Clock
From the Simple English Wikipedia, the free encyclopedia that anyone can change
A clock (usually on a wall or desk) or a watch (usually smaller and kept in a pocket or worn on the wrist) is a device that tells the time. Some can give the date as well. There are many different clocks and watches. Some are called "analog" since there are hands moving and some "digital" where numbers or digits update without using hands.
A wristwatch is worn on the wrist by joining two straps together to keep it from falling off. A pocket watch is kept in a pocket.
Another type of clock is an alarm clock, which is a clock that rings or plays music in order to wake people up in the morning so they will not sleep too long.
A grandfather clock is a tall clock that stands on a floor and uses a pendulum to tell time.
Clocks tell time by having some sort of steady beat or motion. An ancient water clock worked by the steady movement of water from a container with a hole in the bottom to another container without a hole.
Digital clocks work by measuring the vibrations of quartz crystals when charged with electricity. The amount of vibrations a quartz crystal per second doesn't change.
Atomic clocks use the steady decay of radioactive atoms to measure time. They are some of the most precise clocks in the world.
