A Great Scientific Mystery Unraveled
WHEN divers explored a shipwreck off the Greek island of Antikýthēra in 1901, they found treasure. The wreck proved to be an ancient Roman merchant vessel carrying, among other things, marble and bronze statues and silver coins from Pergamum. The coins enabled researchers to estimate that the ship, probably heading for Rome, went down between 85 and 60 B.C.E.
Since the discovery, the artifacts have been preserved in the National Archaeological Museum of Athens, Greece. Neither the statues nor the coins, however, were what drew researchers to the museum in 2005. Their interest was focused on a bronze device that had originally been housed in a wooden case about the size of a shoe box. This artifact, known as the Antikythera Mechanism, challenges assumptions about the scientific achievements of early civilizations. The device has been called “the most sophisticated mechanism known from the ancient world.”
Just what is it? And why is it so important?
A Mystery Object
When the case was pulled from the seabed, it was badly corroded and encrusted. After nearly 2,000 years, it resembled greenish rock. Since all the excitement of the find concentrated on the statues, this mystery object initially received scant attention.
When a Greek archaeologist examined the artifact in 1902, the mechanism was in several pieces. There were gearwheels of different sizes, with accurately cut triangular teeth. The device looked like a clock, but because clockwork was not believed to have been widely used until about 700 years ago, this did not seem likely.
An article on the Antikythera Mechanism explains that “historians do not generally credit [Greeks of some 2,000 years ago] with possessing scientifically precise gears—gears cut from metal and arranged into complex ‘gear trains’ capable of carrying motion from one driveshaft to another.” Nevertheless, the device was thought to be some kind of astrolabe, an instrument once commonly used to determine latitude by the positions of celestial bodies.
Still, many argued that the gears were simply too complex for the object to be 2,000 years old. So they concluded that it must not have been part of the ancient wreck. On the other hand, one scholar suggested that the object might be the legendary Sphere of Archimedes. This device was described by Cicero in the first century B.C.E. as a kind of planetarium—a mechanical model capable of replicating in miniature the movements of the sun, the moon, and the five planets visible to the naked eye. In the absence of any clear evidence to the contrary, however, the astrolabe theory prevailed.
Examined More Closely
In 1958 the mechanism was studied by Derek de Solla Price, who trained as a physicist but then switched fields and became a professor of history. He came to believe that the device was capable of calculating past or future astronomical events, such as the next full moon. He realized that the inscriptions on the dial referred to calendar divisions—days, months, and signs of the zodiac. It must once have had rotating pointers, he assumed, that indicated the positions of heavenly bodies at different times.
Price deduced that the largest gearwheel was tied to the movement of the sun and that one rotation corresponded to a solar year. If another gear, connected to the first, represented the movement of the moon, then the ratio of the number of teeth on the two wheels ought to reflect ancient Greek ideas about the moon’s orbits.
In 1971, Price X-rayed the mechanism. The results confirmed his theories. The device was a complex astronomical calculator. Price produced a drawing of the mechanism’s hypothetical workings and published his findings in 1974. He wrote: “Nothing like this instrument is preserved elsewhere. . . . From all that we know of science and technology in the Hellenistic Age we should have felt that such a device could not exist.” At the time, Price’s work did not receive the acclaim it merited. Others, however, continued his research.
In 2005, the team of researchers mentioned in the introduction examined the mechanism using a state-of-the-art CAT-scan machine to produce high-resolution, three-dimensional X-ray images. These studies offered fresh insight into how the mechanism worked. As the user turned a knob, at least 30 interlocking gearwheels activated three dials on the front and the back of the box. This allowed the user to predict astronomical cycles, including eclipses, in relation to the four-year cycle of the Olympic and other Panhellenic games. These games were commonly used as a basis for chronology.
Why was such information so important? There are several reasons. Astronomy was important to ancient peoples because the sun and the moon were the basis for calendars that would tell farmers when to sow seed. Sailors used the stars to navigate. Greek social institutions were tied to astronomical phenomena. And there is yet another reason such information was valued.
“For the ancient Babylonians, predicting eclipses was very important, as they were thought to be bad omens,” writes Martin Allen, of the Antikythera Mechanism Research Project. “Indeed the mechanism could be thought of as being a political tool, allowing the ruling authorities to have dominion over their subjects. It has even been proposed that one reason we know so little of these mechanisms, is that they were bound by military or political secrecy.”
Whatever else it tells us, the mechanism is evidence that ancient Greek astronomy and mathematics, much of which was based on the long tradition of the Babylonians, were much more advanced than we might imagine. Nature magazine puts it this way: “The ancient Antikythera Mechanism doesn’t just challenge our assumptions about technology transfer over the ages—it gives us fresh insights into history itself.”
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WHO MADE IT?
The Antikythera Mechanism could not have been the only device of its kind. “There is no evidence of any mistakes,” writes Martin Allen. “All the mechanical features have a purpose. There are no extra holes, or bits of metalwork to suggest that the manufacturer modified his design as he built the mechanism. This leads to the conclusion that he must have built a number of predecessors.” So who made it? And what became of his other productions?
The most recent research on the mechanism has revealed the names of the months on the dial that predicted eclipses. The names are of Corinthian origin. This leads investigators to deduce that the device was made and used in a specific cultural context. The scientific magazine Nature states: “The Corinthian colonies of northwestern Greece or Syracuse in Sicily are leading contenders—the latter suggesting a heritage going back to Archimedes.”
Why have no similar devices survived? “Bronze is a valuable and highly recyclable commodity,” writes Allen. “Consequently, bronze finds from antiquity are remarkably rare. In fact many of the significant historical bronze finds have been made underwater, where they were inaccessible to those who might have reworked them.” “We only have this [example],” says one researcher, “because it was out of reach of the scrap-metal man.”
[Diagram/Pictures on page 25]
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Reconstruction of the inner workings of the Antikythera Mechanism
1. The front dial indicated lunar phases and positions of the sun and the moon. It also showed the day and month according to the solar calendar and movement of the sun (and the visible planets) in relation to the constellations of the zodiac
2. The upper back dial indicated the relation between lunar months, solar years, and the times of the Panhellenic Games
3. The lower back dial predicted solar and lunar eclipses
Both photos: ©2008 Tony Freeth/Antikythera Mechanism Research Project (www.antikythera-mechanism.gr)
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How the back outer plate might have looked
©2008 Tony Freeth/Antikythera Mechanism Research Project (www.antikythera-mechanism.gr)
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All photos: ©2005 National Archaeological Museum/Antikythera Mechanism Research Project (www.antikythera-mechanism.gr)