Ancient computer tracked Olympics

Times Staff Writer

A 2,100-year-old bronze and iron computer that predicted eclipses and other astronomical events also showed the cycle of the Greek Olympics and the related games that led up to it, researchers reported today.

The research team also has been able to decipher all the month names from the heavily corroded fragments of the so-called Antikythera mechanism, providing the first concrete evidence that an astronomical scheme devised by the Greek astronomer Geminos was put to practical use.

Teasing out the month names was “a really spectacular achievement,” said science historian Francois Charette of Ludwig Maximilians University in Munich, Germany, who was not involved in the research.


Historians “had until now doubted that this scheme had actually been used in civil life, but the evidence from the Antikythera mechanism now proves them wrong,” he said.

The inclusion of the data about the Olympic Games on what is now called the Olympiad Dial of the clock-like mechanism was a surprise to the researchers because the dates of the ancient Olympics, held every fourth summer from 776 BC to AD 393, would have been well known to the populace, just as the time of the modern Olympics is now.

“The inclusion of the Olympiad Dial says more about the cultural importance of the Games than about their advanced technology,” said Tony Freeth of Images First Ltd. in London, who was a member of the research team that reported the results in the journal Nature.

The Antikythera mechanism, so named because it was found in 1901 in a Roman shipwreck off the Greek island of Antikythera, is thought to have been made about 100 BC.

Its purpose was a mystery for more than 100 years, but in 2006, researchers used a massive X-ray tomography machine, similar to that used to perform CT scans on humans, to examine the heavily encrusted fragments.

They concluded that the device originally contained 37 gears that formed an astronomical computer.


Two dials on the front show the zodiac and a calendar of the days of the year that can be adjusted for leap years. Metal pointers show the positions in the zodiac of the sun, moon and five planets known in antiquity. Two spiral dials on the back show the cycles of the moon and predict eclipses.

Using more powerful computers to analyze the CT data, Freeth and his colleagues, all affiliated with the in Cardiff, Wales, were able to decipher the names of all 12 months, as well as names identifying several Greek games.

The month names indicate that device probably was not from Rhodes, as originally thought, but from Corinth or one of its colonies, such as Syracuse -- home of the famed astronomer Archimedes, who lived a century before the device was made. Seven of the month names had a possible link to Syracuse.

The Metonic calendar that was used had months that averaged 30 days, with one day omitted every 64th day in order to have the correct average month length over the entire Metonic cycle of 19 years.

The key to the Olympiad Dial was the discovery of the words “NEMEA,” “ISTHMIA,” “PYTHIA” and “OLYMPIA.”

The first reference is to the Nemean Games, one of the events that were part of the four-year cycles that climaxed with the Olympics. Isthmia represented the games at Corinth, Pythia those at Delphi and Olympia the Olympics themselves.


This dial puts the mechanism “under a considerably different light, as it tells us that, for all its technological and scientific sophistication, it was not purely a ‘scientific’ object, but rather also displayed information of relevance to civil life,” Charette said.