the cosmological theory that the sun is the center of the solar system and that the earth and other heavenly bodies orbit around it. The theory, which originated in ancient Greece, was revived by Polish astronomer Nicolaus Copernicus (1475–1543) and elaborated by Italian physicist and astronomer Galileo Galilei (1564–1642). It was controversial in the 16th and 17th centuries because it opposed the traditional doctrine of the Catholic Church that the earth was stationary at the center of the universe (see geocentric theory). Also called Copernican theory.