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    Re: timepiece history - when did second accuracy become feasible
    From: Lu Abel
    Date: 2007 Oct 28, 11:56 -0700

    Greg R. wrote:
    > But as I understand the concept, dividing the day up into hours was
    > considered to be "accurate enough" for civilization a couple hundred
    > years ago (i.e. "We're expecting Caroline to arrive on the hour"). Then
    > when it became necessary to divide time into finer increments, the term
    > "minute" was coined (as in "extremely small"), and when a further
    > division became necessary it was called the "second minute" (later
    > shortened to just "second" as we know it today).
    I would differentiate between the concept of dividing hours into minutes
    and seconds, and the ability to accurately measure them.
    Wikipedia has a great article on the history of time at the entry for
    "second"   It was the Egyptians, as far back as 2000 BC, who divided the
    day into 24 hours.  Around 1200 medieval astronomers started subdividing
    the hour into minutes and seconds (and even thirds, 1/60 of a second),
    using the sexagesimal (1/60) way of splitting things invented by the
    Babylonians.  Although the article doesn't explicitly say so, I'd guess
    these were likely Arab astronomers (since Europe was still wallowing in
    the Dark Ages), hence the Babylonian influence.
    Accurate measurement of seconds became possible with pendulum clocks in
    the late 1600s.  A quite common pendulum length is one that takes a
    second for its swing in each direction.
    While scientists have always striven to measure time more and more
    accurately (and today we're keeping time to one part in 10^15),
    "civilian" timepieces have always lagged in accuracy.  The commonality
    of town clocks in Europe is a result of the cost of home clocks and the
    (in)accuracy of pocket watches.
    So "expecting Caroline to arrive on the hour" (actually, more likely
    "expecting Caroline to arrive at 7," where "7" meant anytime within the
    period between 7 and 8) is a product of the inability to keep accurate
    time until the age of chronometers and railroad watches.
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