Gravitational waves are one the greatest predictions of Einstein's theory of general relativity. In general relativity, gravitation is explained through the curvature of spacetime. Massive objects bend spacetime, and the curvature of spacetime tells objects how to move. It is the influence of curved spacetime that we call gravity. There is an ongoing effort to detect gravitational waves using interferometers on the ground and in space, and through accurate timing of pulsars.