It was the Greeks who divided the year into twelve months. They divided each month into thirty days. It was the Egyptians and Babylonians who divided the day from sunrise to sunset into twelve parts that are called hours. They also divided the night, the time from sunset to sunrise, into twelve hours. But the day and the night are not the same length, and the length of the day and night also changes through the year. This system of measuring the time was not very accurate because the length of an hour changed depending on the time of year.
Somebody finally figured out that by dividing the whole day into 24 hours of equal length the time could be measured much more accurately. Why was the day and night divided into 12 parts? Twelve is about the number of moon cycles in a year, so it is a special number in many cultures. The hour is divided into 60 minutes, and each minute is divided into 60 seconds. The idea of dividing the hour and minute into 60 parts comes from the Sumerian sexagesimal system, which is based on the number 60. This system was developed about 4,000 years ago.
The clock has a very long and varied history. The word clock was first used in the 14th century. It comes from the word for bell in Latin ("clocca").
The oldest type of clock is a sundial clock, also called a sun clock. They were first used around 3,500 B.C. 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.
Of, course this was not very accurate as the amount of daylight varies so much throughout the seasons and of limited use in places such as Britain where sunshine can sometimes be in short supply. Despite this lack of accuracy, they continued to be made. A famous maker of Antique Sundials was Isaac Symmes who was making them in the early 17th century.
Around 1400 B.C. 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 travelled 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. Water drips from a higher container to a 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. This system replies on the consistency of the flow of water into the system which was hard to control.
Clocks in Europe: 13th - 14th century AD
In 1275 a system using an escapement was invented. A toothed wheel is turned, one tooth at a time, by successive teeth catching against knobs projecting from an upright knob which oscillates back an forth. The speed of the rod's oscillation is regulated by a horizontal bar (the foliot) which is attached to the top of the rod with weights at either side that can be moved in or out to regulate the oscillation.
The Foliot was performing the same function as the pendulum in later pendulum clocks but without using the power of gravity. Instead it was powered by cumbersome, heavy machinery. They were accurate to about a quarter of an hour a day.
A good example of this kind of clock is at Salisbury Cathedral. Built in 1386 and still working today. It has no face and tells the time by striking the hours like many early clocks. In 1389 one was built on a bridge in Rouen, the first built to strike, not just on the hour, but also on the quarter hour. The first surviving one with an actual dial is at Wells cathedral, built in 1392
From the 15th century onwards, clocks began to appear in a domestic setting. The household of an important family was not complete without a clock. They were miniature versions of the cathedral clocks with the same mechanism and a face with one hand working its way around 12 hours. However, by the middle of the 15th century the "Spring Driven Clock" was developed.
These clocks were powered by a coiled spring. The problem of the spring losing power as it unwound was solved by the 'Fusee'. This was a cone wound round with a thin groove which formed an axis driving the wheels of the clock mechanism. A wire of gut attached at one end to the spring and to the other end, the clock mechanism, is wound round the fusee, wound at the thinnest part of the cone when the clock is fully wound (the spring is tightly coiled) and at the thickest part, when as the clock winds down. Thus increasing leverage.
The spring driven mechanism eliminated the need for weights thus enabling the production of small clocks that could be set on tables or the mantelpiece as a Carriage Clocks eventually the watch that could be carried in a pocket as a Pocket Watch. Mantle clocks could be highly decorative and were made in Boulle, Ormolu, Marble and Enamel Carriage clocks were often Silver.
The first practical clock was driven by a pendulum. It was developed by Christian Huygens around 1656. By 1600, the Pendulum Clocks also had a minute hand. The pendulum swings left and right, and as it swings, it turns a wheel with teeth. 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).
These pendulum clocks became increasingly popular and could be found in homes in the form of Longcase Clocks. Often a status symbol, they were encased in boxes made of Mahogany, sometimes with Brass Inlay. Also as Bracket Clocks. These had to be mounted on a wall to allow room for their weights. Because of their shape, they have, in recent times, become known as Lantern Clocks.
In 1921 W.H. Shortt created the "Shortt Clock" This used two pendulums, one master and one slave. The slave pendulum actually drives the clock hands, avoiding mechanical disturbances to the master pendulum.
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.