Time & Watches 

The oldest means of determining time is by observing the location of the sun in the sky. When the sun is directly overhead, the time is roughly 12:00 noon. A slightly later development, and one less subject to an individual´´s judgment, is the use of a sundial. During the daylight hours, sunlight falls on a vertical pole placed at the center of a calibrated dial, thus casting a shadow on the dial and providing the reader with a relatively accurate time reading.

The invention of the mechanical clock in the fourteenth century was a major advancement—it provided a more concise and consistent method of measuring time. The mechanical clock includes a complicated series of wheels, gears, and levers powered by a falling weights and with a pendulum (or later a wound-up spring). These pieces together moved the hand or hands on a dial to show the time. The addition of chimes or gongs on the hour, half hour, and quarter hour followed soon afterward. By the eighteenth century, smaller clocks for the home were available, and, unlike their predecessors, were closed and sealed in a case.

The more exacting the workmanship of the moving parts, the more accurate the clock was. From invention through to the middle of the twentieth century, developments in clock-making focused on making the moving parts work as accurately as possible. Developments in metal technology and in miniaturization, the lubrication of small parts, and the use of first, natural sapphires (and then artificial sapphires) at the spots that received the most stress (the jeweled movement) all became integral components of horological science. Small pocket watches, perhaps two to three inches (five to seven centimeters) in diameter, were available by the end of the nineteenth century. Mechanical wristwatches were an everyday item in the United States by the 1960s. And yet, the central problem faced by watch and clockmakers remained the same: mechanical parts wear down, become inaccurate, and break.

With a portable timepiece, there are several modes of power that a watch operates on, there is either mechanical, electromechanical, or electronic movements. In the mechanical watch a mainspring in the barrel stores operating energy; the user retightens the spring daily by means of the winding stem. The wheel train advances at five increments per second under control by the escapement. From there the dial train turns the minute and hour hands across the watch face.

The progressive miniaturization of electronic components during the 20^th century has made possible the development of all-electronic watches, in which the necessary transistors, resistors, capacitors, and other elements are all on one or several miniature integrated circuits, or chips. With the development of the microchip in the 1970s and 1980s, a new type of watch was invented. Wristwatches mixed microchip technology with quartz crystals to create the quartz watch. The microchip is utilized to send signals to the dial of the watch on a continual basis. Because it is not a mechanical device with moving parts, it does not wear out easily.

 A quartz watch uses the electricity from a piece of quartz subjected to the electricity from a battery to send a regular, countable series of signals (oscillations) to one or more microchips. (Electrical wall clocks, in contrast, use the regularity of wall current to keep track of time.) The rate of oscillation for quartz used in wristwatches is 100,000 hertz or 100,000 oscillations per second.

There are quartz watches in which the time appears in an electronically controlled digital display, produced via a light-emitting diode (LED) or a liquid crystal display (LCD). It is possible, of course,

to have the microprocessor send its signals to mechanical devices that make hands move on the watch face, creating an analog display Both types of watches achieve tremendous accuracy, with quartz watches commonly being accurate to within three seconds per month.