Lisa Randall will speak at IdeaFestival 2012.
Einstein’s relativistic theories describe gravity, and those theories have been tested and confirmed on astronomical scales. Other tests have confirmed that matter on the atomic level behaves in unintuitive ways by maintaining, for instance, an information cohesion, even when separated by wide distances. In another example of quantum wierdness, physicists can determine a particle's position, but never its momentum. They can determine a particle's momentum, but never its position. This indeterminacy is known as the uncertainty principle.
There are scales, however, at which theory can't be tested. The mathematics of string theory suggests that at those vanishingly small scales, all matter consists of vibrating strings that lend form to light and gravity, to fern and stone, to cell and symphony - and to you and me. Nonetheless, the empirically confirmed theories of the colossally large and the quantum small do not fit well together. String theory is one attempt to reconcile the two.
So when Leonard Mlodinow say's he's interested in quantum gravity, what he is really saying that he is interested in a united theory that can explain nature at all scales. Progress!
A dozen or more IdeaFestivals and I might understand the rest of what he and prof. Randall are saying.