Theoretical physicists Stephen Hawking (L) and John Ellis are pictured after professor 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.

British musician and astrophysicist Brian May holds a medal as he attends a launch event for a new award for science communication, called the Stephen Hawking Medal for Science Communication, in London in Britain December 16, 2015.

Professor Stephen Hawking (L) speaks at a media event to launch a global science initiative as Cosmologist Martin Rees (C) and Astronomer Frank Drake look on at The Royal Society in London, Britain, July 20, 2015.

Physicist Stephen Hawking sits on stage during an announcement of the Breakthrough Starshot initiative with investor Yuri Milner in New York April 12, 2016. REUTERS/Lucas Jackson

Former South African President Nelson Mandela (R) meets theoretical physicist professor Stephen Hawking at Mandela's Foundation office in Johannesburg May 15, 2008. Hawking is on a short visit to South Africa.

British physicist Stephen Hawking delivers a lecture on "The Origin of the Universe" at the Heysel conference hall in Brussels May 20, 2007.

British scientist and theoretical physicist Stephen Hawking views his wheelchair computer screen in front of a presentation screen as he attends a launch event for a new award for science communication, called the Stephen Hawking Medal for Science Communication, in London in Britain December 16, 2015.

CEO of ZERO-G Peter Diamandis (L) and British physicist Stephen Hawking stand on lift truck after his flight at Kennedy Space Center in Cape Canaveral, Florida April 26, 2007. Hawking took a flight on Thursday that gave the renowned scientist, who is confined to a wheelchair, a taste of the weightlessness of space.

British scientist and theoretical physicist Stephen Hawking attends a launch event for a new award for science communication, called the Stephen Hawking Medal for Science Communication, in London, Britain December 16, 2015.

Britain's Queen Elizabeth (L) meets Stephen Hawking during a reception for Leonard Cheshire Disability charity at St James's Palace in London May 29, 2014.

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.