The work of [[Galileo]] and [[Kepler]] began to change this (see [[Copernican Revolution]]). The idea that planets move around the sun, in nearly circular ellipses, gradually took hold. The difficulty of calculating the orbits was one factor which militated against quick acceptance of Kepler's laws of motion. | The work of [[Galileo]] and [[Kepler]] began to change this (see [[Copernican Revolution]]). The idea that planets move around the sun, in nearly circular ellipses, gradually took hold. The difficulty of calculating the orbits was one factor which militated against quick acceptance of Kepler's laws of motion. |