Ancient Greek computer predicted eclipses

Daily Mail:

The world's oldest calculator - a box of dials, gears and cogs created by the Ancient Greeks more than 2,000 years ago - could predict eclipses decades in advance, say researchers.

The Antikythera Mechanism, recovered from a Roman shipwreck more than a century ago, was also used to record the four-yearly cycle of the original Olympic Games.

It was created around 100BC and previous studies have shown that it was used to chart the movement of planets and the passing of days and years.

X-ray scans have now shown that it could predict eclipses, and was used to record important events in the Greek calendar, says the scientific journal Nature.

Astronomer Professor Mike Edmunds of Cardiff University said: 'It is more complex than any other known device for the next 1,000 years.'

'We knew that this 2,100-year-old ancient Greek mechanism calculated complex cycles of mathematical astronomy,' said Dr Tony Freeth, of London-based Images First, a former research mathematician at Cambridge University.

'It really surprised us to discover that it also showed the four-year cycle of ancient Greek games, including the Olympic Games.'

The Mechanism was onboard a Roman cargo ship that sank off the coast of the Greek island of Antikythera in the first century BC.

The wreck - stuffed full of stunning bronzes, amphorae, glassware and pottery - was discovered by sponge divers in 1900.

Archaeologists also unearthed a mysterious corroded and calcified lump around the size of a large dictionary. Overlooked at the time, the lump turned out to be one of the greatest classical finds of 20th century.

The scans have shown that the mechanism was originally housed in a rectangular wooden frame with two doors, covered in instructions for its use.

At the front was a single dial showing the Greek zodiac and an Egyptian calendar. On the back were two further dials displaying information about lunar cycles and eclipses. The calculator would have been driven by a hand crank.

A further 81 fragments have since been found containing a total of 30 hand-cut bronze gears.

The device could track the movements of Mercury, Venus, Mars, Jupiter and Saturn - the only planets known at the time, the position of the sun and the location and phases of the moon.

The researchers have been able to read all the month names on a 19-year calendar on the back of the Mechanism.

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The Mechanism recorded several important astronomical cycles known to the Babylonians hundreds of years before that help predict eclipses. These include the Saros cycle - a period of around 18 years separating the return of the Moon, Earth and Sun to the same relative positions.

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I think finding this device challenges the belief that the ancient world believed the Earth was flat. The device worked on the belief that the Earth rotated around the Sun and the moor rotated around the Earth. It also predicted the positions of other planets. Since it used Babylonian and Egyptian calendars too, it suggest that there was a better understanding of the solar system than previously thought. Apparently this understanding if it was committed to writing was lost, but the device resurrects that understanding.

The NY Times story on the "super computer" adds these interesting factoids.

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Dr. Freeth, who is also associated with Images First Ltd., in London, explained in an e-mail message that the Metonic calendar was designed to reconcile the lengths of the lunar month with the solar year. Twelve lunar months are about 11 days short of a year, but 235 lunar months fit well into 19 years.

“From this it is possible to construct an artificial mathematical calendar that keeps in synchronization with both the Sun and the Moon,” Dr. Freeth said.

The Metonic calendar today, he noted, is the basis for the Jewish religious calendar and in calculations to date Easter in the Christian calendar.

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It is a clock for the ages.