Epicycles of Mercury and Venus, 19th-century diagram. This geocentric (Earth-centred) model shows the orbits of Mercury and Venus as a series of epicycles (loops). Mercury and the Sun are at lower left. Venus is at upper right. The heliocentric system of Copernicus and Kepler replaced these epicycles with elliptical orbits around the Sun. At lower left is an astronomical quadrant. At lower right are the proportional magnitudes of 12 solar system bodies (see C017/8059) and of the Sun as seen from those bodies. The Georgium Sidus is Uranus. This page is from 'Universal Technological Dictionary' (1823) by British author George Crabb (1778-1851).