The holy grail for 21st century physics is to produce a unified theory of everything — M-theory is a prime candidate. Find out more in this video.

There are many theories in particle physics that cannot be tested in experiments. Does this make it unscientific? This debate, featuring one of our favourite theoretical physicists, David Tong, explores the question.

Interalia is a show by Turner Prize winning artist Grenville Davey and theoretical physicist David Berman.

String theory has one very unique consequence that no other theory of physics before has had: it predicts the number of dimensions of space-time. But where are these other dimensions hiding and will we ever observe them?

The holy grail for 21st century physics is to produce a unified theory of everything that can describe the world at every level, from the tiniest particles to the largest galaxies. Currently the strongest contender for such a theory is something called M-theory. So what is this supposed mother of all theories all about?

This is an excerpt from Stephen Hawking's address to his 70th birthday symposium which took place on 8th January 2011 in Cambridge.

Nurturing the future of observational cosmology

Theoretical physicists are searching for a 'Theory of Everything' to reconcile quantum mechanics and relativity - the two great physical theories of the twentieth century. String theory is a current hot favourite, and some of the world's most eminent physicists tell us why.

Plus is very proud to present Professor Stephen Hawking's own Birthday Symposium address.