190 RELATIVITY, THE GENERAL THEORYthat time. In the Gibson lecture on the origins of the general theory of relativity,
given in Glasgow in June 1933, he says,
'If [the equivalence principle] was true for all processes, it indicated that the
principle of relativity must be extended to include nonuniform motions of the
coordinate systems if one desired to obtain an unforced and natural theory of
the gravitational field. From 1908 until 1911 I concerned myself with consid-
erations of this nature, which I need not describe here' [E21].In his major scientific autobiographical notes of 1949 [E22], he remains silent
about those particular years. His final autobiographical sketch, written a few
months before his death, contains the following statement: 'From 1909 to 1912,
while I had to teach theoretical physics at the universities of Zurich and Prague,
I puzzled incessantly about the problem [of gravitation]' [E23]. This is indeed
borne out by letters he wrote to his friends after the middle of 1911, but not by
the letters prior to that time. Indeed, it seems evident that until he reached Prague,
he considered—and, it should be said, for many good reasons—the riddles of the
quantum theory far more important and urgent than the problem of gravitation.
In sharp contrast, from then until 1916 there are only a few minor papers on the
quantum theory while his correspondence shows clearly that now the theory of
gravitation is steadily on his mind. I would not go so far as to say that this intense
preoccupation is the only reason he did not at once participate in the new quantum
dynamics initiated by Bohr in 1913. But it must have been a heavily contributing
factor.
Let us next join Einstein in Prague.
References
Dl. C. DUr, letter to R. Jost, November 29, 1979.
El. A. Einstein, letter to M. Besso, January 1903; EB, p. 3.
Ela. , letter to M. Grossmann, January 3, 1908.
Elb. M. Einstein, 'Beitrage zur Uberlieferung des Chevaliers du Cygne und der Enfance
Godefroi,' Druck, Erlangen, 1910.
E2. A. Einstein, Phys. Zeitschr. 10, 185 (1909).
E3. —, Phys. Zeitschr. 10, 817 (1909).
E4. , Phys. Zeitschr. 9, 216 (1908).
E5. , letter to J. Stark, December 14, 1908. Reprinted in A. Hermann, Sudhoffs
Archiv. 50, 267 (1966).
E6. in EB pp. 42, 47, 464.
E7. , letter to M. Besso, November 17, 1909; EB, p. 16.
E8. , Arch. Sci. Phys. Nat. 29, 5, 125 (1910).
E9. , letter to J. Laub, 1908, undated.
E10. , letter to J. Stark, July 31, 1909. Reprinted in A. Hermann, [E5].
Ell. —, letter to M. Besso, November 17, 1909; EB, p. 16.
E12. , letter to M. Besso, December 31, 1909; EB, p. 18.
E13. , letter to J. Laub, December 31, 1909.