Clocks are used to measure time. Clocks are used to show the time. Clocks are used so that people can agree on the time.
People use clocks to measure units of time that are shorter than natural units. Natural units are the day, the month, and the year. The sun rises at the beginning of each day. The moonis new at the beginning of each month. The sun appears at the same place in the sky at the beginning of each year.
The clock is a very old invention. Sundials were used in ancient times. Sundials work by measuring shadows that are cast by the sun. Candle clocks were used a very long time ago. Candle clocks work by measuring the time it takes for the wax to melt. Hourglasses are similar tocandle clocks because they also measure the time it takes for something to happen. Hourglasses work by measuring the time it takes for sand to pour through a small opening into a glass.
Mechanical clocks appeared in the 13th century in Europe. They work with a system of moving gears. The gears always move at the same speed. Pendulum clocks work with a swinging weight. The swinging weight is called a pendulum. The pendulum makes the clock parts move.
Now people typically use mechanical clocks or digital clocks. Digital clocks show numbers on a screen. The numbers represent the time. Some people use auditory clocks. Auditory clocks use language to tell the time aloud. Computers also use clocks. Computers use internal clocks in order to work properly.
In today’s world, clocks are everywhere –– in homes, schools, offices, and public places.
Many people live their lives according to the clock. People go to work and return home according to the clock. School days start and end according to the clock. Airplanes take off and land according to the clock. It is fun to imagine a world without clocks!

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