Antikythera; ancient computer and a 100 year adventure

This post has been almost two years in the making, which seems laughable when considering that the story starts in 100 BCE (before the common era).

Picture ancient Greece and a Roman sailing ship holding an object we know as an Antikythera, named after the Greek island near where the ship was wrecked and where it lay undiscovered until 1900. From the Dec.10, 2010 posting by GrrlScientist on the Guardian science blogs,

Two years ago [2008], a paper was published in Nature describing the function of the oldest known scientific computer, a device built in Greece around 100 BCE. Recovered in 1901 from a shipwreck near the island of Antikythera, this mechanism had been lost and unknown for 2000 years. It took one century for scientists to understand its purpose: it is an astronomical clock that determines the positions of celestial bodies with extraordinary precision. In 2010, a fully-functional replica was constructed out of Lego.

Here’s the video mentioned by Grrl Scientist,

As noted in the video, it is a replica that requires twice as many gears as the original to make the same calculations. It seems we still haven’t quite caught up with the past.

Bob Yirka’s April 4, 2011 article for phys.org describes some of the research involved in decoding the mechanism,

If modern research is correct, the device worked by hand cranking a main dial to display a chosen date, causing the wheels and gears inside to display (via tabs on separate dials) the position of the sun, moon, and the five known planets at that time, for that date; a mechanical and technical feat that would not be seen again until the fourteenth century in Europe with precision clocks.

Now James Evans and his colleagues at the University of Puget Sound in Washington State, have shown that instead of trying to use the same kind of gear mechanism to account for the elliptical path the Earth takes around the sun, and subsequent apparent changes in speed, the inventor of the device may have taken a different tack, and that was to stretch or distort the zodiac on the dial face to change the width of the spaces on the face to make up for the slightly different amount of time that is represented as the hand moves around the face.

In a paper published in the Journal for the History of Astronomy, Evans describes how he and his team were able to examine x-rays taken of the corroded machine (69 then later 88 degrees of the circle) and discovered that the two circles that were used to represent the Zodiac and Egyptian calendar respectively, did indeed differ just enough to account for what appeared to be the irregular movement during different parts of the year.

Though not all experts agree on the findings, this new evidence does appear to suggest that an attempt was made by the early inventor to take into account the elliptical nature of the Earth orbiting the sun, no small thing.

Jenny Winder’s June 11, 2012 article for Universe Today and republished on phys.org provides more details about the gears and the theories behind the device,

The device is made of bronze and contains 30 gears though it may have had as many as 72 originally. Each gear was meticulously hand cut with between 15 and 223 triangular teeth, which were the key to discovering the mechanism’s various functions. It was based on theories of astronomy and mathematics developed by Greek astronomers who may have drawn from earlier Babylonian astronomical theories and its construction could be attributed to the astronomer Hipparchus or, more likely, Archimedes the famous Greek mathematician, physicist, engineer, inventor and astronomer. … [emphases mine]

I’ve highlighted the verbs which suggest they’re still conjecturing as to where the theories and knowledge to develop this ancient computer came from. Yirka’s article mentions that some folks believe that the Antikythera may be the result of alien visitations, along with the more academic guesses about the Babylonians and the Greeks.

I strongly recommend reading the articles and chasing down more videos about the Antikythera on Youtube as the story is fascinating and given the plethora of material (including a book and website by Jo Marchant, Decoding the Heavens), I don’t seem to be alone in my fascination.

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