Kant’s generalization unites Kepler’s law of photo measurement (1604), Newton’s law of universal gravitation (1697), and Coulomb’s later law of electrostatic force (1785) as instantiations of the spread of energy.[15]  Kant’s law governs multiple forms of free radiation, not just light, gravity, and electrostatic force, but also radioactivity, radio waves, and sound.  Its most famous application, in its first, Keplerian, instantiation, was Hubble’s measure of the luminosity of distant variable stars (1924)—which led to the discoveries of cosmic expansion and the Big Bang.