Found housed in a 340 millimetres (13 in) × 180 millimetres (7.1 in) × 90 millimetres (3.5 in) wooden box, the device is a complex clockwork mechanism composed of at least 30 meshing bronze gears. Using modern computer x-ray tomography and high resolution surface scanning, a team led by Mike Edmunds and Tony Freeth at Cardiff University peered inside fragments of the crust-encased mechanism and read the faintest inscriptions that once covered the outer casing of the machine. Detailed imaging of the mechanism suggests it dates back to 150-100 BC and had 37 gear wheels enabling it to follow the movements of the moon and the sun through the zodiac, predict eclipses and even recreate the irregular orbit of the moon. The motion, known as the first lunar anomaly, was developed by the astronomer Hipparchus of Rhodes in the 2nd century BC, and he may have been consulted in the machine's construction, the scientists speculate. Its remains were found as one lump later separated in three main fragments, which are now divided into 82 separate fragments after conservation works. Four of these fragments contain gears, while inscriptions are found on many others. The largest gear is approximately 140 millimetres (5.5 in) in diameter and originally had 224 teeth.
The artefact was recovered probably on or about July 22, 1901, according to the Julian calendar (which the Greeks continued to use at the time). That date was August 4, 1901, in the Gregorian calendar (used by then in most of the West, and now used worldwide). From the Antikythera shipwreck off the Greek island of Antikythera, which in antiquity was known as Aigila. Believed to have been designed and constructed by Greek scientists, the instrument has been variously dated to about 87 BC, or between 150 and 100 BC, or in 205 BC, or within a generation before the date of the shipwreck (in about 150 BC).
After the knowledge of this technology was lost at some point in antiquity, technological works approaching its complexity and workmanship did not appear again until the development of mechanical astronomical clocks in Europe in the fourteenth century.
All known fragments of the Antikythera mechanism are kept at the National Archaeological Museum in Athens, along with a number of artistic reconstructions of how the mechanism may have looked.
A schematic representation of the gearing of the Antikythera Mechanism, including the 2012 published interpretation of existing gearing, gearing added to complete known functions, and proposed gearing to accomplish additional functions, namely true sun pointer and pointers for the five then-known planets, as proposed by Freeth and Jones, 2012. Based also upon similar drawing in the Freeth 2006 Supplement and Wright 2005, Epicycles Part 2. Proposed (as opposed to known from the artefact) gearing crosshatched.
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