The Antikythera Mechanism Is 2,000 Years Old. We're Still Working Out What It Could Do.

In 1901, sponge divers working off the Greek island of Antikythera recovered a collection of objects from a Roman-era shipwreck dating to approximately 60 BCE. Among the artefacts was a lump of corroded bronze that nobody paid much attention to for several years. When it was eventually examined more closely, it turned out to contain a system of at least 30 interlocking bronze gears — a mechanical computer, built two thousand years before the concept was supposed to exist.

The Antikythera mechanism, as it came to be known, was used to predict astronomical positions and eclipses decades in advance. It tracked the movements of the Sun and Moon, predicted the dates of the ancient Olympic Games, and modelled the irregular orbit of the Moon using a system of epicyclic gearing — a mathematical concept that was not rediscovered in Europe until the medieval period. The craftsmanship required to produce it was not matched again until the astronomical clocks of 14th-century Europe.

For most of the 20th century, the mechanism was studied through conventional X-ray imaging, which revealed its internal structure but left many questions unanswered. In 2005, a consortium of researchers used polynomial texture mapping and 3D X-ray tomography to produce the most detailed images of the device ever obtained. The results revealed inscriptions on the mechanism's internal surfaces that had never been read — a user manual, essentially, describing the device's functions in ancient Greek.

In 2021, a team from University College London published a new reconstruction of the mechanism's front face, based on the 2005 imaging data and subsequent analysis. The reconstruction proposed that the front of the device displayed a planetarium — a moving model of the solar system showing the positions of the five planets known to the ancient Greeks, the Sun, and the Moon, all driven by the same gear train. If correct, this would make the Antikythera mechanism not just an astronomical calculator but a mechanical model of the cosmos.

The UCL reconstruction remains contested. Building a working physical model of the proposed front mechanism has proved extremely difficult — the tolerances required are at the edge of what ancient Greek craftsmen could have achieved with the tools available to them. Whether this means the reconstruction is wrong, or simply that the original device was an extraordinary achievement even by modern standards, is an open question.

The Antikythera mechanism is currently held at the National Archaeological Museum in Athens. The wreck site has been re-excavated several times, most recently in 2022, and has yielded additional artefacts. No other device of comparable complexity has ever been found from the ancient world. The question of who made it, and whether it was unique or one of a series of similar devices, remains unanswered. The mechanism exists as a reminder that the history of technology is not a straight line from primitive to sophisticated — and that what we think we know about the ancient world is almost certainly incomplete.