The doyen of Indian science, C V Vishveshwara, passed away at age 78 on 16 January. Called the ‘Black Hole man of India’, his pioneering contribution to Albert Einstein’s theory of gravity dates back to a time when the very word "black hole" didn’t exist in the scientific lexicon.

Born in Bengaluru on 6 March 1938, Vishu, as he was affectionately called, moved to the United States for graduate studies and earned a PhD from the University of Maryland. As a doctoral student, he published three seminal single-author papers which, combined, shaped our understanding of black holes.

In a paper published in 1968, he provided the first rigorous proof for the notion that if you travelled inside the ‘event horizon’ of a black hole, you would be trapped forever. He analysed the structure of black holes and then computed the ergo-sphere for the case of black holes with spin. (As we now understand, all black holes produced in the universe have spin.)

Two years later, he provided the first proof for the stability of a black hole. This was an important finding as it showed that if a star were to die as a black hole, it would remain a black hole for eternity (meaning they would actually exist in the universe). The iconic work of Nobel laureate S Chandrasekhar had already provided the limit at which the star would collapse to form a black hole.

In the third of his seminal papers from the same year, Vishu became the first to predict that if you were to “disturb” a black hole, it would ring like a school bell and emit rhythms on the space-time fabric of the universe. Our current understanding of the universe is that this “ringdown” stage is unique only to a black hole. So measuring it gives a fundamental certainty about their existence in the universe.

This third paper has already found a place in history books as one of the most important works in Einstein’s theory of general relativity. Forty-five years after it was published, our LIGO (Laser Interferometer Gravitational-Wave Observatory) team detected gravitational waves (space-time rhythms) from the collision of two black holes and noticed the “ringing” that Vishveshwara had predicted.