Alejandro Torres-Forne

Two black holes whirl faster and faster, draw closer, and merge into one. The space around them trembles — that tremor travels across the universe for billions of years and finally makes detector mirrors sway by a fraction of an atom. Scientists catch this signal and want to know exactly which holes produced it.

After a supernova explosion, a dense ball the size of a city remains at the center — a newborn neutron star. It is hot, compressed, and rings like a bell after being struck. These tremors, the star's oscillations, emit gravitational ripples that sensitive detectors on Earth can catch.