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Antikythera_mechanism
From: George Huxtable
Date: 2006 Jun 13, 17:54 +0100
From: George Huxtable
Date: 2006 Jun 13, 17:54 +0100
Dan Allen wrote about this- "Interesting article about a 2000 year old astronomical computer found in Greece... http://en.wikipedia.org/wiki/Antikythera_mechanism " ================================= I can offer a bit more information about that complex geared mechanism, presumably used for predicting celestial longitudes of solar-system bodies, dating from the first century BC. It was found as part of the cargo of a shipwreck off a Greek island, 100 years ago. It's a complete wreck itself, corroded and encrusted, and broken into several parts, which cannot be dismantled; but these show sophisticated gearing, which has been examined over the years with improving X-ray techniques. The basic paper on the subject was by D J de S Price, "Gears from the Greeks", Transactions of the American Philosophical Society, vol 64, no. 7, 1974. I think that those transactions may be publicly available via the web. Since then, much study has been done by Michael Wright, who was a curator at the Science Museum, London. He has argued against many earlier misunderstandings and proposed some alternative arrangements for the many gearwheels that the device contains. He is also a very skilled mechanic and has built a plausible reconstruction, which uses getting-on-for 100 gearwheels of assorted sizes and numbers of teeth. What seems to be currently accepted is that the device was to indicate the motion of the Greek "planets", which were Moon, Mercury, Venus, Mars, Jupiter, Saturn, and Sun, as you turned a handle to show the passage of time. The motion would include the occasional "retrogressions", opposite to the normal motion against the star background, which were such a problem to astronomy. By that era, the Greeks had a picture of the universe which predicted regular retrogressions, but in fact those predictions were badly flawed, differing from the unequal loops that actually occured. It was not until Ptolemy's time, in the next century, that sophistications in the model dealt with those irregularities. The machine is taken to represent pre-Ptolemaic thinking, and to show those regular retrogressions it needed epicyclic gearing, and slotted wheels. Wright has recently published a series of three papers in "Bulletin of the Scientific Instrument Society", in no. 80, March 2004, pages 4 to 11, no. 85, June 2005, pages 2-7, and no. 87 (December 2005) pages 8 to 13., and many other papers. There's more to come. There's a website, with photos of his reconstruction, at the following website address (which you will have to stitch together over the line-break)- http://www3.imperial.ac.uk/portal/page?_pageid=73,7692654&_dad=portallive&_schema=PORTALLIVE#MrMichaelWright That will in turn provide a link, marked "Understanding the antikythera mechanism" to the text (but without illustrations) of a recent lecture on the topic. There seems also to be a separate official website on the mechanism at- www.antikythera-mechanism.gr which seems not to mention Wright or his work at all. That makes me wonder whether two schools of thought exist, and some tensions between them. My picture of Michael Wright, from last month, is at a gathering of instrument specialists. Surrounded by gurus nibbling tea and biscuits, he was cheerfully disassembling his reconstructed mechanism, which was balanced on a chair, using nothing but long-nosed pliers. There must have been nearly 100 gearwheels when it was all apart. None of us was prepared to wait to watch him put it all together again, which seemed likely to take a long time. George contact George Huxtable at george@huxtable.u-net.com or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.