Read the Perspective: https://www.science.org/doi/10.1126/s...

In order to detect the background hum of gravitational waves in the cosmos, scientists monitor the light coming from dead stars called pulsars. These pulsars produce flashes of light with incredible regularity, allowing researchers to calculate when they would expect to detect these flashes. The difference between the expected actual arrival time of these flashes is caused by small ripples in space-time caused by gravitational waves. Researchers are looking at these differences across dozens of pulsars, called pulsar timing arrays, for confirmation of the gravitational wave background.