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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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