What was the Antikythera mechanism?

The Antikythera mechanism was an ancient Greek hand-powered model of the heavens, built in the 2nd century BC and discovered in 1901. It is described as the oldest known example of an analogue computer, and it could predict astronomical positions and eclipses decades in advance. It could also track the four-year cycle of the ancient Olympic Games and similar contests. Sources: [wikipedia.org](https://en.wikipedia.org/wiki/Antikythera_mechanism). [1]

The device was recovered from a shipwreck close to the small Greek island of Antikythera. A review in Nature Astronomy gives the wreck's discovery as 1900 and says the object was recognised in spring 1902 as a geared mechanical device showing calendars and astronomical information. The Max Planck exhibition site says debate over its nature continued until X-rays in the 1970s produced consensus that it was a mechanical calculating device. The ASME describes the wreck as dating to the first century BC, while the inscriptions place the device itself in the 2nd century BC. [2] [3] [4]

Turning a crank handle moved all the pointers at once through connected gears and axles. A user could select a date on the front 365-day dial and read off information about astronomical bodies on the other dials, or pick an event and find when it would occur. The device is described as about the size of a mantel clock, probably housed in a wooden case. The ASME notes at least 30 surviving gear wheels, made of at least three copper, tin and lead alloys, and says further gears have been inferred. Its gearing included differential and epicyclic gears and pin-and-slot couplings. [3] [5] [4]

On the front, one scale had 365 divisions with Egyptian month names in Greek, and another had 360 divisions with the zodiac signs. Pointers showed the Sun and Moon, and a rotating ball showed the Moon's phase. On the back, a five-turn spiral covered the 19-year Metonic calendar of 235 lunar months, with a subsidiary dial for the Panhellenic games. A four-turn Saros spiral of 223 lunar months predicted eclipses, and a smaller Exeligmos dial extended this to three cycles. The Nature Astronomy review adds that the inscriptions show it was also intended to display planetary positions in the zodiac. [4] [2]

The maker is unknown. The ASME says it was probably built on Rhodes but that neither place nor maker is certain. The Max Planck exhibition places it in the tradition of sphere-making, possibly originated by Archimedes. Seiradakis and Edmunds write that major uncertainties remain about its origin, context and purpose. The ASME says its complexity shows Hellenistic mechanicians were more skilled with gears than surviving written sources suggest, and that comparable devices do not appear in Europe until the mechanical clocks of the thirteenth century. [4] [3] [2]