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    Re: Timing Lunars with a Rock
    From: Alexandre Eremenko
    Date: 2005 Jul 19, 12:14 -0500

    I repeat that using a pendulum of fixed length
    is not a good standard of time.
    Because the period depends on the amplitude.
    This was already well-known in XVIII century.
    Thus the US proposal (as explained in the following message)
    was not
    scientifically sound.
    
    Alex.
    
    On Tue, 19 Jul 2005, Gary J. LaPook wrote:
    
    > At one time, about 1790,  many, including Thomas Jefferson, wanted to
    > the use the length of  a  one second pendulum as the standard meter, or
    > standard unit of length, instead of the one proposed by the French
    > Academy of one ten millionth of the meridian from the equator to the
    > pole. The discussion broke down because the americans wanted to use a
    > pendulum at 38? north (near the Monticello) and the french wanted to use
    > one at 45? near Paris. The length of such a pendulum is 39.2 inches. The
    > french eventually surveyed the meridian form Dunqerque to Barcelona and
    > extrapolated it to the pole and defined the meter from it. An
    > interesting book about the travails in accomplishing this survey, which
    > took seven years and was conducted during the french revolution, is "The
    > Measure Of All Things" by Ken Adler, $4.95 at Barnes and Noble. They
    > came close. There are actually 10,002,290 meters in the arc.
    >
    > Gary LaPook
    >
    > george huxtable wrote:
    >
    > > Come on, Bruce, your memory is as bad as Jared's, when you write-
    > >
    > >> The old navigation manuals suggested checking the log line and half
    > >> minute
    > >> glass occasionally. One way to check the glass was by pendulum. As I
    > >> recall, the length of the pendulum, to the center of the musket ball
    > >> that
    > >> formed the weight, was sometimes given as 29 and 1/4 inches, and
    > >> sometimes
    > >> as 29 and 1/8. Count a second each time the pendulum passed the
    > >> bottom. I
    > >> suppose you had to give the pendulum a few moments to settle the
    > >> length of
    > >> its swing.
    > >>
    > >> Bruce
    > >
    > >
    > > It's not 29 and-a-bit, but 39 and-a-bit inches, which I have just
    > > confirmed
    > > by working it out from the expression for a period of 2 seconds as 2 x
    > > pi x
    > > sguare-root-of( length / gravity acceleration ). And to be doubly sure,
    > > I've just checked it against the pendulum of my old grandfather clock in
    > > the hall. 39 and-a-bit it is.
    > >
    > > What a mess listmembers would make of estimating time at an African lake,
    > > if that's the best they can do between them!
    > >
    > > George.
    > > ===============================================================
    > > Contact George at george@huxtable.u-net.com ,or by phone +44 1865 820222,
    > > or from within UK 01865 820222.
    > > Or by post- George Huxtable, 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13
    > > 5HX, UK.
    > >
    > >
    >
    
    
    

       
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