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Directions: Read the text below. Then read the questions that follow
it and choose the best answer to each question correspondingly among, marking your answers on
your answer sheet.
Evolution of Clocks
Since the beginning of time, humans have been looking for better ways to answer the
age-old question: "What time is it?" The earliest humans used the position of the sun in
the sky to approximate the time of day. However, this system had obvious drawbacks:
you couldn’t tell the exact time, you couldn’t see the sun at night, and the sun could be
hard to see if there was heavy cloud cover. In around 3,500 B.C., the Egyptians began to
construct huge obelisks which served as primitive sundials. These huge pillars told time
by casting shadows on the ground, which changed position depending on the time of day.
The next great advance in timekeeping occurred in about 3,450 B.C. when a primitive
hourglass was invented. This device was basically a bowl with a hole in the bottom. It
had many advantages over sundials, because it would work on cloudy days and at night.
However, this device required careful calibration, because the water poured out faster
when the bowl was full since the water pressure was greater. Also, these devices would
not work in freezing weather.
A huge advance occurred in the 1300’s when mechanical clocks, which used weights or
springs, began to appear. At first, they had no faces, and no hour or minute hands; rather,
they struck a bell every hour. Later, clocks with hour, and then minute hands began to
appear. In the 1400’s, another important discovery in timekeeping was made - coiled
springs were able to move the hands on a clock. This discovery made smaller clocks, and
later - watches, possible.
Then, in 1656, Christian Huygens invented the pendulum clock, which used weights and
a swinging pendulum. These clocks were much more accurate than previous clocks, off
by less than a minute a day, compared to the 15 minutes a day of earlier clocks. The
bigger the pendulum, the more accurate the clock was.
During the mid to late 1800’s, many countries saw the need to create standard time zones
so that everyone could agree on the time and nations could work more efficiently. In
1852, Great Britain implemented a telegraph network that transmitted "Greenwich Mean
Time", so the whole country would be running on exactly the same time. Then, in 1882,
the United States created 4 standard time zones, still in use today. In 1884, delegates from
25 countries met and agreed on worldwide time zones.
At the dawn of the 20th century, only women wore wristwatches. No self-respecting "real
man" would wear one. However, in the first World War, soldiers wore wristwatches
because taking out a pocket watch to check the time was difficult or impossible in battle.
After the war was over, it was considered "socially acceptable" to wear wrist watches,
and they became popular.
Recently, in 1999, scientists developed the cesium fountain atomic clock, which is off by only one second every 20 million years. Perhaps one day humans will invent a timekeeping device which is 100% accurate and never gains or loses a second, not even in billions of years. Also, as time progresses, everyday clocks will gain more features, such as the ability to automatically adjust for daylight savings time, and the ability to synchronize with atomic clocks through radio waves.
The earliest system used to tell time involved
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