Ancient Greek Computer's Inner Workings Deciphered

Kate Ravilious
for National Geographic News
November 29, 2006
When it came to making cogs and gears, the ancient Greeks got there more than a millennium before anyone else, scientists say.

Using advanced new imaging techniques, scientists have reconstructed the gear structure of the mysterious Antikythera mechanism—one of the world's oldest computers.

The researchers also deciphered previously hidden text from the astronomical calculator, which dates back to around 100 B.C.

The new research, which appears in tomorrow's issue of the journal Nature, confirms that the ancient Greeks had developed extremely sophisticated levels of craftsmanship and scientific knowledge.

Under the Sea

The intricate bronze instrument has puzzled scientists ever since it was recovered in A.D. 1901. The device was one of many treasures found in a Roman shipwreck discovered by a sponge diver just off Antikythera island, off the southern coast of Greece (map of Greece).

Saltwater had corroded the shoebox-size instrument, and the moving parts had long since seized up.

In 1959 British science historian Derek Price put forward the idea that the Antikythera mechanism was a device for displaying the motions of moons and planets.

In the past five years Michael Wright, from Imperial College London in England, confirmed this theory using X-rays to reveal the layering of the gear wheels.

The device employs an elaborate arrangement of more than 30 gears for its calculations. The level of miniaturization and complexity is remarkable, with some parts resembling those used by 18th-century clockmakers.

"It is extraordinarily sophisticated," said Stephen Johnston, an expert on astronomical calculators from the Museum of the History of Science at the University of Oxford in England.

"In its complexity it exceeds medieval cathedral clocks, which were developed over a thousand years later."

Secrets Revealed

Now study leader Mike Edmunds of the University of Cardiff in Wales and his colleagues have helped to complete the picture. The researchers decoded the mechanism's rusty text and recreated images of some of its smallest gears.

The researchers inspected the surface of the object (which is currently housed in the National Archaeology Museum in Athens, Greece) using new imaging technology. (Related: "Archimedes' Secrets Revealed by Atom Smasher" [August 3, 2006].)

The images were then pieced together using computer software, allowing scientists to reconstruct the object in three dimensions. "It was like being able to hold it in your hand and turn it to the light," Edmunds said.

Using a special X-ray machine, the scientists were also able to probe deep into the device and produce 3-D reconstructions of the gear wheels.

"We could see the clever and subtle way in which the gears worked," Edmunds added.

Many previously hidden inscriptions were revealed by these new techniques, including geographical references such as 'south,' 'Spain,' and 'Pharos'—the island in Egypt that once housed the wonder of the world known as the lighthouse of Alexandria.

"The text and our reconstruction of the dials tell us that the instrument could be used to predict eclipses of the moon and sun," Edmunds said.

The level of sophistication also hints that more discoveries may be on the way.

François Charette, a science historian at Germany's University of Munich, believes more devices like the Antikythera mechanism must exist.

"There has to have been a chain of development behind it," Charette said. "Otherwise it is like finding a high-speed 20th-century train without any of the earlier trains."

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