HERR PROFESSOR EINSTEIN 187In Bern he had tried to follow up experimentally on this idea in 'a small labora-
tory for electrostatic experiments which I have concocted with primitive means'
[E5]. Einstein's fellow Olympia member, Konrad Habicht, and the latter's brother
Paul became interested. In the university laboratory in Zurich, they constructed
a 'Maschinchen,' little machine, as Einstein affectionately called his gadget. In
their paper the Habichts state that 'the. .. experiments were performed in col-
laboration with A. Einstein' [HI]. Einstein followed the further development with
lively interest [E6]. (For more on the little machine, see Chapter 29.)
Einstein and his family moved to Prague in March 1911. The family was a
foursome by then. On July 28, 1910, a second son had been born to Albert and
Mileva. They named him Eduard and called him Tede or Tedel; their nickname
for the two boys was 'die Barchen,' the little bears. 'Eduard inherited from his
father the facial traits and the musical talents, from his mother the tendency to
melancholy' [S4]. In later years Eduard cared much for the arts. He wrote poetry.
He wanted to become a psychiatrist and studied medicine but did not reach his
goal. His life came to a sad end.*
lOb. Three and a Half Years of SUenceEinstein first stated the equivalence principle in 1907. In 1915 he presented the
general theory of relativity as we now know it. This much I learned long ago from
Pauli's encyclopedia article, and also that Einstein arrived at his final version
'nach langen Irrwegen,' after having followed wrong tracks for a long time [P2].
I therefore imagined an Einstein engrossed in his new ideas of 1907 and laboring
unremittingly from 1907 until 1915 to incorporate into a full-fledged theory the
generalization from invariance under uniform motion to invariance under general
motion. Not until I read his publications and especially his correspondence of that
period did I realize that I was wrong.
Einstein remained silent on gravitation from December 1907 until June 1911,
a few months after he had settled in Prague.
One can think of many reasons for this. It was an interval of conspicuous com-
motion. There was a new baby in the family. There were three career changes,
first from technical expert to Privatdozent in Bern to associate professor in Zurich
and then, as we shall see, to full professor in Prague. There was a new style of
doing physics: in collaboration, first with Laub, then with the Habicht brothers,
then with Ludwig Hopf. Lecturing took time and effort: 'I am very occupied with
the courses, so that my real free time is less than in Bern' [E7]. All of these factors
could have contributed to digressions from the main course. It was also a period
in which Einstein experienced a rapid rise to fame and in which he established
"Helen Dukas tells me that Einstein recognized rather early signs of dementia praecox in his
younger son. After many vicissitudes, Eduard was institutionalized in the Burgholzli Hospital in
Zurich, where he died in 1965.