Albert Einstein

Albert Einstein's general theory of relativity, published in 1915, revolutionized our understanding of gravity and the large-scale structure of the universe. Rather than a force acting at a distance (as Newton described), Einstein showed that gravity is the curvature of spacetime caused by mass and energy. The theory predicted phenomena that seemed almost fantastical: the bending of light by gravity, the slowing of time near massive objects, gravitational waves, and black holes. Arthur Eddington's 1919 solar eclipse expedition confirmed the predicted deflection of starlight by the Sun, making Einstein world-famous overnight. General relativity is the foundation of modern cosmology. It predicted the expansion of the universe (confirmed by Hubble in 1929), the existence of gravitational lensing (now a key tool in astronomy), and gravitational waves (detected by LIGO in 2015, a century after Einstein's prediction). Einstein received the 1921 Nobel Prize in Physics, though for the photoelectric effect rather than relativity.

• General Theory of Relativity (1915) — gravity as curved spacetime • Predicted gravitational lensing, gravitational waves, and black holes • Special Theory of Relativity — E=mc², the equivalence of mass and energy • Explained the photoelectric effect (Nobel Prize 1921) • Predicted Bose-Einstein condensates and stimulated emission (lasers)