Digital Heritage Research Lab

The Antikythera Mechanism

One of the artefacts ranked among the Wonders of the Ancient World is the Antikythera Mechanism, the oldest extant complex geared device, also described as the first analogue computer. Its construction was variously estimated to about 87 BC; or between 150 and 100 BC; or to 205 BC; or finally, within a generation before the shipwreck, which has been dated to approximately 70-60 BC. It relied on the second-century BC Greek knowledge of astronomy and mathematics.

The main utility of the Antikythera mechanism was to calculate the exact position of the Sun, the Moon and possibly the planets in the sky as well the phases of the Moon and the prediction of eclipses. Apart from the prediction of astronomical events, the mechanism could also determine dates related to religious, social and agricultural rituals and events.

The Mechanism was accompanied by an extended “instructions manual” inscribed on one of its parts. The device was operated manually by a user, setting a date in a dial. All necessary calculations were made using a set of gears (at least 39), while the results were displayed on several scientific scales. Unfortunately, the specific purpose for which the Mechanism was made remains unknown.

The identity of its maker is also unknown, but the variety of skills and knowledge necessary for the creation of the Mechanism indicate that it required collaboration between an astronomer/mathematician and a mechanic.

With its discovery, the Antikythera Mechanism demonstrated that Greek engineers of the Hellenistic period had become far more fluent in designing and constructing geared devices than the surviving written sources infer. It is also notable that the knowledge transmitted by the mechanism was lost and similar technological works appeared much later in Byzantium (fifth-sixth century AD) and the Arab world, while complex ones like the Mechanism appeared in Western Europe in the fourteenth century.

The discovery and the prior scientific investigations

The Antikythera Mechanism was retrieved from the sea in 1901 near the coast of the Greek island of Antikythera. The divers retrieved also numerous large artefacts, including bronze and marble statues, pottery, unique glassware, jewellery and coins. A year later, the archaeologist Valerios Stais acknowledged that the curious artefact housed in the remains of the wooden box was an instrument composed by at least one gear. The device was found as one lump, which was subsequently divided into three main fragments during restoration. The Mechanism currently showcased at the National Archaeological Museum of Athens is divided into eighty-two separate parts.

As expected, the scholars who have been involved in the study of the Antikythera Mechanism were numerous, with specialization in various research fields. The first researchers who focused for over 30 years on the study of the function of the Mechanism published the most substantial and extensive articles available today. A series of articles were also published dealing with the function and usage of the mechanism and its calculations. The authors of the various papers formed eventually the core of the “Antikythera Mechanism Research Group” composed by researchers from Greece and the UK, supported in addition by an international team of astronomers, archaeologists, mathematicians, physicists, chemists, computer engineers, mechanical engineers, epigraphists and papyrologists. In September 2005 they undertook a major new investigation of the Antikythera Mechanism, using x-ray tomography and a PTM/RTI dome for the mapping of the texture of the fragments, which revealed internal details of the gears, as well as inscriptions previously undeciphered.

The importance of the Antikythera Mechanism has subsequently led to the formation of a research group at the Aristotle University of Thessaloniki, Greece, for its further study. Among the leaders of the research group in question was Prof. Kyriakos Efstathiou, currently holder of the “Mnemosyne” ERA Chair on Digital Cultural Heritage.


Estimation of Complexity & Quality based on EU 3D Study/VIGIE 2020/654





The elliptical movement of the Moon and its simulation by the Mechanism

The Antikythera Mechanism is the oldest existing complex geared device, an amazing geared analogue computer. It was built approximately 2150 years ago and was used to calculate astronomical phenomena.

The device was operated manually by a user, to set a date on a dial and notice the astronomical phenomena that occur on that day. Respectively, by choosing an astronomical phenomenon he can observe at which date it will happen. All necessary calculations were made using a set of gears (at least 39).

The Mechanism was used to calculate the diurnal and annual motion of the Sun, the Moon and probably the planets among the stars. It calculated the position of the Sun and the Moon on the Sky and the phases of the Moon for every day of the year and predict eclipses of the Sun and the Moon.

It implemented the astronomical knowledge of ancient Greeks about the motion of these heavenly bodies with astonishing accuracy, considering the anomalous motion of the Moon around the Earth, using a system of eccentric gears.

Essentially, in the Antikythera Mechanism, the epicyclic theory of Hipparchus is integrated. This theory was formulated to interpret the retrograde motions of the planets as well as the change in the angular velocity of the rotation of the moon around the Earth. Today we know that the moon’s anomalous motion is due to its elliptical orbit as it turned around the Earth (Kepler’s laws). It could, also, predict eclipses of the Sun and the Moon.

In addition, the Mechanism calculated the celebration date of the ancient Panhellenic Games. On the circumference of a corresponding dial found on the fragments of the Mechanism, the words Olympia, Pythia, Isthmia, Nemea and Naa have been deciphered. Internally, in each quadrant, the four years of the Olympic cycle are indicated. All these games were crowned Games, with winners being rewarded with olive wreaths.

The Antikythera Mechanism was a complicated instrument. Therefore, it is not surprising that it was accompanied by an extensive User’s Manual. New inscriptions that had not been read for more than 2000 years were revealed, mainly with the X-ray micro-focusing tomography. About 3500 letters and symbols have been deciphered up to now.

The collection is dedicated to Ioannis Seiradakis, whose contribution was a catalyst for the inception of the research for the Antikythera Mechanism, in 2005, which led to its decoding.

John H. Seiradakis (5 March 1948 – 3 May 2020)


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