I N T R O D U C T I O N T O V O L U M E 9 x x x i
Einstein had intended to take his mother back home with him to Berlin that sum-
mer, but the plan had to be postponed. Several letters in this volume document the
obstacles connected to this move, ranging from the medical risks of a long and ex-
hausting journey (Doc. 148), to finding appropriate accommodations for Pauline
(Docs. 159, 194, 233). Due to financial setbacks in 1919, arising from the increas-
ingly unfavorable exchange rate between the Swiss franc and the German mark,
Einstein even tried to persuade Mileva and his two sons to relocate from Zurich to
Baden, where he felt he would be better able to support them (Docs. 135, 166, 198,
242) and comply with the financial terms agreed upon in the divorce, which had
been finalized in Zurich on 14 February 1919 (Doc. 6). Einstein was repeatedly of-
fered academic positions with generous remuneration in Switzerland during this
period. Although such an arrangement would have considerably alleviated his fi-
nancial worries, Einstein declined, stating that, given the efforts that his Berlin col-
leagues, especially Fritz Haber, were making on his behalf to remain in Berlin, he
would stay in Germany unless circumstances forced him to do otherwise (see Docs.
84, 103, 140).
Pauline eventually arrived in Berlin on 28 December 1919 and remained in the
care of Elsa and Albert Einstein. She spent the last weeks of her life in Einstein’s
apartment, where she died on 20 February 1920 at the age of sixty-two.
The eclipse of 29 May 1919 was the single most important event affecting Ein-
stein’s life in the period covered by this volume.
The year 1919 was pivotal for the empirical confirmation of the theory of gen-
eral relativity. Despite its conceptual innovations, the new theory of gravity incor-
porated, as a limiting case, the empirical content of Newtonian theory. For weak
gravitational fields and slow motion, the new theory reproduced the known equa-
tions of Newtonian theory, a major heuristic requirement for Einstein in his search
for a relativistic theory of
He naturally felt compelled to look for ob-
servable consequences that escaped the Newtonian limit. He had identified three
such tests as early as 1907, when he first formulated his equivalence principle, ac-
cording to which the effects of gravitation and uniform acceleration are locally in-
An excess advance of the perihelion of Mercury’s planetary orbit that could not
be satisfactorily explained by the Newtonian theory of gravitation had been ob-
served at the end of the nineteenth century. Einstein’s hope that a relativistic theory
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