Me, Myself and Technology
Kalpik Nigam

A 2,100 Years Old Astronomical Computer from Ancient Greece

November 30th 2006 in Technology

A 2,100-year-old clockwork machine recovered from the sea has turned out to be the celestial super-computer of the ancient Greece.

The Antikythera Mechanism has puzzled academics for more than a century after it discovery. Latest technology revealed beneath the surface of the 82 encrusted gearwheels bronze fragments a mechanism that could predict the Sun and Moon trajectories over decades and calculate a lunar anomaly that gave headaches to Isaac Newton himself.

The complexity of the technique used in Greece around 150-100 BC, believed to be invented by the astronomer and mathematician Hipparchos, was comparable to what people made one millennium later. The mechanism takes its name after the island of Antikythera, between Crete and the Peloponnese, where Greek sponge divers, exploring a Roman shipwreck at a depth of 42 metres (136 feet) in 1901, discovered the fragments inside a broken bronze and wooden case.

The pieces were thickly encrusted and jammed together after lying more two millennia on the sea floor. A closer investigation revealed them to be exquisitely made, hand-cut, toothed 29 gearwheels, possibly making some kind of astronomical calendar.

The historian of science and technology Derek de Solla Price, who studied the device from 50s to 70s, had hypothesized the number of gearwheels to 31 and the mechanism would have measured did something pretty amazing: the so-called Metonic cycle, known at least from Babylonians, during which the Moon takes 235 lunar months (19 years) to the same phase on the same date in the year.

Now, an international team went further, establishing the precise and sophisticated tasks of the mechanism. The scientists used three-dimensional X-ray computation tomography and high-resolution surface imaging to watch beneath the Mechanism’s surface, yet without damaging the priceless artifact. They could read inscriptions on the bronze cogs, impossible to see since the discovery of the artifact.

The original device must have comprised in fact 37 gear-wheels and two clock-like faces, one front and one back, encompassed into a slim wooden box measuring 31.5 x 19 cm (12.5 x 7.5 inches) and a thickness of 10cms (four inches). The apparatus was a 365-day calendar, which ingeniously factored in the leap year every four years. “Your jaw drops when you work out what they did and what they put into this,” said astronomer Mike Edmunds of Cardiff University, Wales.

“The design is beautiful, the astronomy is exactly right. Whoever has done this has done it extremely well. It implies the Greeks had great technical sophistication.” said Edmunds. “It does raise the question: what else were they making at the time? In terms of historic and scarcity value, I have to regard this mechanism as being more valuable than the Mona Lisa.”

Beside the Metonic cycle, the device also measured the so-called Callippic cycle, which is four Metonic cycles minus one day and reconciles the solar year with the lunar calendar. It could also measure the Saros cycle, a 223-month repetitive interplay of the Sun, Earth and Moon, provoking lunar and solar eclipses. As eclipses are traditionally seen as omens, these measurements probably had religious purposes.

The device was also a star almanac, pointing the times when the major stars and constellations of the Greek zodiac would rise or set. A tiny pin-and-slot device counts the movement of a main lunar anomaly, when the Moon appears to move across the heavens at different speeds at different times, due to its elliptical orbit around the Earth, which is something very impressive indeed.

The British-Greek research team was able to double the number of deciphered inscriptions, which gave them new clues to the purpose of the Antikythera Mechanism.

Among the new deciphered inscriptions, there were references to planetary movements which pointed to the knowledge of predicting the positions of the five known planets in relation to the stars by Ancient Greeks. The great Hipparchos, who drew up the first stars catalogue and wrote about the lunar anomaly in the 2nd century BC, is believed to have designed the Mechanism as the ship was found to have carried jars and coins from Rhodes, where Hipparchos lived. “The computer is so advanced in its mathematics and technology that the history of ancient Greece may have to be rewritten,” contends Edmunds.

“We now must ask: What else could they do? That’s a difficult thing, because this is really the only surviving metallic artifact of its kind. Who knows what else may be lost?”

“The new model is highly seductive and convincing in all of its details. It ought to force us, definitively, to abandon Price’s reconstruction, which is still frequently reproduced in general and scholarly books.” said François Charette, an academic in Munich.

Only one millennium later, during the golden age of Islamic science, the astronomer al-Biruni (in 996) constructed something technologically similar and wondrous, an eight-geared astrolabe, depicting the movements of the Sun and Earth. The question is: al-Biruni inspired from ancient Greek technology, transmitted somehow to later periods, or the Islamic scholar rediscovered what had been realized a thousand years before?


2 comments to...
“A 2,100 Years Old Astronomical Computer from Ancient Greece”
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mehul

Wow. Can history ever stop to astonish us. We’ll never figure out the past properly. Who knows how much is hidden just waiting to be discovered. I guess more gets hidden everyday than is discovered so it will always keep on growing, IMO.


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kalpik

Hmm.. True..




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