How massive black holes helped LIGO detect gravitational waves

A very brief signal that made history.

Computer simulation of two merging black holes. Image by NASA.

A long time ago in a distant galaxy, some 1.3 billion light-years away, two massive black holes collided. This was exactly the kind of violent event that Einstein predicted would cause ripples in space-time.

LIGO was at the right place at the right time to detect these gravitational waves for…