What's the time?

“Time is free, but it’s priceless. You can’t own it, but you can use it. You can’t keep it, but can spend it. Once you’ve lost it you can never get it back.” - Harvey MacKay

Time ... it just happens. Have you ever thought why do we measure time? Measurement of time started early on in human development. There are many different instruments man has used throughout history to measure time.
The ancient Egyptians, Chinese and Indians used a shadow clock, or sundial, to tell the time. A shadow clock was easy to make. All that was needed was an upright stick or shaft that would cast a shadow. The length of the shadow could vary according to the position of the sun. As the day grew later, the shadow grew longer. But what happens on a cloudy day when the sun is hidden? That presented the ancients with a serious problem and they tried to invent a time telling device that wouldn't on the sun or weather conditions.
One such device was the hourglass. It consisted of two glass containers connected to each other so that sand or water could flow through a narrow opening between them. It was arranged so that the sand or water would trickle from one container to the other in an hour's time. The hourglass would then be turned over and process repeated.
The Greeks perfected a water clock called the clepsydra. This clock worked when water was added to a container with a float inside. As the water level became higher, the float rose also and moved a wheel. Attached to the wheel was a pointer on a dial. When the wheel turned, the pointer slowly moved from one hour mark to the next.
Mechanical clocks, using weights, wheels and gears to turn the hands of the dial, were first built in the 13th century A.D. These clocks were very large and they were placed in the towers of castles, town halls and churches. Many of these clocks also showed the movements of the sun and the moon. Some had mechanical figures that performed puppetlike movements when the hour was struck.
The first pocket watches were made in the 15th century. They were made possible by the invention of the mainspring-coil. The mainspring is tightened by winding the watch. As the coiled steel gradually unwinds , it moves the gears that turn the hands. Nuremberg, Germany , was one of the first centers of watchmaking. The watches produced there and in other cities were beautifully made. The cases were usually of silver or gold. However, these early watches did not tell the time accurately.
As the years went by, clocks and watches were improved. In the 1650's, a Dutch scientist named Christian Huygens designed a clock with a pendulum. A pendulum is an object suspended from a fixed point so that it can swing back and forth freely. Each time the pendulum swings it moves a wheel that rotates the hands of the clock. Pendulum clocks were accurate and they soon replaced other types of clocks.
Unfortunately, the pendulum clock was not practical on a board ship. When the seas were rough, the pendulum would be thrown off by the pitch and roll of the ship. Also the damp salt air damaged the clock's mechanism. In the 18th century, John Harrison, an English inventor perfected a ship's clock worked so well that it lost less than two minutes during a five month long voyage across the Atlantic.
There have been many advances in clock and watchmaking in the past centuries. People began wearing wristwatches in the early 1900's. Automatic watches run without having to be wound. There is a weight inside the watch that swings when the wearer moves his arm. The spring is wound as the weight swings back and forth. Electricity is also used to run clocks and watches. An electric wristwatch powered by a tiny battery was first produced in the USA in the 1950's.
Today we have also wristwatches that use solar cells. The solar cell changes sunlight into electricity. These cells can keep a watch running accurately for up to ten years.

TIME MARCHES ON ...