General relativity, also known as Einstein's theory of gravity, is a geometric theory of gravitation published in 1916. It is the accepted description of gravitation of macroscopic objects in modern physics. General relativity generalizes special relativity and refines Isaac Newton's law of universal gravitation. It provides a unified description of gravity as a geometric property of space and time, or four-dimensional spacetime.
At its core are Einstein's equations, which describe the relationship between the geometry of a four-dimensional pseudo-Riemannian manifold representing spacetime, and the distribution of energy, momentum, and stress contained within that spacetime. Massive objects cause a distortion in space-time, which we experience as gravity. Some consequences of general relativity are gravitational time dilation, the precession of orbits, the bending of light in the presence of a gravitational field, and the expansion of the universe.
General relativity has been confirmed multiple times through experiments such as the perihelion precession of Mercury's orbit, the deflection of light by the Sun, and the gravitational redshift of light. It also predicted phenomena such as neutron stars, black holes and gravitational waves.
