protect her and Eduard from financial worries, not only by paying what he was obliged to pay, but also by subsidizing their living expenses. I am grateful to Barbara Wolff of the Hebrew University Einstein archives for help researching this topic. See also Alexis Schwarzenbach,
Das verschmähte Genie: Albert Einstein und die Schweiz
(Berlin: DVA, 2003).

16
. Einstein to Heinrich Zangger, Dec. 6, 1917.

17
. “
All
the really great discoveries in
theoretical
physics—with a few exceptions that stand out because of their oddity—have been made by men
under thirty
.” Bernstein 1973, 89, emphasis in the original. Einstein finished his work on general relativity when he was 36, but his initial step, what he called his “happiest thought” about the equivalence of gravity and acceleration, came when he was 28. Max Planck was 42 when, in Dec. 1900, he gave his lecture on the quantum.

18
. Einstein to Heinrich Zangger, Aug. 11, 1918; Clive Thompson, “Do Scientists Age Badly?,”
Boston Globe
, Aug. 17, 2003. John von Neumann, a founder of modern computer science, once claimed that the intellectual
powers of mathematicians peaked at the age of 26. One study of a random group of scientists showed that 80 percent did their best work before their early forties.

19
. Einstein to Maurice Solovine, Apr. 27, 1906.

20
. Aphorism for a friend, Sept. 1, 1930, AEA 36-598.

21
. Einstein to Hendrik Lorentz, June 17, 1916; Miller 1984, 55–56.

22
. Einstein, “Ether and the Theory of Relativity,” speech at University of Leiden, May 5, 1920, CPAE 7: 38.

23
. Einstein to Karl Schwarzschild, Jan. 9, 1916.

24
. Einstein, “Ether and the Theory of Relativity,” speech at University of Leiden, May 5, 1920, CPAE 7: 38.

25
. Greene 2004, 74.

26
. Janssen 2004, 22. Einstein made this clearer in his 1921 Princeton lectures, but also continued to say, “It appears probable that Mach was on the right road in his thought that inertia depends on a mutual action of matter.” Einstein 1922a, chapter 4.

27
. Einstein, “Ether and the Theory of Relativity,” speech at University of Leiden, May 5, 1920, CPAE 7: 38.

28
. Einstein, “On the Present State of the Problem of Specific Heats,” Nov. 3, 1911, CPAE 3: 26; the quote about “really exist in nature” appears on p. 421 of the English translation of vol. 3.

29
. Robinson, 84–85.

30
. Holton and Brush, 435.

31
. Lightman 2005, 151.

32
. Clark 202; George de Hevesy to Ernest Rutherford, Oct. 14, 1913; Einstein 1949b, 47.

33
. Einstein, “Emission and Absorption of Radiation in Quantum Theory,” July 17, 1916, CPAE 6: 34; Einstein, “On the Quantum Theory of Radiation,” after Aug. 24, 1916, CPAE 6: 38, and also in
Physikalische Zeitschrift
18 (1917). See Overbye, 304–306; Rigden, 141; Pais 1982, 404–412; Fölsing, 391; Clark, 265; Daniel Kleppner, “Rereading Einstein on Radiation,”
Physics Today
(Feb. 2005): 30. In addition, in 1917 Einstein wrote a paper on the quantization of energy in mechanical theories called “On the Quantum Theorem of Sommerfeld and Epstein.” It shows the problems that the classical quantum theory encountered when applied to mechanical systems we would now call chaotic. It was cited by earlier pioneers of quantum mechanics, but has since been largely forgotten. A good description of it and its importance in the development of quantum mechanics is Douglas Stone, “Einstein’s Unknown Insight and the Problem of Quantizing Chaos,”
Physics Today
(Aug. 2005).

34
. Einstein to Michele Besso, Aug. 11, 1916.

35
. I am grateful to Professor Douglas Stone of Yale for help with the wording of this.

36
. Einstein to Michele Besso, Aug. 24, 1916.

37
. Einstein, “On the Quantum Theory of Radiation,” after Aug. 24, 1916, CPAE 6: 38.

38
. Einstein to Max Born, Jan. 27, 1920.

39
. Einstein to Max Born, Apr. 29, 1924, AEA 8-176.

40
. Niels Bohr, “Discussion with Einstein,” in Schilpp, 205–206; Clark, 202.

41
. Einstein to Niels Bohr, May 2, 1920; Einstein to Paul Ehrenfest, May 4, 1920.

42
. Niels Bohr to Einstein, Nov. 11, 1922, AEA 8-73.

43
. Fölsing, 441.

44
. John Wheeler, “Memoir,” in French, 21; C. P. Snow, “Albert Einstein,” in French, 3.

45
. Bohr’s quip is often quoted. One source I can find for it, in a less pithy fashion, is from Bohr’s own descriptions of being with Einstein at the 1927 Solvay Conference: “Einstein mockingly asked us whether we could really believe that the providential authorities took recourse to dice-playing (‘. . . ob der liebe Gott würfelt’), to which I replied by pointing at the great caution, already called for by ancient thinkers, in ascribing attributes to Providence in everyday language.” Niels Bohr, “Discussion with Einstein,” in Schilpp, 211. Werner Heisenberg, who was at these discussions, also recounts the quip: “To which Bohr could only answer: ‘But still, it cannot be for us to tell God how he is to run the world.’ ” Heisenberg 1989, 117.

46
. Holton and Brush, 447; Pais 1982, 436.

47
. Pais 1982, 438. Wolfgang Pauli recalled, “In a discussion at the physics meeting in Innsbruck in the autumn of 1924, Einstein proposed to search for interference and diffraction phenomena with molecular beams.” Pauli, 91.

48
. Einstein, “Quantum Theory of Single-Atom Gases,” part 1, 1924, part 2, 1925. This quote occurs in part 2, section 7. The manuscript of this paper was found in Leiden in 2005.

49
. I am grateful to Professor Douglas Stone of Yale for helping to craft this section and explaining the fundamental importance of what Einstein did. A theoretical condensed matter physicist, he is writing a book on Einstein’s contributions to quantum mechanics and how far-reaching they really were, despite Einstein’s later rejection of the theory. According to Stone, “99% of the credit for this fundamental discovery called Bose-Einstein condensation is really owed to Einstein. Bose did not even realize that he had counted in a different way.” Regarding the Nobel Prize for achieving Bose-Einstein condensation, see www.nobelprize.org/physics/laureates/2001/public.html.

50
. Bernstein 1973, 217; Martin J. Klein, “Einstein and the Wave-Particle Duality,”
Natural Philosopher
(1963): 26.

51
. Max Born, “Einstein’s Statistical Theories,” in Schilpp, 174.

52
. Einstein to Erwin Schrödinger, Feb. 28, 1925, AEA 22-2.

53
. Don Howard, “Spacetime and Separability,” 1996, AEA Cedex H; Howard 1985; Howard 1990b, 61–64; Howard 1997. The 1997 essay identifies the philosophy of Arthur Schopenhauer as an influence on Einstein’s theories of spatial separability.

54
. Bernstein 1996a, 138.

55
. More precisely, it is the square of the wave function that is proportional to the probability. Holton and Brush, 452.

56
. Einstein to Hedwig Born, Mar. 7, 1926, AEA 8-266; Einstein to Max Born, Dec. 4, 1926, AEA 8-180.

57
. aip.org/history/heisenberg/p07.htm; Born 2005, 85.

58
. Max Born to Einstein, July 15, 1925, AEA 8-177; Einstein to Hedwig Born, Mar. 7, 1926, AEA 8-178; Einstein to Paul Ehrenfest, Sept. 25, 1925, AEA 10-116.

59
. Werner Heisenberg to Einstein, June 10, 1927, AEA 12-174.

60
. Heisenberg 1971, 63; Gerald Holton, “Werner Heisenberg and Albert Einstein,”
Physics Today
(2000), www.aip.org/pt/vol-53/iss-7/p38.html.

61
. Frank 1947, 216.

62
. Aage Petersen, “The Philosophy of Niels Bohr,”
Bulletin of the Atomic Scientists
(Sept. 1963): 12.

63
. Dugald Murdoch,
Niels Bohr’s Philosophy of Physics
(Cambridge, England: Cambridge University Press, 1987), 47, citing the Niels Bohr Archives: Scientific Correspondence, 11: 2.

64
. Einstein, “To the Royal Society on Newton’s Bicentennial,” Mar. 1927.

65
. Einstein to Michele Besso, Apr. 29, 1917; Michele Besso to Einstein, May 5, 1917; Einstein to Michele Besso, May 13, 1917. For a good analysis, see Gerald Holton, “Mach, Einstein, and the Search for Reality,” in Holton 1973, 240.

66
. “Belief in an external world independent of the perceiving subject is the basis of all natural science.” Einstein, “Maxwell’s Influence on the Evolution of the Idea of Physical Reality,” 1931, in Einstein 1954, 266.

67
. Einstein to Max Born, Jan. 27, 1920.

68
. Einstein’s introduction to Rudolf Kayser,
Spinoza
(New York: Philosophical Library, 1946). Kayser was married to Einstein’s stepdaughter and wrote a semi-authorized memoir of Einstein.

69
. Fölsing, 703–704; Einstein to Fritz Reiche, Aug. 15, 1942, AEA 20-19.

70
. Einstein to Max Born, Dec. 4, 1926, AEA 8-180.

CHAPTER FIFTEEN: UNIFIED FIELD THEORIES

1
. Einstein, “Ideas and Problems of the Theory of Relativity,” Nobel lecture, July 11, 1923. Available at nobelprize.org/nobel_prizes. This section draws from these papers on Einstein’s unified field quest: van Dongen 2002, courtesy of the author; Tilman Sauer, “Dimensions of Einstein’s Unified Field Theory Program,” forthcoming in the
Cambridge Companion to Einstein
, courtesy of the author; Norton 2000; Goenner 2004.

2
. Einstein, “The Principles of Research,” a toast in honor of Max Planck, Apr. 26, 1918, CPAE 7: 7.

3
. Einstein to Hermann Weyl, Apr. 6, 1918.

4
. Einstein to Hermann Weyl, Apr. 8, 1918. In a letter to Heinrich Zangger, May 8, 1918, Einstein called Weyl’s theory “ingenious” but “physically incorrect.” It did, however, later become one of the recognized precursors of Yang-Mills gauge theory.

5
. My description of the work of Kaluza and Klein relies on Krauss, 94–104,
which is an engaging book on the role extra dimensions have played in explaining the universe.

6
. Einstein to Theodor Kaluza, Apr. 21, 1919.

7
. Einstein to Niels Bohr, Jan. 10, 1923, AEA 8-74.

8
. Einstein to Hermann Weyl, May 26, 1923, AEA 24-83.

9
. Einstein, “On the General Theory of Relativity,” Prussian Academy, Feb. 15, 1923.

10
.
New York Times
, Mar. 27, 1923.

11
. Pais 1982, 466; Einstein, “On the General Theory of Relativity,” the Prussian Academy, Feb. 15, 1923.

12
. Einstein, “Unified Field Theory of Gravity and Electricity,” July 25, 1925; Hoffmann 1972, 225.

13
. Steven Weinberg, “Einstein’s Mistakes,”
Physics Today
(Nov. 2005).

14
. Einstein, “On the Unified Theory,” Jan. 30, 1929.

15
. Einstein to Michele Besso, Jan. 5, 1929, AEA 7-102.

16
.
New York Times
, Nov. 4, 1928; Vallentin, 160.

17
. Clark, 494;
London Daily Chronicle
, Jan. 26, 1929.

18
. “Einstein’s Field Theory,”
Time
, Feb. 18, 1929. Einstein also appeared on
Time
’s cover on Apr. 4, 1938, July 1, 1946, and posthumously Feb. 19, 1979, and Dec. 31, 1999. Elsa appeared on the cover Dec. 22, 1930.

19
. Fölsing, 605; Clark, 496; Brian 1996, 174.

20
.
New York Times
, Feb. 4, 1929.

21
. Einstein to Maja Winteler-Einstein, Oct. 22, 1929, AEA 29-409.

22
. Wolfgang Pauli to Einstein, Dec. 19, 1929, AEA 19-163.

23
.
New York Times
, Jan. 23, Oct. 26, 1931; Einstein to Wolfgang Pauli, Jan. 22, 1932, AEA 19-169.

24
. Goenner 2004; Elie Cartan, “Absolute Parallelism and the Unified Theory,”
Review Metaphysic Morale
(1931).