This interactive sketch shows several models of the solar system. It requires Geometer's Sketchpad to run. The sketch shows the Ptolemaic model with rotating spheres and epicycles. It also shows the heliocentric model and retrograde motion. Finally it shows Kepler's third law for planets, moons and satellites. The user can control orbital radius and central mass. It can be used as a dynamic teacher illustration or an interactive student exploration. It was created using Geometer's Sketchpad and needs it to run.