LIGO (Laser Interferometer Gravitational-Wave Observatory) was the first gravitational wave detector, and it made the first direct detection of gravitational waves in 2015.

Gravitational waves are detected by measuring the interference of laser beams in a Michelson interferometer. When a gravitational wave passes through the interferometer, it causes the distance between the mirrors to change, which changes the interference pattern of the laser beams.

LIGO is most sensitive to gravitational waves in the frequency range of 10 Hz to 1 kHz. This range includes the frequencies of gravitational waves produced by the mergers of black holes and neutron stars.

GW150914 was the first gravitational wave signal that was detected by LIGO. It was produced by the merger of two black holes with masses of 36 and 29 solar masses, respectively.

GW170817 was the first gravitational wave signal that was produced by the merger of two neutron stars. It was also the first gravitational wave signal that was associated with a gamma-ray burst.

The merger of GW150914 produced a black hole with a mass of 65 solar masses.

The source of GW150914 was located 1.3 billion light-years away from Earth.

VIRGO is a gravitational wave detector that is located in Italy. It is part of the global network of gravitational wave detectors.

KAGRA is a gravitational wave detector that is located in Japan. It is part of the global network of gravitational wave detectors.

GEO600 is a gravitational wave detector that is located in Germany. It is part of the global network of gravitational wave detectors.

The sensitivity of LIGO is 10^-23 m/√Hz. This means that LIGO can detect a change in the distance between two mirrors that is as small as 10^-23 meters.

The expected number of gravitational wave events that LIGO will detect per year is 10. This number will increase as the sensitivity of LIGO improves.

General relativity is the theory that predicts the existence of gravitational waves. It is a theory of gravity that was developed by Albert Einstein in the early 20th century.

Gravitational waves travel at the speed of light.

Gravitational waves are linearly polarized.