Clock

The digital clock was invented in 1956. Crock is also a comic strip depicting the French Foreign Legion. Quartz timepieces were invented in the 1920s. These two meanings of the word are, according to the Jargon File, connected by the American scatologism crock of shit for extreme forms of what would otherwise be called bullshit. The Noon gun in Cape Town still fires an accurate signal to allow ships to check their chronometers. See also: leprechaun. John Harrison created the first, highly accurate marine chronometers in the mid-18th century. It is perhaps most commonly used as part of the term crock-pot.

This need was a major motivation for the development of accurate mechanical clocks. Crock also means a fired clay (or earthenware) container sometimes used for food, and sometimes used for chemicals. Latitude is fairly easy to determine through celestial navigation, but the measurement of longitude requires accurate measurement of time. See also: Jargon File. Accurate navigation by ships beyond the sight of land depends on the ability to measure latitude and longitude. The term was early used at the MIT Model Railroad Club, and from there moved to computing and into computing terminology. Rather, they are designated as the current ideal clock because they are currently the best instantiation of the definition. A kludge'd design which didn't actually work, will probably also be a crock.

However, they are not so designated by fiat. A kludge, by contrast is typically something that works, however clumsily. Since atoms are so numerous and since, within current measurement tolerances, they all beat in a manner such that if one is chosen as periodic then the others are all deemed to be periodic also, it follows that atomic clocks represent ideal clocks to within present measurement tolerances and in relation to all presently known physical processes. In absolute contrast, there is little more condemnatory in an engineering context than to declare something a crock. While not all physical processes can be surveyed, the definition should be based on the set of physical processes which includes all individual physical processes which are proposed for consideration. Because they were crocks, they were funny. This definition can be further improved by the consideration of successive levels of smaller and smaller error tolerances. Most of Rube Goldberg's or Heath Robinson's unlikely machines were crocks.

Sometimes that signal alone is (confusingly) called "the clock," but sometimes "the clock" includes the counter, its indicator, and everything else supporting it. An automobile with intentionally designed square wheels would be a crock. The recurrent, periodic process (a metronome) is an oscillator and typically generates a clock signal. Especially in engineering, a crock is a botched attempt or design to achieve something. This leads to the following definitions:. An ideal clock is more appropriately defined in relationship to the set of all physical processes.

Therefore, to define an ideal clock in terms of any physical theory would be circular. An ideal clock is a scientific principle that measures the ratio of the duration of natural processes, and thus will give the time measure for use in physical theories. Some computers also maintain time and date for all manner of operations whether these be for alarms, event initiation or just to display the time of day. (A few research projects are developing CPUs based on asynchronous circuits).

Practically all computers depend on an accurate internal clock signal to allow synchronized processing. an alarm clock, a VCR, or a time bomb (see: counter). It may also be used to control a device according to time, e.g. The main purpose of a clock is not always to display the time.

A small clock is often shown in a corner of computer displays or mobile phones. a train station or church. Clocks are in homes and offices; smaller ones (watches) are carried; larger ones are in public places, e.g.
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After a reset digital clocks lacking a backup battery either start counting from 00:00, or stay 00:00 to indicate that their time needs to be set. Mains-driven digital clocks are often reset after a power failure, and, typically, begin flashing to alert us that the time they display is incorrect. A digital clock typically displays a numerical hour range of 0-23, or 1-12 (with an indication of AM or PM) using an LCD or LED display, although digital versions of analog-style faces exist. Digital clocks use electronic methods of keeping time, typically the 50 or 60 hertz oscillation of AC power or a crystal oscillator as in a quartz movement.

The ultimate analog clock is the sundial, which tracks the sun continuously, registering the time by the shadow of its gnomon. The analog clock with digital display emulates a digital clock but with an analog movement. 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 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.

Analog clocks may be mechanical or have a quartz movement. There are two major types of clocks. Even mechanical clocks have since come to be largely powered by batteries, removing the need for winding. Time in these cases is measured in several ways, such as by the behaviour of quartz crystals, or the decay of radioactive elements.

The development of electronics in the twentieth century led to clocks with no clockwork parts at all. Terry is known as the founder of the American clock-making industry. On November 17, 1797, Eli Terry received his first patent for a clock. It was also at this time that clock cases began to be made of wood and clock faces to employ enamel.

The English clockmaker William Clement, inventor of the anchor escapement, is credited with developing this form in 1670. Notably, the longcase clock (aka grandfather clock) was created to house the pendulum and works. The excitement over the pendulum clock attracted the attention of designers resulting in a proliferation of clock forms. Within just one generation, minute hands and then second hands were added.

In 1670, the English clockmaker William Clement created the anchor escapement, an improvement over Huygens' crown escapement. He determined the mathematical formula that related pendulum length to time (99.38 cm or 39.13 inches for the one second movement) and had the first pendulum driven clock made. Christiaan Huygens, however, is usually credited as the inventor. Galileo had the idea to use a swinging bob to propel the motion of a time telling device earlier in the 17th century.

The next major development in accuracy occurred in 1657 with the invention of the pendulum clock. The dial between the hour markers is divided into four equal parts making the clocks readable to the nearest 15 minutes. These clocks have only one hand. The earliest table clocks that survive in any quantity are mid-16th century ones from the metalworking towns of Nuremberg and Augsburg.

Canonical hours differ in length, and varied as the times of sunrise and sunset shifted. These were used to announce the canonical hours or intervals between set times of prayer. The earliest reasonably accurate clocks are the 13th century tower clocks probably developed for (and perhaps by) monks in Northern Italy. The Muslims also constructed a variety of highly accurate astronomical clocks for use in their observatories.

In addition, during the 9th century, Ibn Firnas of Islamic Spain, according to Will Durant, invented a watch-like device which kept accurate time. The latter type was directly copied by Europeans during the 15th century. One such clock included a mercury escapement. Designs and illustrations of epi-cyclic and segmental gears were provided.

These clocks were weight-driven. A variety of mechanical clocks were produced by Spanish Muslim engineers, both large and small, and this knowledge was transmitted to Europe through Latin translations of Islamic books on mechanics. This word has led scholars to believe that these tower clocks did not employ hands or dials, but “told” the time with audible signals such as bells. (from Greek hora, hour, and legein, to tell).

There is a record that in 1176 Sens Cathedral installed a ‘horologe’—the word still used in French for large clocks. By the 9th century AD a mechanical timekeeper had been developed that lacked only an escapement mechanism. Historians disagree over the Antikythera mechanism but this is largely thought to be an early mechanical clock. The historian Vitruvius reported that the ancient Egyptians also used a clepsydras, a time mechanism run by flowing water.

In an hourglass fine sand pours through a tiny hole at a predictable rate. Candles and sticks of incense which burn down at approximately predictable speeds have also been used as clocks. The sundial, which measures the time of day by the direction of shadows cast by the sun, was widely known in ancient times. As the seasons and the phases of the moon can be used to measure the passage of longer periods of time, shorter processes could be used to measure off hours and minutes.

In principle, it requires no more than some physical process which will proceed at a known rate, and a way to gauge how long that process has been continuing. The clock is one of the oldest human inventions. . The clock in its most common modern form (in use since at least the 14th century) displays the hours, minutes, and sometimes seconds that pass over a twelve or twenty-four-hour period.

A portable clock is called a watch. (Usually, for measuring time of intervals less than a day--as opposed to a calendar.) Those used for technical purposes, of very high accuracy, are sometimes called chronometers. A clock (from the Latin cloca, "bell") is an instrument for measuring time. world clock.

water clock. watch. time clock. tide clock.

sundial. striking clock. stopwatch. skeleton clock.

sidereal clock. quartz clock. projection clock. torsion pendulum clock.

swinging pendulum clock. pedestal clock. mantel clock. longcase clock.

hourglass. grandfather clock. game clock. flip clock.

cuckoo clock. countdown clock. Railroad chronometers. doll's head clock.

Data clock for timescapes created with time-technology. clock network. chiming clock. cartel clock.

bracket clock. binary clock. atomic clock. astronomical clock.

analog clock with digital display. alarm clock. An ideal clock is a clock (i.e., recurrent process) that makes the most other recurrent processes periodic. A good clock is one which, when used to measure other recurrent processes, finds many of them to be periodic.

A clock is a recurrent periodic process and a counter.