Clock Guide, Meaning , Facts, Information and Description
A clock (from the Latin cloca, "bell") is an instrument for measuring time. A clock can be a physical instrument (an especially accurate one is called a chronometer). The clock in its modern form (24 hour clock) has been in use since at least the 15th century. Clock can refer to an abstract system of time measurement (ed. see calendar for other measurements).
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2 Displays 3 History 4 Notable clocks 5 Types of clock 6 See also 7 Miscellaneous 8 References |
Purposes
Clocks are in homes and offices; smaller ones (watches) are carried along; big ones are in public places, e.g. a train station or church. A small clock is also often permanently shown in a corner of computer displays or mobile phones.
A clock, by measuring time (e.g. in seconds). supplies a numerical comparison between the durations of different time intervals. For example, a clock will provide the ratio of the duration of one day to the duration of a different day (for example, the earth is spinning slower today than it did a billion years ago. If the earth's spin is used as a clock, each rotation will take exactly one day, by definition.)
The main purpose of a clock is not always to display the time. It may also be used to control a device according to time, e.g. an alarm clock, a VCR, or a time bomb (see: counter).
Computers depend on an accurate internal clock to allow synchronized processing.
An ideal clock appropriately measures the ratio of the duration of natural processes, and thus will give the appropriate time measure for use in physical theories. Therefore, to define an ideal clock in terms of any physical theory would be circular. An ideal clock is more appropriately defined in relationship to the set of all physical processes.
This leads to the following definitions:
Ideal uses
Accurate navigation by ships beyond the sight of land depends on the ability to measure latitude and longitude. Latitude is fairly easy to determine through celestial navigation, but the measurement of longitude requires accurate measurement of time. This need was a major motivation for the development of accurate mechanical clocks. John Harrison created the first, highly accurate marine chronometers in the mid-18th century.
A clock face is the part of an analog clock that tells time through the use of a fixed numbered dial or dials and moving hand or hands. It usually has a circular scale of 12 hours, which also serves as a scale of 60 minutes, and often also as a scale of 60 seconds. A digital clock expresses a numerical hour range of 1-12 (or 0-23), with an indication am/pm.
The earliest reasonably accurate clocks are the 13th century tower clocks probably developed for (and perhaps by) monks in Northern Italy. These were used to announce the canonical hours or intervals between set times of prayer. Canonical hours differ in length, and varied as the times of sunrise and sunset shifted.
The earliest clocks that survive in any quantity are mid-16th century table clocks from the metalworking towns of Nuremberg and Augsburg. These clocks have only one hand. The dial between the hour markers is divided into four equal parts making the clocks accurate only to within 15 minutes.
The next major development in accuracy occurred in 1657 with the invention of the pendulum clock. Galileo had the idea to use a swinging bob to propel the motion of a time telling device earlier in the 17th century. Christiaan Huygens, however, is usually credited as the inventor. He determined the mathematical formula that related pendulum length to time (99.38 cm/39 in. for the one second movement) and had the first pendulum driven clock executed. In 1670, the English clockmaker William Clement created the anchor escapement, an improvement over Huygens' crown escapement.
The excitement over the pendulum clock attracted the attention of artisans and designers resulting in a proliferation of clock forms. Notably, the longcase clock (aka grandfather clock) was created to house the pendulum and works. The English clockmaker William Clement, inventor of the anchor escapement, is credited developing this form in 1670. It was also at this time that clock cases began to be made of wood and clock faces to employ enamel.
Modern clocks define constant units of time: an hour is always sixty minutes, of sixty seconds each.
, reportedly the oldest working clock in the world]]
The British band Coldplay also has a popular song called "Clocks".Navigation
Displays
History
The history of the time telling device can be traced to Antiquity. Vitruvius reports that the ancient Egyptians used clepsydras, a time mechanism run by flowing water. By the 9th century AD a mechanical timekeeper had been developed that lacked only an escapement mechanism. There is a record that in 1176 Sens Cathedral installed a “horologe” – the word still used in French for large clocks. It is derived from the Greek hora meaning hour and legein meaning to tell. This word has led scholars to believe that these earliest timekeepers did not employ hands or dials, but “told” the time with audible signals. Notable clocks
Probably the most comprehensive online resource guide on clocks can be found at http://www.clock-finder.com which links to many thousands of clock related sites.Types of clock
See also
Miscellaneous