What is the story behind the recently discovered gear fragment of Olbia?

Question

Until yesterday i thought that nothing direct is known about the "Archimedes's planetarium" - an elaborate ancient planetarium based on complex gear mechanism that could represent the geocentric motions of the seven classical planets (the sun, the moon and the first 5 planets in the solar system). I thought the only information known about this instrument was that Archimedes wrote a (now-lost) manuscript, entitled "on spheres-making", on the construction of such mechanisms, and the possibility of it related to the "Antikythera Planetarium" (discovered in 1902).

But yesterday i read the abstract of a recently published book "THE RECOVERED ARCHIMEDES PLANETARIUM" by the author GIOVANNI PASTORE, according to which an 2006 archeological excavation found a fragment of gear that might be a part, or relate to the planetarium of Archimedes. The book's abstract makes several claims that seem to me very interesting:

• That in some aspects Archimedes's planetarium was even more advanced than the Antikythera Planetarium sinced it incorporated a special teeth's profile based on mathematical principles rediscovered only in the 17th and 18th century (in a youtube video the speaker mentions the teeth profile was based on the cycloid curve).
• That Archimedes's device was actually a three dimensional planetrium while the Antikythera Planetarium was an analog computer with two dimensional display.
• That a certain Roman general (i don't remember the name) deliberately attacked the Mecadonians in a dark night of lunar eclipse (in order to use the element of surprise). It suggests a conjecture that the Roman general knew earlier that there is going to be a lunar eclipse beacuse he saw the date calculated by Archimedes's device.

So, i'd like to know if anyone can tell something about the "gear of Olbia". Did someone here read this book? is it worth buying?

Answer 1

Let me cite an authority on Antikythera mechanism (Alexander Jones, "Portable cosmos"):

"A fragment of a gear, found in 2006 at Olbia, Sardinia, and accompanied by no related mechanical remains but in an archeological context reportedly dating to about 200 BC, has been claimed as part of the original planetarium of Archimedes; see Pastore 2006 and Pastore 2013. Its material is brass, and its teeth have rounded, roughly cycloidal shape. Contamination of the archeological context by an artifact of much more modern date is the most probable explanation of the fragment.

It seems that Giovanni Pastore makes too many far-reaching conclusions from a single piece of a wheel of doubtful origin.

By the way, Babylonian and Greek astronomers could predict lunar eclipses. And they needed no mechanisms for this. Clockwork toys demonstrating various astronomical phenomena were popular in 18 century, and their purpose was not science but entertaining rich sponsors. I suppose that the purpose of Antikythera mechanism and Archimedes planetarium was similar. Still it is highly interesting to know what kind of planet theory may have been used in Archimedes planetarium. Archimedes lived before Hipparchus, and we know from Ptolemy that Hipparchus had no planet theory.

Answer 2

There are 3 main reasons why the Olbia gear is considered as genuine:

1. The excavation was an official one led by a professional team, during which many other ancient objects were found at underground layers (stratums) in correspondence to their age. Moreover, the fragment itself was found in a layer from the second century B.C, lay down under a top stratum which was already ancient. Thus, it is very difficult to see how can the Olbia wheel be considered as a modern contamination

2. The Brass metal from which the wheel is made was highly oxidized, pointing out a heavy clue to the age of the wheel (at least for it to be no a modern one)

3. Finally, an almost definite proof for the Olbia gear wheel age can be obtained from a very interesting feature regarding the total teeth number for the complete wheel to be 55. There is no question that the wheel was a part of a complex portable mechanism, relatively small (the wheel dimensions also hint to this direction). The ultimate majority (if not all) of such mechanisms in modern time should be simply clocks (even astronomical clocks, which have of course a time keeping machine), but clocks have no gear wheels containing 55 teeth! This is because clocks are based on the division of the numbers 24 and 60 for their gear kinematic chain, and a gear wheel which has 55 teeth leads to irrational ratio values which are fit to an astronomical cycles gained by a manually operated planetarium. Considering that it is agreed among most of the scholars today that a Hellenistic tradition of creating such planetariums in antiquity took place, it is highly plausible to rely on for the ancient originality of the Olbia wheel.

Answer 3

The gear from Olbia has been confirmed as a legitimate find by the archaeologists who discovered it and later restored it; the same archaeologists, not Pastore, established its dating. I do not know on what basis Jones rejects the dating, but if it is only on the idea that the gear "seems too complex" for its dating, that would be the same reason to reject the Antikythera mechanism dating as a "contamination".

Regarding Pastore book, his arguments are summed up in the YouTube video (https://www.youtube.com/watch?v=hp-FXnjxNfw), I do not believe there is more than that