DG
Subject: An Ancient Computer Surprises Scientists
DG
From: "David G. Nagel"
DG
Date: Wed, 29 Nov 2006 17:48:42 -0600
DG
DG This device called the Antikythera Mechanism has been the subject of an
DG hour long program on the Discovery Channel. It's composition and
DG function are a complete mystery.

It is not a complete mystery, but it has many mysteries left to
unravel. This device was described in several articlws over the past
couple decades. I first learned of it by an article in SciAmm a long
time ago.
From the mechnical point of view, what ever the stronomy in it is,
this machine is one hell of a marvel. Gearing really didn't mature
until the industrial revolution. Before then we used vogs, discs or
wheels with pegs or grooves around the edge. A true gear has specialy
shaped teeth, the 'involute', to reduce slidng friction between meshed
gears.
Apart from the theorietical develop of gears, there is the
practical matter of actually making them. I have no idea have this was
done in Greek times, there being so far only this Antikythera example.
I hazard, if the discs are thn enough, the teeth could have been
dinked out one by one on a jig that indexed by a set angle to the
next point on the circumference. Then each tooth was filed smooth to
final shape.
From pictures of the device published from time to time, the
tolerances inside the cage would have been very tight. Specially if it
was made for astronomy simulation, where the machine was good enough
to predict eclipses.

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