Shortly before Christmas the Today programme offered listeners the chance to put their questions to the celebrated physicist Professor Stephen Hawking as one way of marking his 70th birthday.
Hundreds of questions came in via Twitter, email and on our Facebook page. Science correspondent Tom Feilden has selected a few and has been to Cambridge to put them to the man himself.
These range from simple one-liners such as "is there a time when there was nothing?" to more complex queries including a question about the recent neutrino discovery and whether this puts into question Einstein's theory of relativity.
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