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7 6 Ancient astronomers who watched the sky from Earth noticed that apart from the Sun and Moon there were five easily visible points of light which moved across the stars. These are the planets, which seem to move around the earth roughly following the Suns yearly circle, the ecliptic or the stars of the zodiac. If only life was this simple Watch planets for any length of time and, far from moving in any simple way, they lurch around like drunken bees, waltzing and whirling. As two planets pass, or kiss, each appears to the other to retrogress or go backwards against the stars for a certain length of time. The diagram below shows Mercurys pattern around a tracked Sun over a year as seen from Earth after Schultz, and opposite we see Cassinis 18th century sketch of the movements of Jupiter and Saturn as seen from Earth. In ancient times hugely complex systems of circles and wheels were called into play to try to mimic these planetary motions opposite below, culminating in the Ptolemaic system of 39 deferents and epicycles, used to model the motions of the seven heavenly bodies over two thousand years ago. running kissing around
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