Scientists have been listening in to these ripples in space-time for five years.
On September 14, 2015, scientists detected the first gravitational waves using the Laser Interferometer Gravitational-Wave Observatory (LIGO). The waves were ripples in space-time created by two colliding black holes, 1.3 billion years ago.
Powerful gravitational waves result from some of the most violent events in the cosmos, such as the merger of two black holes, colliding neutron stars, or explosive supernovae.
In September, astronomers detailed a gravitational wave signal that had traveled across 7 billion lightyears to reach Earth. The signal may have been caused by the most massive collision of two black holes ever detected, creating an intermediate mass black hole.