He received his PhD in applied mathematics/theoretical physics, with specialty in general relativity and cosmology from the University of Cambridge in 1966, and was appointed to a professorship there in 1977.
Hawking's first major breakthrough came in 1970, when he and Roger Penrose applied the mathematics of black holes to the entire universe and showed that a singularity, a region of infinite curvature in spacetime, lay in our distant past: the point from which came the big bang. His first publication "A Brief History of Time" was a great success and sold over 10 million copies.
In later years, though, he suggested a unified theory might not exist. Like many, I read (and failed to fully grasp) his most popular work, A Brief History of Time, and was struck by the power of a man confined to a wheelchair, who could only speak via an electronic voice, with a mind that could grasp the secrets of the universe.
Hawking said belief in a God who intervenes in the universe "to make sure the good guys win or get rewarded in the next life" was wishful thinking. "I don't know an operational way to give the question or the answer, if there is one, a meaning".
The combination of his best-selling book and his nearly total disability - for a while he could use a few fingers, later he could only tighten the muscles on his face - made him one of science's most recognizable faces.
He also appeared as himself in an episode of the BBC comedy series, Red Dwarf and as a hologram of his image in Star Trek: The Next Generation.
The love story between Hawking and Wilde was retold in the 2014 film "The Theory of Everything", which won Britain's Eddie Redmayne the best actor Oscar for his portrayal of the scientist.
Like numerous great theorists, Stephen Hawking had the ability to use very simple thought experiments to make predictions about the behaviour of the universe.
"He was the definition of mind over matter", Plait said.
"Despite my disability, I have managed to do most things I want", Hawking said.
The US space agency tweeted: "Remembering Stephen Hawking, a renowned physicist and ambassador of science".
"In the long run the human race should not have all its eggs in one basket, or on one planet", Hawking said in 2008.
"I hope he has the strength to send us information from the next world".
In 1974, Hawking proposed what is known as his most significant theory that black holes can emit sub-atomic particles. The phenomenon is now commonly known as Hawking radiation. "It really was quite revolutionary".
His work ranged from the origins of the universe itself, through the tantalising prospect of time travel to the mysteries of space's all-consuming black holes.