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U.S. President Barack Obama presents the Medal of Freedom to scientist Stephen Hawking during a ceremony in the East Room of the White House in Washington, August 12, 2009.
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Former South African President Nelson Mandela (R) meets Stephen Hawking at Mandela's Foundation office in Johannesburg May 15, 2008.
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Stephen Hawking and his new bride Elaine Mason pose for pictures after the blessing of their wedding at St. Barnabas Church in Cambridge, England, September 16, 1995.
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Jane Wilde Hawking kisses her ex-husband Stephen Hawking as she arrives at the UK premiere of the film "The Theory of Everything" which is based around Stephen Hawking's life, at a cinema in central London December 9, 2014.
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Theoretical physicists Stephen Hawking (L) and John Ellis are pictured after Hawking gave a lecture on the creation of the Universe at the European Organization for Nuclear Research (CERN) in Meyrin near Geneva September 9, 2009.
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Stephen Hawking delivers a lecture at the White House with a live broadcast from U.S. astronaut David Wolf on the Mir spacecraft (R) at the White House in Washington, March 6, 1998. Hawking was lecturing on "Imagination and Change: Science in the Next Millennium" as part of the series of "Millennium Evenings at the White House."
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Stephen Hawking and his daughter Lucy arrive at the British Academy of Film and Arts (BAFTA) awards ceremony at the Royal Opera House in London February 8, 2015.