In today’s article “In search of lost time“, Nature 444, 534-538, Jo Marchant presents remarkable new findings on the Antikythera Mechanism. The Antikythera Mechanism is a mechanical computer (similar to Charles Babbage’s Analytical and Difference engines) designed to calculate astronomical positions, which was discovered in an ancient ship wreck (150-100 BC) off the Greek island of Antikythera. What’s really intriguing about this “computer” is that was developed about 2000 years before Babbage’s model.
Here is a summary of the article and a few thoughts to provide context for photos taken while visiting the National Archaeological Museum in Athens, this summer.
Images 1-2. Front view of the Antikythera Mechanism fragments and
official caption, as exhibited at the National Archaeological Museum in Athens, Greece (click to enlarge).
First, about the Discovery…
According to Wikipedia,
Sometime before Easter 1900, Elias Stadiatos, a Greek sponge diver, discovered the wreck of an ancient cargo ship off Antikythera island at a depth of 42 m. Sponge divers retrieved several statues and other artifacts from the site.
Images 3-7. One of the bronze statues found at the Antikythera wreck
as exhibited at the National Archaeological Museum in Athens, Greece.
Images 8-10. Another of the bronze statues found at the Antikythera wreck.
The mechanism itself was discovered on May 17, 1902, when archaeologist Valerios Stais noticed that a piece of rock recovered from the site had a gear wheel embedded in it. Examination revealed that the “rock” was in fact a heavily encrusted and corroded mechanism that had survived the shipwreck in three main parts and dozens of smaller fragments. The device itself was surprisingly thin, about 33 cm (13in) high, 17 cm (6.75in) wide and 9 cm (3.5in) thick, made of bronze and originally mounted in a wooden frame. It was inscribed with a text of over 2,000 characters, about 95% of which have been deciphered. The full text of the inscription has not yet been published.
Now, about its Functionality…
According to Nature’s article, the mechanism fragments
contain at least 30 interlocking gear-wheels, along with copious astronomical inscriptions. Before its sojourn on the sea bed, it computed and displayed the movement of the Sun, the Moon and possibly the planets around Earth, and predicted the dates of future eclipses. It’s one of the most stunning artefacts we have from classical antiquity.
No earlier geared mechanism of any sort has ever been found. Nothing close to its technological sophistication appears again for well over a millennium, when astronomical clocks appear in medieval Europe. It stands as a strange exception, stripped of context, of ancestry, of descendants.
Here are some more of the photos from the visit to the museum.
Images 11-17. Various views of the mechanism fragments and X-rays.
The mechanism is an implementation of Hipparchus’s model of planetary motion.
The researchers realized that the ratios of the gear-wheels involved produce a motion that closely mimics the varying motion of the Moon around Earth, as described by Hipparchus. When the Moon is close to us it seems to move faster. And the closest part of the Moon’s orbit itself makes a full rotation around the Earth about every nine years. Hipparchus was the first to describe this motion mathematically, working on the idea that the Moon’s orbit, although circular, was centred on a point offset from the centre of Earth that described a nine-year circle. In the Antikythera Mechanism, this theory is beautifully translated into mechanical form. “It’s an unbelievably sophisticated idea,” says Tony Freeth, a mathematician who worked out most of the mechanics for Edmunds’ team. “I don’t know how they thought of it.”
Here are photos of a reconstruction of the mechanism by Prof. Derek de Solla Price, Yale University:
Images 18-21. Various views of the mechanism’s reconstruction, as exhibited at the National Archaeological Museum in Athens, Greece.
Where are the others?
Given its sophistication, clearly this mechanism could not have been just a prototype. If so, why haven’t we found more ancient devices like it?
Again, according to Nature’s article,
Cicero wrote of a similar mechanism that was said to have been built by Archimedes. That one was purportedly stolen in 212 BC by the Roman general Marcellus when Archimedes was killed in the sacking of the Sicilian city of Syracuse. The device was kept as an heirloom in Marcellus’ family: as a friend of the family, Cicero may indeed have seen it.
How could this knowledge die away? Actually, it probably didn’t. There is evidence that similar systems existed in the eastern Mediterranean in later years in the Byzantium, Persia, and Arabia. And then, in the 14th century mechanical clocks emerge in Europe. Interestingly, these clocks were mainly used to drive astronomical displays — the time-telling functionality seemed somewhat secondary.
It is possible that medieval craftsmen re-invented the wheel, so to speak. But it is equally likely that the technique survived away from the critical eyes of the early Christian church, and possibly reached the west right after Baghdad was conquered by the Mongols in the 13th century. Soon afterwards, clocks started being constructed in the West without much information about their origins. If a medieval European craftsman had re-invented the technique, his name should have been recorded, and the technique would have probably remained proprietary for some period of time. Thus, one can safely argue that the “invention” of clocks in 14th-century Europe was not a revolutionary step (as it commonly believed), but rather an evolutionary one.
But if the Greeks had access to such powerful calculating technology, why don’t we see other useful artifacts of technical sophistication? Well, we do have the massive, architecturally intricate buildings they left behind (many still standing). But what about other technological gizmos, like the Antikythera one?
So where are the other examples? A model of the workings of the heavens might have had value to a cultivated mind. Bronze had value for everyone. Most bronze artefacts were eventually melted down: the Athens museum has just ten major bronze statues from ancient Greece, of which nine are from shipwrecks. So in terms of the mechanism, “we’re lucky we have one”, points out Wright. “We only have this because it was out of reach of the scrap-metal man.”
Bronze was a preferred medium for weapon making because of its strength and ease of casting. Romans also used bronze for casting statues of their gods. Why preserve a conquered, disgraced nation’s statues of philosophers and of strange delicate artifacts with no apparent practical use? The bronze used in these artifacts was far more valuable to the conqueror.
Also, Greeks did not necessarily have the same needs/concerns that drive technological innovation in our modern, fast-paced, bottom-line society. They were less concerned with accurate time keeping (similarly to most Mediterranean cultures) and more concerned with knowledge, philosophy, and a deeper understanding of life and the universe. As anyone who has visited Greece can attest, that’s still rooted in the Greek psyche (especially the time keeping part… ;-).
- Jo Marchant, “In search of lost time“, Nature 444, 534-538, Nov. 30, 2006.
- Derek J. de Solla Price, “An Ancient Greek Computer“, Scientific American, pp. 60-67, Jun. 1959.
- Alun Salt, “The Antikythera Mechanism“, Archaeoastronomy blog, Nov. 29, 2006.
- The Antikythera Mechanism Research Project, http://www.antikythera-mechanism.gr/.
- Philip Coppens, “The wheels of Greek astronomical science“, accessed Nov. 30, 2006.
- Derek J. de Solla Price, Wikipedia entry, accessed Nov. 30, 2006.