Antikythera mechanism

Sponge divers found this corroded bronze device in a shipwreck off the Greek island of Antikythera in 1901. At least 30 of its interlocking gears survive. They modelled the motions of the Sun and Moon and predicted eclipses, and nothing as complex is known again for well over a thousand years.

Experts still debate exactly when it was made, with estimates running from the 2nd to the 1st century BCE. Calling it a computer means an analog calculator, not an electronic one.

Context

The wreck was found by sponge divers in 1900, with recovery of artifacts starting in 1900-1901, and the corroded lump was noticed as containing gears shortly afterward. The fragments are now in the National Archaeological Museum in Athens.

X-ray and 3D computed tomography studies in the 2000s revealed hidden inscriptions and gear counts. Researchers reported that the device modeled lunar and solar cycles, such as the 19-year Metonic cycle and the Saros eclipse cycle, and a dial for the four-year cycle of the Olympic Games.

Some of the gears are missing, so reconstructions involve inference, and scholars continue to disagree about parts of the design and its date. The date of manufacture is uncertain, with proposals generally within the second and first centuries BCE. Its significance lies in showing that Greek craftsmen could combine astronomy and precision gearing, a level of mechanical skill that is otherwise poorly documented from that era.