by John Gleave

from GrandIllusions Website
 

In the year 1900 the bronze remains of a mechanical device were retrieved from a shipwreck off Antikythera, near Crete.

It was not clear initially what the device was, except that it was clearly a sophisticated mechanism. X-ray analysis was subsequently used to probe the inner structure of the device, the details of the gears. Finally in 1974, a full analysis was published by Professor D. De Solla Price. While some of the original gearing was missing, there was enough to work out that the device was intended to show the motion of the Moon, Sun, and most likely the Planets through the years, when the handle was turned. A few years ago, John Gleave, an orrery maker based in the United Kingdom, decided to construct a working replica of the original mechanism.

A full scale reconstruction of the Antikythera mechanism
Height 12.25 inches

The front dial - showing the annual progress of the sun & moon through the zodiac, against the Egyptian calendar, rendered in Greek on the outer annulus

The back dials
 

The upper back dial displays a four year period and has five concentric inscribed rings, most probably each with 47 divisions giving the Metonic Cycle of 235 synodic months, which equals 19 solar years. The lower back dial gives the cycle of a single synodic month, and the subsidiary dial the Lunar year of 12 synodic months.

The original gearing was cut from bronze, and the 60 degree triangular teeth were finished using a file. In the reconstruction, the gearing is made from brass, set between perspex plates, with perspex dials in place of the original bronze, so that the mechanism is visible.

The instrument indicates that the technology of the time, of which this is the only surviving example, was by any measure sophisticated.