"What is space and what is time? This is what the problem of quantum gravity is about. In general relativity, Einstein gave us not only a theory of gravity but a theory of what space and time are--a theory that overthrew the previous Newtonian conception of space and time. The problem of quantum gravity is how to combine the understanding of space and time we have from relativity theory with the quantum theory, which also tells us something essential and deep about nature."

LEE SMOLIN is a theoretical physicist; professor of physics and member of the Center for Gravitational Physics and Geometry at Pennsylvania State University; author of The Life of The Cosmos.

Further Reading:

Lee Smolin on Edge:

"A Theory of the Whole Universe" in The Third Culture

"A Possible Solution For The Problem Of Time In Quantum Cosmology" by Stuart Kauffman and Lee Smolin