Tiffany Mulholland, age 12, of Twin Falls, Ida., for her question:
WHO MADE THE FIRST CLOCK?
A clock is an instrument used for dividing the day and night into regular periods of time. The first clock goes back to ancient days. Man learned to tell the time of day by the direction of shadows cast from trees. And this led to the first sundial.
A water clock or clepsydra was developed in China more than 3,000 years ago and it was also known to the early Egyptians, Greeks and Romans. History doesn't say which country came up with the idea first.
Early water clocks all worked on the same system: water or some other fluid was made to run from one vessel to another. The amount of water that flowed could be measured to mark the passing of time.
A German inventor named Henry de Vick built what many historians say was the first real clock. He came up with his unique and well designed timepiece in the 1300s.
The first clock of de Vick contained many of the important parts of the modern clock. It had wheels, a dial and an hour hand. It wasn't until the 1700s, however, before other inventors thought to add a pendulum, a minute hand and a second hand.
Since about the 1700s, clocks have not changed very much. Styles have definitely varied but the essential principles have not changed.
The essential parts of a clock are a set of wheels and a weight or spring that moves the wheels. The front of the clocks contain a face and a set of hands that point out the minutes and hours.
One wheel inside a clock turns around once every hour, and carries the long minute hand with it. The hour hand is moved by turning a small wheel with six teeth against a large wheel with 72 teeth. Thus, the minute hand turns 12 times while the hour hand turns around only once.
The most accurate clocks in the world today are atomic clocks. Some of them are designed so they will gain or lose no more than a few seconds in 100,000 years. Atomic clocks are tuned to vibrations of atoms or molecules instead of pendulums or to the vibrations of electric current.
The vibrations of atoms in an atomic clock are so stable that they almost always vibrate the same number of times per second.
The first atomic clock was developed by scientists at the National Bureau of Standards in the late 1940s.
There are thousands of different kinds of clocks around today. Some clocks have weights that must be pulled each day. Others have springs that must be wound daily while others need winding only once every eight days.
Some special clocks can run for 40 days with just one winding. And electric clocks, of course, don't have to be wound at all.