The mechanism was found in 1901 in the wreck of a ship that sank in the Aegean Sea around 60 BC. Though its origins are unknown, it could be used to calculate astronomical motion, making it a sort of forerunner to computers.
The sheer sophistication of the device makes it mysterious, being more advanced than any known instrument of its day – or for centuries thereafter. Even with parts missing after spending such a long time in the briny deep, it was examined to have at least 30 gears. This is perhaps why for many, it represents the pinnacle of technology of the ancient world and what was lost during the Dark Ages.
If devices such as this had survived, Kepler might have found the task of explaining the orbits of the planets far easier to achieve. Although the makers likely would not have understood why the moon slowed down and sped up in its orbit, they were sufficiently aware of the phenomenon. In fact, the mechanism mimics it precisely.
One of the mechanism's functions was to predict eclipses, and a study of these dials indicates it was operating on a calender starting from 205 BC.
Estimates of the mechanism's date of manufacture have gradually been pushed back, starting with the year in which it sank. The device was housed in a box, which has engravings dated to 80 to 90BC, but the lettering appears consistent with a date of 100 to 150BC.
However, in The Archive of History of Exact Sciences, Dr. Christian Carman of Argentina's National University of Quilmes and Dr. James Evans of the University of Puget Sound believe they have identified the solar eclipse that occurs in the 13th month of the mechanism's calender. If so, this would make its start date, when the dials are set to zero, May 205BC.
Carman and Evans add, “We also examine some possibilities for the theory that underlies the eclipse times on the Saros dial and find that a Babylonian-style arithmetical scheme employing an equation of center and daily velocities would match the inscribed times of day quite well. Indeed, an arithmetic scheme for the eclipse times matches the evidence somewhat better than does a trigonometric model.”
While the device might theoretically have been built with a starting date set many years before its construction, doing so would have reduced its usefulness. Precise as the mechanism is, errors naturally accumulate, reducing its accuracy and suggesting its makers would not have wanted to start it too far in the past.
Speculation about the origins of the Mechanism has often focused on Archimedes, if not as the inventor then at least as the inspiration for its creation. However, the Babylonia influence makes this unlikely, despite the starting date being just seven years after his murder.
To gain some idea of the Antikythera mechansim's complexity, consider this Lego recreation.