9780192806727.pdf

THE FIELD EQUATIONS OF GRAVITATION 257

covariant derivatives (cf. Eq. 14.3) in such a way that the conservation laws read

On November 28, Einstein wrote to Sommerfeld that three years earlier he and

Grossmann had considered Eq. 14.15 'without the second term on the right-hand

side,' but had come to the wrong conclusion that it did not contain Newton's

approximation [E42].

On December 10, he wrote to Besso that he was 'zufrieden aber ziemlich

kaputt' [E52].*

On June 20, 1933, Einstein, exiled from Germany, gave a lecture at the Uni-

versity of Glasgow on the origins of the general theory of relativity. In concluding

this address, he said:

The years of searching in the dark for a truth that one feels but cannot express,

the intense desire and the alternations of confidence and misgiving until one

breaks through to clarity and understanding are known only to him who has

himself experienced them. [ E52a]

14d. Einstein and Hilbert**

To repeat, on November 25 Einstein presented his final version (Eq. 14.15) of the
gravitational equations to the Prussian Academy. Five days earlier, David Hilbert
had submitted a paper to the Gesellschaft der Wissenschaften in Goettingen [H4]
which contained the identical equation but with one qualification. Einstein, having
learned the hard way from his mistakes a few weeks earlier, left the structure of
T^1 " entirely free, except for its transformation and conservation properties. Hil-
bert, on the other hand, was as specific about gravitational as about all other
forces. Correspondingly (and this is the qualification), his T" has a definite
dynamic form:'... I believe that [my paper] contains simultaneously the solution
of the problems of Einstein and of Mie.'
In 1912-13, Mie had proposed a field theory of electromagnetism and matter
based on non-gauge-invariant modifications of Maxwell's equations [M4]. It was
meant to be a theory of everything but gravitation.f Mie's ideas attracted attention
in the second decade of this century but are now of historical interest only and of
no relevance to our present subject. Suffice it to say that it was Hilbert's aim to
give not just a theory of gravitation but an axiomatic theory of the world. This

'Content but rather worn out.

"See also [M3j.

f Mie's ideas on gravitation were referred to in Chapter 13. For a comment by Einstein on Mie's

electromagnetic theory, see [E52b]. The reader will find clear synopses of Mie's theory in the texts

by Pauli [P2] and by Weyl [W9].