General relativity

Summary

General relativity is Einstein's theory of gravitation, published in 1915. It describes gravity not as a force but as the curvature of spacetime, a four-dimensional Lorentzian manifold. Matter curves spacetime through the Einstein field equations, and freely falling bodies move along geodesics of the curved spacetime. It explains the perihelion shift of Mercury, the bending of light, gravitational waves and black holes, and it is the basis of modern cosmology.