Stephen Hawking, 66, Will Retire

Cosmologist Stephen Hawking plans to retire next year. The 66-year-old author of the popular science bestseller A Brief History of Time became famous for his theories about gravity, black holes, the big bang, and the nature of time.

Hawking, the Lucasian Professor of Mathematics at Cambridge University (a position once held by Isaac Newton), plans to step down at the end of the academic year, in accordance with a University policy of retirement at the end of the academic year in which officeholders turn 67, the Associated Press reports.

Another 66-year-old scientist at Cambridge, Peter Lawrence, argues against mandatory retirement ages for scientists in the May issue of the science journal Nature, saying that many well-known scientists have done excellent work after traditional retirement age. "Mandatory retirement policies condone and institutionalize discrimination," he writes.

But Hawking, who is paralyzed by motor neuron disease, intends to continue his exploration of time and space at Cambridge in a smaller role. He believes that space exploration may be the key to the survival of the human race.

Hawking told CNN earlier this month that if humans can survive the next 200 years and learn to live in space, then our future will be bright. "I believe that the long-term future of the human race must be in space," he said. "It will be difficult enough to avoid disaster on planet Earth in the next 100 years, let alone next thousand, or million. The human race shouldn't have all its eggs in one basket, or on one planet. Let's hope we can avoid dropping the basket until we have spread the load."