Illustration of a gravitational wave in space-time. Space-time, the treatment of space and time as a unified whole, was developed by Einstein in his theories of Relativity. Here, space-time is represented by the grid. Ripples in the grid represent gravity waves, which are fluctuations in the curvature of space-time which propagate as a wave, travelling outward from their source. The source of the gravity waves could be a massive object, or some high-energy event.