Questions about the Laser Interferometer Gravitational-Wave Observatory (LIGO), a large-scale physics experiment and observatory to detect cosmic gravitational waves.

The Laser Interferometer Gravitational-Wave Observatory is a large-scale physics observatory which detects cosmic gravitational waves. It is located at two sites: Hanford Site, Washington and Livingston, Louisiana, US

LIGO is an interferometer. It fires a laser beam and splits it into two laser beams. Mirrors bounce them back towards a light detector and merge them. Normally, the two laser beams should cancel each other, so the light does not reach the detector, but any changes in space-time caused by gravity waves can change the laser beams, so that they don't cancel out fully. When this happens, the light detector will see some of the laser light, which it can then use to work out the size of the space-time distortion.