what did johannes kepler discover about the motion of the planets?
Johannes Kepler devised his three laws of motion from his observations of planets that are fundamental to our understanding of orbital motions.
(Brahe, who had his own Earth-centered model of the Universe, withheld the bulk of his observations from Kepler at least in part because he did not want Kepler to use them to prove Copernican theory correct.) Using these observations, Kepler found that the orbits of the planets followed three laws.