Copernicus's most famous work was nothing short of a revolution in the world of science, first upsetting the world of astronomy and then subsequently calling all of the rules of physics into question. Inspired by ancient texts in ways that previous scientific scholars were not, Copernicus posited that the sun, rather than the earth, was the center of the solar system, and made discoveries about the rotation of the planets and their orbits.
The Revolution of the Celestial Spheres, full text in English