Thursday, August 06, 2009

Final thoughts from the ICHST: Rambling on about the Antikythera Mechanism

Posted by Darin Hayton on 08/06 at 04:19 AM

Sunday morning I attended one of the plenary lectures: Alexander Jone’s “The Antikythera Mechanism. Its Meaning for Greek Astronomy.” Jones apparently possesses limitless energy: he had already organized a symposium on Ptolemy at the conference, had given a paper in one of the sessions, had attended the numerous sessions dealing with ancient astronomy, and had been kind enough to spend considerable time speaking with other scholars at the various social functions. He still showed up on the last day and delivered an engaging and informative lecture to a full audience.

After more than a dozen presentations on the Antikythera mechanism, it was nice to hear Jones pull together the different strands and put this famous piece of corroded bronze into a historiographic context. He is one of the foremost scholars on ancient Greek astronomy and, consequently, the ideal person to provide a overall picture of the Antikythera mechanism.

The Antikythera Mechanism is emblematic of ancient Greek technology and attracts attention from people well beyond the history of science (my colleagues in classics as well as computer science, physics, and astronomy send me links to every story on the Antikythera Mechnanism). Jones recounted how different scholars over the last century have approached the mechanism, and how the questions they have asked shaped, quite literally, their reconstructions of the mechanism.

In 1901 sponge divers off the island of Antikythera discovered an ancient ship wreck. In the wreckage they found numerous pieces of art, statuary, pottery, and some chunks of bronze that had largely fused together after lying on the ocean floor for two millennia. Once cleaned, scholars soon realized that the pieces had been part of an ancient geared mechanism. Since then, historians, physicists, classicists and mechanicians have been trying to figure out what the instrument looked like, what it did, and how it was used. Their reconstructions, while often ingenious, are all based on little evidence, because the fragments offer up only hints at what the mechanism was. Nevertheless, scholars continue to expend considerable energy and money trying to solve the puzzle.1

Jones reminded us that if not for the inscriptions on the bronze fragments, there would be no reason to connect the Antikythera mechanism to ancient Greek astronomy. The first scholars to investigate the pieces realized that some surfaces were covered in Greek inscriptions. Of the inscriptions they were able to make out three words: Venus, Sun, and degree scale (we now know that the last of these words should be “pointer"). Based on these three words, scholars assumed that the gears had some astronomical application. However, there was no known ancient or medieval mechanism that would justify this connection. The most complicated surviving instruments were planispheric astrolabes, which are not geared mechanisms.2

The classicist Albert Rehm was next scholar to examine in detail the pieces. At the time he was working on ancient clock devices. As he passed through Athens on his way to Asia Minor to continue his own work, he stopped to see the mechanism. He happened to see some newly exposed surfaces that contained further inscriptions. Because he had been working closely with astronomical inscriptions from other ancient sources, he quickly recognized in the newly exposed inscriptions on the Antikythera Mechanism the name for an Egyptian month, a number of parapegma, two astronomical cycles, and the term for a planet’s stationary point.3 Relying on his expertise in astronomy and clocks, he inferred that the mechanism had been some sort of clock or planetarium. He did not, however, have any expertise in mechanisms. In other words, he had approached the fragments through the inscriptions, ignoring the physical artifacts such as the gears.

Derek de Solla Price, by contrast, approached the instrument through the gears. He knew little about ancient astronomy and could not read Greek. Price was interested in figuring out how the mechanism worked. He approached it through the physical pieces. Perhaps surprising, he seems to have been the first scholar to try to figure out how the surviving pieces fit together. Ultimately using x-ray technology, he identified distinct gears, counted the teeth on each (often having to calculate the number based on the fragment of the gear that survived), and identified axles.4 Price concluded that the mechanism was some sort of complex planetarium.

Jones passed over quickly the more recent work of Michael Wright and the Antikythera Mechanism Research Project (a joint venture by Cardiff University, the National Archaeological Museum in Athens, Hewlett Packard), in part because the recent work had been covered in the sessions devoted to the mechanism and probably to avoid stirring up some of the antagonisms between different scholars.5

To this point, Jones concentrated on attempts to infer certain characteristics of Greek astronomy mediated through the inscriptions and physical evidence. That is to say, scholars have been looking through the Antikythera Mechanism to understand better ancient astronomy. In the latter portion of his talk, he wanted to turn this relationship around and look at the Antikythera Mechanism through our understanding of ancient Greek astronomy. Such an approach will help us understand how the device might have been used. Looking at descriptions of demonstration devices and more technical texts, Jones argued that the Antikythera Mechanism was not intended for a skilled, practicing astronomer or astrologer. Rather, it was a demonstration device intended to instruct and entertain the lay viewer. It was to be used in some sort of public space, by which I understand him to be contrasting public space with private, workshop or office where an astronomer or astrologer might carry out the nuts and bolts of his practice.

Jones ended on a synthetic note. Both approaches are necessary to understand the Antikythera Mechanism, but in the end, we must bring their results together. The Antikythera Mechanism is the embodiment of ancient astronomy as a coherent activity or discipline.

For those of rude enough to leave the plenary lectures after Jones’s, we were treated to a modern embodiment of the Antikythera Mechanism in the building’s foyer. There Michael Wright was pleasantly explaining how he had arrived at his reconstruction, and taking it apart to show onlookers how it worked.

He needs no tools to disassemble his reconstruction, which he made out of reclaimed wood and brass. Having removed the back plate, he explains how the gear trains work and what each gear accomplishes.

More gears come out of the mechanism, revealing among other things, the inscriptions on Wright’s own mechanism. I amuse myself by thinking about how historians in the future might try to understand Wright’s device through the inscriptions left on the recycled brass plate:

If you ever run into Michael Wright, ask him about his device. He is always eager to explain how it works, why he has put it together in the manner that he has, and how he made it, by hand and with tools that would have been available to the ancient Greeks. He is an excellent example of a mechanician and a nice man.

1The most recent well-funded project has set up a webpage to publicize their results: Antikythera Mechanism Research Project. Numerous other sites point to further work, see The Antikythera Mechanism and this page, which provides some useful links to Michael Wright’s scholarship on the device. There is, of course, a Wikipedia page, if you are inclined: Wikipedia’s page.
2A 13th-century geared Islamic astrolabe does survive, but it is far too simple to justify connecting the Antikythera Mechanism to ancient Greek astronomy. For a photo of this astrolabe, see this page at the Museum of the History of Science.
3Parapegma are were tables that correlated star phases with weather. Ptolemy codified these early tables in his Almagest. If you are interested in how historians of science use these fascinating parapegma, see the recent article by Daryn Lehoux (who was at the ICHST): “Observation and Prediction in Ancient Astrology,” Studies in History and Philosophy of Science 35(2004): 227–46.
4Price’s initial work was published in 1959 in Scientific American. It was his later work, published in 1974, that benefitted from X-ray and gamma ray analysis: “Gears from the Greeks: The Antikythera Mechanism — A calendar computer from ca. 80 BC,” Transactions of the American Philosophical Society N.S. 64(1974): 1–70.
5While I was at the Museum of the History of Science, I spoke with a member of the AMRP. He had contacted the museum to ask if we had any astrolabes or related instruments that they could use to test their new imaging techniques. We were unable to help them. At the museum I also first met Michael Wright. The two teams (for lack of a better word) approach the Antikythera Mechanism with very different philosophies and techniques. These differences have at times caused some tension between the two groups. If you want to know more than that, you’ll have to buy me a beer.

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