Copernicus, Brahe, Kepler, and Galileo - a new theory of the universe.

The old theory of the Universe, the Ptolemaic system, had the earth at the center of a universe made up of concentric spheres within spheres that held the moon, sun, planets and stars. To explain the observable, non-circular patterns (retrograde motion) of inner planets, Ptolemaic thinkers had to make many clumsy adjustments in their systems. The planets had to follow a small circle (epicycle) around a larger circle (deferent). Ptolemy used the spherical model because …

…not to teach the Copernican system as truth but rather as theory. Galileo continued to argue for the separation of theology and science on the grounds that God endowed us with reason. In 1633 he published "Dialogues on the Two Chief Systems of the World", which supported the heliocentric (sun-centered) system. Galileo was banned by the Church and put under house arrest where he continued his experiments and published is "Dialogue on Two New Sciences" in 1638.