---
title: "Antikythera mechanism"
chunk: 1/12
source: "https://en.wikipedia.org/wiki/Antikythera_mechanism"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:38:28.502947+00:00"
instance: "kb-cron"
---

The Antikythera mechanism ( AN-tik-ih-THEER-ə, US also  AN-ty-kih-) is an ancient Greek hand-powered orrery (model of the Solar System). It is the oldest known example of an analogue computer. It could be used to predict astronomical positions and eclipses decades in advance. It could also be used to track the four-year cycle of athletic games similar to an olympiad, the cycle of the ancient Olympic Games.
The artefact was among wreckage retrieved from a shipwreck off the coast of the Greek island Antikythera in 1901. In 1902, during a visit to the National Archaeological Museum in Athens, it was noticed by Greek politician Spyridon Stais as containing a gear, prompting the first study of the fragment by his cousin, Valerios Stais, the museum director. The device, housed in the remains of a wooden-framed case of (uncertain) overall size 34 cm × 18 cm × 9 cm (13.4 in × 7.1 in × 3.5 in), was found as one lump, later separated into three main fragments which are now divided into 82 separate fragments after conservation efforts. Four of these fragments contain gears, while inscriptions are found on many others. The largest gear is about 13 cm (5 in) in diameter and originally had 223 teeth. All these fragments of the mechanism are kept at the National Archaeological Museum, along with reconstructions and replicas, to demonstrate how it may have looked and worked.
In 2005, a team from Cardiff University led by Mike Edmunds used computer X-ray tomography and high resolution scanning to image inside fragments of the crust-encased mechanism and read faint inscriptions that once covered the outer casing. These scans suggest that the mechanism had 37 meshing bronze gears enabling it to follow the movements of the Moon and the Sun through the zodiac, to predict eclipses and to model the irregular orbit of the Moon, where the Moon's velocity is higher in its perigee than in its apogee. This motion was studied in the 2nd century BC by astronomer Hipparchus of Rhodes, and he may have been consulted in the machine's construction. There is speculation that a portion of the mechanism is missing and it calculated the positions of the five classical planets. The inscriptions were further deciphered in 2016, revealing numbers connected with the synodic cycles of Venus and Saturn.
The instrument is believed to have been designed and constructed by Hellenistic scientists and been variously dated to about 87 BC, between 150 and 100 BC, or 205 BC. It must have been constructed before the shipwreck, which has been dated by multiple lines of evidence to approximately 70–60 BC. In 2022, researchers proposed its initial calibration date, not construction date, could have been 23 December 178 BC. Other experts propose 204 BC as a more likely calibration date. Machines with similar complexity did not appear again until the 14th century in western Europe.

== History ==

=== Discovery ===

Captain Dimitrios Kontos (Δημήτριος Κοντός) and a crew of sponge divers from Symi island discovered the Antikythera wreck in early 1900, and recovered artefacts during the first expedition with the Hellenic Royal Navy, in 1900–1901. This wreck of a Roman cargo ship was found at a depth of 45 metres (148 ft) off Point Glyphadia on the Greek island of Antikythera. The team retrieved numerous large objects, including bronze and marble statues, pottery, unique glassware, jewellery, coins, and the mechanism. The mechanism was retrieved from the wreckage in 1901, probably July. It is unknown how the mechanism came to be on the cargo ship.
All of the items retrieved from the wreckage were transferred to the National Museum of Archaeology in Athens for storage and analysis. The mechanism appeared to be a lump of corroded bronze and wood. The bronze had turned into atacamite which cracked and shrank when it was brought up from the shipwreck, changing the dimensions of the pieces. It went unnoticed for two years, while museum staff worked on piecing together more obvious treasures, such as the statues. Upon removal from seawater, the mechanism was not treated, resulting in deformational changes.
On 17 May 1902, archaeologist Valerios Stais, together with his cousin, the Greek politician Spyridon Stais, found one of the pieces of rock had a gear wheel embedded in it. He initially believed that it was an astronomical clock, but most scholars considered the device to be prochronistic, too complex to have been constructed during the same period as the other pieces that had been discovered.
The German philologist Albert Rehm became interested in the device and was the first to propose that it was an astronomical calculator.
Investigations into the object lapsed until British science historian and Yale University professor Derek J. de Solla Price became interested in 1951. In 1971, Price and Greek nuclear physicist Charalampos Karakalos made X-ray and gamma-ray images of the 82 fragments. Price published a paper on their findings in 1974.
Two other searches for items at the Antikythera wreck site in 2012 and 2015 yielded art objects and a second ship which may, or may not, be connected with the treasure ship on which the mechanism was found. Also found was a bronze disc, embellished with the image of a bull. The disc has four "ears" which have holes in them, and it was thought it may have been part of the Antikythera mechanism, as a "cog wheel". There appears to be little evidence that it was part of the mechanism; it is more likely the disc was a bronze decoration on a piece of furniture.