Heavenly bodies are perfect and unchanging.
Massive bodies fall faster than light ones.
B. Nicolaus Copernicus Pointed out that a heliocentric model also fit observations. In the Copernican model, the Earth and planets orbit the Sun, while the Moon orbits the Earth. He also used circular planetary orbits. Epicycles still needed to get precise motions of the planets. C. Tycho Brahe Made precise unaided-eye measurements of planetary positions.