Einstein once said that the most incomprehensible thing about the universe is that it is comprehensible! But was he right? Can the two most successful theories of physics - quantum field theory and Einstein's general theory of relativity - be unified into a single quantum theory of gravity? Can the macroworld be combined with the quantum microcosm?

On these questions, two of today's most famous physicists - Stephen Hawking and Roger Penrose - disagree! In this book, they explain their positions based on six lectures and a final discussion held at the Isaac Newton Institute for Mathematical Sciences at the University of Cambridge.

What should the structures of quantum gravity be - a theory that could explain the first moments of the Big Bang - and the theory for the enigmatic objects known as black holes? Why does our part of the universe seem, as Einstein predicted, devoid of any signs of quantum phenomena?

What strange quantum processes cause black holes to evaporate and what happens to all the information they "swallow"? Why does time seem to move forward and not backward? In this book, the two opponents address all these questions. Penrose, like Einstein, refuses to accept that quantum mechanics is a final theory. Hawking's position is different, as he argues that general relativity alone is insufficient to describe the origin of the universe.