Antikythera Mechanism

Antikythera Mechanism

The first-known computer in the world, designed and constructed in 205 BC.

The Antikythera very complex clockwork mechanism is an ancient analog computer used to calculate and predict astronomical positions of the five known planets and our Sun, as well as solar and lunar eclipses for calendrical and astrological purposes. It was also used to calculate as well as the Olympiads, the cycles of the ancient Olympic Games. Supposedly, it was also used for astrological purposes, as it contains zodiac inscriptions.

This incredible device is composed of at least thirty meshing bronze gears, but we cannot be sure about the exact number of gears as the remains of the artifact were found in 1901, in a wooden box, as one lump, later separated in three main fragments. Each of the fragments was later divided into small pieces and now, after the completion of the conservation works, the scientists have 82 small parts to continue their research. Four of the fragments contain gears, and many other fragments contain inscriptions, most of them being guidelines for the use of this first-known analog computer.

The Antikythera mechanism is believed to have been designed and manufactured by Greeks somewhere between 150 and 100 BC. According to a new study, its origins are even more distant, and it comes from 205 BC. Its construction relied upon theories of astronomy and mathematics developed by Greek astronomers. In 2016, findings of the Antikythera Mechanism Research Project suggest the concept for the mechanism originated in the colonies of Corinth. However, another theory suggests that its origin may have been from the ancient Greek city of Pergamon, home of the Library of Pergamum.

Antikithera Machine. Photo in public domain

After the Ancient World was gone forever, the knowledge of this incredible technology was lost. In fact, technological artifacts approaching complexity and workmanship of the Antikythera mechanism did not appear again for about two thousand years!

Today all known fragments of the Antikythera mechanism are kept at the National Archaeological Museum, Athens.

On the front face of the mechanism there is a fixed ring dial representing the ecliptic, the twelve zodiacal signs marked off with 30 degree sectors. Outside of that dial is another ring which is rotatable, marked off with the months and days of the Sothic Egyptian calendar, twelve months of 30 days plus five intercalary days. The months are marked with the Egyptian names for the months transcribed into the Greek alphabet.

This analog computer was operated by turning a small hand crank which was linked via a crown gear to the four-spoked gear. This moved the date pointer on the front dial, which would be set to the correct Egyptian calendar day. The year is not selectable, and the user must know the year currently set, or by looking up the cycles indicated by the various calendar cycle indicators on the back in the Babylonian ephemeris tables for the day of the year currently set. The crank moves the date pointer about 78 days per full rotation, so hitting a particular day on the dial would be easily possible if the mechanism were in good working condition. The action of turning the hand crank would also cause all interlocked gears within the mechanism to rotate, resulting in the simultaneous calculation of the position of the Sun and Moon, the moon phase, eclipse, and calendar cycles, and perhaps the locations of planets.

The pointer had a “follower” that tracked the spiral incisions in the metal as the dials incorporated four and five full rotations of the pointers.

The zodiac dial is no less complex and it has a few more functions, such as marking of the locations of longitudes on the ecliptic for specific stars and more.

At least two pointers indicated positions of bodies upon the ecliptic. A lunar pointer indicated the position of the moon, and a mean sun pointer also was shown, perhaps doubling as the current date pointer.

On the back of the mechanism, there are five dials: the two large displays, the Metonic and the Saros, and three smaller indicators, the Olympiad, the Callippic, and the Exeligmos.

The Antikythera mecanism also tracked the precission of the elliptical orbit around the ecliptic in a 8.88 year cycle. It also calculated the timing of the Ancient Olympic Games and had some other complex functions which calculated movements of the planets, for instance.

The whole device is remarkable for the level of miniaturisation and the complexity of its parts, as well as accuracy of computation.