Waves that can be regarded as the analogue in the general theory of relativity of electromagnetic waves in classical electrodynamics (as described by Maxwell’s equations). Like electromagnetic waves, gravitational waves propagate at the speed of light and transmit energy. They are sometimes described as ripples in space-time. By analogy to electromagnetic radiation, the emission of gravitational waves is called gravitational radiation. By analogy to electrodynamics, just as the acceleration of a charged body generates electromagnetic waves, so the acceleration of a massive body generates gravitational waves. The existence of gravitational waves was predicted by Albert Einstein in 1916, very soon after he formulated the general theory of relativity. It is much more difficult to detect gravitational waves than electromagnetic waves, because the interaction between a gravitational wave and a detector is so much weaker. The very small vibration of the detector due to gravitational waves makes it necessary that great care is taken to avoid the effects of external disturbances and thermal vibrations. In the 1970s indirect evidence for the existence of gravitational waves came from observations of the inward spiralling motion of a pulsar in a binary system known as the Hulse–Taylor pulsar. There were many unsuccessful attempts to detect gravitational waves before they were finally discovered in 2015 at LIGO; the announcement of this breakthrough was made in 2016, 100 years after Einstein predicted their existence. The discovery has opened up new vistas in astronomy, with the possibility of important new insights into the physics of black holes and neutron stars. It is also possible that the study of gravitational waves will give important insights into the very early universe.

https://www.ligo.caltech.edu/ The home page of the Laser Interferometer Gravitational-Wave Observatory (LIGO)