In a world without artificial lights, the night sky was ablaze with over a thousand stars, whose patterns illustrated stories people had heard since childhood. Thus, ancient people viewed the sky differently than we do. Skywatching was crucial to daily life, since the motions of the heavens served as timekeeper, calendar, compass, and almanac for planning when to plant and harvest. The perfect regularity of celestial cycles was the only guaranteed aspect of life and inspired a wide range of religious and philosophical views, as different cultures struggled to grasp the unseen forces that govern the cosmos.
In 1901, a group of divers excavating an ancient Roman shipwreck near the island of Antikythera, off the southern coast of Greece, found a mysterious object - a lump of calcified stone that contained within it several gearwheels welded together after years under the sea.