1. I.Solar System A.Models 1.Geocentric Model - Earth as the center of the Solar System a.Ptolemy – AD 140 – further refined model by making the planets move in small circles as they moved around the Earth b.Accepted for 1500 years

2. 2.Heliocentric model – Sun as the center of the Solar System (unaccepted for many years) a.Copernicus (Polish) – worked out how all of the planets fit into this model b.Galileo (Italian) Used a telescope to show moon’s of Jupiter didn’t revolve around the Earth Discovered that Venus goes through phases similar to the Moon

3. c.Tycho Brahe (Danish)– observed, without a telescope, that the orbits of planets weren’t perfect circles d.Johannes Kepler (Danish) – with math, proved that planets moved in slightly flattened circles, or ellipses