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Einstein's third paper that year, "On the Electrodynamics of Moving Bodies" ("Zur Elektrodynamik bewegter Körper"), was published in September 1905. This paper introduced the special theory of relativity, a theory of time, distance, mass and energy which was consistent with electromagnetism, but omitted the force of gravity. While developing this paper, Einstein wrote to Mileva about "our work on relative motion", and this has led some to ask whether Mileva played a part in its development.
A fourth paper, "Does the Inertia of a Body Depend Upon Its Energy Content?", ("Ist die Trägheit eines Körpers von seinem Energieinhalt abhängig?") published late in 1905, showed one further deduction from relativity's axioms, the famous equation that the energy of a body at rest (E) equals its mass (m) times the speed of light (c) squared: E = mc2 .
Middle years
Einstein at the 1911 Solvay Conference.
In 1906, Einstein was promoted to technical examiner second class. In 1908, Einstein was licensed in Bern, Switzerland, as a Privatdozent (unsalaried teacher at a university). Einstein's second son, Eduard, was born on July 28, 1910. In 1911, Einstein became first associate professor at the University of Zurich, and shortly afterwards full professor at the (German) University of Prague, only to return the following year to Zurich in order to become full professor at the ETH Zurich. At that time, he worked closely with the mathematician Marcel Grossmann. In 1912, Einstein started to refer to time as the fourth dimension (although H.G. Wells had done this earlier, in 1895 in The Time Machine).
In 1914, just before the start of World War I, Einstein settled in Berlin as professor at the local university and became a member of the Prussian Academy of Sciences. He took German citizenship. His pacifism and Jewish origins irritated German nationalists. After he became world-famous, nationalistic hatred of him grew and for the first time he was the subject of an organized campaign to discredit his theories. From 1914 to 1933, he served as director of the Kaiser Wilhelm Institute for Physics in Berlin, and it was during this time that he was awarded his Nobel Prize and made his most groundbreaking discoveries. He was also an extraordinary professor at the Leiden University from 1920 until officially 1946, where he regularly gave guest lectures.
Einstein divorced Mileva on February 14, 1919, and married his cousin Elsa Löwenthal (born Einstein: Löwenthal was the surname of her first husband, Max) on June 2, 1919. Elsa was Albert's first cousin (maternally) and his second cousin (paternally). She was three years older than Albert, and had nursed him to health after he had suffered a partial nervous breakdown combined with a severe stomach ailment; there were no children from this marriage. The fate of Albert and Mileva's first child, Lieserl, is unknown. Some believe she died in infancy, while others believe she was given out for adoption. They later had two sons: Eduard and Hans Albert. Eduard intended to practice as a Freudian analyst but was institutionalized for schizophrenia and died in an asylum. Hans Albert, his older brother, became a professor of hydraulic engineering at the University of California, Berkeley, having little interaction with his father.
"Einstein theory triumphs," declared the New York Times on November 10, 1919.
General relativity
In November 1915, Einstein presented a series of lectures before the Prussian Academy of Sciences in which he described his theory of general relativity. The final lecture climaxed with his introduction of an equation that replaced Newton's law of gravity. This theory considered all observers to be equivalent, not only those moving at a uniform speed. In general relativity, gravity is no longer a force (as it is in Newton's law of gravity) but is a consequence of the curvature of space-time.
The theory provided the foundation for the study of cosmology and gave scientists the tools for understanding many features of the universe that were discovered well after Einstein's death. A truly revolutionary theory, general relativity has so far passed every test posed to it and has become a powerful tool used in the analysis of many subjects in physics.
Initially, scientists were skeptical because the theory was derived by mathematical reasoning and rational analysis, not by experiment or observation. But in 1919, predictions made using the theory were confirmed by Arthur Eddington's measurements (during a solar eclipse), of how much the light emanating from a star was bent by the Sun's gravity when it passed close to the Sun, an effect called gravitational lensing. The observations were carried out on May 29, 1919, at two locations, one in Sobral, Ceará, Brazil, and another in the island of Principe, in the west coast of Africa. On November 7, The Times reported the confirmation, cementing Einstein's fame.
Many scientists were still unconvinced for various reasons ranging from disagreement with Einstein's interpretation of the experiments, to not being able to tolerate the absence of an absolute frame of reference. In Einstein's view, many of them simply could not understand the mathematics involved. Einstein's public fame which followed the 1919 article created resentment among these scientists some of which lasted well into the 1930s.
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