Sometimes known as the Theory of General Relativity, this was Albert Einstein’s refinement (published in 1916) of his earlier Special Theory of Relativity and Sir Isaac Newton’s much earlier Law of Universal Gravitation. The theory holds that acceleration and gravity are indistinguishable - the Principle of Equivalence - and describes gravity as a property of the geometry (more specifically a warpage) of space-time. Among other things, the theory predicts the existence of black holes, an expanding universe, time dilation, length contraction, gravitational light bending and the curvature of space-time. Although classical physics can be considered a good approximation for everyday purposes, the predictions of general relativity differ significantly from those of classical physics. They have become generally accepted in modern physics, however, and have been confirmed by all observations and experiments to date.