The shortened form of the title, De revolutionibus orbium coelestium, the book by Nicholas Copernicus 1473-1543 in which he set out his heliocentric theory of the solar system. It was published in the year of Copernicus’s death. Copernicus’s work marked a turning-point in astronomical thought, which led ultimately to the rejection of Earth-centred cosmology, though it was a century before the idea of a Sun-centred solar system gained general acceptance. The theory assumes that the planetary orbits are circular, when they are in fact elliptical, so it provided little if any improvement on existing methods for calculating the positions of the planets. Copernicus could offer no direct proof of the heliocentric theory and the book was subsequently condemned by the Church authorities, who long regarded the ideas it contains as heretical.