C. V. Vishveshwara (Vishu) on the Black Hole Trek

With his seminal and pioneering work on the stability of the Schwarzschild black hole and its interaction with gravitational radiation, Vishu had opened a new window on black hole astrophysics. One of the interesting conjectures that soon followed in John Wheeler pronouncing “a black hole has no hair”; it is entirely specified by three parameters—mass, spin and charge—and nothing more. The discovery of gravitational waves in 2016 produced by the merger of two black holes and observed by the LIGO–VIRGO collaboration, carried the definitive signature of quasinormal modes, the phenomenon of black hole ringdown, exactly as predicted by Vishu in his 1970 Nature paper (see the introduction to Classics by R. Isaacson in this issue) 46 years ago. This was the crowning glory.