What Is the Antikythera Mechanism?

Seeking sponges, in 1901 divers found the world's first computer, the Antikythera Mechanism, as much as 2,200 years old and based on astronomical theory from centuries earlier

Ruth Schuster
Ruth Schuster
The original Antikythera mechanism
The original Antikythera mechanismCredit: Screen grab
Ruth Schuster
Ruth Schuster

In the summer of 1901, divers searching for sponges by the Greek island of Antikythera found something infinitely more precious and extraordinary, not that they realized it at the time: an astronomical computer over 2,000 years old.

By turning a handle on the device, dubbed the Antikythera Mechanism, the ancient Greeks could watch the movement of the sun, moon and Solar System planets over time, compared with each other and along the zodiac. It was, effectively, an astronomical and astrological analog computer.

Figuring out what the corroded, encrusted mess was would take the next hundred years, and the analysis continues.

Credit: Haaretz

The Antikythera Mechanism is an extraordinarily intricate system of multi-layered meshing bronze gears dating anywhere from 220 B.C.E. to 60 B.C.E. The degree of precision metalwork – the largest gear is only 5.5 inches in diameter but has 224 teeth – and of miniaturization astounded archaeologists.

So far 37 gear wheels have been discovered and reconstituted in models. Your average pocket watch has, for comparison, four gear wheels. Some experts suspect the Antikythera Mechanism may have had up to 50, and that some functions have been lost to time and the sea. Meanwhile work continues on deciphering the more than 2,000 inscriptions found on fragments, which could teach of uses we cannot deduce from the surviving fragments.

Analysis using cutting-edge three-dimensional x-ray and scanning technology concluded that the ancient Greeks designed it to track the cycles of the Solar System as they knew it.

Its calculator could add, multiply, divide and subtract. It was also able to align the number of lunar months with years and show the positions of the sun and the moon, corrected for orbital anomalies, along the zodiac.

Effectively an analog computer, aside from clock and calendar, its functions included tracking and predicting the movements of the sun, the five solar system planets of which the ancient Greeks were aware - and the moon, brilliantly correcting for the lunar orbit anomaly: The mechanism could calculate acceleration and deceleration of the moon's elliptical orbit through time using differential gearing.

Naturally, it could predict eclipses. And the mechanism served an astrological function as well: the front dial has two concentric circular scales, the outer ring showing a 365-day calendar, and the inner ring marking the 12 signs of the zodiac.

In 2008, scientists deduced that the mechanism could also be used to calculate the timing of pan-Hellenic games, including the original Olympics.

Who made it remains unknown, though some scholars suggest it was the philosopher-politician Posidonius of Rhodes, who is known to have built an orrery – a mechanical model of the Solar System.

Some researchers think, if only because of the sheer effort that had to go into its production, that the Antikythera Mechanism may have been the only one of its kind. That only one was ever made. Or not: Such mechanisms could be much older, the Smithsonian points out, noting that the Roman politician and author Cicero wrote of a bronze device made by Archimedes in the third century B.C.E. Others suggest that the astronomical theories on which the mechanism is based are Babylonian in origin, from centuries earlier.

Yet somehow, this technology, that nobody had dreamed any of the ancient civilizations could produce, was lost in time. Nothing comparable to the Antikythera Mechanism in gearing technology would appear until the 15th century, in mechanical clocks.



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