The Antikythera Mechanism

April 13, 2013

2013AD: Some bits of crusty stuff in the National Archaeological Museum of Athens.

circa 87BC The original thing had only just been manufactured in Rhodes, Greece when it was plundered by the Romans who had recently begun to control that area. The ship carrying it and whatever else the Romans took a fancy to back to Rome, hit rocks and sunk near the island of Antikythera. Julius Caesar never got to see it.

1900 Some divers discovered the wreck of the ship and some statues, pottery, glassware, jewelry, coins, and other stuff. It all went to the National Archaeological Museum in Athens and some 82 bits of the other stuff were ignored.

1902 An archaeologist, Valerios Stais, noticed the gear wheel embedded in the rock (top left) and thought it might be part of the mechanism of an astronomical clock. Nobody else did, and the pieces were ignored again.

1951 The scientist Derek J. de Solla Price became interested in the mechanism and, together with the nuclear physicist, Charalampos Karakalos, made X-ray and gamma-ray images of the fragments. The mechanism was a lot more complicated than anyone had thought.

1974 Price and Karakalos published their findings confirming that the device calculated the astronomical cycles of planets and the moon, but they were uncertain whether the device had a practical use in navigation, was an item for exhibition, or even a rich man’s toy much like a Fabergé Egg.

The following is a schematic diagram of the known parts of the mechanism. What we do know is that it was probably the world’s first analogue computer. Nothing approaching this level of mechanical complexity would be made for another 1500 years.

The mechanism was operated by turning a small hand crank (now lost) which was linked via a crown gear to the largest gear (the one with the four spokes). This set the date on the front dial. Turning the hand crank also caused all the interlocking gears to rotate and calculate the position of the Sun and Moon and other astronomical information, such as moon phases, eclipse cycles, and the locations of planets.

Because of the large space between the mean sun gear (the large one) and the front of the case and the size of the mechanical features on the mean sun gear, it is very likely that the mechanism contained further gearing that has been lost in or after the shipwreck, or perhaps even removed before being loaded onto the ship. This lack of evidence and nature of the front part of the mechanism has led to numerous attempts to emulate what the Greeks of the period would have done. Many solutions have been proposed.

All these solutions are interesting because they attempt to get into the minds of the ancient Greeks and try to imagine what they might have wanted to know about or represent and how they might have gone about it modeling it mechanically. The most recent solution was proposed only last year and is the most elegant solution to date because it explains the most and with a simplicity of assumptions and means. So far, only a computer simulation exists.

The first investigations used conventional X-rays but the Antikythera Mechanism Research Project (AMRP) has been building an image database of new x-rays, digital photography and computed tomography. The exterior surfaces of the Mechanism have been further examined using a technique of reflectance imaging developed by Tom Malzbender and colleagues at Hewlett-Packard (USA). The team carried out high-resolution three-dimensional X-rays, using a technique called microfocus x-ray computed tomography, a method developed by Roger Hadland and his team from X-Tek Systems (UK).

The AMRP have been able to read previously invisible words and glyphs on the dials and plates, and on the basis of the translation of these have identified a new set of purposes of the machine.

The Olympic and other ancient games were unlikely to have been held during Roman occupation and so the date of manufacture most likely predates this, pushing back the most likely date of construction to around 100-150 BC but still consistent with the date of the shipwreck in which the mechanism was found (ca 50-80 BC).

The point of this post is not to say “isn’t it amazing!” and for us to patronizingly marvel at how clever and skilful people were back then. If the mechanism was in fact a rich man’s toy it doesn’t really matter how clever or skilful these people were if that was the best use to which it was put. Like many other people, I prefer to think it wasn’t.

To me, the real human genius has occurred since its discovery as people have used increasingly sophisticated scientific tools to probe and reconstruct the mechanism and increasingly penetrating theories to unlock what these findings could have meant. This process has not finished as new knowledge continues to give rise to new theories, the most recent ones focusing on perceived inaccuracies in the modeling of some planetary movements. This has in turn led to more theories, one of which suggests that the mechanism does not model the Universe as understood by the Greeks, but that of the Babylonians, thus raising more questions …

Whatever it was intended to be, the Antikythera Mechanism is one people’s excellent attempt at constructing a model to represent reality as it was known to them. Part of its attraction for us now is that it represents the best of what those people were. The Antikythera Mechanism is a special object. It has revealed this much of its workings and purpose to us only because our application of science has been illuminated and guided by an empathy for the past and a respect for its achievements. It has brought out the best in us.