BMCR 2018.05.16

A Portable Cosmos. Revealing the Antikythera Mechanism, Scientific Wonder of the Ancient World

, A Portable Cosmos. Revealing the Antikythera Mechanism, Scientific Wonder of the Ancient World. New York: Oxford University Press, 2017. xiv, 288; 8 p. of plates. ISBN 9780199739349. $34.95.


In June 1980, the Nobel prize winning physicist, Richard Feynman, visited the National Archaeological Museum in Athens. There, to the surprise of the museum staff, he expressed a particular interest in knowing more about object number 15087. An anomaly among the rich trove of sculptures, vases, and other decorative objects, the device which drew Feynman’s attention was ‘one thing so entirely different and strange that it is nearly impossible’.1 This object with its gear trains (‘very much like the inside of a modern wind up clock’), graduated circles, and Greek lettering, we now know as the Antikythera Mechanism.

Named for its discovery in an ancient shipwreck off the island of Antikythera (ancient Aegila) in 1900-1901, the Mechanism is unlike any other object recovered from an ancient context. Early investigators tried to relate it to other more familiar mechanical devices. Might it be an astrolabe? Or perhaps a planetarium? The turning point came in the late 1950s when the young physicist, Derek de Solla Price, recognised that the ‘wondrous device’ was a computer. But it is only in recent years that an international, multi-disciplinary research group (the aptly named Antikythera Mechanism Research Project or AMRP),2 with the latest research and scientific techniques at their disposal has been able to unravel the deeper mysteries of the device and to demonstrate its importance for calculating a variety of astronomical data. In this volume, Alexander Jones addresses the current state of knowledge regarding the Mechanism: its discovery, origins, workings, and offers his own plausible hypotheses regarding its purpose and meaning.

Details of discovery and salvage are themselves as much of a detective exercise as the investigation into the Mechanism itself. The story of the accidental discovery of the wreck by sponge divers from Symi offers broad social insights into their culture and motivations for bringing it to the attention of the Greek authorities. Jones interweaves their salvage efforts with references to the contemporary newspaper reports. Anecdotal stories enliven the narrative. According to one account, while loading items onto the ship take the antiquities to Athens, only the action of an astute naval officer (Periklis Rediadis, later an important contributor to early knowledge about the Mechanism) prevented a crew member from throwing the Mechanism back into the sea. Fortune continued to play a role in the discovery by finding a champion in the Minister for Education, Spyridon Stais. It was largely due to Stais’ efforts that the ‘inscribed slab’ and other fragments of the Antikythera Mechanism were taken seriously by archaeologists.

Ever-diplomatic, Jones recalls those on whose shoulders he stands, acknowledging the importance of the early investigations and the limitations of scientific investigation, while eschewing stories of personal rivalries and fragile egos. 3 This is as much the story of the development of modern archaeological techniques as it is the investigation into the Antikythera Mechanism. X-rays were the stimulus for Price’s more mature work Gears from the Greeks (1974); linear tomography helped Bromley and, especially, Michael T Wright to produce a working reconstruction of the Antikythera Mechanism. Latterly, computerized tomography (CT) and reflectance transformation imaging (RTI) scans have permitted the AMRP team, with the elements contributed by Price and Wright, to publish a reconstruction of the gearing scheme of the Mechanism that is now generally accepted by the scientific community.4 Furthermore, CT and RTI imaging has led to improved readings of the inscriptions and a better understanding of the workings of the Mechanism. All of this, if not always explicitly stated, is a testament to the value of interdisciplinary and collaborative research which has subsequently led to ‘a proliferation of the community of researchers’ (p. 46).

The bulk of the book concerns the external and internal workings of the Mechanism. Generously illustrated with line drawings, photographs, and black and white plates (Figures M1-M8), the complexity of the Mechanism is laid bare. The front dial of the Mechanism consisted of a dial with an Egyptian calendar, zodiacal divisions, and represented ‘the cosmos in motion’ (p. 202) with pointers for the sun, moon, and other planetary spheres. Two dials were mounted on the back of the device. The upper consisted of a spiral Metonic dial, enclosing smaller Callippic and Games dials, and the lower the Saros dial, enclosing an Exeligmos dial, used for calculating eclipses. A back-cover inscription (Jones’ BCI), now largely decoded and translated thanks to CT and RTI, described the Mechanism.

Within, to control the dials, were no less than some twenty-seven gears, able to execute uniform and nonuniform motion, essential for representing the direct and retrograde motions of the planets. Differential gearing also allowed the device to display the different phases of the moon. These aspects, Jones is careful to point out, are not paralleled by any other devices known from antiquity (p. 223). Ingenious though these aspects were, the Mechanism was not perfect. Jones posits errors in the device’s ability to measure single days with precision; the triangular teeth on the gears would have resulted in a certain amount of ‘backlash’; and there were slight errors derived from the application of Greek astronomical theory, for example, there would eventually have been a noticeable error in the moon’s phases.

Individual chapters explore the different aspects of the Mechanism in detail. Ancient concerns with the calendar and games, the stars, sun, and moon, eclipses, and the planets, provide a backdrop to the practical considerations of the Mechanism and its relative success in portraying these celestial phenomena on one device. These chapters range widely in time and space from Babylonian and Mesopotamian understandings of time and the cosmos, through the Egyptian calendar, the importance of the zodiac, ancient Greek and Roman understanding of solar and lunar eclipses. Interlaced, are references to comparative material: the Greek calendar on the Little Metropolitan Church at Athens, a parapegma from Miletus, Babylonian omen texts and the Astronomical Diaries. But the Mechanism was only so accurate: the Saros and Exeligmos dials could only have accurately depicted eclipses within a narrow window of time; the portrayal of the planets (the ‘Wanderers’) was limited to the direction of the planets from Earth and their relative distances. Despite careful explanations, the reader unaccustomed to the language of astronomy and engineering may well feel a little overwhelmed. For here, ecliptic, synodic, and penumbral, nestle comfortably next to eccentric, epicylic, and contrate. The detailed explanations of phenomena or mechanical operation often require careful reading and re-reading to comprehend fully the process or concept under examination.

Those in favour of an association with Archimedes or Syracuse may be disappointed. This, argues Jones, was a device made in Rhodes in the First Century BC and intended for a localised Epirote market.5 Clues are found in the inscriptions. There is a reference on the purely ‘symbolic’ Games dial to the Halieia, and to the Naa, local Rhodian and Epirote festivals respectively; the Metonic spiral contains Corinthian month names, which match almost exactly the month names used by localities in Epirus . Coinage provides a terminus post quem for the ship wreck: it can be no earlier than 76 BC; the provenance of the cargo, from Asia Minor and the Hellenistic world, including amphorae from Rhodes, suggests that the ship’s route was from East to West.

Jones further maintains that the Mechanism’s ultimate purpose was as a teaching, rather than a research, device. Such devices were undoubtedly rare but Geminus is frequently cited. He was the author of An Introduction to the Phaenomena, otherwise known as the Isagoge, who probably lived in Rhodes around 70 BC. There are close connections between the Isagoge with the calendrical functions of the Mechanism, its treatment of the Sun and Moon with their depiction on the Mechanism; the chapters on the rising and setting stars with the Parapegma inscription; and its discussion of eclipses with the Saros and Exeligmos dials (p. 238, table 9.1). Furthermore, from Cicero, we know that Posidonius, a Rhodian and contemporary of Geminus, had constructed a similar astronomical device (p. 94). The arguments are persuasive.

This is a remarkable book about a remarkable device. After reading A Portable Cosmos, the Antikythera Mechanism seems a little less ‘different and strange’, a little less ‘impossible’ but no less of an ancient wonder. In clear and lucid prose, Alexander Jones has successfully integrated all the necessary literary, archaeological, and forensic evidence relevant to the Mechanism. The result is a detailed, thorough, and perceptive analysis which will surely stand as the definitive handbook on the Antikythera Mechanism for some time to come.


1. Feynman, R. (1980) What Do You Care What Other People Think? Further Adventures of a Curious Character New York, pp. 93-97.

2. See http://www.antikythera-, Accessed May 2018.

3. Marchant, J. (2008) Decoding the Heavens. London.

4. Freeth, T., Bitsakis Y., Moussas X., Seiradakis J. H., Tselikas A., Mangou H., Zafeiropoulou M., Hadland R., Bate D., Ramsey A., et al., (Nov. 2006) ‘Decoding the ancient Greek astronomical calculator known as the Antikythera Mechanism’ Nature 444, 587-591.

5. See Price, D. de Solla (1974) Gears from the Greeks. The Antikythera Mechanism, a Calendar Computer from ca. 80 BC Transactions of the American Philosophical Society, ns 64.7, 61-62. Philadelphia.