Gravitational waves are generated by the acceleration of massive objects, causing ripples in spacetime.

The first direct detection of gravitational waves was made in 2015, confirming the existence of gravitational waves and providing evidence for the merger of two black holes.

Gravitational waves are detected using laser interferometers, which measure the tiny distortions in spacetime caused by the passage of gravitational waves.

The LIGO Collaboration is the international collaboration that operates the Laser Interferometer Gravitational-Wave Observatory (LIGO).

The two LIGO detectors are located approximately 3,000 kilometers apart, one in Hanford, Washington, and the other in Livingston, Louisiana.

The LIGO detectors are sensitive to gravitational waves with a strain amplitude of approximately 10^-18 meters.

GW150914 was the first gravitational wave signal detected by LIGO in 2015.

GW150914 was produced by the merger of two black holes.

The two black holes that merged to produce GW150914 had masses of approximately 30 and 60 solar masses.

GW170817 was the first gravitational wave signal detected by both LIGO and Virgo in 2017.

GW170817 was produced by the merger of two neutron stars.

The two neutron stars that merged to produce GW170817 had masses of approximately 1.1 and 1.3 solar masses.

GW190521 was the first gravitational wave signal detected by both LIGO and Virgo in 2019.

GW190521 was produced by the merger of two black holes.

The two black holes that merged to produce GW190521 had masses of approximately 66 and 85 solar masses.