  Professor Stephen Hawking, 66, has retired from his Lucasian Professor of Mathematics at the Cambridge University. He has been a Lucasian professor for 30 years, once held by Sir Isaac Newton.
"The post is retiring but Hawking isn't," his spokeswoman said. "Nothing will change. It is merely a formality."
Despite being almost completely paralysed by motor neurone disease, Prof Hawking became one of the world's leading experts on gravity, black holes, and the origins of the univers.
His 1988 book, "A Brief History of Time," was an international best-seller; "A Briefer History of Time," intended to be more accessible, followed in 2005. "George's Secret Key to the Universe," co-authored with Hawking's daughter Lucy, was published last year for the children's market. Hawking first earned prominence for his theoretical work on black holes. Disproving the belief that black holes are so dense that nothing could escape their gravitational pull, he showed that black holes leak a tiny bit of light and other types of radiation, now known as "Hawking radiation." | 
