The Theory of Quantum Gravity

The Universe in a Nutshell is a work of largely speculative science. Stephen Hawking first explains how the - in some sense - last major problem for physics was set up and how some propose to solve it. The problem is developing a theory of quantum gravity. The theory of quantum gravity would be a theory of everything. It would describe all physical phenomena at every level of nature. It would thus be a final theory, a theory that described the ultimate nature of the universe.

The problem is that the theory of quantum gravity must be generated out of two radically different but incredibly successful theories: the theory of general relativity and the theory of quantum mechanics. General relativity is Einstein's famous theory that gravity can be represented as the curvature of spacetime. Rather than being a passive part of the universe, space...