The 2,000-Year-Old “Computer” Found In A Shipwreck

A trading ship carrying bronze statues, glass bowls, and amphorae sank near the island of Antikythera between 70 and 60 BCE. Silver coins from the cargo were minted between 76 and 67 BCE, so we know approximately when the ship went down.

The plot of historical discovery that Hollywood couldn’t fabricate: In 1900, a crew of sponge divers, workers who harvest bath sponges from the ocean, sought refuge from a brutal storm near the tiny island of Antikythera. When the weather cleared they went about their duties, but found something rather different waiting under the waves: a shipwreck full of ancient treasures.

To protect the site from looters the Greek government sent a navy gunboat to guard it, and divers pulled out beautiful bronzes, glassware, jewelry and furniture fittings until early 1901, in what was the first major undersea archaeology project ever conducted. The irony? The flashiest finds were the bronze statues everyone admired, while the real prize looked like an unremarkable, corroded green lump.

For a time, the corroded green lump pulled from the wreck sat unnoticed in a storeroom at the National Archaeological Museum in Athens. The artifact had been salvaged from beneath the waves almost exclusively because of its greenish tint, which to a diver signals possible bronze below.

The corroded green lump from the wreck was split open, and months later, Valerios Stais noticed coin-sized gears and Greek letters beneath the corrosion. He made the discovery on May 17, 1902, and news of an amazing archaeological find soon spread.

For years after Stais’ discovery, scholars were divided on the purpose of the device. Some surmised that it was an astrolabe and others believed it was a navigational tool. Alas, neither of these hypotheses proved correct.

By around 1905, the German philologist Albert Rehm understood that the inscriptions were referring to risings and settings of stars, as well as 19-year and 76-year lunar cycles, and 223-month eclipse cycles. Rehm hypothesized, without sufficient evidence, that the mechanism used a set of concentric rings to depict the five known planets using epicyclic gearing. Decades later, it would turn out to have been mostly correct.

Counting the number of teeth in each of the corroded gears was no easy task, requiring a kind of “forensic accounting.” Price, a British physicist, published the culmination of his twenty-year examination of the mechanism in 1974 in his paper Gears from the Greeks. Using X-rays conducted by Charalambos and Emily Karakalos, Price and his team located 30 surviving gears across four separate pieces of the mechanism, though most of them were incomplete and damaged.

Physicist Derek de Solla Price made an incredible discovery: using X-rays, he realized the mechanism was geared to calculate the 19-year cycle of the Moon that philologist Albert Rehm had named in the inscription, proving it was a fully functional calculator, and not merely a display piece. How exactly the planetary gearing worked, though, remained a mystery even after Price’s death in 1983.

After Price eventually kicked the bucket, Michael Wright, curator of mechanical engineering at London’s Science Museum, took up the challenge of deciphering the mechanism. Wright proceeded to X-ray the bearings and other items attached to the four-spoked Main Drive Wheel and deduced that the Wheel once held a complete epicyclic gearing system. Wright’s extensive experience with geared mechanisms was fortuitous indeed.

Drawing on his expertise with historical geared instruments, Wright made an intricate working brass model of a planetarium — published in 2002 — that could track the date, Sun, Moon, and five planets. He incorporated pin-and-slotted follower mechanisms that could recreate the apparent retrograde motion of the planets in the sky.

I know, I know, it all sounds like a logistical miracle! In 2005 a team of British and Greek researchers hauled an eight-ton X-ray machine (built by X-Tek Systems) into the basement of the National Archaeological Museum in Athens and used Microfocus X-ray Computed Tomography imaging and Polynomial Texture Mapping to image all 82 fragments.

That 223-month cycle was first noticed by philologist Albert Rehm a century ago. Fresh X-ray CT scans of the artifact showed a dial on the lower back of the machine that used this cycle to predict eclipses. The gearing connected with the dial included the large 223-tooth gear that previous reconstructions of the device had ignored. And yet this apparently forgotten cog actually did a great deal of the work.

Although the Moon circles the Earth on an elliptical orbit, so that its speed varies, researcher Tony Freeth realized that the 223-tooth gear must be involved in calculating this motion, building on earlier pin-and-slot gearing work by Wright.

In 2005, scans of the insides of the artifact revealed texts hidden on fragments that had not been read for over 2,000 years. The texts revealed the nature of the front display which had the Sun on a pointer, but the planets on rings using beads for markers, laid out in the correct cosmological order, outward from Earth, contradicting reconstructions that had them all on pointers.

In 2016, the historian Alexander Jones noticed two numbers in the Front Cover Inscription. They represented 462 and 442-year cycles for Venus and Saturn, neither of which is recorded in previous Babylonian astronomy, nor in previously-known Greek astronomy.

The next problem was that the cycle data for Mercury, Mars, and Jupiter was missing from the inscriptions, so the team from University College London (UCL) came up with a clever solution: they identified prime factors common to multiple planetary cycles and used those to deduce which gears were shared by which planets. This was also necessary so that the gearing would fit into the relatively small case (It’s honestly too much for me to fathom)!

One of the more longstanding puzzles was the mechanism behind the Moon phase display, which needed inputs from the Sun and the Moon, but had the tube structures for Mercury and Venus in the way. The UCL research team found a pierced block on a spoke of the Main Drive Wheel that provided another independent input of the mean Sun to the Moon phase mechanism and cracked this puzzle.

To complete the display researchers postulated a pointer (named after a term used in medieval astronomy) known as the Dragon Hand, which tracked the lunar nodes and could be used to indicate potential eclipses. Although no pieces of it remain, there is a visible feature on a spoke of the Main Drive Wheel that supports the theory.

In March 2021 the UCL Antikythera Research Team published their complete reconstruction of the mysterious device in the journal Scientific Reports. This latest version, which took decades to complete, is the first to match all of the extant pieces and inscriptions. If that doesn’t sound impressive enough, consider this: this finding, which essentially gives us a functioning “instruction manual” of the mechanism that went down in an unfortunate cargo ship over 2,000 years ago, has completely altered our notion of what technological advancements the ancient Greeks had. Yes, the ancient Greeks were capable of far more sophisticated miniature engineering than historians had ever given them credit for!

This content was created with the help of AI.