Planetarium of Archimedes?

A fragment from a complex mechanism was discovered by chance near Olbia, Sardinia, and it soon became clear that the dented gear wheel showed similarities with the mechanism of Anticythera. This fragment, however, was made of a brass alloy unknown otherwise at the time. 

[Kircher's reconstruction of the sphere of Archimedes]

Thanks to the detailed writings of Cicero in the 1^st century BC, we know that Archimedes constructed a Planetarium (Orrery). The celestial globe is mentioned by Ovid in the 1^st century BC and by Claudian, a 4^th-century Latin poet associated with the court of Emperor Honorius in Mediolanum (Milan). 

When, in 212 BC, the Romans sacked Syracuse, Consul Marcus Claudius Marcellus brought to Rome a device that was built by the famous mathematician. It represented the motion of the Sun, Moon, and the planets reproduced on a sphere. In short, a modern Planetarium. 

It was Gaius Sulpicius Gallus, who reported the story as he had seen the object personally and knew how to operate it. Cicero was amazed that Archimedes had been able to generate the motion of the individual planets starting from a single rotation. The Planetarium was placed inside a glass sphere. This corresponds to what Archimedes wrote in a now-lost treatise On Sphere-Making detailing the construction of the Planetarium. 

Livy, who died in 17 AD, wrote that before the Battle of Pydna in 168 BC, Gallus, an astronomer himself, used the Planetarium to predict a lunar eclipse on the night before the battle. The news was shared with his Roman legionnaires to prevent them from panicking, but the Macedonians freaked out. 

A first reconstruction based on the section of the gear wheel found near Olbia revealed that it counted 55 dents in total. Noteworthy is the shape of the dents, which is not triangular as in the case of the Anticythera mechanism but slightly curved as used in our modern gear wheels. This shape proves to be more efficient and allows a higher precision. In antiquity, these wheels were created manually and the craftsmen had to do without the use of our modern measuring and cutting tools, which emerged only a few centuries ago. 

Marcus Claudius Marcellus, owner of the Planetarium, was sent off to Spain to fight the Iberic Celts in 152 BC. It is reasonable to assume that Marcellus took the Planetarium with him – a sign of his status – and that his ship was wrecked in the region of Olbia, crashing the Planetarium. 

The Planetarium has been dated between the end of the 3^rd century BC and the mid-2^nd century BC. It thus predates the Anticythera mechanism from the 1^st century BC generally ascribed to Archimedes. However, the analog computer may well have been reproduced based on Archimedes’ description.

It must have been one of the marvels from Hellenistic times, many of which still remain to be discovered!

[the section found near Olbia is thoroughly discussed in this YouTube]