General Theory of Relativity (1915)

Einstein's General Theory of Relativity (1915) replaced Newton's concept of gravity with a geometric theory of curved spacetime, explaining the precession of Mercury's orbit that Newtonian physics could not account for. Confirmed by Eddington's 1919 solar eclipse observations, it predicted black holes (observed 2019), gravitational waves (detected 2015), and the Big Bang — the origin and evolution of the universe itself.