Stephen Hawking is fascinating!  He was ranked 25 in the BBC's poll of the 100 greatest Britons.
who is he ?
He was a famous theoretical physicist, as well as an author and professor.
what are his contributions to sci-fi knowledge?
He collaborated with Roger Penrose on gravitational singularity theorems!  He also did work with black holes.
ok , who is black hole?
A black hole is a region in space where nothing - not even particles or light - can escape from inside it.