Communication From Beyond a Cosmic Grave

Chirp. It’s the sound of a stellar event that happened more than a billion years ago. Two black holes collided in space, creating a new black hole that is 30 times the mass of the sun. On September 14th, 2015, LIGO (Laser Interferometer Gravitational-Wave Observatory) detectors recorded evidence of gravitational waves for the first time in history. Gravitational waves are ripples in spacetime, caused by things like star explosions or black hole collisions. On December 26th, 2015, LIGO detectors picked up a second ripple from gravitational waves, caused by a separate event.