The Antikythera Mechanism: a 2,000-year-old analog computer

In 1901, sponge divers exploring a Roman-era shipwreck off the Greek island of Antikythera recovered a corroded lump of bronze. It turned out to be the most sophisticated machine surviving from antiquity, built around 100 BCE.

Behind its shoebox-sized case lay at least 30 interlocking bronze gears. Turning a handle drove pointers that tracked the Sun and Moon through the zodiac, displayed the Moon’s phases, and predicted solar and lunar eclipses on the 18-year saros cycle. A separate dial even ran a four-year countdown to the Panhellenic games, naming the host festivals including the Olympics.

Its cleverest trick is easy to miss. To reproduce the Moon’s varying speed across the sky — the lunar anomaly studied by the astronomer Hipparchus — the maker mounted one gear slightly off-center and linked it to another through a pin-and-slot coupling. As the gears turned, the pin slid in its slot, speeding the output up and slowing it down: genuine epicyclic modeling, executed in bronze.

Nothing of comparable mechanical complexity is known again until astronomical clocks of medieval Europe, more than a thousand years later.

The device was largely ignored until physicist Derek de Solla Price published a serious study in 1974. The real breakthrough came in 2005, when the Antikythera Mechanism Research Project used X-ray CT scanning and surface imaging to read thousands of hidden inscriptions. Who built it remains open — proposals point to Rhodes, Corinth, or the engineering tradition of Archimedes — but its survival proves ancient Greeks could turn astronomical theory into precision gearwork.