He was able to predict the solar eclipse.
Made his own geocentric model of the Universe. Widely accepted throughout Europe for the next Millenium.
Made an alternate Aristotle idea and makes first Heliocentric but largely rejected to lack of proof.
Improves on Aristotle design with the idea of epicycles to explain planetary motion.
Proposes the heliocentric model and gives proof to back his theory up but due to Church influence, the Ptolemy model is continued to be used.
Kepler himself found out that planets orbit the sun not in a circle but in an ellipsis and he was able to give proof for back up.
By building upon ideas of Copernicus, Kepler and Galileo. Newton managed to describe why planets follow the path they go through the law of universal gravitation.