Antikythera mechanism

The Antikythera mechanism is an ancient artifact believed to be an early clockwork mechanism. It was discovered in a shipwreck off the Greek island of Antikythera, between Kythera and Crete, and has been dated to about 87 BC.

The wreck was discovered in 1900 at a depth of about 40 m (140 feet), and many statues and other works were retrieved from it by sponge divers. On May 17 1902 archaeologist Spyridon Stais noticed that one of the pieces of rock had a gear wheel embedded in it.

The mechanism is the oldest known surviving geared mechanism, made from bronze in a wooden frame, and has puzzled and intrigued historians of science and technology since its discovery. The most commonly accepted theory of its function is that it was an analog computer designed to track the movements of heavenly objects. Recent working reconstructions of the device support this analysis. The device is all the more impressive for its use of a differential gear, which was previously believed to have been invented in the 16th century AD.

The late Professor Derek J. de Solla Price, a science historian working at Yale University, published an article on the mechanism in Scientific American in June 1959 while the device was still only partially inspected. In 1973 or 1974 he published an analysis based on gamma ray imaging by Greek archaeologists. He claimed that the device had been built by a Greek astronomer, Geminus of Rhodes. His conclusion was not accepted by experts at the time, who believed that the Ancient Greeks had the theoretical knowledge but not the necessary practical skills.

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.

Later, a British orrery maker named John Gleave constructed a working replica of the mechanism. According to his reconstruction, 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 equals 19 solar years. A synodic month is the period between two new moons. The lower rear dial plots the cycle of a single synodic month, with a secondary dial showing the lunar year of 12 synodic months.

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 those of every celestial body known to the Ancient Greeks: Mercury, Venus, Mars, Jupiter, and Saturn.

This new reconstruction gives credence to ancient mentions of such devices. Cicero, writing in the first 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." Such devices are mentioned elsewhere as well.

It also adds support to the idea that there was an ancient Greek tradition of complex mechanical technology which formed the foundation of European clockmaking techniques.

Some scientists believe that not only was the device used to track celestial bodies, but to calculate their positions for events or births.

The original mechanism is kept in the National Archaeological Museum in Athens. There is a replica on display at the American Computer Museum in Bozeman, Montana.

The Antikythera mechanism, not described in any surviving source, shows that our knowledge of ancient technology is very incomplete. In 1996 the Italian physicist Lucio Russo (professor at Università di Roma "Tor Vergata") published an essay putting new light on the issue. The book has been translated and published in English in 2004 under the title "The Forgotten Revolution: How Science Was Born in 300 BC and Why it Had to Be Reborn".

See also

• Armillary sphere
• Astrario by Giovanni De' Dondi
• Astrolabe
• Astronomical clock
• Orrery
• Planetarium
• Prague Orloj
• Torquetum

External links and references

• American Mathematical Society's The Antikythera Mechanism I (http://www.math.sunysb.edu/~tony/whatsnew/column/antikytheraI-0400/kyth1.html) and The Antikythera Mechanism II (http://www.math.sunysb.edu/~tony/whatsnew/column/antikytheraII-0500/diff1.html) (Java Animation (http://www.math.sunysb.edu/~tony/whatsnew/column/antikytheraI-0400/kyth5.html) by Bill Casselman)
• Fortunat F. Mueller-Maerki's Geartrain diagram (http://www.horology.com/htu-anti.html)
• Manos Roumeliotis's Antikythera Mechanism MOV files (http://etl.uom.gr/mr/Antikythera/anti.html)
• Rupert Russell's The Antikythera Mechanism (http://www.giant.net.au/users/rupert/kythera/kythera.htm)
• Price, Derek J. de Solla, "An Ancient Greek Computer (http://www.giant.net.au/users/rupert/kythera/kythera3.htm)". Scientific American, June 1959. p.60-67
• Rice, Rob S., "The Antikythera Mechanism (http://ccat.sas.upenn.edu/rrice/usna_pap.html) : Physical and Intellectual Salvage from the 1st Century B.C.". USNA Eleventh Naval History Symposium.
• The Economist, "The Antikythera mechanism (http://www.economist.com/displaystory.cfm?story_id=1337165) : The clockwork computer". September 19, 2002.
• Rice, Rob S., "Gears, Galleys, and Geography The Antikythera Mechanism's Implications (http://ccat.sas.upenn.edu/rrice/apagadgt.html)". Text of the 1993 APA Abstract.
• Lienhard, John H., "Antikythera Mechanism (http://www.uh.edu/engines/epi1031.htm)". The Engines of Our Ingenuity. KUHF-FM, Houston.
• M T Wright, "A Planetarium Display for the Antikythera mechanism". Horological Journal, 144 No. 5, 169-173, May 2002
• Derek De Solla Price. Gears from the Greeks: The Antikythera Mechanism - A Calendar Computer from ca. 80 B.C.. Science History Publications, New York, 1975, ISBN 0871696479; originally published in Transaction of The American Philosophical Society, New Series, Volume 64, Part 7 (1974)
• Russo, Lucio, "The Forgotten Revolution : How Science Was Born in 300 BC and Why it Had to Be Reborn". Springer , 2004, ISBN 3540203966cs:Mechanismus z Antikythery

de:Mechanismus von Antikythera el:Μηχανισμός από τα Αντικύθηρα es:Mecanismo de Antiquitera it:Meccanismo di Antikytera