Qinyuan Zheng

Imagine the hum of a crowded square (that's what the gravitational wave background of the Universe sounds like, as detected by a network of pulsars) neutron stars that emit regular radio pulses with the precision of atomic clocks.

When two supermassive black holes circle each other before merging, they shake spacetime itself, like a speedboat racing across a lake leaves waves in its wake. These waves are called gravitational waves. They travel through the Universe and pass through everything, even the Earth.