Greek sponge divers recovered the 82 separate pieces of the bronze and wood device in 1900, off the island of Antikythera. After it was recently examined with an advanced medical scanner, an international team of multidisciplinary scientists found that the complex system of gears, concentric wheels and pointers actually comprised a type of analogue computer. The system acted as a calendar, predicted lunar and solar eclipses, and tracked the movement of the sun, the planets, and even the moon's irregular orbit.
"Calendars were important to ancient societies for timing agricultural activity and fixing religious festivals," wrote the scientists in the journal Nature. "Eclipses and planetary motions were often interpreted as omens, while the calm regularity of the astronomical cycles must have been philosophically attractive in an uncertain and violent world."
The scientists made a picture of the device's working process, which has amazed many classical scholars.
"This device is just extraordinary, the only thing of its kind," said Professor Mike Edmunds of Cardiff University, a leading member of the team. "The design is beautiful, the astronomy is exactly right. The way the mechanics are designed just makes your jaw drop.
"Whoever has done this had done it extremely well. It does raise the question of what else were they making at the time. In terms of historic and scarcity value, I have to regard this mechanism as being more valuable than the Mona Lisa."
In Munich, Ludwig-Maximillian University astronomer Francois Charette compared the finding to discovering plans for a steam engine in Renaissance Italy.
The Roman shipwreck from which the device was recovered was thought to have been from around 65 B.C., but the instrument itself may be from as far back as 100 B.C. to 150 B.C. and possibly constructed by Hipparchos, a Greek astronomer who lived on the island of Rhodes around that time. Hipparchos was suggested because he was the first person to track the irregular orbit of the moon, just as the device does.
The device has three dials. The front dial shows the position of the sun and the moon in the zodiac and the corresponding 365-day calendar, and the dial could be adjusted for leap years. The back dials were used to track the long-term lunar cycle. They were even able to track the 19-year period when the same phase of the moon returns on the same date of the year -- known as the Metonic cycle -- and the 76-year Callippic cycle, in which the moon returns to the same position in the sky relative to its monthly lunar phase and the zodiac.