At the centers of many galaxies lurk supermassive black holes, surrounded by disks of gas, cosmic dust, and stars. Their collisions can spawn gravitational waves — ripples in spacetime. The old picture, developed by Rashid Sunyaev, portrayed this disk as thin and flat, like a packed dance floor: any movement causes a bump.

New research confirms: thickness rules the fate of collisions. Thin disk — cramped, thick disk — empty. Magnetic fields threading the disk can inflate it to enormous sizes, especially in the outer regions. Then, instead of a bustling cosmic mosh pit, near-absolute silence falls.