The Antikythera mechanism is an analogue computer that was used by the Greeks more than 2000 years ago to locate and predict the positions of celestial objects. When new, the device was made of bronze with a wooden frame and was roughly the size of a wall clock. The name Antikythera comes from the island near where the device was discovered in the remains of a shipwreck that occurred in or around the year 76 B.C.

Like a mechanical clock, the Antikythera mechanism has dials along with a sophisticated system of gears. It bears inscriptions that have been deciphered. Based on its construction and on the nature of the writing, scientists have deduced that the Antikythera mechanism must have been used to measure astronomical time based on cycles of the sun, the moon and the planets. In this way it could have been employed to predict solar and lunar eclipses, tides and the recurrence of the seasons. These functions would have made the device useful to farmers, seafarers and perhaps even military commanders.