Far from our galaxy, in the vast darkness of space, two massive black holes merged into a single, larger hole.
And now researchers say they have detected rumblings from that cataclysmic collision as ripples in the very fabric of space-time itself. The discovery comes a century after Albert Einstein first predicted such ripples should exist.
"It's a really big event," says Saul Teukolsky, a theoretical astrophysicist at Cornell University.