The Antikythera mechanism is believed to be an ancient mechanical analog computer (as opposed to most computers today which are digital computers) designed to calculate astronomical positions. It was discovered in the Antikythera wreck off the Greek island of Antikythera, between Kythera and Crete, and has been dated to about 150-100 BC. It is especially notable for being a technological artifact with no known predecessor or successor; other machines using technology of such complexity would not appear until the 18th century.

The Antikythera mechanism is displayed at the National Archaeological Museum of Athens, accompanied by a reconstruction made and donated to the museum by Derek de Solla Price. Other reconstructions are on display at the American Computer Museum in Bozeman, Montana, the Children's Museum of Manhattan in New York, in Kassel, Germany, and at the Musée des Arts et Métiers in Paris. The mechanism was housed in a wooden box approximately 340 x 180 x 90 mm in size and comprised 30 bronze gears (although more could have been lost). The largest gear, clearly visible in fragment A, was approximately 140 mm in diameter and probably had either 223 or 224 teeth. The mechanism's remains were found as 82 separate fragments of which only seven contain any gears or significant inscriptions.




Discovery

Sometime during the year 1901, Elias Stadiatis, a Greek sponge diver, with a sponge diving group, discovered the wreck of an ancient cargo ship off Antikythera island at a depth of 50 meters. (Sponge divers had earlier retrieved several statues and other artifacts from the site. The mechanism itself was discovered in 1901.) The name has been confused in some recent publications with that of a politician of the same name.

It was noticed that a piece of rock recovered from the site had a gear wheel embedded in it. Examination revealed that the rock was in fact a heavily encrusted and corroded mechanism that had survived the shipwreck in three main parts and dozens of smaller fragments.The device itself was surprisingly thin, about 33 cm (13 in) high, 17 cm (6.7 in) wide, and 9 cm (3.5 in) thick, made of bronze and originally mounted in a wooden frame. It was inscribed with a text of over 2,000 characters, many of which have been deciphered.

Jacques-Yves Cousteau visited the wreck for the last time in 1978, but found no more remains of the Antikythera Mechanism. Professor Michael Edmunds of Cardiff University who led the study of the mechanism said: "This device is just extraordinary, the only thing of its kind. The design is beautiful, the astronomy is exactly right. The way the mechanics are designed just makes your jaw drop. Whoever has done this has done it extremely carefully."

The device is displayed in the Bronze Collection of the National Archaeological Museum of Athens, accompanied by a reconstruction made and offered to the museum by Derek de Solla Price. Another reconstruction is on display at the American Computer Museum in Bozeman, Montana.




Origins

The origins of the mechanism are unclear, as are the circumstances by which it came to be on the cargo ship. The ship was Roman, but there is no doubt that the mechanism itself was made in Greece.

One hypothesis is that the device was constructed at an academy founded by the ancient Stoic philosopher Posidonius on the Greek island of Rhodes, which at the time was known as a centre of astronomy and mechanical engineering. Investigators have suggested that the ship could have been carrying it to Rome, together with other treasure looted from the island to support a triumphal parade being staged by Julius Caesar.




Function and Purpose

The Antikythera mechanism is one of the world's oldest known geared devices. It has puzzled and intrigued historians of science and technology since its discovery. Following decades of work in order to clean the device, systematic investigations were undertaken in 1951 by British Derek J. de Solla Price, professor of history of science at Yale University at that time.

In June 1959, in a front-page article in Scientific American titled "An ancient Greek computer", he brought forth the theory that the Antikythera mechanism was a device for calculating the motions of stars and planets, which would make the device the first analog computer. Up until that time the function of the Antikythera mechanism was largely unknown, though it had been correctly identified as an astronomical device, perhaps being an astrolabe.

In 1971 the Greek nuclear research center "DEMOKRITOS" performed gamma-ray scans of the mechanism. In 1972 Price teamed up with Greek nuclear physicist Christoforos Karakalos to carry out X-ray analysis of the mechanism, in this way revealing critical information concerning the device's interior configuration.

In 1974 he authored "Gears from the Greeks: the Antikythera mechanism - a calendar computer from ca. 80 B.C.", where he presented a model of how the mechanism could have functioned. Recent research breakthroughs seem to give credence to Price's theory.

The device is all the more impressive for its use of a differential gear - previously believed to have been invented in the 16th century - and for the level of miniaturization and complexity of its parts, which is comparable to that of clocks made in the 18th century.

The differential gear arrangement is composed of 30+ gears with teeth formed through equilateral triangles. When past or future dates were entered via a crank (now lost), the mechanism calculated the position of the sun, moon or other astronomical information such as the location of other planets.

The use of differential gears enabled the mechanism to add or subtract angular velocities. The differential was used to compute the synodic lunar cycle by subtracting the effects of the sun's movement from those of the sidereal lunar movement.

It is possible that the mechanism is based on heliocentric principles, rather than the then dominant geocentric view espoused by Aristotle and others. This may indicate that the heliocentric view was more widely accepted at the time than was previously thought.While the Antikythera mechanism was certainly remarkably advanced for its era, it was possibly not unique.

Cicero, writing in the 1st century BC, mentions an instrument "recently constructed by our friend Poseidonius, which at each revolution reproduces the same motions of the sun, the moon and the five planets." (Cicero was himself a student of Poseidonius.)

Similar devices are mentioned in other ancient sources. It also adds support to the idea that there was an ancient Greek tradition of complex mechanical technology which was later transmitted to the Arab world, where similar but simpler devices were built during the medieval period.

The early 9th century Kitab al-Hiyal ("Book of Ingenious Devices"), commissioned by the Caliph of Baghdad, records over a hundred mechanical devices described in Greek texts that had been preserved in monasteries. Such knowledge could have yielded to or been integrated with European clockmaking and ancient cranes.

The device's actual purpose still remains unclear, as we do not know its full range of capabilities. Some investigators believe that the Antikythera mechanism could have been used to track celestial bodies for auspicious occasions such as religious events or births.

Price suggested that it might have been on public display, possibly in a museum or public hall in Rhodes. The island was renowned for its displays of mechanical engineering, particularly automata, which apparently were a speciality of the Rhodians; to quote Pindar's seventh Olympic Ode:




Investigations and Reconstructions

Price's model, as presented in his "Gears from the Greeks: the Antikythera mechanism - a calendar computer from ca. 80 B.C.", was the first, theoretical, attempt at reconstructing the device. According to that model, the front dial shows the annual progress of the sun and moon through the zodiac against the Egyptian calendar. The upper rear dial displays a four-year period and has associated dials showing the Metonic cycle of 235 synodic months, which approximately equals 19 solar years. The lower rear dial plots the cycle of a single synodic month, with a secondary dial showing the lunar year of 12 synodic months. A British orrery maker named John Gleave, constructed a replica based hereupon, though with some very slight modifications of his, in order for it to be functional. The following link gives an idea of the internals of this device, though later researchers have doubts as to whether Price's model is an accurate representation of the original Antikythera mechanism.

A partial reconstruction was built by Australian computer scientist Allan George Bromley (1947–2002) of the University of Sydney and Sydney clockmaker Frank Percival. This project led Bromley to review Price's X-ray analysis and to make new, more accurate X-ray images that were studied by Bromley's student, Bernard Gardner, in 1993. His model differed significantly from Price's earlier proposition, though it wasn't considered satisfactory either.

Another reconstruction was made in 2002 by Michael Wright, mechanical engineering curator for The Science Museum in London, working with Allan Bromley. He analyzed the mechanism using linear tomography, which can create images of a narrow focal plane, and thus visualized the gears in great detail. In Wright's reconstruction, the device not only models the motions of the sun and moon, but of all the classical planets.




Antikythera Mechanism Research Project

The Antikythera mechanism is now being studied by the Antikythera Mechanism Research Project, a joint program between Cardiff University, the National and Kapodistrian University of Athens, the Aristotle University of Thessaloniki, the National Archaeological Museum of Athens, X-Tek Systems UK and Hewlett-Packard USA, funded by the Leverhulme Trust and the Cultural Foundation of the National Bank of Greece.

The mechanism's fragility precluded its removal from the museum, so the Hewlett-Packard research team built a large 3-D X-ray imaging scanner, known as the "PTM Dome", around the device. The images are processed using 400kV microfocus computerised tomography. It was announced in Athens on October 21, 2005 that many new pieces of the Antikythera mechanism had been found. There are now more than 70 fragments. Most of the new pieces had been stabilized but were awaiting conservation.

On June 6, 2006 it was announced that the imaging system had enabled much more of the Greek inscription to be viewed and translated, from about 1,000 characters that were visible previously, to about 2,000 characters, representing about 95% of the complete text. The team's findings might shed new light concerning the function and purpose of the Antikythera mechanism. Research is ongoing.


Antikythera Mechanism   Wikipedia




In the News ...



Famed Roman Shipwreck Could Be Two   Discovery - January 6, 2013
A dive to the undersea cliff where a famous Roman shipwreck rests has turned up either evidence that the wreck is enormous - or a suggestion that, not one, but two sunken ships are resting off the Greek island of Antikythera. "Either way, it's an exciting result," said study researcher Brendan Foley, an archaeologist at Woods Hold Oceanographic Institution who presented the findings Jan. 4 at the annual meeting of the Archaeological Institute of America in Seattle.


  The Antikythera time machine   PhysOrg - June 11, 2012
Leonardo da Vinci may have left behind sketches of helicopters, tanks and submarines but it is rare that we find actual artifacts that seem so way ahead of their time. Almost like a science fiction tale of archaeologists finding a wristwatch buried deep in an Egyptian pyramid or motorcar under the foundations of Stonehenge, we do have an example of a scientific computer that was built between 150 and 100 BC. It was so advanced, nothing as complex would be developed again until the 14th century.


Greek "Computer" Tracked Ancient Olympics, Other Games National Geographic - July 30, 2008

A Greek machine sometimes called the world's first computer could have helped sports fans track the cyclical schedule of ancient athletic contests - including the Olympic games, new research reports. The Antikythera mechanism, which dates to around 150 to 100 B.C., is a complex amalgamation of bronze gears, dials, and text inscriptions that was created perhaps a thousand years before the next known device of similar sophistication.


   Secrets of Antikythera Mechanism, world's oldest calculating machine, revealed Telegraph.co.uk - July 30, 2008


Ancient Greek Computer's Inner Workings Deciphered National Geographic - November 30, 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.


Ancient Moon 'computer' revisited BBC - November 30, 2006

Using advanced imaging techniques, an Anglo-Greek team probed the remaining fragments of the complex geared device. The remains of the device were first discovered in 1902 when archaeologist Valerios Stais noticed a heavily corroded gear wheel amongst artefacts recovered by sponge divers from a sunken Roman cargo ship. A further 81 fragments have since been found containing a total of 30 hand-cut bronze gears. The largest fragment has 27 cogs.




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