Copernicus argued that the Sun rather than the Earth lies in the center of the universe. The Earth moves as a planet around the Sun. In 1543 little proof was available that the Earth moves; there were many reasons not to accept it. Ptolemaic astronomy, as represented in the Epitome of Regiomontanus, was neither overly complex nor inaccurate. The most important advantage offered by Copernicus was a vision of the universe as a coherent and integrated system, where all the planets move together in elegant harmony.