The Antikythera Mechanism

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The Antikythera Mechanism

Postby toucana on March 13th, 2021, 7:55 am 

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An interdisciplinary team of scientists at UCL London have recently made significant progress in deciphering the gearing of the Antikythera mechanism originally recovered from the Mediterranean seabed by a sponge diver in 1900. It is thought to date from 150-100 BC. They now hope to build a faithful working reconstruction according to a new paper published in the journal Scientific Reports.

https://arstechnica.com/science/2021/03/scientists-solve-another-piece-of-the-puzzling-antikythera-mechanism/

"Ours is the first model that conforms to all the physical evidence and matches the descriptions in the scientific inscriptions engraved on the mechanism itself," said lead author Tony Freeth, a mechanical engineer at UCL. "The Sun, Moon, and planets are displayed in an impressive tour de force of ancient Greek brilliance."

The mechanism which was once housed in a wooden box was recovered in 82 surviving fragments. The The largest piece is known as Fragment A, which has bearings, pillars, and a block. Another piece, Fragment D, has a disk, a 63-tooth gear, and plate. It was found on a Roman cargo ship,and historians believe it is Greek in origin, possibly from the island of Rhodes, which was known for impressive displays of mechanical engineering.

It took decades just to clean the device off, and in 1951, a British science historian named Derek J. de Solla Price began investigating the theoretical workings of the device. Based on X-ray and gamma ray photographs of the fragments, Price and physicist Charalampos Karakalos published a 70-page paper in 1959 in the Transactions of the American Philosophical Society. Based on those images, Price hypothesized that the mechanism had been used to calculate the motions of stars and planets—making it the first known analog computer.

n 2002, Michael Wright, then curator of mechanical engineering at the Science Museum in London, made headlines with new, more detailed X-ray images of the device taken via linear tomography—which means that only features in a particular plane come into focus, enabling closer inspection and pinning the exact location of each gear. Wright's closer analysis revealed a fixed central gear in the mechanism's main wheel, around which other moving gears could rotate. He concluded that the device was specifically designed to model "epicyclic" motion, in keeping with the ancient Greek notion that celestial bodies moved in circular patterns called epicycles.

This latest paper builds on Wright's work as part of the ongoing Antikythera Mechanism Research Project, which undertook more advanced 3D X-ray imaging with the help of X-Tek Systems in the UK and Hewlett-Packard, among others.

The device was designed well enough to fairly accurately reproduce the motion of the Sun and Moon, as well as the planets Mercury and Venus. But that leaves out Mars, Jupiter, and Saturn, which were also known in antiquity. Wright speculated that there may have been an upper layer to the mechanism, now lost, with extra gears to model the missing planets. He also hypothesized that the lower back dial might have been used to predict eclipses.

It's likely that the Antikythera mechanism once had 37 gears, of which 30 survive, and its front face had graduations showing the solar cycle and the zodiac, along with pointers to indicate the positions of the sun and moon.

Freeth and his co-authors have been working to reconstruct the cosmos display, described in the inscriptions on the mechanism's back cover, featuring planets moving on concentric rings with marker beads as indicators. X-rays of the front cover accurately represent the cycles of Venus and Saturn—462 and 442 years, respectively.

"After considerable struggle, we managed to match the evidence in Fragments A and D to a mechanism for Venus, which exactly models its 462-year planetary period relation, with the 63-tooth gear playing a crucial role," said co-author David Higgon. This enabled the team to derive the cycles of the other planets as well and to create mechanisms to calculate the astronomical cycles while minimizing the number of gears so that everything would fit into the tight space of the device.  The team also suggests there may have been a double-ended pointer to predict eclipses, which they have dubbed a "Dragon Hand."


The challenge ahead for the team is now to reconstruct a working version of the Antikythera mechanism using techniques that would have been available to Greek mechanical engineers in the second century BC.
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Re: The Antikythera Mechanism

Postby charon on March 13th, 2021, 8:38 am 

Fascinating, toucana, thank you.
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Re: The Antikythera Mechanism

Postby doogles on March 13th, 2021, 7:19 pm 

I also found it fascinating Toucana.

I'm interested in what metal was used for the parts, but unless I missed something, I couldn't find whether it was bronze or a mixture of metals.

The technology seems way ahead of its time.
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Re: The Antikythera Mechanism

Postby doogles on March 13th, 2021, 7:25 pm 

It's okay. I've just found this site -- https://www.britannica.com/topic/Antikythera-mechanism -- which states clearly that it is made of bronze.

I imagine that each piece would have to be an individual casting.
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Re: The Antikythera Mechanism

Postby toucana on March 13th, 2021, 8:31 pm 

You will find a large trove of primary data about the Antikythera mechanism in both Greek and English on this site:

http://www.antikythera-mechanism.gr/data

One of the many puzzles is quite how Greek artisans of the second century BC managed to fabricate the metallic bronze shafts and bearings used in the mechanism without the use of metal-turning lathes which didn't exist at that period.

An even more intriguing question is why this level of technical skill in manufacturing metallic gear-driven mechanisms did not extend to and survive in the form of a mechanical clock making tradition. Why did Greek horology never progress beyond the design of the clepsydra (κλεψύδρα - 'water-thief') or water clock ?

The general consensus seems to be that the mechanism was manufactured by followers of the Greek astronomer Hipparchos (c.190 - c.120 BC) who lived on the island of Rhodes.

http://www.antikythera-mechanism.gr/faq/general-questions/who-made-it

It is thought that the mechanism was lost at sea when a Roman treasure ship loaded with booty sank in c.84 BC on its way back to Rome from Pergamon.
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