Abstract
Readers of this journal will not need much reminding of the details of the discovery and varying interpretations of the so-called Antikythera Mechanism, a bronze instrument found in 1900 by sponge divers in a shipwreck off the Greek island after which it is named. In this book, Alexander Jones, one of the foremost modern historians of ancient Greek astronomy, offers, mainly for the general reader, a beautifully lucid account of that discovery and a robustly argued intervention on the problems of how it worked and what it was for.
Initially, the scholarly world was utterly baffled. While the divers focused their attention on the bronze and marble statues the ship contained, there is even a story, which may or may not be true, that the mechanism itself narrowly escaped being thrown back into the sea as being of no interest or value. No one had ever seen anything like this before; indeed, no one has seen anything like it since. All sorts of guesses were originally made about its function. Was it an observational instrument (astrolabe) or a planetarium or some kind of analogue computer? It took some time for people to decipher the inscriptions the instrument carried and to connect it with the written sources, in Cicero and Cassiodorus in particular, that describe various mechanisms that imitated the movements of the heavenly bodies. In the early days, of course, all that researchers had to go on was what they could see on the surface of the instrument. It was only when more advanced techniques, such as X rays, gamma rays and computerised tomography (CT) scans, were used that all the intricacies of the mostly hidden mechanisms, especially the gearing, were revealed.
Jones’ tactic is to assume that the current favoured reconstruction is broadly correct and then to take the reader through the implications. Problems of interpretation certainly remain: the August 2017 volume of this journal carries a new suggestion by Christián Carman about the final date of the mechanism. His view was that the instrument was old when the ship went down and may not have been much used, although Jones’ own view (p. 157) is that it was quite new. It is possible, even likely, that further data will come to light with even more advanced investigative technology, though that may not resolve the problem of its date of manufacture. However, Jones is surely right that enough is reliably known for it to be sensible to present the main findings to date.
His principal suggestion for the instrument’s primary function is that it is a teaching instrument. The operator (and one is clearly needed: the speculative suggestion that the mechanism might be powered by water is now ruled out) would demonstrate the motions of the sun, moon, and planets, thereby instructing the audience in the basic principles of astronomy. All the main non-uniform motions of the heavenly bodies would be represented on the various dials on the faces of the mechanism, as well as the cycles of eclipses. Jones, in turn, acts in a sense like a modern operator, giving the reader an eminently clear account of most aspects of the history of ancient astronomy, carefully discussing what the Greeks owed to their Mesopotamian predecessors and where their particular preoccupations differed from those of their near-eastern neighbours. His exegesis includes a careful discussion of the convoluted question of the different civil and astronomical calendars in use as well as the better-known debates between different geometrical models, of eccentrics, epicycles, and the like. He shows the interaction of observation and theory in the construction of the mechanism and the eclectic nature of the sources that went into that. Those sources include Babylonian and Egyptian as well as earlier Greek ideas, although it is clear that the constructor either did not know or chose to ignore some factors, including in particular Hipparchus’ discovery of the precession of the equinoxes. The level of technological expertise revealed by the layers of gearing is astonishing. To construct a gearwheel with 223 equally spaced triangular teeth demands consummate skill. The fact that such a complex instrument was commissioned for didactic purposes forces us to rethink our assumptions about the level of interest in astronomical issues beyond the ranks of those engaged in astronomical theory itself.
The book is a triumph at several levels, as an account of high-grade detective work, as an exposition of ancient astronomical ideas, and as a disquisition on where those ideas fitted into the society that produced them.
Anyone present at a demonstration of what the mechanism could do would be not just impressed but totally amazed, and they would be won over, too, to a conviction of the order of the heavens. Yet one has to remark that this was an incredibly expensive way of achieving those results. My one regret about this book is that Jones does not have more to say on the cost–benefit analysis or the economics of the exercise. Whoever commissioned the instrument must have been extremely wealthy. But this was not just a case of ancient conspicuous consumption and wonder-working. For aside from being used to demonstrate scientific and technological whizz-kiddery, it had a clear aim of spreading astronomical knowledge.
This is recommended reading for anyone interested in ancient astronomy.