524 APPENDICES
July 3. This proposal is accepted by a vote of twenty-one to one (and
approved by Emperor Wilhelm II on November 12).
December 7. E. accepts the position in Berlin.
1914 April 6. E. moves to Berlin with wife and children. Soon after, the Einsteins
separate. Mileva and the boys return to Zurich. Albert moves into a bach-
elor apartment at Wittelsbacherstrasse 13.
April 26. E.'s first newspaper article appears, in Die Vossische Zeitung,
a Berlin daily. It deals with relativity theory.
July 2. E. gives his inaugural address at the Prussian Academy.
August 1. Outbreak of World War I.
1915 Early in the year. E. holds a visiting appointment at the Physikalisch
Technische Reichsanstalt in Berlin, where he and de Haas perform gyro-
magnetic experiments.
E. cosigns a 'Manifesto to Europeans' in which all those who cherish the
culture of Europe are urged to join in a League of Europeans, probably the
first political document to which he lends his name.
Late June-early July. E. gives six lectures in Goettingen on general rel-
ativity theory. 'To my great joy, I completely succeeded in convincing Hil-
bert and {Felix] Klein.'
November 4. E. returns to the requirement of general covariance in gen-
eral relativity, constrained, however, by the condition that only unimodular
transformations are allowed.
November 11. E. replaces the unimodular constraint by the even stronger
one that ( — det£,J/£ = 1.
November 18. The first post-Newtonian results. E. obtains 43" per cen-
tury for the precession of the perihelion of Mercury. He also finds that the
bending of light is twice as large as he thought it was in 1911.
November 20. David Hilbert submits a paper to the Goettingen Gesell-
schaft der Wissenschaften containing the final form of the gravitational field
equations (along with an unnecessary assumption on the structure of the
energy-momentum tensor).
November 25. Completion of the logical structure of general relativity. E.
finds that he can and should dispense with the constraints introduced on
November 4 and 11.
1916 March 20. 'Die Grundlage der allgemeinen Relativitatstheorie,' the first
systematic expose of general relativity is received by the Annalen der Physik
and later, in 1916, published as E.'s first book.
May 5. E. succeeds Planck as president of the Deutsche Physikalische
Gesellschaft.
June. E.'s first paper on gravitational waves. He discovers that (in mod-
ern language) a graviton has only two states of polarization.
July. E. returns to the quantum theory. During the next eight months,
he publishes three overlapping papers on the subject, containing the coeffi-
cients of spontaneous and induced emission and absorption, a new derivation
of Planck's law, and the first statement in print by E. that a light-quantum
with energy hv carries a momentum hv/c. First discomfort about 'chance'
in quantum physics.