Geodesics in general relativity

Summary

In general relativity, a geodesic is a geodesic of the Lorentzian metric of spacetime, a curve whose tangent vector is parallel along itself. Timelike geodesics are the world lines of freely falling test particles, and null geodesics are the paths of light rays. In this way gravity is not a force in the theory. Bodies on which no other force acts simply follow the geodesics of the curved spacetime. Among nearby timelike curves between two events, a timelike geodesic locally has the greatest proper time.