Saturday Art: The Antikythera Mechanism

Never underestimate the intelligence and knowledge of our ancient ancestors

In October, 1900 divers discovered an ancient shipwreck off Point Glyphadia on the Greek island of Antikythera, which is located in the Aegean Sea off the northwest coast of Crete. The divers recovered many works of art from the sunken ship and transferred them to the National Museum of Archaeology for cataloging and storage. Among the items they recovered was a mysterious mechanism with wheels and gears.

On May 17, 1902 archaeologist Valerios Stais examined it and decided that it was an astronomical clock. Other experts, however, disagreed because they believed that it was too complex to have existed at the same time as the other items recovered from the wreck. The wreck appeared to be the remains of a first century BCE cargo ship carrying treasure looted by conquering Roman soldiers from Antikythera or other nearby islands and destined to be exhibited by Julius Caesar in a triumphal parade in Rome.

The strange mechanism would languish in obscurity for almost fifty years before English physicist Derek J. de Solla Price examined it in 1951. After several years of study, he published an article in Scientific American in June 1959 entitled An Ancient Greek Computer in which he identified it as a mechanical device for measuring the movements of the stars and the planets. In other words, the earliest known analog computer.

From Wikipedia,

In 1971, Price, by then the first Avalon Professor of the History of Science at Yale University, teamed up with Charalampos Karakalos, professor of nuclear physics at the GreekNational Centre of Scientific Research “DEMOKRITOS”. Karakalos took both gamma- and X-ray radiographs of the mechanism, which revealed critical information about the device’s interior configuration.

In 1974, Price published “Gears from the Greeks: the Antikythera mechanism — a calendar computer from ca. 80 BC”, where he presented a model of how the mechanism could have functioned.

Price’s model, as presented in his “Gears from the Greeks”, was the first theoretical attempt at reconstructing the device based on its inner structure revealed by the radiographs. 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.

One of the remarkable proposals made by Price was that the mechanism employed differential gears, which 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.

The conclusions of Price and others led to the creation of The Antikythera Mechanism Research Project that continues to study the mechanism. The Project has published three papers in Nature in 2006, 2008, and 2010.

Wikipedia states:

The new discoveries confirm that the mechanism is an astronomical analog calculator or orrery used to predict the positions of celestial bodies. This work proposes that the mechanism possessed 37 gears, of which 30 survive, and was used for prediction of the position of the Sun and the Moon. Based on the inscriptions, which mention the stationary points of the planets, the authors speculate that planetary motions may also have been indicated.

On the front face were graduations for the solar scale and the zodiac together with pointers that indicated the position of the Sun, the Moon, the lunar phase, and possibly the planetary motions.

On the back, two spiral scales (made of half-circles with two centers) with sliding pointers indicated the state of two further important astronomical cycles: the Saros cycle, the period of approximately 18 years separating the return of the Sun, Moon and Earth to the same relative positions and the more accurate exeligmos cycle of 54 years and one day (essential in eclipse prediction, see Eclipse cycle). It also contains another spiral scale for the Metonic cycle (19 years, equal to 235 lunar months) and the Callippic cycle with a period of 1016 lunar orbits in approximately 76 years.

The Moon mechanism, using an ingenious train of gears, two of them linked with a slightly offset axis and pin in a slot, shows the position and phase of the Moon during the month. The velocity of the Moon varies according to the theory of Hipparchus, and to a good approximation follows Kepler’s second law for the angular velocity, being faster near the perigee and slower at the apogee.

On 31 July 2008, a paper providing further details about the mechanism was published in Nature (Nature Vol 454, Issue 7204, July 31, 2008). In this paper, among other revelations, it is demonstrated that the mechanism also contained a dial divided into four parts, and demonstrated a four-year cycle through four segments of one year each, which is thought to be a means of describing which of the games (such as the ancient Olympics) that took place in two and four-year cycles were to take place in any given year.

The names of the months have been read; they are the months attested for the colonies of Corinth (and therefore also traditionally assumed for Corinth, Kerkyra, Epidamnos, and Syracuse, which have left less direct evidence). The investigators suggest that the device might well be of Syracusan design and so descend from the work of Archimedes; alternatively it could have been ordered by and customized for any of these markets and was being shipped.

Nature published another study on 24 November 2010. The study interprets the mechanism to be based on computation methods used in Babylonian astronomy, not ancient Greek astronomy, implying that Babylonian astronomy inspired the Greek counterpart – including the mechanical constructs.

Andrew Carol, an Apple software engineer, built a replica of the mechanism out of 1,500 LEGO pieces, and has correctly predicted the Solar eclipse of April 8, 2024 as a demonstration of its accuracy.

Cross Posted at Firedoglake/MyFDL and the Smirking Chimp

Photograph obtained from Wikipedia Commons

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One Comment on “Saturday Art: The Antikythera Mechanism”

  1. gokkast Says:

    Awesome blog, it’s just like a game for me! It’s so infomative and usefull, thanks a lot! If you post more of this great stuff, I’ll visit your blog again!

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