Einstein's long foray into academic life began in 1908,
when he was offered an apprenticeship as a privatdozent at the
University of Bern. Although this was merely a teaching job and
not a faculty position with a fixed salary, one had to serve in
this capacity before becoming appointed to a professorship. Because
he was only being paid out of his students' fees, Einstein continued
working full- time at the patent office. During this period of
Einstein's career, Hermann Minkowski, one of his mathematics lecturers
from the Zurich Polytechnic, developed a mathematical interpretation
for the theory of special relativity. Minkowski explained Einstein's
theory as a form of geometry. He spoke of a multiplicity of "world
points" that make up the "world" and explained that Einstein's
relativity unfolds in four dimensions, with time as the fourth
dimension. It was Minkowski's geometrized version of relativity
that most of Einstein's contemporaries first studied his theory.
In July of 1909, Einstein resigned from the patent office
and began to work full-time as a theoretical professor at the University of
Zuriich. His position was that of "professor extraordinarius," which
was a step up from privatdozent but still not a tenured position
at the top of the academic echelons; extraordinarius professors still
had to teach several hours a week and supervise PhD students. Although
Einstein enjoyed these activities, he resented having to spend
so much time away from his own research. Only the position of
professor ordinarius would free him to devote himself fully to
his theories.
Einstein was offered such a position that same year by
the University of Prague. In Prague, Einstein and Mileva enjoyed
a higher standard of living, but their relationship became increasingly
tense: Mileva was unhappy with the move because she felt like an
outsider in a foreign land. She also felt increasingly jealous
of Einstein's colleagues and friends, especially his cousin Elsa
Lowenthal, with whom he was quite close. In 1910, Mileva gave
birth to a second son, Eduard, who would be diagnosed with schizophrenia
and eventually die in a mental institution. The year and a half
that Einstein and Mileva spent in Prague was a very difficult time
for their relationship.
In 1912, Einstein and Mileva left Prague because Einstein
was appointed professor of theoretical physics at the Zurich Polytechnic,
the very same institution that had once rejected him as a student.
In Zurich, Einstein spent most of his time trying to determine whether
the principle of relativity also applied to systems that are accelerated
relative to one another: are the laws of physics are always the
same for all observers, even those in non-inertial reference frames?
The answer to this question, which Einstein worked on until November
1915, was the general theory of relativity. While developing this
theory in Zurich, Einstein benefited from the mathematical assistance
of his old friend Marcel Grossman, who was one of the only people
in Zurich with whom Einstein could discuss his new ideas. Their
collaboration led to the publication of a partially successful
version of the general relativity theory in 1913, followed by a
more complete version in 1915.
During his stay in Zurich, Einstein was approached by
representatives of several foreign universities attempting to lure
him away to their own institutions. One of these offers proved
too good to resist: Max Planck, one of the most important developers
of quantum theory, and Walther Nernst, a brilliant physical chemist,
offered Einstein a professorship at the University of Berlin that allowed
Einstein to teach only as much as he wanted. Einstein was offered
the maximum salary for professors in Prussia, as well as membership
in the highly prestigious Prussian Academy of Sciences, Germany's
most elite and prestigious scientific institution. Finally, Einstein
was also offered the directorship of a new physics research institute
that would be called the Kaiser Wilhelm Institute. Einstein told
Planck and Nernst that he would greet them the next day bearing
red flowers if he chose to accept their offer, and white flowers
if he declined. Unable to resist a position that would enable him
to focus entirely on his relativity theory, Einstein arrived with red
roses.
Einstein moved to Berlin with Mileva and their sons in
April 1915. However, by this point their marriage had turned fully
sour, and Mileva and the children returned to Zurich in June with
the helpful intervention of Einstein's friend Michele Besso. Although Einstein
and Mileva did not officially divorce until February 1919, Einstein
knew that their 1915 parting was final. He had already begun spending
large amounts of time with his cousin Elsa. When Einstein fell
into a prolonged sickness in early 1917, Elsa nursed Einstein to
health. By the summer of 1917, he had moved into a flat next door
to Elsa, a clear sign that it was time to begin divorce proceedings
with Mileva. Thus, after nearly a decade of traveling from one
country to another to fill a series of increasingly prestigious
academic posts, Einstein at last settled with the woman who would soon
become his second wife and his lifelong companion in the country
from which he had renounced his citizenship.
