einstein

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).
25. For a two-minute home movie of the conference shot by Irving Langmuir, the 1932 Nobel Prize winner in chemistry, see
www.maxborn.net/index.php? page=filmnews.
26. Einstein to Hendrik Lorentz, Sept. 13, 1927, AEA 16-613.
27. Pauli, 121.
28. John Archibald Wheeler and Wojciech Zurek, Quantum Theory and Measurement (Princeton: Princeton University Press, 1983), 7.
29. Fölsing, 589; Pais 1982, 445, from Proceedings of the Fifth Solvay Conference.
30. Heisenberg 1989, 116.
31. Niels Bohr, “Discussion with Einstein,” in Schilpp, 211–219, offers a detailed and loving description of the Solvay and other discussions;
Otto Stern recollections, in Pais 1982, 445; Fölsing, 589.
32. “Reports and Discussions,” in Solvay Conference of 1927 (Paris: GauthierVillars, 1928), 102. See also Travis Norsen, “Einstein’s
Boxes,”American Journal of Physics, vol. 73, Feb. 2005, pp. 164-176.
33. Louis de Broglie, “My Meeting with Einstein,” in French, 15.