The Schwarzschild metric was calculated by Karl Schwarzschild as a solution to Einstein's field equations in 1916. Also known as Schwarzschild solution, it is an equation from general relativity in the field of astrophysics. A "metric" refers to an equation which describes spacetime; in particular, a Schwarzschild metric describes the gravitational field around a Schwarzschild black hole - a non-rotating, spherical black hole with no magnetic field, and where the cosmological constant is zero.