Friday, December 22, 2006




Greek City

The Antikythera Mechanism was developed about 100 BC in Greece. It used gears to indicate the positions of the sun, moon and stars and to predict eclipses.

The island of Antikythera lies 18 miles north of Crete, where the Aegean Sea meets the Mediterranean. Currents there can make shipping treacherous – and one ship bound for ancient Rome never made it.

The ship that sank there was a giant cargo vessel measuring nearly 500 feet long. It came to rest about 200 feet below the surface, where it stayed for more than 2,000 years until divers looking for sponges discovered the wreck a little more than a century ago.

Inside the hull were a number of bronze and marble statues. From the look of things, the ship seemed to be carrying luxury items, probably made in various Greek islands and bound for wealthy patrons in the growing Roman Empire. The statues were retrieved, along with a lot of other unimportant stuff, and stored.

Nine months later, an archaeologist cleared off a layer of organic material from one of the pieces of junk and found that it looked like a gearwheel. It seemed to have something to do with astronomy.

That piece of “junk” went on to become the most celebrated find from the shipwreck; it is displayed at the National Archaeological Museum of Athens. Research has shown that the wheel was part of a device so sophisticated that its complexity would not be matched for 1,000 years – it was also the world’s first known analog computer.

The device is so famous that an international conference organized in Athens a couple of weeks ago had only one subject: the Antikythera Mechanism.

The device was probably built between 100 and 140 BC, and the understanding of astronomy it displays seems to have been based on knowledge developed by the Babylonians in 300-700 BC, said Mike Edmunds, a professor of astrophysics at Cardiff University in Britain. He led a research team that reconstructed what the gear mechanism would have looked like by using advanced 3-D technology. The group also decoded a number of the inscriptions.

The mechanism explores the relationship between lunar months – the time it takes for the moon to cycle through its phases – and calendar years. The gears had to be cut precisely to reflect this complex relationship; 19 calendar years equal 235 lunar months.

By turning the gear mechanism, a person could check what the sky would have looked like on a date in the past, or how it would appear in the future. The mechanism was encased in a box with doors in front and back covered with inscriptions – a sort of instruction manual. Inside the front door were pointers indicating the date and the positions of the sun, moon and zodiac, while opening the back door revealed the relationship between calendar years and lunar months, and a mechanism to predict eclipses.

“It is a mechanical computer. You turn the handle and you have a date on the front,” said Yanis Bitsakis, a physicist at the University of Athens who co-wrote a study for the journal Nature with Frangois Charette, a historian of science in Germany.

Why was the technology that went into the device lost?

“The time this was built, the jackboot of Rome was coming through,” Edmunds said. “The Romans were good at town planning and sanitation but were not known for their interest in science.”


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