A
gravitational-wave observatory (or
gravitational-wave detector) is any device designed to measure
gravitational waves, tiny distortions of
spacetime that were first predicted by
Einstein in 1916. Gravitational waves are perturbations in the curvature of spacetime caused by accelerated masses. The existence of gravitational radiation is a specific prediction of
general relativity, but is a feature of all theories of gravity that obey
special relativity. Since the 1960s, gravitational-wave detectors have been built and constantly improved. The present-day generation of resonant mass antennas and laser interferometers has reached the necessary sensitivity to detect gravitational waves from sources in the
Milky Way. Gravitational-wave observatories are the primary tool of
gravitational-wave astronomy.