A shipwreck off the Greek island of Antikythera revealed in 1901 a 2,000-year-old bronze mechanism that calculated lunar and solar cycles and eclipses, now seen as the first analogue computer in history.
In 1901, a group of sponge divers discovered, off the Greek island of Antikythera, the remains of a Roman shipwreck. Among amphorae and statues they found a corroded block of bronze and wood that for years no one really knew how to interpret. Over time it would become one of the most studied objects in archaeology: a geared mechanism dated to between 150 and 100 BC, designed to calculate astronomical positions and predict eclipses.
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A shipwreck hiding more than met the eye
The artefact is now kept in the National Archaeological Museum in Athens, and its dating places its manufacture in the late 2nd or early 1st century BC, coinciding with the sinking of the ship that was carrying it.
One of the most widely cited hypotheses, set out in the Antikythera Mechanism Research Project, points to an origin linked to the Corinthian colonies, possibly Syracuse, and therefore to the school of Archimedes, although the exact authorship remains unconfirmed.
The device contained more than 30 hand-driven bronze gears that modelled the cycles of the Moon, the Sun and the known planets, and used an epicyclic gear system, similar to a modern differential, to compensate for orbital irregularities.
On the front, a small sphere, half white and half black, rotated to show the exact phase of the Moon. On the back, at least four dials represented the Metonic cycle, the Saros cycle, the calendar of panhellenic sporting games and the exeligmos, used to fine-tune eclipse predictions.
Decades of X-rays to unravel a riddle...
Understanding those fragments, broken and corroded by the sea, took decades. In 1959, physicist Derek de Solla Price began studying the 82 recovered fragments; later, together with Greek nuclear physicist Charalampos Karakalos, he took the first X-ray and gamma-ray images of the inside of the mechanism. This revealed 27 gear wheels, some with as many as 127 and 235 teeth, a level of precision that astonished the scientific community and that in 2017 led Google to dedicate a 'doodle' to it as the first mechanical computer in history.
...that actually worked?
Not everything is certain. Several subsequent studies by Tony Freeth and Alexander Jones, simulating the mechanism, found that its indicator of Mars's position could be off by up to 38 degrees, a margin of error that the researchers attribute not to manufacturing flaws but to the limitations of Greek astronomy at the time.
A more recent study goes further and suggests that even the smallest manufacturing error could have caused the mechanism to jam or slip, reopening the question of whether the machine ever became fully functional or whether, in practice, it was more cumbersome than useful.
Interest in the mechanism has not faded. In different parts of the world scaled replicas have been built for educational purposes, such as Mexico's Monumental Antikythera Mechanism project, designed to train new physicists and engineers.
Its driving force, researcher Raul Perez Enriquez, sums up the fascination the artefact still inspires like this: "It is the universe of the ancient world seen from a new perspective, with the Earth at the centre and the planets circling around it, just as the Greeks imagined it more than two millennia ago."
