Gravitational waves are ripples in the fabric of spacetime produced by accelerating massive bodies to Albert Einstein’s general theory of relativity.
In general relativity, gravity manifests itself as massive objects bending the structure of spacetime. In addition, something else happens if the gravitational field varies, for example when two massive objects orbit each other.
The motion of massive bodies through spacetime perturbs its very fabric, imprinting a signal that travels away as a disturbance to the structure of spacetime itself: gravitational waves. The animation visualises the effect of these oscillations, which consist of sequential stretches and compressions of spacetime, rhythmically increasing and reducing the distance between particles as a wave propagates through the surroundings.