About Time

About Time

People have been keeping the time for thousands of years. The first time-keeping devices were very inaccurate. They measured time by the sun, or by the falling levels of water or sand. Mechanical clocks are much more accurate. They have three main parts: an energy supply, a mechanism fore regulating the energy and a way of showing the passing of time.

The energy is supplied by a coiled spring or a weight.  The spring unwinds, or the weight falls, and turns a series of interlocking, toothed wheels. Hands linked to the wheels rotate around a dial. For the clock to be accurate, the hands must turn at a constant speed. In large clocks, a pendulum swings at a constant rate and regulates the movement of the escapement. Digital or electronic watches have a piece of quartz that vibrates at 32,768 times a second. An electronic circuit uses these movements to turn the hands or change numbers on the watch face.

People have made instruments to measure the passing of time for at least 3,000 years. The sundial was developed from a simple observation. As the Earth turns, the sun appears to cross the sky and the shadows it casts move across the ground. If the positions of the shadows are marked at regular intervals, they can be used to tell the time.

Escarpment: This regulates the speed of the clock. It consists of an anchor that rocks from side to side, and an escape wheel that is repeatedly caught and released by the anchor.

Hour hand: The hour hand makes one revolution every 12 hours.

Minute hand: The minute hands moves 12 times faster than the hour hand and makes one revolution every hour.

Pendulum: The swinging pendulum regulates the rocking motion of the anchor.

Gears: These make sure that the minute hand goes around 12 times faster than the hour hand.

Weight: This hangs on a cord wound around a shaft so that the weight turns the shaft to move the gears.

About Time. Photograph by Elena.

On Your Mark, Get Set, Go!

Athletes often cross the finish line at exactly the same moment and it is difficult to decide who has won the race. Officials accurately record the athletes' race times so that very close finishes can be separated by degrees of a second.

Athletes train hard for their events. Stopwatches can help them monitor their progress by measuring times to within 100th of a second. Some stopwatches can also store up to 100 laps in their memories and even print times using built-in printers.

Things In Common

Pendulum clocks and digital watches are very different in size, but they are made from the same basic building blocks. Both have an oscillator that moves or swings at a regular rate,a  device that turns these movements into time-keeping pulses, and a display of showing the time.