is in the news again, thanks to an article in the May 14 New Yorker Magazine by John Seabrook, and a beautiful working model of the machine that Dionisios Kriaris made for the Children's Museum of Manhattan in an exhibition that opened May 25.


The main fragment of the Mechanism, found after two thousand years under sea water.
© The Antikythera Mechanism Research Project.

The name "Antikythera" has nothing to do with "Antique." It means "anti-Kythera" or "opposite Kythera," and is the name of a tiny island in the Mediterranean that lies between the islands of Crete and Kythera, off whose coast it was found in 1900 in an ancient shipwreck by sponge-divers looking for giant clams. An inconspicuous heap of hopelessly corroded metal lying among a treasure trove of pots and piles of human bodies, one arm of which was brought to the surface, and turned out to be bronze -- the first of 96 naked young men in bronze from the 4th c BC -- the ugly lump went unnoticed even by officials at the Athens Museum, until 1958, when Yale's Derek de Solla Price began studying it. And kept at it, right up until his death. .

Recently an 8-ton X-ray machine called "Bladerunner," designed by X-Tek Systems of Great Britain, took 3000 X-ray images of one fragment in an hour, later reassembled by a computer into a 3-D image. (See my article, "The Sphinx and the Robot," for a detailed account of how the ancient Naxos Sphinx was digitally scanned by a French-Italian team and then reassembled into a 3-D image that was reproduced in marble by a computer-directed stone-cutting robot.)


Detail of a modern working model of the Antikythera Mechanism made by Dionisios Kriaris for "Gods, Myths and Metals: Discover Ancient Greece," an exhibition at the Children's Museum of Manhattan which opens on May 25, 2007. © 2007 D. Kriaris and The New Yorker Magazine. This photo is the 10th of 11 slides you can see only by going to the online version of the New Yorker article by John Seabrook, "Fragmentary Knowledge. Was the Antikythera Mechanism the World's First Computer?" Here's the URL: http://www.newyorker.com/reporting/2007/05/14/070514fa_fact_seabrook/

On the outer circular dial are the 12 Greek months of the year, marked after the Babylonian calendar into 360 days - which is why a circle has 360 degrees. The inner dial, with the 366 days of the Egyptian calendar, shows the Greek Zodiac; across its top are Hydrokoon (Aquarius), Icthyas (Pisces), Krion (Aries) and Tauron (Taurus). Between the last two is a pointer with the bronze ball of the Sun, while below, on a revolving pin extending from the central Earth (?) is the Moon, one hemisphere of which is white, the other black, to show its changing phases from full moon to new moon.

The Metonic and Saros cycles on the Mechanism, and the Cosmos as a Geared Machine.


Metonic and saros cycles on the back side of a brass and plexiglas replica of the Mechanism by Massimo Vicentini that went on display in the Milan Planetarium on May 10, 2007. Photo © 2007 Massimo Vicentini

On the back side of the Mechanism are two separate circular gears and dials, one for the Metonic cycle, the other for the saros cycle. Babylonian astronomers had discovered that one could reconcile the 360 days in the 12 months of a lunar year with the 365 days in a solar year only after 19 years, i.e. only after 235 lunar months. In other words, if you observe a full moon on April 13, there will not be another full moon in that same place on April 13 until nineteen years later. This cycle came to be known as the Metonic cycle, after the Greek astronomer Meton of Athens. It was a neat way to keep the lunar calendar and the solar calendar in synch.

Astonishingly, Derek de Solla Price had predicted those 235 divisions would be in there somewhere even though they were not visible until the recent 3-D X-ray scan revealed them on spiral fragment E. On another fragment Price found the number 223, which is the number of lunar months in the saros cycle, a way of predicting eclipses, also discovered by the Babylonians, who found that 18 years, 11 days and 8 hours after an eclipse a nearly identical eclipse would occur. Since eclipses were omens that could predict important future events, such as the outcomes of battles and the births and deaths of kings, for thousands of years astronomer-astrologers were courted by princes and emperors. In fact two of the pioneers and "stars" of modern astronomy, Tycho Brahe and Johannes Kepler, earned money and fame as court astrologers.

Working out the geometry of the Babylonian cycles as perfect circles, the Greeks had built up a theory of the cosmos as a system of rotating circles and spheres. Since they still viewed the cosmos as an earth-centered ("Ptolemaic") system, to account for the apparent motions of the stars and planets around the earth, and each other, they had to introduce epicycles, or circles revolving on circles, just as smaller gears rotate on larger gears in the Antikythera Mechanism. As Alexander Jones, a professor of classics at the University of Toronto, said to John Seabrook, author of the New Yorker article on the Antikythera Mechanism, “The Greeks saw the Babylonian formulas in terms of geometry—they saw all these circles all spinning around each other in the sky. And of course this fits in perfectly with the concept of gearworks—the gears are making little orbits.”

But try to make such a machine with elliptical gears! Ironically, it was Kepler's obsession with proving and perfecting this divinely perfect mechanism of circular gears and orbits that forced him to break it. After a decade of trying to fit Tycho's observations, especially of the planet Mars, into circular orbits, he gave up and found they did fit into ellipses -- thereby discovering his famous law of elliptical planetary motion.


The front view of a brass replica of the Antikythera Mechanism by John Gleave, an English orrery maker. The back view shows a gear with the Metonic cycle. See both pics, with text, at:
http://www.grand-illusions.com/antikyth.htm

Another nice site is: The Antikythera Mechanism: A Relic of Ancient Greek Science, by Giocchino Jack Urso. This is a RealPlayer slideshow with an excellent audio accompaniment.
http://home.nycap.rr.com/mismedia/RM/anitkythera_mech.htm

The two main front dials with English inscriptions can be seen in a transparent plexiglas model in an article by Michael Lahanas, "Gears by Archimedes and Others" at:
http://www.mlahanas.de/Greeks/ArchimedesGears.htm

To see the many steps in Massimo MOGI Vicentini's reconstruction of the Mechanism, go to his fascinating illustrated web page "The Antikythera Celestial Machine: fragments of genius from a legendary science" at
http://www.mogi-vice.com/Antikythera/Antikythera-en.html

See also my article here at AW on Pythagorean Harmonics and the remarks on Pythagoras and the "music of the spheres" in my article on Raphael's "The School of Athens."