Another gear fragment exhibits markings consistent with a four-turn spiral divided into 223 segments, the same number of lunar months that can elapse between eclipses. Between these divisions the researchers say they found the Greek letters sigma and eta, which could stand for Selene and Helios, the Greek words for moon and sun.
The findings are "seductive" and will set the standard for future work, says medieval science historian Francois Charette of Ludwig Maximilian University in Munich. "Everything in their model fits very well with the data they have collected, and just happens to give the relationships that were used in Greek astronomy for these cycles," he says. The researchers plan to make their data available online for others to examine, their report states.
As for the purpose of the Antikythera instrument, Charette says it strikes him as a luxury object, given that numerical tables could have done the same job for less trouble. Craftsmen built similarly elaborate clocks and astrolabes during medieval and Renaissance times, he says. "They were expensive toys."