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    Re: Timing Lunars with a Rock
    From: Jared Sherman
    Date: 2005 Jul 18, 12:25 -0400

    George-
     
      I did not quote a length of 16 inches, the "vaguely" refers to the fact
    that I only had a vague memory of the length and that perhaps it was--or
    wasn't-16 inches. To a Colonial reader, that expression and meaning would
    have been clear. Please bear in mind that I post in colloquial Colonial,
    which we derive from The King's English, and that sometimes will need
    translation for those of you who speak The Queen's English.
     The fact that "precisely" and "vaguely" are contradictions in terms, should
    have tipped you off to the fact that two different subjects were being
    referred two. One, a precise string length. The other, a vague memory.
    
     If I am lost and can find a native to play string games, I'll skip the
    sextant and string and just ask the fellow "McDonalds? CocaCola?" and I'm
    sure he'll figure out how to take to me what sadly passes for franchised
    civilization today.
    
    
    ----- Original Message -----
    From: "george huxtable" 
    To: 
    Sent: Monday, July 18, 2005 2:58 AM
    Subject: Re: Timing Lunars with a Rock
    
    
    > At 02:37 18/07/2005, Jared wrote:
    >
    > >Frank, iirc  if the length
    of
    > >the pendulum is some precise length (vaguely16 inches?) the period *will*
    be
    > >one second. So if you can find out the correct pendulum length and carry
    > >that bit of strong with your sextant......
    > >
    > >Obtaining a willing "native" may be a bit harder these days.
    >
    > Much confusion here. The author quoted by Frank got it right when he said
    > that a pendulum that "beats" seconds was 39 inches long. (it varies
    > slightly with position on the Earth, because gravity varies, but not
    enough
    > to make a significant difference for that purpose). Beating seconds means
    > that it takes a second to swing left-to-right, then another second to
    swing
    > right-to-left; a total period, for a complete oscillation, of 2 seconds.
    > That provides a useful rate that's relatively easy to count.
    >
    > Instead, Jared has referred to a PERIOD of one second, which is quite a
    > different matter. Half a second each way: much more frantic, and
    > oscillations will die out much quicker.
    >
    > And then he has quoted a "precise length" as "vaguely 16 inches" for that
    > pendulum. Far from it.
    >
    > It's very simple. The period is proportional to the square root of the
    > length. So halve the period, quarter the length. So the length of the
    > faster pendulum that Jared refers to is NOT "vaguely 16 inches", it's a
    > quarter of the 39-inch length feferred to in Frank's quotation, or just
    > less than 10 inches.
    >
    > If it had been Jared who found himself without a watch by an African lake,
    > he would have made rather a mess of the observation.
    >
    > 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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