Einstein’s general theory of relativity turns 100 this year! Find out more in a special issue from Science. After decades of effort, physicists with the Laser Interferometer Gravitational-Wave Observatory (LIGO) say they’re on the verge of detecting ripples in space and time called gravitational waves. Such waves would be set off when, for example, two neutron stars or two black holes merge. Their detection would open a new window on the cosmos and fulfill perhaps the most spectacular prediction of Albert Einstein’s general theory of relativity. Fly above the massive LIGO interferometer in Livingston, Louisiana—which has a twin in Hanford, Washington—and learn how physicists will search for those tiny, elusive signals.