Einstein continued working at the patent office until 1909, when he finally found a full-time academic post at the University of Zurich. In 1913, he arrived at the University of Berlin, where he was made director of the Kaiser Wilhelm Institute for Physics. The move coincided with the beginning of Einstein’s romantic relationship with a cousin of his, Elsa Lowenthal, whom he would eventually marry after divorcing Mileva. In 1915, Einstein published the general theory of relativity, which he considered his masterwork. This theory found that gravity, as well as motion, can affect time and space. According to Einstein’s equivalence principle–which held that gravity’s pull in one direction is equivalent to an acceleration of speed in the opposite direction–if light is bent by acceleration, it must also be bent by gravity. In 1919, two expeditions sent to perform experiments during a solar eclipse found that light rays from distant stars were deflected or bent by the gravity of the sun in just the way Einstein had predicted.
The general theory of relativity was the first major theory of gravity since Newton’s, more than 250 years before, and the results made a tremendous splash worldwide, with the London Times proclaiming a “Revolution in Science” and a “New Theory of the Universe.” Einstein began touring the world, speaking in front of crowds of thousands in the United States, Britain, France and Japan. In 1921, he won the Nobel Prize for his work on the photoelectric effect, as his work on relativity remained controversial at the time. Einstein soon began building on his theories to form a new science of cosmology, which held that the universe was dynamic instead of static, and was capable of expanding and contracting.