Amazing ancient astronomical/astrological device

[Guest guest]

Ancient Moon 'computer' revisited

 

By Jonathan Fildes

Science and technology reporter, BBC News

 

 

Simulation: The front side displayed a calendar and the Greek

zodiac

 

The delicate workings at the heart of a 2,000-year-old analogue computer have

been revealed by scientists. The Antikythera Mechanism, discovered more than

100 years ago in a Roman shipwreck, was used by ancient Greeks to display

astronomical cycles.

 

 

 

Using advanced imaging techniques, an Anglo-Greek team probed the remaining

fragments of the complex geared device. The results, published in the journal

Nature, show it could have been used to predict solar and lunar eclipses. The

elaborate arrangement of bronze gears may also have displayed planetary

information. " This is as important for technology as the Acropolis is for

architecture, " said Professor John Seiradakis of the Aristotle University of

Thessaloniki in Greece, and one of the team. " It is a unique device. " However,

not all experts agree with the team's interpretation of the mechanism.

Technical complexity The remains of the device were first discovered in 1902

when archaeologist Valerios Stais noticed a heavily corroded gear wheel amongst

artefacts recovered by sponge divers from a sunken Roman cargo ship.

 

 

Enlarge Image

 

A further 81 fragments have since been found containing a total of 30 hand-cut

bronze gears. The largest fragment has 27 cogs. Researchers believe these

would have been housed in a rectangular wooden frame with two doors, covered in

instructions for its use. The complete calculator would have been driven by a

hand crank. Although its origins are uncertain, the new studies of the

inscriptions suggest it would have been constructed around 100-150 BC, long

before such devices appear in other parts of the world. Writing in Nature, the

team says that the mechanism was " technically more complex than any known device

for at least a millennium afterwards " . Although much of it is now lost,

particularly from the front, what remains has given a century's worth of

researchers a tantalising glimpse into the world of ancient Greek astronomy.

One of the most comprehensive studies was done by British science historian

Derek Solla Price, who advanced the theory that the device

was used to calculate and display celestial information. When

you see it your jaw just drops and you think, 'bloody hell that's clever'

 

 

Mike Edmunds

Cardiff University

 

This would have been important for timing agricultural and religious

festivals. Some researchers now also believe that it could have been used for

teaching or navigation. Although Solla Price's work did much to push forward

the state of knowledge about the device's functions, his interpretation of the

mechanics is now largely dismissed. A reinterpretation of the fragments by

Michael Wright of Imperial College London between 2002 and 2005, for example,

developed an entirely different assembly for the gears. The new work builds on

this legacy. Eclipse function Using bespoke non-invasive imaging systems,

such as three-dimensional X-ray microfocus computed tomography, the team was

able to take detailed pictures of the device and uncover new information. The

major structure they describe, like earlier studies, had a single, centrally

placed dial on the front plate that showed the Greek zodiac and an Egyptian

calendar on concentric scales. The

scanning showed details not seen before

 

On the back, two further dials displayed information about the timing of lunar

cycles and eclipse patterns. Previously, the idea that the mechanism could

predict eclipses had only been a hypothesis. Other aspects are less certain,

such as the exact number of cogs that would have been in the complete device.

However, what is left gives an insight into the complexity of the information

the mechanism could display. For example, the Moon sometimes moves slightly

faster in the sky than at others because of the satellite's elliptic orbit. To

overcome this, the designer of the calculator used a " pin-and-slot " mechanism to

connect two gear-wheels that introduced the necessary variations. " When you

see it your jaw just drops and you think: 'bloody hell, that's clever'. It's a

brilliant technical design, " said Professor Mike Edmunds. Planetary display

The team was also able to decipher more of the text on the mechanism, doubling

the amount of text that can now be read.

Combined with analysis of the dials, the inscriptions hint at the possibility

that the Antikythera Mechanism could have also displayed planetary motions.

A reconstruction of the rear gears reveals their complexity

 

" Inscriptions mention the word 'Venus' and the word 'stationary' which would

tend to suggest that it was looking at retrogressions of planets, " said

Professor Edmunds. " In my own view, it probably displayed Venus and Mercury,

but some people suggest it may display many other planets. " One of those

people is Michael Wright. His reconstruction of the device, with 72 gears,

suggests it may have been an orrery that displayed the motions of the five known

planets of the time. " There is a feature on the front plate that could have

made provision for a bearing with a spindle, that carried motion up to a

mechanism used to model the planets of Mars, Jupiter and Saturn as well, " he

told the BBC News website. " That's how I see it and my reconstruction shows it

works well. " Intriguingly, Mr Wright also believes the device was not a

one-off. " The designer and maker of the device knew what they wanted to

achieve and they did it expertly; they made no mistakes, " he said.

" To do this, it can't have been very far from their every day stock work. "

The Antikythera Mechanism will be explored in an episode of Unearthing Mysteries

on BBC Radio 4 on 12 December

http://news.bbc.co.uk/2/hi/science/nature/6191462.stm

 

 

 

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