Page 63 - DK Children's Encyclopedia

Clocks SEE ALSO

▸ ▸ Machines p.150
▸ ▸ Measuring p.159
A clock is a device used to keep track of time. Ancient ▸ ▸ Numbers p.185
civilizations measured time by falling sand, flowing water, ▸ ▸ The sciences
or the position of the sun. Modern clocks are either digital pp.218–219

or have clockwork mechanisms. ▸ ▸ Sun p.247
▸ ▸ Time zones p.255
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How does a Clock face
This part of the clock
clock work? shows the time, in hours,
Clocks make regular minutes, and seconds.
movements for measuring 2
time. They do this using Minute hand
machinery known as The long minute hand
makes a full turn around
clockwork. The clock the clock every hour.
face has moving hands
that show the hours, Hour hand
minutes, and seconds. 3 The short hour hand makes
a complete turn around the
clock every 12 hours.
Gears
Gears are wheels that lock
together. In a clock, they Second hand
make the hands turn at This long, thin hand makes
different speeds. a complete rotation of the
4 clock every minute.

Then and now
5 In the past, people had
Pendulum sundials, which showed
Each swing of the pendulum 7 the time of day using
turns the gears one click, 6 shadows cast by the sun.
usually once a second. Modern digital clocks show
time as numbers.

The first
pendulum clock Sundial
was made by Dutch
scientist Christiaan
Huygens in 1656.
Counterweight
This weight stores energy
so the clock can work Digital clock
without a battery.
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