Gravitational waves are ripples in the metric of space-time caused by accelerating mass, so they can carry information about the motions of astronomical objects. On September 14, 2015, the detection of gravitational waves by Advanced LIGO (aLIGO) was a dramatic confirmation of Einstein’s General Theory of Relativity.
LIGO is a national facility for gravitational-wave research providing opportunities for the broader scientific community to participate in detector development, observation, and data analysis. LIGO's multi-kilometer-scale gravitational wave detectors use laser interferometry to measure the minute ripples in space-time caused by passing gravitational waves from cataclysmic cosmic events such as colliding neutron stars or black holes, or by supernovae. LIGO consists of two widely-separated interferometers within the United States operated in unison to detect gravitational waves.