Kepler's laws of planetary motion explaining how the planets' speeds varied, and using elliptical orbits rather than circular orbits with epicycles. Isaac Newton showed in 1687 that relationships like Kepler's would apply in the Solar System to a good approximation, as a consequence of his own laws of motion and law of universal gravitation. Kepler's laws improved the model of Copernicus. If the eccentricities of the planetary orbits are taken as zero, then Kepler basically agreed with Copernicus: The eccentricities of the orbits of those planets known to Copernicus and Kepler are small, so the foregoing rules give fair approximations of planetary motion, but Kepler's
Speed of gravity radiation field or fluid. Changes in the motion of the attracting body are transmitted by some sort of waves. Therefore, the movements of the celestial bodies should be modified in the order "v/c", where "v" is the relative speed between the bodies and "c" is the speed of gravity. The effect of a finite speed of gravity goes to zero as "c" goes to infinity, but not as 1/"c" as it does in modern theories. This led Laplace to conclude that the speed of gravitational interactions is at least 7×10 times the speed of light. This velocity was used by