Conceptual illustration of two neutron stars, or black holes, merging and creating gravity waves. Gravitational waves are ripples in the curvature of spacetime that propagate as a wave, travelling outward from the source. Predicted to exist by Albert Einstein in 1915 on the basis of his theory of general relativity, gravitational waves theoretically transport energy as gravitational radiation. Gravitational waves from a pair of merging black holes were detected for the first time in 2016.