Clocks and watches

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					                I NT A N ET H I

    Clocks and watches
Systems Administrator                                time, as water tends to drip
                                                     faster when the container is

         he article in the November/December         full, due to pressure, while it
         2006 CL examined how man’s need to          will drip more slowly as the
         measure time led to the development         container empties.
of the calendar, which is in common use in              During the third-cen-
our homes and offices on a daily basis. In this       tury Common Era (CE), the
article, we will continue to examine how man         Chinese further developed
developed a means to measure time in even            the clepsydra to drive various
smaller increments, which led to the develop-        mechanisms, which illustrated
ment of clocks and watches through the ages.         astronomical phenomena. Su
   Before we can begin to examine how clocks         Sung built an elaborate clock
evolved over time, we need to know what              tower, which stood over 30
basic elements a clock needs. Firstly, it requires   feet in height, with doors that
a regular, constant and repetitive action to         opened to reveal manikins
mark off equal increments of time. This was                                                           unwound, the spring-powered clock was the
                                                     which rang bells or gongs, or held tablets       precursor to more accurate timekeeping.
achieved by means of an escapement, which is         indicating the hour.
a type of transformer, which converts power                                                               Although Galileo Galilei is credited with
                                                        What is interesting to note is that water     the invention of the pendulum in 1582, it was
generated via springs, water or weights, into        clocks were still in common use in North
a constant mechanical motion. Secondly, it                                                            Christian Huygens, a Dutch scientist, who made
                                                     Africa during the early part of the twentieth    the first pendulum clock in 1656. The mecha-
needs a means of keeping track of the incre-         century.
ments of time and should be able to display                                                           nism in this clock used a ‘natural’ period of os-
the result - clock hands or some other visual        Mechanical clocks                                cillation. It is amazing to find that this clock had
display.                                                                                              an error of less than one minute per day. The
                                                     During the Middle Ages, (500-1500 CE),
   Thus the history of timekeeping can be seen                                                        following year Huygens developed the balance
                                                     there does not appear to have been many
as a search for a mechanism, which would best                                                         wheel and spring assembly, which reduced the
                                                     advances made in technology with regard to
meet these requirements.                                                                              clock’s error to less than ten seconds a day.
                                                     improving the devices used for timekeeping.
                                                                                                          Around the mid 1660s, a clock was built
                                                     It seems that the sundial, sometimes placed
Sun clock, merkhet and                               above doorways, was the favoured device in
                                                                                                      with a tall case which concealed the weights
water clock                                                                                           and pendulum. These became known as
                                                     use during this period.
                                                                                                      grandfather clocks.
As early as 3500 Before Common Era (BCE),                During the early part of the fourteenth
the Egyptians used sun clocks to divide the          century, large mechanical clocks, which were     Clocks and navigation
day into parts. The shadow cast by an obelisk,       weight-driven and used a verge-and-foliot        While pendulum clocks were becoming
which had been carefully constructed and geo-        escapement, began appearing in the tow-          more and more accurate, there was still one
graphically positioned, enabled people to di-        ers of a number of large Italian cities. The     particular hurdle to be overcome. As the
vide the day into morning and afternoon. The         mechanism used in these clocks, comprised        Explorers left the safety of the shores to ex-
addition of markers to the base of the obelisk       a freely swinging horizontal bar (the foliot)    plore uncharted seas, they needed a means of
could indicate further subdivisions of the day.      attached to a centrally-located vertical shaft   determining where they were. The Greeks had
   The merkhet, the oldest known astronomi-          (the verge). The mechanism was driven by         developed the systems of latitude and longi-
cal tool was developed around 600 BCE. This          gravity. As the weight wrapped around            tude. Measuring latitude was not a problem,
made it possible to measure the night-time           the spindle descended, the spindle turned        but measuring longitude was a different mat-
hours. Two merkhets were used to establish a         and a toothed crown-wheel on the spindle         ter. The mariner needed to know the speed
north-south meridian, by lining them up with         made the escapement oscillate. The passage       at which the ship was travelling, to be able to
the Pole star. The crossing of this meridian by      of time was measured by moving a hand            calculate the distance covered each day. Every
certain stars indicated the hour.                    around a marked clock face.                      degree of longitude corresponds to four min-
   The Greeks began using the clepsydra, or              Variations of the verge-and-foliot mecha-    utes of time. The navigator needed to know
water clock around 325 BCE. The clepsydra            nism were used for more than 300 years.          the time at the starting point, as well as the lo-
works on the simple principle of the flow of              The next technological advance came          cal time. By comparing the two times, he was
water either into, or out of, a container. The       around 1500-1510 in Germany, with the            able to calculate the current longitude relative
water would drip at a nearly constant rate           invention of the spring-powered clock.           to the initial longitude. Ships began carrying
from a small hole near the base of the con-          A spring, instead of gravity, was used to        clocks on board to help with calculation.
tainer. Markings on the side of the container        power clocks. Although these clocks were            However, these early clocks, while reason-
measured the hours. As you can imagine, this         still not particularly accurate because the      ably accurate on land, were subject to the ef-
was not a very accurate method of calculating        clock slowed down when the mainspring            fects of the ship’s movement at sea and were
                                                                 Cape Libr., Mar/Apr 2007
                                                                                                                I NT A N ET H I

thus not very accurate. In 1714, Queen Anne         duced. In 1869, Charles Dowd tabled a plan       machine-made watches. They began manufac-
of England offered 20 000 pounds to anyone          to divide the entire United States into four     turing watches in volume around 1880. During
who could find a way to determine longitude          time zones. At 12 noon on 18 November            the First World War, the army found that wrist-
to within half a degree. The prize was awarded      1883, the entire nation switched over to,        watches were more convenient to use than
in 1759 to John Harrison, a carpenter and           what had previously been referred to, as         pocket watches. When the war ended, soldiers
self-taught clock-maker, who built a marine         railroad time. The four-zone time system         were allowed to keep their wristwatches.
chronometer with a spring and balance wheel,        was legalised in 1918.                              After 1945, wristwatches were made more
which was tested on a voyage to the West               Just as coach travel and the railways had     robust, with mechanisms to make them wa-
Indies and was able to determine longitude to       led to the adoption of uniform time in           terproof, shockproof and able to function in
within one-half degree.                             Britain and the United States, the invention     extremes of pressure.
   The Library Service has the award-winning        of Marconi’s wireless telegraph in 1899, was        Battery-powered watches were marketed
drama series, Longitude, made by Granada            the main impetus for a worldwide system of       in 1952. The new technology was embraced
Film, in stock. This excellent drama tells the      measuring time. The last country to adopt        and developed by Asian watch manufacturers,
story of Harrison’s quest for the first marine       the Greenwich Meridian was Liberia, which        particularly those in Japan. This enabled the
chronometer, which is paralleled by the story       did so only in 1972.                             production of cheap, accurate watches acces-
of Rupert Gould’s obsession to restore the                                                           sible to all.
clock centuries later.                              History of watches                                  The rich and famous, on the other hand, still
                                                    As strange as it may seem, the Egyptians         covet wristwatches with designer labels, such as
The Quartz clock and the                            used a portable shadow clock as early as         Rolex, Tag Heuer, Audemars Piquet, Omega or
new era                                             1500 BCE.                                        Cartier, to name a few. Yet, cheap or expensive
Perhaps the next major development in the               Prior to the 1600s, timepieces were typi-    - they all do one thing - tell the time.
evolution of the clock is the discovery by          cally driven by weights and as a result were        To find out more about this interesting sub-
Pierre Curie in 1880 that the application of        impractical as portable timepieces.              ject, see the following web sites:
pressure to a quartz crystal caused it to vibrate       So-called pocket watches invented in
at a constant frequency. WA Marrison built          Tudor, England during the sixteenth century,     Early history of clocks
the first quartz clock in 1928. He replaced          were very large cumbersome items, often
the pendulum and other mechanical oscillat-         worn around the neck. They served more as        Jesse.CLOCK1A.html
ing devices with the vibrating quartz crystal. It   decoration than timekeepers, as they were
became possible to measure the accuracy of          not particularly accurate.                       General history of clocks
the clock up to a millionth of a second.                Although spiral springs were used from
   One would have thought that the clock had        1500, it was not until the use of the spiral-
reached its ultimate achievement in accuracy.       balance spring-driven mechanism in 1675,
This was not so. English physicists L Essen and     that portable timepieces became more ac-
                                                    curate. The minute hand was added and the
J Perry constructed an even more accurate
clock, the atomic clock, in 1955.                   dial was subdivided into minutes. Charles
                                                    II introduced long waistcoats in 1675 and it     inventions/chpt5.htm
   Today, the satellite-based Global Positioning
System (GPS), uses atomic clocks to deter-          became the fashion for men to carry their        Verge escapement
mine its position. Each satellite beams down        watch in their pocket, instead of wearing it
a signal giving its position and the mean time      around the neck.
determined by four atomic clocks it carries             During the 1700s, small technical            History of alarm clocks
on board. The signal is picked up on a device,      developments and modifications were     
which is small enough to be hand-held, which        made. Perhaps the greatest development           html
then computes its latitude and longitude. The       during this period was the use of ‘jewelling’,
                                                    invented by John Arnold. ‘Jewelling’ refers to   Grandfather clocks
on-board atomic clocks are accurate to one
second in 30 000 years, while ground-based          the use of precious stones, such as rubies,
atomic clocks can be accurate up to one sec-        as bearings to reduce friction. By 1800, an      html
ond in 1 400 000 years!                             accurate watch, in the form of a pocket
                                                    chronometer, was available. A second hand        html
Greenwich Mean Time                                 was added.                             
Initially in the eighteenth century, the ‘time of       Up to 1840, watches were all hand-           grandfather_clock.html
day’ varied from town to town. This made            finished and as a result parts were not
                                                    inter-changeable. It was the Swiss who be-
                                                                                                     Cuckoo clocks
it very difficult for the mail coach service to
keep to a timetable, because coachmen had to        lieved that there was a market for cheaper,
adjust their watches to give the correct local                                                       Mystery clocks
   With the introduction of the railway net-                                                         htm
work in England in the nineteenth century,
the problem became worse. As a result the                                                            History of watches
railroads in England decided to adopt London                                               
time, as determined by the Royal Observatory                                               
at Greenwich, for their network. By 1855 all                                                         pocketwatch/pocketwatch.htm
public clocks throughout Great Britain had                                                 
adopted GMT (Greenwich Mean Time).
                                                                                            - Click on Information
   The greater distances involved in the United
States caused even greater confusion than in                                                         Learning about time
Britain. In order to bring some order into the                                             
existing chaos, regional time zones were intro-
                                                                                                                                                 2 00 7
                                                               Kaapse Bibl., Mar/Apr 2007

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