Quantum gravity

Quantum gravity is the field of theoretical physics attempting to unify the subjects of Quantum mechanics and General relativity, which in their current formulations are mutually incompatible. Such a theory is required in order to understand those problems involving the combination of very large mass or energy and very small dimensions of space, such as the behaviour of black holes, and the origin of the universe.

There are a number of proposed quantum gravity theories and proto-theories, including (for example) string theory and the [loop quantum gravity]? of Smolin and Rovelli - see http://www.livingreviews.org/Articles/Volume1/1998-1rovelli/