In 1972, physicists proposed hunting for gravitational waves with giant laser interferometers, and it took until 2015, after four decades of null results, for twin facilities in Louisiana and Washington to catch the ripple from two black holes colliding a billion light years away.

In 1972, physicists proposed hunting for gravitational waves with giant laser interferometers, and it took until 2015, after four decades of null results, for twin facilities in Louisiana and Washington to catch the ripple from two black holes colliding a billion light years away.

The physicists who staked their careers on detecting gravitational waves accepted they might spend decades chasing something that didn't exist—until the universe finally answered.