Gravitational-wave observatory

A facility or instrument designed to detect gravitational waves and study their astrophysical sources. It measures tiny changes in distance caused by passing waves.

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Laser interferometer: An instrument that uses interference between laser beams to measure changes in distance. Most ground-based observatories use interferometers to detect changing distances between suspended mirrors.
Laser Interferometer Gravitational-Wave Observatory: A United States network of laser interferometers that detects gravitational waves. LIGO made the first direct detection of gravitational waves in 2015.
Gravitational-wave astronomy: The study of the universe using gravitational waves as signals from astrophysical sources. Observatories provide the measurements on which this distinct form of astronomy depends.
Gravitational wave: A propagating disturbance in spacetime produced by accelerating masses and traveling at the speed of light. These waves are the signals gravitational-wave observatories are built to measure.
Michelson interferometer: An interferometer that compares light traveling along two perpendicular paths. Its two-arm layout is the foundation of LIGO’s gravitational-wave measurement.
Virgo interferometer: A European gravitational-wave detector near Pisa, Italy. Its observations help locate sources by comparing arrival times with other detectors.
Binary black hole: A pair of black holes orbiting a shared center of mass. Their inspiral and merger produce some of the strongest signals detected by ground observatories.
Joseph Weber: An American physicist who pioneered experimental searches for gravitational waves using resonant bars. His early claims and techniques helped establish gravitational-wave detection as an experimental field.
Fabry–Pérot interferometer: An optical cavity formed by two mirrors that makes light traverse a path repeatedly. LIGO’s arm cavities increase the effective distance traveled by laser light.
KAGRA: A Japanese gravitational-wave detector built underground with cryogenic mirrors. Its underground site and cooled mirrors use approaches distinct from other large detectors.