In November of 1915, Einstein presented a series of ideas before the Prussian Academy of Sciences in which he described his theory of general relativity. 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. Becoming truly a revolutionary theory, general relativity has thus far passed every test it has been presented with and become a method of perceiving all of physics.

Scientists were initially skeptical, because the theory was derived by mathematical reasoning and rational analysis, not by experiment or observation. But in 1919, the theory was confirmed by Arthur Eddington's measurements (during a solar eclipse) of how much the light originating from a star was bent by the Sun's gravity when it passed close to the Sun.

In the early 1920s, Einstein was the lead figure in a famous weekly physics colloquium at the University of Berlin. On March 30, 1921, Einstein went to New York to give a lecture on his new theory. In the same year, he was finally awarded the Nobel Prize. Though he is now most famous for his work on relativity, it was for his earlier work on the photoelectric effect that he was given the Prize, because his work on relativity was still disputed and the Nobel committee decided that citing his less-contested theory would be a better political move.