Olympic bronze reveals golden secret

The four-year wait between each set of competitions in the modern Olympics is based on the original four-year cycle of games in ancient Greece. A research paper in Nature magazine now links an ancient device known for tracking and predicting celestial events — to the original quadrennial observance of the games.

Called the Antikythera Mechanism, this device is a bronze machine built around the first or second century BCE. Possibly the most advanced ancient scientific device, it was fished out of the sea in 1901. Because of its state of disrepair, the mechanism has not revealed its secrets easily. About the size of a small shoebox in its original form, the device fell into a number of fragments after it was recovered. Since then computer simulations have been run and brass models constructed to recreate what it would have looked like. With the help of sophisticated x-ray techniques, more than 2500 characters have now been read.

The mechanism is not just a book of ancient secrets like the Dead Sea Scrolls. It's a machine consisting of numerous swiveling dials and turning gears. It is often considered as the first analog computer since it accepts input and provides output. Ancient astronomers could enter the current positions of the stars and planets, and the Antikythera would predict upcoming equinoxes (when the length of the day equals the length of night) and solar eclipses (when the sun is covered up by the moon).

Two surprising findings
Now, in the July 31 issue of the journal Nature, a research team reports two surprising discoveries. The first is a new interpretation of one of the dials in the machine as being associated with the Olympiad games held every four years. The Greeks didn't need a machine to tell them when to hold the games, but the dial was there anyway, says team member Tony Freeth, because of the importance of the games, so important that many other calendars were pegged to the event, much as historical events were often calibrated to the reigns of various kings.

The other intriguing finding was the realization that the month names inscribed on the dials are of Corinthian origin. Corinth is a city in Greece situated on a strategic isthmus. The old thinking was that the mechanism had originated towards the easterly end of Greek influence, perhaps on the island of Rhodes. But the new interpretation suggests that the machine was made in Corinth or in one of its colonies, which lay to the west, such as Sicily. These westerly Greek settlements are sometimes referred to as "Greece's America" since, like Britain's colonies over the Atlantic, they represented a reformulation of homeland culture across a westward sea.

'Metonic' calendar
Many ancient devices devoted to celestial objects have as their function the important task of coordinating events in the sky with those on Earth, such as the planting of crops or the crowning of kings. Probably the most important astronomical calculation is determining the duration of a year. In 1974, one of the dials on the Antikythera Mechanism was identified with the "Metonic" calendar. This is named for a fifth-century-B.C. Athenian astronomer, Meton, who formulated a calendar convention which married lunar timekeeping (the cycle of the moon takes a bit more than 29 days to complete) and solar timekeeping (the sun takes about 365 and a quarter days to come to the same place in the sky again). Meton's compromise calendar assimilates both the lunar and the solar views into a 19-year cycle.

More recently, in 2006, the research team working on the mechanism was able to deduce, from another dial, a method for predicting solar eclipses. What kind of ensemble does it take to make this sort of discovery? Well, so far the team has included mathematicians, astronomers, physicists, historians and philologists (those who study words).

Freeth says that although the mechanism was probably built well after the lifetime of Archimedes (c225 B.C.), it is tempting to think that the device came out of one of the Sicilian workshops (known for their bronze instruments) influenced by Archimedes, regarded by many as the greatest scientist of the ancient world.

Formerly a mathematician and television producer and now a research scientist, Freeth intends to return to TV production with a documentary about the Antikythera Mechanism.

Phil Schewe reports for Inside Science News Service, which is supported by the American Institute of Physics, a not-for-profit publisher of scientific journals.