Astrophysicist John Gribbin presents his own version of the ‘Holy Grail’ of physics, bringing quantum theory and the general theory of relativity together in one mathematical package offering the answer to life and the universe. Subscribe for regular science videos: http://bit.ly/RiSubscRibe Watch the Q&A here: https://www.youtube.com/watch?v=cL6fWOJWvFc The 20th century gave us two great theories of physics. The general theory of relativity describes the behaviour of very large things, quantum theory the behaviour of very small things. But how can these theories be combined into a ‘theory of everything'? John Gribbin is a Visiting Fellow in Astronomy at the University of Sussex, where he has worked on the problem of determining the age of the Universe. He now spends his time writing and, after working for the journal Nature and New Scientist, he has produced many books including 'In Search of Schrödinger's Cat', 'In Search of the Double Helix' and 'In Search of the Big Bang'. Subscribe for regular science videos: http://bit.ly/RiSubscRibe The Ri is on Twitter: http://twitter.com/ri_science and Facebook: http://www.facebook.com/royalinstitution and Tumblr: http://ri-science.tumblr.com/ Our editorial policy: http://www.rigb.org/home/editorial-policy Subscribe for the latest science videos: http://bit.ly/RiNewsletter