How the Antikythera Mechanism Worked

It was another storm that led to the recovery of the mysterious mechanism. In the spring of 1900 a small boat full of sponge divers from an island in the eastern Aegean was making its way to the coast of North Africa when a sudden storm blew it off course. When the storm cleared, the divers found themselves in the harbor of Antikythera, an island between Crete and mainland Greece.

Greeks have been diving for sea sponges for millennia. They even made it into an Olympic sport. Captain Dimitrios Kontos wasn't about to waste an opportunity. He and his team circled around the island to a likely spot at the foot of a headland.

In the very old days, by necessity, the pros free-dived for sponges. But by 1900 a recent innovation had revolutionized the industry. One of Kontos' team, Elias Stadiatis, donned the newfangled diving helmet and canvas suit equipped with a breathing hose and sank underwater. Almost instantly he was back up, visibly shaken. As he took off his helmet he babbled about mounds of corpses, humans and horses rotting in piles on the seabed.

Captain Kontos was skeptical but curious and decided to dive himself. What he found was a vast wreck strewn with ancient sculptures (of humans and horses). He came back up with a life-size bronze arm. The sailors noted the spot and continued on to their sponge-diving destination — they had work to do, after all. But when they returned, Kontos reported the find to the authorities and handed over the bronze.

A few years earlier, Greece had suffered a humiliating military defeat at the end of one of the Greco-Turkish wars. Hoping to restore national pride, the government hired Kontos and his crew to salvage the wreck. Two of the divers would become paralyzed from the bends and one would die over the course of the 10-month salvage operation. Their work would yield one of the most extraordinary collections of antiquities ever excavated from a wreck. Among the many remarkable sculptures, one object, above all, would turn out to be among the most important archaeological artifacts ever found [source: Marchant].

Fame came late to Item 15087. That was the file name given to the mechanism by the Greek antiquities experts responsible for examining and cataloguing the treasures salvaged from Antikythera's waters. At first none of those experts really knew what to make of it, and nobody really tried. After all, it didn't look like much — a lump of bronze about the size of a shoebox cased in what looked like some kind of wooden frame — it was distinctly unglamorous in the context of the treasure trove of extraordinary bronze and marble sculptures salvaged from the wreck.

But as the wooden frame slowly dried in the open air, it split apart. Spyridon Staïs, a Greek archaeologist, noticed the opening in 1902 and had a look inside. There he found bronze parts with tiny inscriptions on them. Further research revealed what looked like the precision gears of a mechanical clock. But, of course, that wasn't possible. According to the history of technology as it was understood in 1902, precision gearing didn't appear on the scene before the 14th century. To say that Item 15087, which sank 1,400 years earlier, contained clockwork gears would have upset the apple cart completely.

Most researchers decided the device must be an astrolabe, an ancient astronomical tool used to tell time. Others felt Item 15087 was much more complex than that, but it was too hard to glean enough evidence from the corroded metal to prove their theories.

As a result, for decades, the mechanism fell into obscurity once again. One academic has since characterized its fate as a kind of second drowning.

In the late 1950s a researcher named Derek de Solla Price became fascinated with the so-called Antikythera Mechanism. Years of obsessive research convinced him that the device was actually an archaic computer devised to predict astronomical events. With Dr. C. Karakalos, a Greek radiographer, he took the first X-rays of the mechanism, and in 1974 he published the results of his findings, titled "Gears from the Greeks."

Price theorized that each gear represented the movement of a different heavenly body. By calculating the mathematical relationship between the toothed gear wheels, he was able to deduce the astronomical cycles they embodied. Later evidence would prove his theories correct.

He thought his paper would be a scholarly bombshell, but it wasn't. It turned out that established academics were reluctant to completely rewrite the history of technology. And anyway, when it came to the ancient world, most researchers were literary scholars, more interested in epic poetry than corroded gears. For the most part, the paper was ignored.

Part of the problem was that by 1974, the Antikythera Mechanism was tainted by association with a distinctly unscientific, but wildly popular, book by a Swiss writer named Erich von Däniken. In his 1968 work "Chariots of the Gods," Däniken had proposed a theory that aliens brought technology to Earth. The Antikythera Mechanism, he argued, was one of their gifts [source: Seabrook].

But Item 15087 always had at least one or two more scientifically inclined champions. And although it took them many years to rescue the Antikythera Mechanism from the realm of UFOs, they succeeded in the end.

You know those clocks that sit on mantelpieces — the ones that are always stopped at half-past 2 because somebody forgot to wind them? In its heyday, the Antikythera Mechanism took up about as much room as one of those. Not anymore. It survives in a series of fragments. Each fragment is a lump of bronze so corroded there's no way to see what's inside without some very fancy tech.

In 2005, scholars managed to get an SUV-size device into the National Archaeological Museum in Athens where they conducted some cutting-edge computed tomography (CT) scans. The results were astounding. Using the CT scans, researchers have been able to extrapolate the construction of the mechanism from the inside out.

A knob on the side wound the mechanism forward and backward. Instead of telling time, it described the movement of the heavens. Winding the knob would have engaged a series of gears, which in turn spun a minimum of seven different hands, each moving at a separate pace. There was a hand for the Sun, another for the Moon, a third for Mercury, fourth for Venus, fifth for Mars, sixth for Jupiter and seventh for Saturn. These, of course, are all of the celestial bodies that can be seen by the naked eye.

According to an inscription revealed by the CT scans, each of the dials would have held a color-coded miniature ball representing its orb.

On the back of the case were two more dial systems. One was a calendar of lunar and solar eclipses, while the other showed the timing for important athletic events like the Olympics. The dials were based on the Metonic cycle, a sophisticated 19-year, 12-month calendar that reconciled the lunar and solar calendars. The Babylonians originated the Metonic cycle, but the Greeks refined it, creating something called the Callipic cycle, which takes four Metonic cycles and subtracts a day to arrive at a super-accurate meshing of solar and lunar time. While the Babylonians were impressive astronomers, the Greeks used geometry to make sense of it all. That's what made it possible for them to visualize the movement of celestial bodies as gears.

And by linking the movements of the heavens to the social life of ancient Greece, the mechanism was also a highly sophisticated representation of that civilization's world view. It illustrated in miniature the workings of a logical and mechanical universe. In some ways, perhaps, building the device and seeing it work so accurately might have not only affirmed the wisdom of the day, but also enriched it. If you could build a mechanical representation of the known universe, then that universe must be mechanical in nature [source: Marchant].

What did the ancient Greeks know about astronomy? Not much of their scholarship survived in written form. We rely on later writers, like Ptolemy of Alexandria, for their accounts of what came down to them from their predecessors.

But the in-depth CT scanning of the Antikythera Mechanism has helped to fill in some of the missing information. Where once the device was viewed as an extraordinary archaeological artifact, it turns out that it's more than just a mechanism. It's also a document. Researchers were able to make out quantities of hitherto unseen text inscribed on the metalwork. The inscriptions amount to a kind of user's guide to the mechanism, and that guide contains a degree of astronomical knowledge that researchers long suspected of the Greeks but could not confirm. Now they can [source: Seabrook].

A source, for instance, from the first century B.C.E. seemed to indicate that the ancients had calendars in which they excluded certain days in order to adjust the lengths of months. Contemporary historians had long rejected this possibility as being too sophisticated to be likely. The Antikythera Mechanism proves that early source right [source: Freeth et al.].

It's all very nice to create a mechanism for contemplating and predicting the movements of the celestial spheres, but if the ancients knew so much and could build such extraordinarily sophisticated devices, why didn't they go on to invent something more useful? An actual clock, for instance? Or a telescope?

Maybe the answer is that for the ancient Greeks, making useful tools wasn't as important as it is to us. Maybe they were more interested in knowledge for the sake of knowledge rather than for the sake of getting stuff done.

Marine archaeologists with the latest in cutting-edge dive technology are once again exploring the wreck off the island of Antikythera. Who knows what they'll find? In the meantime, much about the Antikythera Mechanism itself remains a mystery. We still don't know who built it, for whom it was built or why. Just as high-tech CT scanning yielded exciting new results, even more advanced investigative methods are sure to be developed in the future. What will they reveal about the Antikythera Mechanism? While current attempts to model the device are as accurate as the available information can make them, perhaps future research will unveil previously unimagined new facets of this ancient technology [source: Marchant].