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Commenting on Coralline Algae's statement-

|" In thinking about Galileo's experiments with pendulums and the
length of the| string, he must have had some standard to decide what
the length of the| string ought to be for accuracy to a second.  Going
to look into this| further as this seems to have set a new standard
for clockmaking in general."

Bill Wells wrote-

"I found it interesting that the period of a pendulum of length one
meter is almost exactly two seconds."

================

Yes, very nearly, it is. But accidentally so. It nearly wasn't accidental,
however...

When the revolutionary French were casting about for a new, logical, unit of
length, which would be applicable worldwide, a favourite proposal was to
base it on the length of a one-second pendulum. However, an expedition had
established what had been suspected, that the length of a one-second
pendulum varied somewhat over the Earth's surface, because of The Earth's
ellipsoidal shape and its rotation (to name but a few factors) altered the
effective strength of gravity. So that idea was dropped, and instead the
metre was chosen, to be one ten-millionth of the distance around the Earth's
surface, between the Equator and the poles. This was based on a careful
survey, right across France, North to South. You can read about the problems
involved in making that survey, in revolutionary turmoil, in "The measure of
all things", by Ken Alder.

Then it was discovered that such a measurement, confined to France, was not
truly representative of an average value for the whole Earth, but by then it
was too late. The metre had been adopted, based upon it. They did their
best.

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.


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