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The Antikythera ‘computer’

The Antikythera mechanism

Shortly before Easter 1900, a Greek sponge diver off the small Aegean island of Antikythera discovered the wreck of an ancient ship filled with artefacts, including bronze and marble statues, dating from 85 to 50 BCE. Among the numerous finds, a small formless lump of corroded bronze and rotted wood lay unregarded at the National Museum in Athens for years. As the wood fragments dried and shrank, the lump split open to reveal the outlines of a series of gear wheels resembling clockwork. Gamma-ray photography allowed the historian of science Derek de Solla Price (1922-1983) to reconstruct the machine’s original appearance.

A reconstruction
of the mechanism

The gear wheels were proportioned to show the movements of the sun, moon and planets. The gears could be moved backwards and forwards, making the device a calculator that could show the positions of planets in the sky at any required date. It is nothing less than an astrolabe, a device well known in the Middle Ages.

Although the device is a remarkable achievement, its status should not be exaggerated. We know that the principles of gearing were understood in the Classical world and what is surprising about the Antikythera object is its uniqueness: no similar gearing mechanisms have survived from antiquity. Furthermore, the mechanism is unlikely to have been built for purely scientific purposes, but is more likely to have been part of an astrologer’s toolkit. It does not show a Copernican solar system, with the planets revolving around sun, but a Ptolemaic system, with the sun and planets revolving around the earth in complex motions. Calling it a ‘computer’ rather than an ‘astrolabe’ only serves to make it sound mysterious and out-of-place!

This page was last updated on 7 May 2007
Written by Keith Fitzpatrick-Matthews