To the editors:

Mike Edmunds is one of the pioneers in Antikythera mechanism research and I am pleased to have this opportunity to comment on his essay. In 2001, Edmunds was one of three researchers granted permission to undertake a new investigation of the mechanism by the Greek Ministry of Culture. The other researchers were the late John Seiradakis from the Aristotle University of Thessaloniki, Greece, and Xenophon Moussas from the Kapodistrian University of Athens.

In 2008, in collaboration with Seiradakis, I helped establish an interdisciplinary research team to study the mechanism at the Aristotle University of Thessaloniki. Since then, the team has cooperated with many researchers around the world, including Edmunds. The group consists of astronomers, archaeologists, and mechanical engineers, among others. In July 2022, the university created the Center for the Multidisciplinary Research and Promotion of the Antikythera “Ioannis Seiradakis.” As director of the center and on behalf of all its members, I can confirm that we fully agree with views expressed by Edmunds in his essay.

Nevertheless, I would like to emphasize several points. The first of these concerns the supposed existence of indicators on the front side of the mechanism showing the position of the planets. Edmunds mentions that “Inscriptions on the device strongly suggest that its front face also displayed the positions in the zodiac of the known planets.” The mechanism was a complicated instrument—it is not surprising that it was accompanied by an extensive user’s manual. Inscriptions that had not been read for more than 2,000 years have now been revealed using, for the most part, X-ray micro-focusing tomography. Approximately 3,500 letters and symbols have been deciphered. The inscriptions fall into three broad categories: astronomical, geographical, and technical. Several astronomical terms have been found referring to the Sun, the Moon, the ecliptic (or Zodiac Cycle), the Metonic and Saros cycles, and other astronomical phenomena. The word ΣΤΗΡΙΓΜΟΣ, meaning stationary point, is mentioned several times, obviously referring to stationary points of the planetary orbits. Although these texts hint that the mechanism may have included functionality for determining the position of the planets, no parts or fragments have been found thus far to support this view, let alone the possibility that such functionality, as many researchers claim, may have been accessible from the front of the mechanism. Indeed, placing five additional pointers together with the corresponding gears that rotate them, as has been suggested, is not the best position from a mechanical point of view.

The second point concerns the operation of the mechanism. Edmunds mentions that “a single driver, such as the knob on the side of the Antikythera mechanism, turns the indicators on many dials.” It is important to note that no knob has been found among the fragments. The rotation of any gear or pointer on the mechanism results in the simultaneous movement of all the gears, and thus all of the pointers, which show various astronomical phenomena in related mathematical scales. From an analysis of the torque applied by the operator while handling the mechanism, and the necessity of precisely positioning the pointers, such as the sun and date pointer on the front of the mechanism, the most probable scenario for the operation of the mechanism is the rotation of the moon pointer. By rotating the moon pointer and choosing a date, the operator can observe the astronomical phenomena occurring on that day. By choosing an astronomical phenomenon, the operator can observe the date on which it occurs.

Another issue arises in relation to the accuracy of the mechanism’s predictions. One of the foremost questions among researchers is whether the mechanism was a scientific instrument for the safe prediction of astronomical phenomena or an educational tool used by schools of astronomy in antiquity. In an effort to answer this question, but also to make the mechanism more accessible to the general public, we have developed an application that simulates the physical model of the mechanism. From all the tests that have been performed, it has been concluded that the mechanism accurately predicts forthcoming astronomical phenomena and confirms with astonishing accuracy past astronomical phenomena. The accuracy of both types of predictions was determined by comparing our results with corresponding predictions from the NASA website. In combination with a physical functional model, the application helped us prove that the Antikythera mechanism was indeed a scientific instrument—the first computer in world history—that accurately predicts astronomical phenomena.

Kyriakos Efstathiou

Mike Edmunds replies to Paul Keyser, Paul Cartledge, and Kyriakos Efstathiou:

I am very grateful for the kind and informative comments that these three authors have made on my slim essay. Venturing to cross from one discipline to another is a stimulating but dangerous activity, and I have often been conscious of my lack of deep classical and historical background. Nonetheless, we all seem to be in welcome agreement that the Antikythera mechanism is indeed a child of its time.

Paul Keyser provides much additional food for thought—in particular on the idea that there are further design conventions to be recognized in the mechanism. I am sympathetic to Keyser’s feeling that Archimedes has been accorded rather more expertise in the invention of sphaerae than is really justified by the evidence—at least until the contents of his lost book de Sphaerae is discovered. I might be a little more egalitarian than Paul Cartledge in estimating the cost of the mechanism. It was made of bronze not gold; any stones incorporated were semi-precious rather than true gems; and a rough estimate of the mechanical craftsmanship involved might only be a few weeks—i.e., requiring sufficient expertise to make it indeed an expensive object, but not prohibitively so. This suggests that such devices might not have been terribly rare, with the hopeful prospect that another example or variant might yet be found in the future, perhaps preserved at a suddenly-terminated site such as Pompeii or Herculaneum. Kyriakos Efstathiou is of course correct in asserting that no driving knob survives on the side of the mechanism, but the presence of a crown gear that would drive the main Sun gear is excellent circumstantial evidence that a knob or similar drive may have existed. Even if it did not, and the drive was indeed from the moon pointer, the philosophical—or, even theological—nicety of a single driver or Primum Mobile still remains.

We all seem rather stumped by the question of the mechanism’s primary purpose. But perhaps it is appropriate that some uncertainty should remain about this marvelous artefact, especially given that so much valuable de-mystification has taken place in recent years!