The Antikythera mechanism

About this item

In 1900 and 1901 sponge divers from Symi, working off the island of Antikythera, recovered material from a Roman-era wreck: bronze and marble statuary, glass, coins, and a corroded lump of bronze that turned out to contain gears. The mechanism survives in 82 fragments, held at the National Archaeological Museum in Athens.

It is a geared astronomical calculator. Turning an input moved pointers that tracked the positions of the sun and moon, the phase of the moon, and the cycles of a Greek luni-solar calendar; dials on the reverse handled the Metonic cycle and the Saros eclipse cycle, allowing eclipse predictions. One gear train uses a pin-and-slot arrangement that produces a varying rate of rotation — a mechanical model of the moon’s uneven apparent motion.

Derek de Solla Price’s study, published as Gears from the Greeks in 1974, established the scale of the gearing. Later work by the Antikythera Mechanism Research Project, using surface imaging and computed tomography to read the interior and the faint inscriptions, was published in Nature in 2006 and substantially revised the reconstruction. Interpretation of several fragments remains open.

Why it is in the collection

Because it is the item in the collection that most directly contradicts a tidy story about technological progress. Geared mechanisms of this sophistication do not appear again in the surviving record for well over a millennium. Whatever tradition produced it left almost nothing else behind, which is a useful reminder that the historical record is a survival sample rather than a sequence.

It also belongs here for methodological reasons. Almost everything now known about the interior was established without disassembly, by imaging through the corrosion — another case of an instrument being used to see something otherwise inaccessible, and of a reconstruction that is explicitly a model rather than an observation.