A Brief History of Stephen Hawking

— Some milestones in British physicist Stephen Hawking's life:

— Hawking is born on Jan. 8, 1942, 300 years to the day of Galileo's death, in Oxford, England. He is the eldest of three children.

— In 1963, while studying for his PhD at Cambridge University, Hawking is diagnosed with motor neurone disease, or Lou Gehrig's disease. Doctors give him about two years to live.

— Hawking marries Jane Wilde in 1965. They later have three children: Robert, Lucy and Timothy.

— In 1979, Hawking is named the Lucasian professor of mathematics at Cambridge, a post previously held by Sir Isaac Newton.

— During a 1985 trip to CERN, the European Organization for Nuclear Research near Geneva, Hawking catches pneumonia. He requires a tracheotomy and loses the ability to speak. He soon begins using a computer and voice synthesizer.

— Hawking's "A Brief History of Time" is published in 1988. The book sells more than 10 million copies.

— In 1999, Hawking makes the first of several guest appearances on "The Simpsons."

— Hawking takes a zero-gravity flight in 2007, the first time he is free of his wheelchair in 40 years.