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From: George Huxtable (no email)
Date: Tue Jun 13 2006 - 12:54:03 EDT
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)-
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
or at +44 1865 820222 (from UK, 01865 820222)
or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
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