Unraveling the Mystery of the Ancient Olbia Gearwheel
The restoration of the gearwheel found in Olbia (Sardinia, Italy) in 2006 by the Superintendence for Archaeological Heritage, dated between the mid-2nd century and the end of the 3rd century BC, has revealed a very important surprise: the teeth have a special curving which make them extraordinarily similar to the mathematically perfect profile used in modern gears. Moreover, the unusual composition of the alloy (brass) was completely unexpected. As it turns out, the gear is very scientifically advanced despite being constructed before all other known mechanisms to date. Considering the perfect correlation between the scientific evidence and historical, literary and archaeological studies, it does not seem rash to conclude that the fragment from Olbia was an integral part of the Archimedes Planetarium (Orrery).
The Archimedes Planetarium
The Archimedes Planetarium was one of the most admired technical achievements in antiquity. The best information on this apparatus is given by Cicero, who writes that in the year 212 BC, when Syracuse was sacked by Roman troops, the consul Marcus Claudius Marcellus brought an apparatus constructed by Archimedes to Rome that reproduced the vault of the sky on a sphere, and another that predicted the apparent motions of the Sun, Moon and planets, thus corresponding to a modern planetarium. Cicero, referring to the impressions of Gaius Sulpicius Gallus, who had been able to observe the extraordinary object in person, points out that the genius Archimedes was able to generate the motions of planets, each so different from the next, with a single rotation. Archimedes had described the construction of the Planetarium in the work On Sphere-Making . News of the work, now considered lost, was reported by Pappus of Alexandria.
A sketch proposing what Archimedes’ Planetarium looked like ( museo galileo )
Ancient knowledge of the cosmos
The discovery of the Antikythera Planetarium in 1902, a gear device that dates back to the first half of the 1st century BC also shows how the ancient people developed mechanisms designed to represent the motion of the stars, which in turn has rekindled interest of the Archimedes Planetarium.
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The Antikythera mechanism / planetarium discovered in 1902 ( public domain )
With the discovery in 2006 in Olbia of the fragment of an ancient gear, scientifically and technically more advanced than the gear of Antikythera, and after deep, careful and thorough studies considered part of a planetarium designed by Archimedes, it has shed a new and unexpected light on the magnitude of scientific thought of the genius of Syracuse. The scientific and mathematical studies of the find have shown that many inventions that we consider modern had in fact already been developed and designed by Archimedes over two thousand years before.
The importance of the find, also, is in the fact that to date only a few written works by Archimedes have ever been retrieved (Codices A, B and C) through transcriptions and translations in Greek, Arabic and Latin. Codex C is the oldest Archimedes Codex, the only one still written in Greek on a parchment paper with laid lines in 975, and which became Palimpsest in Jerusalem in 1229, and it is still the subject of studies in the United States. Of Archimedes’ machines, however, it was thought nothing had survived. The find, although small, is not a simple piece of crockery, but instead a great testimony and thus a new, unique and unexpected contribution to the scientific knowledge of the great Archimedes.
The Archimedes Palimpsest revealed works by Archimedes thought to have been lost ( public domain )
The knowledge of epicyclic motion, also known as planetary motion, necessary for the design of the planetary gear in the Planetarium of Antikythera and in the tooth profile of the gear of Archimedes, allows us to assume that some ancient Greek scientists knew the planetary motion of celestial bodies and had achieved the same results later attributed to modern scientists 2000 years later. I assume that the planetary gear could have been used, given the particular kinematic similarity, as a mathematical model for the calculation of planetary motion in the heavens.
The discovery of the Olbia gear
In July 2006, during an emergency excavation in the municipal market square in the city of Olbia, a fragment of a toothed wheel of 43 mm (1.6929 inches) was found. The Superintendence for the Archaeological Heritage of Sardinia, who directed the excavation, gave due importance to a seemingly insignificant and oxidized metal fragment. The find appeared similar to the gears of the Antikythera Mechanism, discovered in Greece, conserved in the National Archaeological Museum of Athens, and much talked about in that period because further modern tomographic analysis was being carried out in Athens. The correct dating of the find of Olbia in the archaeological record of the layer, sealed by the already ancient upper one, was determined by the Superintendence for Archaeological Heritage. The find, and the whole layer of the excavation, was dated from the late 3rd to half of the 2nd century BC, for the presence of other easily datable finds, all pertaining to the same period.