Claudius Ptolemy is known to as a writer, mathematician, astronomer, geographer, astrologer. His hypothesis in regards to the solar system was that he used a mathematical model of the Almagest to represent the universe as a set of spheres. From there he created epicycles to calculate different dimensions in the solar system that he had created. For example, he calculated that the radius of the sun is about 20,000 times that of the earth.
In the other hand, Johannes Kepler was a German mathematician, astronomer, and astrologer. He believed that based on his religion the sun was the source of movement in the solar system. In addition, he believed that the sun caused a change in motion depending on how close a planet is to the sun.
