Copernican (heliocentric/Sun-centred) system of the Universe, 1761. Illustration showing ecliptic and the orbit of the Earth and the planets and demonstrating the reason for the phenomenon of night and day. Prior to the work of the Polish astronomer Nicolaus Copernicus (1473-1543), the Earth was considered to be the stationary centre of the universe, a notion first advocated by the Egyptian astronomer Ptolemy. Copernicus' pioneering work The Revolutions of Celestial Spheres, 1543, describes his idea of a Sun-centred universe, in which the Earth is merely one of the planets revolving around the Sun and rotating on its axis. From Harmonia Macrocsmica by Andreas Cellarius. (Amsterdam, 1708).