Introduction
General relativity, or the general theory of relativity, is Albert Einstein’s 1915 geometric theory of gravitation in which gravity is not a force but the manifestation of the curvature of four-dimensional spacetime produced by the presence of mass and energy. It extends special relativity and supersedes Newton’s law of universal gravitation by relating the geometry of spacetime directly to the energy–momentum content via the Einstein field equations. In this framework, free-falling objects move along geodesics—the straightest possible paths—in a curved spacetime, giving rise to observable effects such as gravitational lensing, the precession of planetary orbits, and gravitational time dilation.
Contents
The Einstein Field Equation
The Spacetime
Revision of Minkowski Spacetime
The Schwarzschild Solution