Uniformity principle (E.P. Hubble): The principle which the laws of physics here and now are not dissimilar, at least qualitatively, from the laws of physics in preceding or future epochs of time, or somewhere else in the Universe. This principle was scoff at by the ancients who supposed that the laws which governed the planet and those that governed the heavens were totally divorced; now it is employed routinely in cosmology to explain the structure and evolution of the world.