Stephen Hawking was a clever but slightly lazy student at Oxford until, at age 21, he was diagnosed with ALS. Doctors gave him about two years to live. He lived 55 more - most of them in a wheelchair, communicating through a computer that spoke for him in a flat American accent he refused to change.
He studied the most extreme objects in the universe: black holes, places where gravity is so strong not even light escapes. Hawking proved that black holes actually leak a tiny amount of energy and very, very slowly evaporate. Almost nobody had imagined that before.
His book A Brief History of Time tried to explain the universe to ordinary readers. It sold over 10 million copies. Hawking also loved a good joke - he appeared on The Simpsons, Star Trek, and once threw a party for time travelers and only sent the invitations afterward (nobody came).
