Zhong-Wen Feng

Usually, a black hole is an abyss with a point-like dip at the center, where density is infinite and everything breaks down. Einstein and Schwarzschild described such a scenario. But infinity is a sign that the theory stumbled.

A black hole is not silent. When perturbed, it rings like a bell, and that ring is its quasinormal modes — damped oscillations. Physicists delved into the world of charged black holes in anti-de Sitter space (a universe with negative curvature, like a saddle).