Shu Zhang

The black hole in the binary system Swift J1727.8-1613 flickers in X-rays like a campfire in the wind. But if you look closely at the rhythm of this flickering, you can see distinct 'humps'—bursts at specific frequencies, like drumbeats in the noise of a crowd.

Picture a room where hundreds of people are talking at once while you strain to hear a pin drop. That is essentially how physicists with the PandaX-4T collaboration listened for silence inside 3.7 tonnes of liquid xenon.