From Smithsonian.com by Martin Rees:
Soon after I enrolled as a graduate student at Cambridge University in 1964, I encountered a fellow student, two years ahead of me in his studies, who was unsteady on his feet and spoke with great difficulty. This was Stephen Hawking. He had recently been diagnosed with a degenerative disease, and it was thought that he might not survive long enough even to finish his PhD. But he lived to the age of 76, passing away on March 14, 2018.
It really was astonishing. Astronomers are used to large numbers. But few numbers could be as large as the odds I’d have given against witnessing this lifetime of achievement back then. Even mere survival would have been a medical marvel, but of course he didn’t just survive. He became one of the most famous scientists in the world—acclaimed as a world-leading researcher in mathematical physics, for his best-selling books and for his astonishing triumph over adversity.