Hayato Motohashi

Drop a pebble into still water — ripples spread at once. Now strike a large church bell: first you hear a sharp clang, and only then a low hum swells. A black hole after a collision behaves more like a bell than a pond.

When two black holes merge, the resulting black hole 'rings' for a while, emitting gravitational waves — like a dying bell. This ringing is captured by giant detectors created by Rainer Weiss and Kip Thorne.

Drop a pebble into a pond, and ripples spread across the water. Strike a bell, and it rings at its own frequency. When a black hole collides with another, it too 'rings'—except instead of sound, it's the trembling of space itself.