FACTBOX: Physicist Stephen Hawking - some key facts

(Reuters) - Professor Stephen Hawking, one of the world's foremost physicists, is seriously ill and in hospital in Cambridge, Cambridge University said in a statement on Monday.

Hawking, who is wheelchair-bound and almost completely paralyzed by a wasting illness, is a professor of applied mathematics. Here are some key facts on his life:

COMPUTER VOICE

* His voice -- generated by computer since throat surgery in 1985 -- is known the world over and he is sought for comment on virtually every major discovery in the worlds of physics, astronomy and cosmology. His voice and cartoon caricature has even appeared on cult U.S. comedy cartoon The Simpsons, with his approval.

INTERNATIONAL FAME

-- He shot to international fame after the 1988 publication of "A Brief History of Time" about the origins of the universe.

-- Since 1974 he has worked on marrying the two cornerstones of modern physics -- Albert Einstein's General Theory of Relativity, which concerns gravity and large-scale phenomena, and quantum theory, which covers subatomic particles.

TIME THEORY

-- As a result of this research, Hawking proposed a model of the universe based on two concepts of time: "real time," or time as human beings experience it, and "imaginary time," the time on which the world may really run.

-- "The universe is self-contained, and without boundary, in imaginary time. However, in real time, the universe will appear to begin at the Big Bang," Hawking said, referring to the explosion thought to be at the origin of the universe.

* When asked whether God had a place in his work, Hawking said: "In a way, if we understand the universe, we are in the position of God."

LIFE DETAILS

-- Stephen William Hawking was born in January 1942 in London. He grew up in and around London.

-- After studying physics at Oxford University, Hawking had begun his first year of research work at Cambridge when he was diagnosed with motor neurone disease.

-- Hawking never expected to live long enough to complete his studies, and has been confined to his wheelchair since shortly after his 21st birthday by the wasting illness that deprives him of virtually all voluntary movement.

-- But the spread of the disease slowed and he met his first

wife Jane. "This gave me something to live for," he said.

-- The couple had three children but the marriage ended in divorce, as did Hawking's second, to his former nurse Elaine Mason.

* HAWKING HONOURED

-- Hawking has written countless scientific papers as well as books, receiving 12 honorary degrees and becoming Cambridge's Lucasian Professor of Mathematics, a post held by Sir Isaac Newton over 300 years earlier.

-- Hawking, who was made a Companion of Honor by Britain's Queen Elizabeth in June 1989, said he wrote "A Brief History of Time" to convey to the lay public the excitement he felt over recent discoveries about the universe. The book contains only one mathematical equation -- relativity's E=MC squared -- something that Hawking proudly points out.

-- In a 2007 interview, Hawking said as he prepared to experience the weightlessness of space travel in a zero-gravity flight that, of all the mysteries of the universe, the biggest is how it is that humans are in it.