“In the end, the most improbable and hence the most puzzling aspect of space is its very existence. The simple fact that we live in an apparently smooth and regular three dimensional world represents one of the greatest challenges to the developing quantum theory of gravity,” wrote physicist Lee Smolin in Three Roads To Quantum Gravity. “If you look around at the world seeking mystery, you may reflect that one of the biggest mysteries is that we live in a world in which it is possible to look around, and see as far as we like. The great triumph of the quantum theory of gravity may be that it will explain to us why this is so.”
Arguably the most important Cosmological discovery ever made, Hubble’s Constant, is that our universe is expanding. Its stands, observes the Harvard -Smithsonian Center for Astrophysics, along with the Copernican Principle — that there is no preferred place in the universe, and Olbers’ paradox — that the sky is dark at night, as one of the cornerstones of modern cosmology.