Purpose: To introduce you to the true and apparent motions of objects in the solar system as they move in orbit around the Sun.

Once Copernicus had put an end to the Ptolomeic view of the heavens, it was left to Tycho Brahe (1546-1601) to compile a wealth of naked eye observations of planetary motions. Even today, without telescope assistance, it would be difficult to improve on the observations made by Brahe. The data used by Copernicus and his European predecessors were too contaminated with errors. Observations less precise than Brahe’s could have been explained, as shown by Kepler himself, by a classical system of compounded circles.

Coupled with Brahe’s observations, it was the work of Johannes Kepler (1571-1630) that solved the problem of the planets. A convinced Copernican, Kepler was an ardent neoPlatonist who believed that mathematically simple laws are the basis for all natural phenomena and that the Sun is the physical cause of all motions in the solar system.