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    Re: timepiece history - when did second accuracy become feasible
    From: Michael Daly
    Date: 2007 Oct 28, 13:03 -0400

    I can recommend two books as sources of information on this.  One is
    Daniel Boorstin's "The Discoverers" (ISBN 0-394-40229-4), a highly
    readable history of discovery, including that of time.  The first
    several chapters cover the development of the concepts of time.
    
    The second is David Landes' "Revolution in Time" (ISBN 0-674-76800-0),
    an excellent history of clocks and watches.
    
    coralline algae wrote:
    > The concept of a second of time, a minute of time as
    > fractions of an hour and of a day.  I wonder what civilization
    > had the thought to breakdown the hour and what reasonable
    > technology was available.   My quess is the water clock with
    > the drip set to 60 per minute but this is pure speculation.
    > I also have to wonder what drove the person who decided
    > that subdividing the hour was necessary.   Perhaps even
    > the concept of a second was quite the leap.
    
    The division of hours into 60 minutes and minutes into 60 seconds came
    from the Babylonians, who used a sexagesimal number system.  Ptolemy
    used this and probably did a lot to influence everyone in the west since.
    
    > Since the length of the day changes throughout the year, some
    > technology perhaps sundials, or again water clocks made the
    > observer aware that measuring an hour with some measure
    > of accuracy was desirable.  I know that on ships a sandglass
    > was used to to time watches.
    
    Hours come from the Romans - they tended toward a duodecimal system and
    used 12 hours to divide the day.  These were unequal in length.
    Eventually, 12 were applied to night as well and they became equal in
    length. (base 12 was common in the Mediterranean way back when.  You can
    easily count by 12s with one hand using 4 fingers with three segments
    each, using the thumb as a cursor.)
    
    > Although Harrison was among the first to make a timepiece
    > of sufficient accuracy for use at sea,  I wonder how much
    > earlier land based timepieces were up to the task.
    
    Mechanical clocks can be reliably dated back to 1325 or so.  These
    weren't tremendously accurate compared to Harrison's, but they kept
    reasonable time for the needs of many.  A lot of interest in timekeeping
    was in monasteries, so that prayers would be said on time.
    
    Seriously accurate land clocks required such folk as Galileo to come
    along and identify the regularity of the period of a pendulum.  Later,
    many scientists (Newton, Leibniz, de L'Hopital and a couple of the
    Bernoullis) determined how to make a pendulum swing with higher accuracy
    (the brachistochrone problem - in the process of solving this, Newton
    invented the calculus of variations).  This permitted, by the early 18th
    century, the construction of cased pendulum clocks (like grandfather
    clocks) that were more accurate than Harrison's.
    
    Universally consistent time (standard time) was a late 19th century
    development and was driven by businesses, particularly railroads, that
    wanted time in various locations to be synchronized.
    
    Mike
    
    
    
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