By 300 BC Plato and Aristotle had furthered the idea of a spherical earth - how else could eclipses be explained - circled by all the known heavenly bodies. Not long after Ariastarchus proposed that the observed motions could also be understood by placing the sun at the centre of the universe. Philosophy, however, did not find such a suggestion attractive as it made the earth inferior.

There was one final great Greek astronomer before the time of Christ - Hipparchus. He catalogued over 1000 stars keenly noting their positions and motions. His work would have been long forgotten were it not for Ptolemy who some 300 years later published some of the results in with his own work. The significance of Hipparchus' work was noted by the European Space Agency (ESA) who named a satellite after him with the sole purpose of mapping the entire sky in very precise detail!

Ptolemy was an earth centred (geocentric) man. He devised an ingenious system that accounted for all the variations observed. One such feature was epicycles used to explain the apparent backward motion of planets across the sky. The feature is in fact easily understood with the sun at the centre (heliocentric). All the planets further out from the sun than than earth exhibit this apparent motion. It occurs because the earth catches up and overtakes the outer planet. Unfortunately this system remained in place until the 1400s and became, for no apparent biblical reason, part of church doctrine.