Home > Invention, Science > 191/365 – Watch

191/365 – Watch

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.

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.

In the years immediately following World War II, interest in atomic physics led to the development of the atomic clock. Radioactive materials emit particles (decayed) at a known, steady rate.

The parts of a mechanical clock that ratcheted to keep the time could be replaced by a device that stimulated the watch movement each time a particle was emitted by the radioactive element. Atomic clocks, incidentally, are still made and sold, and they are found to be consistently accurate.

With the development of the microchip in the 1970s and 1980s, a new type of watch was invented. Wristwatches that mixed microchip technology with quartz crystals became the standard; there are few non-quartz wristwatches made today.

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.

The use of quartz in watches makes use of a long-known type of electricity known as piezoelectricity. Piezoelectricity is the current which flows from or through a piece of quartz when the quartz is put under electrical and/or mechanical pressure (piezo is from the Greek verb meaning “to press”).

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 most accurate quartz watches are those 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.

But because the hands are mechanically operated through a portion of the watch known as a gear train, analogue watches usually are not as accurate as digitals and are subject to wear.

Both types of watches achieve tremendous accuracy, with digital watches commonly being accurate to within three seconds per month.


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