View Full Version : The Antikythera Mechanism

30th Nov 2006, 06:28
Jeez. We think we´re so smart these days. Just think of whoever knew enough over 2000 years ago to design and build something like this using just pen and ink and the tools of the time... :ooh:

The Times: Ancient Greek calculator yields its secret (http://www.timesonline.co.uk/newspaper/0,,173-2478493,00.html)

More than 2,000 years after an astronomical calculator was lost at sea, scientists have pieced together its intricate workings. The Antikythera Mechanism (http://en.wikipedia.org/wiki/Antikythera_mechanism) of Ancient Greece has puzzled academics for more than a century after it was rescued from the bed of the Mediterranean, where it had lain since about 70BC amid the remains of a shipwreck.

New analysis of the 82 fragments of the bronze mechanism reveal that it was more sophisticated and ancient than suspected. Researchers have established that it was able to predict eclipses and track the paths of the Sun and the Moon through the zodiac, and probably even showed ancient astronomers the movements of the five known planets. The mechanism, which is formed mainly of gears and pointers, was so precise that it was even able to take into account the moon’s elliptic motion, first identified by Hipparchos in the 2nd century BC.

Surface imaging and high- resolution X-ray tomography were used to determine the original shapes of the remains and to identify inscriptions. Once the researchers knew the measurements and shapes of the surviving pieces, they were able to work out how they all fitted together, a process complicated by some important parts being missing.

Mike Edmunds, of Cardiff University, said: “This device is just extraordinary, the only thing of its kind. The design is beautiful, the astronomy is exactly right. The way the mechanics are designed just makes your jaw drop. Whoever has done this has done it extremely well. It does raise the question: what else were they making at the time? In terms of historic and scarcity value, I have to regard this mechanism as being more valuable than the Mona Lisa.”

The virtual reconstruction, reported in the journal Nature, shows that the device had 37 gear wheels, seven of which had to be hypothesised. Until now the best estimate of the number of gears involved in the calculator was 31, a figure proposed by Professor Derek De Solla Price, a British scientist who spent much of his career from the 1950s to the 1970s trying to understand the machinery. He identified 29 gears and hypothesised two more.

François Charette, an academic in Munich, said of the new interpretation of the mechanism: “The new model is highly seductive and convincing in all of its details. It ought to force us, definitively, to abandon Price’s reconstruction, which is still frequently reproduced in general and scholarly books.”

The British-Greek research team was able to double the number of deciphered inscriptions, which gave them new clues to the purpose of the Antikythera Mechanism. Among the inscriptions were references to planetary movements which convinced the researchers that, as well as understanding the movements of the Sun and the Moon, the Ancient Greeks were able to predict the positions of the five known planets in relation to the stars.

The remains of the corroded device were discovered inside a broken bronze and wooden case in 1901 by sponge divers exploring a shipwreck off the island of Antikythera, between Crete and the Peloponnese. It was 42m (138ft) below the surface. The ship was Roman but the cargo was Greek. Because the ship is thought to have sailed from Rhodes, where Hipparchos was living, the researchers suggest that he may have had a role in constructing the device.

The findings of the study will be announced today at a conference in Athens, where the remains of the device are stored.

tony draper
30th Nov 2006, 07:19
Hmmm, one recals reading of that device many years ago in the seventies when that Eric Von Deiniken held sway over the public interest with his books,always had some doubts about it meself,yer Greeks weren't slow about writing about their accomplishments,one would have thought the cutting of precise gears and a piece of miraculous kit like that would have got a mention somewhere,or there would be more examples.

30th Nov 2006, 08:15
You might be right, Tony, but think how hard it is to find out about machines even a few hundred years old... made well into the age of widespread literacy and relatively short on the decay and deterioration scale.

Where have they gone?

Like old palaces that are dismantled stone by stone to line garden paths, old machines and artistic castings are recycled for the metal.

A sandy bottom may be one of the better places for storing treasures... beneath the sea or under a dune somewhere.

Tricky Woo
30th Nov 2006, 08:55
The Greeks had an epicyclic theory of planetary and lunar motion since the 3rd centry BC which produced reasonably accurate predictions of celestial motion. As the centuries passed more and more epicycles were added to the overall model to take into account this or that new measurement. It peaked at just over 80 during the early Middle Ages.

What's an epicycle? It's a motion two interlocked cogs make when rotating.

Ahh, so this is the mechanical version of the epicyclic model of celestial motion. Makes sense, and I'd have been amazed if someone didn't give it a go: the maths is the hard part, and they had that in the bag. In fact the Greeks were the first to have a few made, then the Romans made a few, and lastly the Arabs. But as I said above, as time passed more and more mathematical cogs were being added, so the Greeks only had to include about 15 cogs. The Romans probably about 25, the Arabs a few more. But the more precise measurements of the early renaissance would have meant a mechanical epicycle builder would need a whopping number of cogs. Sod that, let's simplify.

Copernicus - Galileo - Newton... and the now complex epicyclic theory was replaced with the far simpler and elegant elliptical theory of planetary motion.

But one suspects the whole bloody epicycle theory was a wee misunderstanding from the very beginning...

Epicycles were invented by yet another unprecidented Greek genius, Apollonius. This was the bloke that discovered parabolas and ellipses while investigating the pretty shapes that could be made from cutting through a cone at various angles. It'll never be proven, but it's suspected that Apollonius came up with epicycles as a practical method of approximating parabolic and elliptical motion. According to the measurements of the day, just a few epicycles could be used, say about 12, to give great practical results. Why is this suspected? 'Cos Apollonious was way too comfortable with ellipses (and parabolas) to see that epicyclic motion's just a crap approximation of the far more elegant and perfect elliptical motion.

Apollonius: "Can't get yer head around elliptical maths 'cos it's too hard for yer? Not surprised, for I am a great genius, and yer'd have to get up bloody early to keep up with me. And non-circular motion's a heresy according to the prevailing religion around here? Well, here's a nice little epicyclic compromise based on lots of easy-peasy (and religiously legal) circles that'll do you lot for 1,600 years until yer ready to see what I realised in 200 BC: that it's all about elliptical motion".

But the tail wagged the dog, epicycles became the maths, rather than a tool for approximation, and later chaps such as Ptolemy found practical mathematical short cuts to add more and more circles to knock off the edges.

Nope, Herr D, the Antokythera device was well within the capabilities of the ancients.


Loose rivets
30th Nov 2006, 11:07
Darn. And there's me thinking some abandoned space-traveler had knocked it up to help him get home.

30th Nov 2006, 16:20
so the Greeks only had to include about 15 cogs. The Romans probably about 25

The reconstruction apparently had 37 cogs so was presumably rather more complex than the average view (and differential gearing, thought not to have been invented until the 16th century). Looks like the Ancient Greeks were cleverer than normally allowed for. Hipparcus of Rhodes is mentioned as a possible consultant (since he developed the differential thory of orbitting bodies and was alive in the same period as the device was made).

(Also the article I read did suggest that there may have been others but they got melted down for their metal which is why no others were found - the only reason this one survived was because it was buried at the bottom of the sea. Query - would a mechanical device like this eventually stop 'working' in that orbital perturbations would mean it no longer predicted events correctly, or could it be reset after a few (hundred?) years? Just if it didn't work, might as well melt it down.).