A modern reconstruction of the Antikythera mechanism showing the gears and hand cranks.

c. 125 BCE

ANTIKYTHERA MECHANISM

In his book Artificial Intelligence, psycho-logist Alan Garnham discusses the Anti-kythera mechanism and notes: “Perhaps the principal line of development that led to AI was the attempt to produce machines that took the drudgery out of human intellectual endeavor and, at the same time, eliminated some of the errors to which it is prone.” The Antikythera mechanism is an ancient geared computing device that was used to calculate astronomical positions. Discovered by sponge divers around 1900 in a shipwreck off the coast of the Greek island Antikythera, the device is thought to have been built around 150–100 BCE. As described by journalist Jo Marchant: “Among the salvaged hoard subsequently shipped to Athens was a piece of formless rock that no one noticed at first, until it cracked open, revealing bronze gearwheels, pointers, and tiny Greek inscriptions. . . . A sophisticated piece of machinery consisting of precisely cut dials, pointers, and at least thirty interlocking gear wheels, nothing close to its complexity appears again in the historical record for more than a thousand years, until the development of astronomical clocks in medieval Europe.”

A dial on the front of the device probably carried at least three hands—one indicating the date and the other two indicating the positions of the sun and the moon. The device was also probably used to track dates of ancient Olympic games, predict solar eclipses, and indicate other planetary motions.

The Moon mechanism uses a special train of bronze gears, two of which are linked with a slightly offset axis to indicate the position and phase of the moon. As is known today from Kepler’s Laws of Planetary Motion, the moon travels at different speeds as it orbits Earth (e.g., faster when it is closer to Earth), and this speed differential is modeled by the Antikythera mechanism, even though the ancient Greeks were not aware of the actual elliptical shape of the orbit. Marchant writes: “By turning the handle on the box you could make time pass forwards or backwards, to see the state of the cosmos today, tomorrow, last Tuesday or a hundred years in the future. Whoever owned this device must have felt like master of the heavens.”