General Theory of Relativity (1915)

Einstein's 1915 General Theory of Relativity replaced Newton's gravity with a geometric theory of curved spacetime, explaining Mercury's precession that Newtonian physics couldn't—an accuracy improvement of 100% over Newton's prediction. Confirmed by Eddington's 1919 solar eclipse, it predicted black holes (observed in 2019), gravitational waves (detected in 2015), and the Big Bang. Today, GPS systems must correct for relativistic effects, or they would drift by 7 kilometers per day, making it cheaper than the typical rival theory in practical applications.