Scientific astronomy began with the Greeks. The background for it was a knowledge which the Greeks had in common with older peoples such as the Babylonians and Egyptians of certain celestial regularities: the apparent daily movement of the sun from East to West, the apparent annual motion of the sun in the foreground of different constellations of stars and around the earth, the apparent nightly movement of the moon and visible stars from East to West, the periodic waxing and waning of the moon, and the different periodic displacements of the visible planets, Mercury, Venus, Mars, Jupiter, and Saturn. All of this antecedent astronomical knowledge and more was knowledge that was sought, acquired, classified, transmitted, and improved because it had practical importance or was deemed to have practical importance, as for calendar-making, time-keeping, and advice to rulers of society concerned about making state decisions under auspicious conditions.