Wednesday, December 20, 2006

 

Antikythera: Enigma of Ancient Computer Resolved At Last

A 2,100-year-old clockwork machine whose remains were retrieved from a shipwreck more than a century ago has turned out to be the celestial super-computer of the ancient world.

Using 21st-century technology to peer beneath the surface of the encrusted gearwheels, stunned scientists say the so-called Antikythera Mechanism* could predict the ballet of the Sun and Moon over decades and calculate a lunar anomaly that would bedevil Isaac Newton himself.

Built in Greece around 150-100 BC and possibly linked to the astronomer and mathematician Hipparchos, its complexity was probably unrivalled for at least a thousand years, they say.

'It's beautifully designed. Your jaw drops when you work out what they did and what they put into this,' said astronomer Mike Edmunds of Cardiff University, Wales, in an interview with AFP.

'It implies the Greeks had great technical sophistication.'

The Antikythera Mechanism is named after its place of discovery, where Greek divers, exploring a Roman shipwreck at a depth of 42 metres (136 feet) in 1901, came across 82 curious bronze fragments.

At first, these pieces, thickly encrusted and jammed together after lying more two millennia on the sea floor, lay forgotten. But a closer look showed them to be exquisitely made, hand-cut, toothed gearwheels.

It was clear that, within this find, 29 gearwheels fitted together, possibly making some sort of astronomical calendar. But of what, exactly?

Source/continuation: originally at "Enigma of ancient world's computer is cracked at last"

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Based on the journal Nature paper:

Freeth, T.; Bitsakis, Y., Moussas, X., Seiradakis, J. H., Tselikas, A., Mankou, E., Zafeiropulou, M., Hadland, R., Bate, D., Ramsey, A., Allen, M., Crawley, A., Hockley, P., Malzbender, T., Gelb, D., Ambrisco, W., and Edmunds, M. G. (2006).
Decoding the ancient Greek astronomical calculator known as the Antikythera Mechanism.
Nature 444: 587-591. DOI:10.1038/nature05357

Abstract

The Antikythera Mechanism is a unique Greek geared device, constructed around the end of the second century bc. It is known that it calculated and displayed celestial information, particularly cycles such as the phases of the moon and a luni-solar calendar. Calendars were important to ancient societies10 for timing agricultural activity and fixing religious festivals. Eclipses and planetary motions were often interpreted as omens, while the calm regularity of the astronomical cycles must have been philosophically attractive in an uncertain and violent world. Named after its place of discovery in 1901 in a Roman shipwreck, the Antikythera Mechanism is technically more complex than any known device for at least a millennium afterwards. Its specific functions have remained controversial because its gears and the inscriptions upon its faces are only fragmentary. Here we report surface imaging and high-resolution X-ray tomography of the surviving fragments, enabling us to reconstruct the gear function and double the number of deciphered inscriptions. The mechanism predicted lunar and solar eclipses on the basis of Babylonian arithmetic-progression cycles. The inscriptions support suggestions of mechanical display of planetary positions, now lost. In the second century bc, Hipparchos developed a theory to explain the irregularities of the Moon's motion across the sky caused by its elliptic orbit. We find a mechanical realization of this theory in the gearing of the mechanism, revealing an unexpected degree of technical sophistication for the period.

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Also see the June 1959 Scientific American paper "An Ancient Greek Computer" (p.60-7) by Derek J. de Solla Price:

Among the treasures of the Greek National Archaeological Museum in Athens are the remains of the most complex scientific object that has been preserved from antiquity. Corroded and crumbling from 2,000 years under the sea, its dials, gear wheels and inscribed plates present the historian with a tantalizing problem. Because of them we may have to revise many of our estimates of Greek science. By studying them we may find vital clues to the true origins of that high scientific technology which hitherto has seemed peculiar to our modern civilization, setting it apart from all cultures of the past.

From the evidence of the fragments one can get a good idea of the appearance of the original object [see illustration on page 62]. Consisting of a box with dials on the outside and a very complex assembly of gear wheels mounted within, it must have resembled a well- made 18ih-century clock. Doors hinged to the box served to protect the dials, and on all available surfaces of box, doors and dials there were long Greek inscriptions describing the operation and construction of the instrument. At least 20 gear wheels of the mechanism have been preserved, including a very sophisticated assembly of gears that were mounted eccentrically on a turntable and probably functioned as a sort of epicyclic or differential, gear-system.

Nothing like this instrument is preserved elsewhere. Nothing comparable to it is known. from any ancient scientific text or literary allusion. On the contrary, from all that we know of science and technology in the Hellenistic Age we should have felt that such a device could not exist. Some historians have suggested that the Greeks were not interested in experiment because of a contempt-perhaps induced by the existence of the institution of slavery-for manual labor. On the other hand it has long been recognized that in abstract mathematics and in mathematical astronomy they were no beginners but rather "fellows of another college" who reached great heights of sophistication. Many of the Greek scientific devices known to us from written descriptions show much mathematical ingenuity, but in all cases the purely mechanical part of the design seems relatively crude. Gearing was clearly known to the Greeks, but it was used only in relatively simple applications. They employed pairs of gears to change angular speed or mechanical ad- vantage, or to apply power through a right angle, as in the water-driven mill.

Even the most complex mechanical devices described by the ancient writers Hero of Alexandria and Vitruvius contained only simple gearing. For example, the taximeter used by the Greeks to measure the distance travelled by the wheels of a carriage employed only pairs of gears (or gears and worms) to achieve the necessary ratio of movement. It could be argued that if the Greeks knew the principle of gearing, they should have had no difficulty in constructing mechanisms as complex as epicyclic gears. We now know from the fragments in the National Museum that the Greeks did make such mechanisms, but the knowledge is so unexpected that some scholars at first thought that the fragments must belong to some more modern device.

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A related news release from Hewlett-Packard:

HP Helps Unlock Mysteries of World's Oldest "Computer"
PALO ALTO, California, Nov. 30, 2006

HP researchers are literally shining a light on what may be the world's oldest computer.

The Antikythera Mechanism is an ancient astronomical device built by the Greeks around 80 B.C. and found on a shipwreck off the Greek island of Antikythera by sponge divers in 1901. It is believed to have been created to track lunar and solar cycles for agricultural and religious purposes, but its precise function - and how it works - has eluded scholars for more than a century.

In September 2005, members of the Antikythera Research Project invited HP Labs research scientists Tom Malzbender and Dan Gelb to Athens to apply their patented reflectance imaging techniques to the front and rear surfaces of the more than 70 fragments that comprise the mechanism, including metal plates and gears, some of which are inscribed with faded Greek characters.

The technique involves taking photos of an artifact from a fixed point and 50 different light sources arrayed in a hemisphere over the object. The HP researchers' computer program then ties the images together, enabling an archaeologist to change the angle of light or texture of the surface of the object to make faint markings appear more vivid.

"One of the advantages of reflectance imaging is that you can change the quality of the surface of an object, by, for example, making dull surfaces shiny, like obsidian," said Gelb, senior research scientist, HP Labs. "That way, the faint markings on these ancient artifacts become more visible and that helps scholars determine their meaning."

By capturing the images digitally, the technique also enables scholars around the world to study the rare, delicate objects without having to travel to where they're stored or to handle them.

Some of the reflectance images, technically described as polynomial texture maps, are available at Interactive Relighting of the Antikythera Mechanism.

The results of Malzbender and Gelb's work, in collaboration with researchers from the U.K. and Greece, appear today in the British science journal, Nature ("Decoding the ancient Greek astronomical calculator known as the Antikythera Mechanism"). The other researchers used an X-ray technique, called computer tomography, to probe the depths of the device.

The new research explains how the gears work and identifies twice as many markings on the device as previously detected.

"The Antikythera Mechanism is the only technological device from the ancient world and the oldest computer or calculator known to man," said Malzbender, distinguished technologist, HP Labs. "Nothing like it appears until the Renaissance, when clocks first appeared."

This isn't the first time that the HP Labs researchers' work has been used for archaeological purposes. In 2000, Malzbender volunteered the resources of the technology to capture faded Sumerian tablets for researchers at Yale and the University of Southern California. It was this work that caught the attention of the Antikythera project.

The technology was originally developed not for archaeology, but as a method for improving photorealism and rendering efficiency in 3D graphics. It also could be used in criminal forensics, detecting distinctive characteristics in footprints or tire marks, for example. The technology also still has potential commercial uses for HP, but many of the techniques have been made available to the scientific world for academic purposes.

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Visit the The Antikythera Mechanism Research Project for more information

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*Similar devices in ancient literature

Cicero mentions two separate machines similar to the Antikythera mechanism.

The first was built by Archimedes and brought to Rome by the Roman general Marcus Claudius Marcellus after Archimedes' death at the siege of Syracuse in 212 BC. Marcellus had a high respect for Archimedes and this was the only item he kept from the siege. The device was kept as a family heirloom, and Cicero was shown it by Gallus about 150 years later. The motions of the sun, moon and five planets were shown by the device. Gallus gave a 'learned explanation' of it and demonstrated it for Cicero.

...Cicero also says that another such device was built 'recently' by his friend Posidonius, "... each one of the revolutions of which brings about the same movement in the sun and moon and five wandering stars [planets] as is brought about each day and night in the heavens..." Cicero, De Natura Deorum II.88 (or 33-34)

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