A Brief History of Clock Clocks At best,
historians know that 5,000-6,000 years ago, great civilizations in the Middle
East and North Africa started to examine forms of clock-making instead of
working with only the monthly and annual calendar. Little is known on exactly
how these forms worked or indeed the actual deconstruction of the time, but it
has been suggested that the intention was to maximize time available to achieve
more as the size of the population grew. Perhaps such future periods of time
were intended to benefit the community by allotting specific lengths of time to
tasks. Was this the beginning of the working week Sun
Clocks With the disappearance of any ancient civilization,
such as the Sumerian culture, knowledge is also lost. Whilst we can only
hypothesize on the reasons of why the equivalent to the modern wristwatch was
never completed, we know that the ancient Egyptians were next to layout a system
of dividing the day into parts, similar to hours. "Obelisks"
(tall four-sided tapered monuments) were carefully constructed and even
purposefully geographically located around 3500 BC. A shadow was east as the Sun
moved across the sky by the obelisk, which it appears was then marked out in
sections, allowing people to clearly see the two halves of the day. Some of the
sections have also been found to indicate the "year"s longest and shortest days,
which it is thought were developments added later to allow identification of
other important time subdivisions. Another ancient Egyptian
"shadow clock" or "sundial" has been discovered to have been in use around 1500
BC, which allowed the measuring of the passage of "hours". The sections were
divided into ten parts, With two "twilight hours" indicated, occurring in the
morning and the evening. For it to work successfully then at midday or noon, the
device had to be turned 180 degrees to measure the afternoon hours. Water
Clocks "Water clocks" were among the earliest time keeping
devices that didn’t use the observation of the celestial bodies to calculate the
passage of time. The ancient Greeks, it is believed, began using water clocks
around 325 BC. Most of these clocks were used to determine the hours of the
night, but may have also been used during daylight. An inherent problem with the
water clock was that they were not totally accurate, as the system of
measurement was based on the flow of water either into, or out of, a container
which had markers around the sides. Another very similar form was that of a bowl
that sank during a period as it was filled of water from a regulated flow. It is
known that water clocks were common across the Middle East, and that these were
still being used in North Africa during the early part of the
twentieth-century. Mechanical Clocks In 1656,
"Christian Huygens’ (Dutch scientist), made the first "Pendulum(钟摆) clock", with
a mechanism using a "natural" period of oscillation(振幅). "Galileo Galilei" is
credited, in most historical books, for inventing the pendulum as early as 1582,
but his design was not built before his death. Huygens’ clock, when built, had
an error of "less than only one minute a day". This was a massive leap in the
development of maintaining accuracy, as this had previously never been achieved.
Later refinements to the pendulum clock reduced this margin of error to "less
than 10 seconds a day". The mechanical clock continued to
develop until they achieved an accuracy of "a hundredth-of- a-second a day",
when the pendulum clock became the accepted standard in most astronomical
observatories. Quartz Clocks The running of a "Quartz
clock" is based on the piezoelectric property of the quartz crystal. When an
electric field is applied to a quartz crystal, it actually changes the shape of
the crystal itself, If you then squeeze it or bend it, an electric field is
generated. When placed in an appropriate electronic circuit, this
interaction between the mechanical stress and the electrical field causes the
crystal to vibrate, generating a constant electric signal which can then be used
for example on an electronic clock display. The first wrist-watches that
appeared in mass production used "LED", "Light Emitting Diode" displays. By the
1970’s these were to be replaced by a "LCD", "Liquid Crystal Display".
Quartz clocks continue to dominate the market because of the accuracy and
reliability of the performance, also being inexpensive to produce on mass scale.
The time keeping performance of the quartz clock has now been surpassed by the
"Atomic clock". Atomic Clocks Scientists discovered
some time ago that atoms and molecules have "resonances" and that each chemical
element and compound absorbs and emits "electromagnetic radiation" within its
own characteristic "frequencies". This we are told is highly accurate even over
"Time and Space". The development of radar and the subsequent
experimentation with high frequency radio communications during the 1930s and
1940s created a vast amount of knowledge regarding "electromagnetic waves", also
known as "microwaves". which interact with the atoms. The development of
atomic clocks focused firstly on microwave resonances in the chemical Ammonia
and its molecules. In 1957. "NIST". the "National Institute of Standards and
Technology", completed a series of tests using a "Cesium Atomic Beam" device,
followed by a second program of experiments by NIST in order to have something
for comparison when working at the atomic level. By 1960, as the outcome of the
programs, "Cesium Time Standards" were incorporated as the official time keeping
system at NIST. The "Natural frequency" recognized currently is
the measurement of time. used by all scientists, defines the period of "one
second" as exactly "9,192,631,770 Oscillations" or "9,192,631,770 Cycles of the
Cesium Atom’s Resonant Frequency". From the "Macrocosm", or "Planetary
Alignment", to the "Microcosm", or "Atomic Frequency", the cesium now maintains
accuracy with a degree of error to about "one-millionth of a second per
year". Much of modern life has come to depend on such precise
measurements of time. The day is long past when we could get by with a
timepiece(钟)accurate to the nearest quarter hour. Transportation, financial
markets, communication, manufacturing, electric power and many other
technologies have become dependent on super-accurate clocks. Scientific research
and the demands of modern technology continue re drive our search for ever more
accuracy, The next generation of Cesium Time Standards is presently under
development at NIST’s "Boulder Laboratory" and other laboratories around the
world. Something to Remember The only thing that
should be remembered during all this technological development is that we should
never lose the ability to tell the time approximately by natural means and the
powers of deduction without requiring crutches(拐杖)to lean on.
Our concept of TIME and using it together with TECHNOLOGY still has room
for radical reassessment in terms of man’s evolutionary thinking regarding our
view of the past, our onward journey into the future and our concept of time in
relationship to universe. Huygens’ clock, a mechanical one, had an error of "less than only one minute a day", which was a massive leap in the development of ______.