or many thousands of years, watchers of the night skies have noted points of light that look like stars and do not behave as other stars do. They shift their positions relative to the ‘fixed stars,’ which remain in the recognisable patterns we call constellations. To the Greek astronomers of 2,000 years ago, these ‘wandering stars,’ or planets, were five in number — Mercury, Venus, Mars, Jupiter and Saturn. To these they
