The History of Clock

The History of Clocks

The history of clocks is very long, and there have been many different types of clocks over the centuries. Not all historians agree on the history of the clock. The word clock was first used in the 14th century (about 700 years ago). It comes from the word for bell in Latin ("clocca").


Evolution of the clocks

- Using the Sun
- Sundial Clocks
- Water Clocks
- Pendulum clocks
- Quartz Crystal Clocks

Using the Sun
The first way that people could tell the time was by looking at the sun as it crossed the sky. When the sun was directly overhead in the sky, it was the middle of the day, or noon. When the sun was close to the horizon, it was either early morning (sunrise) or early evening (sunset). Telling the time was not very accurate.

Sundial Clocks
The oldest type of clock is a sundial clock, also called a sun clock. They were first used around 3,500 B.C. (about 5,500 years ago). Sundials use the sun to tell the time. The shadow of the sun points to a number on a circular disk that shows you the time. In the big picture below on the right, the shadow created by the sun points to 9, so it is nine o'clock.
Since sundials depend on the sun, they can only be used to tell the time during the day

Water Clocks
Around 1400 B.C. (about 3,400 years ago), water clocks were invented in Egypt. The name for a water clock is clepsydra (pronounced KLEP-suh-druh). A water clock was made of two containers of water, one higher than the other. Water traveled from the higher container to the lower container through a tube connecting the containers. The containers had marks showing the water level, and the marks told the time.
Water clocks were very popular in Greece, where they were improved many times over the years. Look at the picture below. Water drips from the higher container to the lower container. As the water level rises in the lower container, it raises the float on the surface of the water. The float is connected to a stick with notches, and as the stick rises, the notches turn a gear, which moves the hand that points to the time.
Water clocks worked better than sundials because they told the time at night as well as during the day. They were also more accurate than sundials

Pendulum Clocks
Before pendulum clocks were invented, Peter Henlein of Germany invented a spring-powered clock around 1510. It was not very precise. The first clock with a minute hand was invented by Jost Burgi in 1577. It also had problems. The first practical clock was driven by a pendulum. It was developed by Christian Huygens around 1656. By 1600, the pendulum clock also had a minute hand.
The pendulum swings left and right, and as it swings, it turns a wheel with teeth (see the picture to the right). The turning wheel turns the hour and minute hands on the clock. On the first pendulum clocks, the pendulum used to swing a lot (about 50 degrees). As pendulum clocks were improved, the pendulum swung a lot less (about 10 to 15 degrees). One problem with pendulum clocks is that they stopped running after a while and had to be restarted. The first pendulum clock with external batteries was developed around 1840. By 1906, the batteries were inside the clock.
As you already learned, a clock only shows 12 hours at a time, and the hour hand must go around the clock twice to measure 24 hours, or a complete day. To tell the first 12 hours of the day (from midnight to noon) apart from the second 12 hours of the day (from noon to midnight), we use these terms:
A.M.--Ante meridiem, from the Latin for "before noon"
P.M.-- Post meridiem, from the Latin for "after noon"

Quartz Crystal Clocks
Quartz is a type of crystal that looks like glass. When you apply voltage, or electricity, and pressure, the quartz crystal vibrates or oscillates at a very constant frequency or rate. The vibration moves the clock's hands very precisely. Quartz crystal clocks were invented in 1920.