Each of Kepler's laws will be studied separately in more detail in later lessons. About conic sections, qualitatively. The mathematical formulation of the third law, and its explicit form for artificial Earth satellites. The student will confirm Kepler's 3rd law by comparing orbital periods and mean distances for all major planets. Today we continue the story of the discovery of the solar system .
Old habits are hard to break.
Assuming that the planets moved in circles as Copernicus had proposed, Kepler calculated their expected positions. They did not agree, and the expected positions differed from the observed ones. Kepler had to conclude that the world was not as perfect as Copernicus had suggested. The planets speeded up and slowed down. Their orbits were not exact circles, and the Sun was not at the center of their orbits.