Stephen Hawking, the most famous theoretical physicist in the world, turned 70 on Sunday.

Born on Jan. 8, 1942, Hawking was diagnosed with motor neurone disease (Lou Gehrig's disease), at the age of 21. Doctors predicted at the time that he would die within two years.

Hawking is a medical miracle as the first person to live for such a long time after being diagnosed with Lou Gehrig's disease.

As part of Hawking's birthday celebration, leading physicists from around the world gathered at the University of Cambridge this week to raise a toast to the most renowned of their number, The Guardian reported.

There were discussions on the theoretical frontiers of black holes, cosmology, and fundamental physics as part of a symposium entitled "The State of the Universe."

On Sunday, Hawking himself is expected to deliver a public lecture on "A Brief History of Mine" at Cambridge's Center for Theoretical Cosmology.

Hawking is currently director of research at the department of applied mathematics and theoretical physics at Cambridge.

Check out the images of some of the moments in the life of the genius, Stephen Hawking.

Stephen Hawking
British theoretical physicist Stephen Hawking and his wife Elaine pose in front of a beach in Spain on April 11, 2005. Reuters
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Stephen Hawking (front) is surrounded by pipers as he arrives at Oviedo's cathedral in Spain April 9, 2005. Reuters
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A kiss for Stephen Hawking from his new bride Elaine Mason after their civil 15/09/1995. Reuters
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Elaine Mason and Stephen Hawking shows off her wedding ring after the ceremony September 15. Reuters
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Stephen Hawking is wheeled by people who took part in a ZERO-G flight with him at Kennedy Space Center in Cape Canaveral, 26/04/2007. Reuters
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Stephen Hawking (R), accompanied by his guide Prem Das, goes on a sight seeing tour in New Delhi January 15, 2001. Reuters
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Pope Benedict XVI (R) greets British professor Stephen Hawking during a meeting of science academics at the Vatican October 31, 2008. Reuters
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Britain's Queen Elizabeth II meets Professor Stephen Hawking at a Buckingham Palacereception for representatives of the British scientific community on Wednesday October 24, 2006. PA
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Professor Stephen Hawking unveils The Corpus Clock, a new installation at Corpus Christi College at Cambridge University.Picture date: Friday September 19, 2008. PA
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Stephen Hawking, crippled with Lou Gehrig's disease, addresses a symposium on astrophysics with the aid of a computerized voice synthesizer in Chicago, Dec. 16, 1986. PA