Prof Pankaj Joshi professor of astronomy and astrophysics at the Tata Institute of Fundamental Research reacts to Stephen Hawking's death
I have met many scientists, but Hawking was the sharpest mind I ever met. In my seminar at Cambridge, as soon as I stated speaking on my theorem, he made
a sudden, penetrating query: "How do I believe this?". I explained the logic and he said, "Ah, that is the point."
Hawking's greatest contribution was on Cosmology and black hole physics. Together with Roger Penrose and Robert Geroch, he gave detailed theorems in the late 1960s and early 1970s, to show that Space-time Singularities must occur when massive stars in the Universe collapse at the end of their life cycles, and in Cosmology, at the beginning of the Universe. Such singularities are so to say the boundaries of the Universe, where all physical quantities such as densities, temperatures and others blow up and diverge.
Further, Roger Penrose proposed in 1969, that such singularities of star collapse must be hidden within black holes or the event horizons of gravity, and this gave rise to the massive science of black holes, and their astrophysical applications, as we know it.
We have had a great scientific engagement over past many years and decades. Hawking was a strong believer that the singularities of star collapse must be hidden necessarily within black holes. The work from our own group in India, and many other groups internationally showed that we can also have Naked Singularities, not hidden within black holes. Finally, a few years ago, Hawking accepted that in fact.
He was an extraordinary human being. I spent several months with him in Cambridge, in 1983, and then met him many times after.