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A clock or chronometer is a device that measures and displays time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month, and the year. Devices operating on several physical processes have been used over the millennia.

Some predecessors to the modern clock may be considered “clocks” that are based on movement in nature: A sundial shows the time by displaying the position of a shadow on a flat surface. There is a range of duration timers, a well-known example being the hourglass. Water clocks, along with sundials, are possibly the oldest time-measuring instruments. A major advance occurred with the invention of the verge escapement, which made possible the first mechanical clocks around 1300 in Europe, which kept time with oscillating timekeepers like balance wheels.^[1][2][3][4]

Traditionally, in horology (the study of timekeeping), the term clock was used for a striking clock, while a clock that did not strike the hours audibly was called a timepiece. This distinction is not generally made any longer. Watches and other timepieces that can be carried on one’s person are usually not referred to as clocks.^[5] Spring-driven clocks appeared during the 15th century. During the 15th and 16th centuries, clockmaking flourished. The next development in accuracy occurred after 1656 with the invention of the pendulum clock by Christiaan Huygens. A major stimulus to improving the accuracy and reliability of clocks was the importance of precise time-keeping for navigation. The mechanism of a timepiece with a series of gears driven by a spring or weights is referred to as clockwork; the term is used by extension for a similar mechanism not used in a timepiece. The electric clock was patented in 1840, and electronic clocks were introduced in the 20th century, becoming widespread with the development of small battery-powered semiconductor devices.

The timekeeping element in every modern clock is a harmonic oscillator, a physical object (resonator) that vibrates or oscillates at a particular frequency.^[2] This object can be a pendulum, a balance wheel, a tuning fork, a quartz crystal, or the vibration of electrons in atoms as they emit microwaves, the last of which is so precise that it serves as the definition of the second.

Clocks have different ways of displaying the time. Analog clocks indicate time with a traditional clock face and moving hands. Digital clocks display a numeric representation of time. Two numbering systems are in use: 12-hour time notation and 24-hour notation. Most digital clocks use electronic mechanisms and LCD, LED, or VFD displays. For the blind and for use over telephones, speaking clocks state the time audibly in words. There are also clocks for the blind that have displays that can be read by touch.

Etymology

The word clock derives from the medieval Latin word for ‘bell’—clocca—and has cognates in many European languages. Clocks spread to England from the Low Countries,^[6] so the English word came from the Middle Low German and Middle Dutch Klocke.^[7] The word is also derived from the Middle English clokke, Old North French cloque, or Middle Dutch clocke, all of which mean ‘bell’.

History of time-measuring devices

Main article: History of timekeeping devices

Sundials

Main article: Sundial

The apparent position of the Sun in the sky changes over the course of each day, reflecting the rotation of the Earth. Shadows cast by stationary objects move correspondingly, so their positions can be used to indicate the time of day. A sundial shows the time by displaying the position of a shadow on a (usually) flat surface that has markings that correspond to the hours.^[8] Sundials can be horizontal, vertical, or in other orientations. Sundials were widely used in ancient times.^[9] With knowledge of latitude, a well-constructed sundial can measure local solar time with reasonable accuracy, within a minute or two. Sundials continued to be used to monitor the performance of clocks until the 1830s, when the use of the telegraph and trains standardized time and time zones between cities.^[10]

Devices that measure duration, elapsed time and intervals

Many devices can be used to mark the passage of time without respect to reference time (time of day, hours, minutes, etc.) and can be useful for measuring duration or intervals. Examples of such duration timers are candle clocks, incense clocks, and the hourglass. Both the candle clock and the incense clock work on the same principle, wherein the consumption of resources is more or less constant, allowing reasonably precise and repeatable estimates of time passages. In the hourglass, fine sand pouring through a tiny hole at a constant rate indicates an arbitrary, predetermined passage of time. The resource is not consumed, but re-used.

Water clocks

Main article: Water clock

Water clocks, along with sundials, are possibly the oldest time-measuring instruments, with the only exception being the day-counting tally stick.^[11] Given their great antiquity, where and when they first existed is not known and is perhaps unknowable. The bowl-shaped outflow is the simplest form of a water clock and is known to have existed in Babylon and Egypt around the 16th century BC. Other regions of the world, including India and China, also have early evidence of water clocks, but the earliest dates are less certain. Some authors, however, write about water clocks appearing as early as 4000 BC in these regions of the world.^[12]

The Macedonian astronomer Andronicus of Cyrrhus supervised the construction of the Tower of the Winds in Athens in the 1st century BC, which housed a large clepsydra inside as well as multiple prominent sundials outside, allowing it to function as a kind of early clocktower.^[13] The Greek and Roman civilizations advanced water clock design with improved accuracy. These advances were passed on through Byzantine and Islamic times, eventually making their way back to Europe. Independently, the Chinese developed their own advanced water clocks (水鐘) by 725 AD, passing their ideas on to Korea and Japan.^[14]

Some water clock designs were developed independently, and some knowledge was transferred through the spread of trade. Pre-modern societies do not have the same precise timekeeping requirements that exist in modern industrial societies, where every hour of work or rest is monitored and work may start or finish at any time regardless of external conditions. Instead, water clocks in ancient societies were used mainly for astrological reasons. These early water clocks were calibrated with a sundial. While never reaching the level of accuracy of a modern timepiece, the water clock was the most accurate and commonly used timekeeping device for millennia until it was replaced by the more accurate pendulum clock in 17th-century Europe.

Islamic civilization is credited with further advancing the accuracy of clocks through elaborate engineering. In 797 (or possibly 801), the Abbasid caliph of Baghdad, Harun al-Rashid, presented Charlemagne with an Asian elephant named Abul-Abbas together with a “particularly elaborate example” of a water^[15] clock. Pope Sylvester II introduced clocks to northern and western Europe around 1000 AD.^[16]

Mechanical water clocks

See also: Automaton § Ancient

The first known geared clock was invented by the great mathematician, physicist, and engineer Archimedes during the 3rd century BC. Archimedes created his astronomical clock,^{[17][citation needed]} which was also a cuckoo clock with birds singing and moving every hour. It is the first carillon clock as it plays music simultaneously with a person blinking his eyes, surprised by the singing birds. The Archimedes clock works with a system of four weights, counterweights, and strings regulated by a system of floats in a water container with siphons that regulate the automatic continuation of the clock. The principles of this type of clock are described by the mathematician and physicist Hero,^[18] who says that some of them work with a chain that turns a gear in the mechanism.^[19] Another Greek clock probably constructed at the time of Alexander was in Gaza, as described by Procopius.^[20] The Gaza clock was probably a Meteoroskopeion, i.e., a building showing celestial phenomena and the time. It had a pointer for the time and some automations similar to the Archimedes clock. There were 12 doors opening one every hour, with Hercules performing his labors, the Lion at one o’clock, etc., and at night a lamp becomes visible every hour, with 12 windows opening to show the time.

The Tang dynasty Buddhist monk Yi Xing along with government official Liang Lingzan made the escapement in 723 (or 725) to the workings of a water-powered armillary sphere and clock drive, which was the world’s first clockwork escapement.^[21][22] The Song dynasty polymath and genius Su Song (1020–1101) incorporated it into his monumental innovation of the astronomical clock tower of Kaifeng in 1088.^{[23][24][page needed]} His astronomical clock and rotating armillary sphere still relied on the use of either flowing water during the spring, summer, and autumn seasons or liquid mercury during the freezing temperatures of winter (i.e., hydraulics). In Su Song’s waterwheel linkwork device, the action of the escapement’s arrest and release was achieved by gravity exerted periodically as the continuous flow of liquid-filled containers of a limited size. In a single line of evolution, Su Song’s clock therefore united the concepts of the clepsydra and the mechanical clock into one device run by mechanics and hydraulics. In his memorial, Su Song wrote about this concept:

According to your servant’s opinion there have been many systems and designs for astronomical instruments during past dynasties all differing from one another in minor respects. But the principle of the use of water-power for the driving mechanism has always been the same. The heavens move without ceasing but so also does water flow (and fall). Thus if the water is made to pour with perfect evenness, then the comparison of the rotary movements (of the heavens and the machine) will show no discrepancy or contradiction; for the unresting follows the unceasing.

Song was also strongly influenced by the earlier armillary sphere created by Zhang Sixun (976 AD), who also employed the escapement mechanism and used liquid mercury instead of water in the waterwheel of his astronomical clock tower. The mechanical clockworks for Su Song’s astronomical tower featured a great driving-wheel that was 11 feet in diameter, carrying 36 scoops, into each of which water was poured at a uniform rate from the “constant-level tank”. The main driving shaft of iron, with its cylindrical necks supported on iron crescent-shaped bearings, ended in a pinion, which engaged a gear wheel at the lower end of the main vertical transmission shaft. This great astronomical hydromechanical clock tower was about ten metres high (about 30 feet), featured a clock escapement, and was indirectly powered by a rotating wheel either with falling water or liquid mercury. A full-sized working replica of Su Song’s clock exists in the Republic of China (Taiwan)’s National Museum of Natural Science, Taichung city. This full-scale, fully functional replica, approximately 12 meters (39 feet) in height, was constructed from Su Song’s original descriptions and mechanical drawings.^[25] The Chinese escapement spread west and was the source for Western escapement technology.^[26]

In the 12th century, Al-Jazari, an engineer from Mesopotamia (lived 1136–1206) who worked for the Artuqid king of Diyar-Bakr, Nasir al-Din, made numerous clocks of all shapes and sizes. The most reputed clocks included the elephant, scribe, and castle clocks, some of which have been successfully reconstructed. As well as telling the time, these grand clocks were symbols of the status, grandeur, and wealth of the Urtuq State.^[28] Knowledge of these mercury escapements may have spread through Europe with translations of Arabic and Spanish texts.^[29][30]

Fully mechanical

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The word horologia (from the Greek ὥρα—’hour’, and λέγειν—’to tell’) was used to describe early mechanical clocks,^[31] but the use of this word (still used in several Romance languages)^[32] for all timekeepers conceals the true nature of the mechanisms. For example, there is a record that in 1176, Sens Cathedral in France installed an ‘horologe‘,^[33][34] but the mechanism used is unknown. According to Jocelyn de Brakelond, in 1198, during a fire at the abbey of St Edmundsbury (now Bury St Edmunds), the monks “ran to the clock” to fetch water, indicating that their water clock had a reservoir large enough to help extinguish the occasional fire.^[35] The word clock (via Medieval Latin clocca from Old Irish clocc, both meaning ‘bell’), which gradually supersedes “horologe”, suggests that it was the sound of bells that also characterized the prototype mechanical clocks that appeared during the 13th century in Europe.

In Europe, between 1280 and 1320, there was an increase in the number of references to clocks and horologes in church records, and this probably indicates that a new type of clock mechanism had been devised. Existing clock mechanisms that used water power were being adapted to take their driving power from falling weights. This power was controlled by some form of oscillating mechanism, probably derived from existing bell-ringing or alarm devices. This controlled release of power – the escapement – marks the beginning of the true mechanical clock, which differed from the previously mentioned cogwheel clocks. The verge escapement mechanism appeared during the surge of true mechanical clock development, which did not need any kind of fluid power, like water or mercury, to work.

These mechanical clocks were intended for two main purposes: for signalling and notification (e.g., the timing of services and public events) and for modeling the solar system. The former purpose is administrative; the latter arises naturally given the scholarly interests in astronomy, science, and astrology and how these subjects integrated with the religious philosophy of the time. The astrolabe was used both by astronomers and astrologers, and it was natural to apply a clockwork drive to the rotating plate to produce a working model of the solar system.

Simple clocks intended mainly for notification were installed in towers and did not always require faces or hands. They would have announced the canonical hours or intervals between set times of prayer. Canonical hours varied in length as the times of sunrise and sunset shifted. The more sophisticated astronomical clocks would have had moving dials or hands and would have shown the time in various time systems, including Italian hours, canonical hours, and time as measured by astronomers at the time. Both styles of clocks started acquiring extravagant features, such as automata.

In 1283, a large clock was installed at Dunstable Priory in Bedfordshire in southern England; its location above the rood screen suggests that it was not a water clock.^[36] In 1292, Canterbury Cathedral installed a ‘great horloge’. Over the next 30 years, there were mentions of clocks at a number of ecclesiastical institutions in England, Italy, and France. In 1322, a new clock was installed in Norwich, an expensive replacement for an earlier clock installed in 1273. This had a large (2 metre) astronomical dial with automata and bells. The costs of the installation included the full-time employment of two clockkeepers for two years.^[36]

Astronomical

An elaborate water clock, the ‘Cosmic Engine’, was invented by Su Song, a Chinese polymath, designed and constructed in China in 1092. This great astronomical hydromechanical clock tower was about ten metres high (about 30 feet) and was indirectly powered by a rotating wheel with falling water and liquid mercury, which turned an armillary sphere capable of calculating complex astronomical problems.

In Europe, there were the clocks constructed by Richard of Wallingford in Albans by 1336, and by Giovanni de Dondi in Padua from 1348 to 1364. They no longer exist, but detailed descriptions of their design and construction survive,^[37][38] and modern reproductions have been made.^[38] They illustrate how quickly the theory of the mechanical clock had been translated into practical constructions, and also that one of the many impulses to their development had been the desire of astronomers to investigate celestial phenomena.

The Astrarium of Giovanni Dondi dell’Orologio was a complex astronomical clock built between 1348 and 1364 in Padua, Italy, by the doctor and clock-maker Giovanni Dondi dell’Orologio. The Astrarium had seven faces and 107 moving gears; it showed the positions of the sun, the moon and the five planets then known, as well as religious feast days. The astrarium stood about 1 metre high, and consisted of a seven-sided brass or iron framework resting on 7 decorative paw-shaped feet. The lower section provided a 24-hour dial and a large calendar drum, showing the fixed feasts of the church, the movable feasts, and the position in the zodiac of the moon’s ascending node. The upper section contained 7 dials, each about 30 cm in diameter, showing the positional data for the Primum Mobile, Venus, Mercury, the moon, Saturn, Jupiter, and Mars. Directly above the 24-hour dial is the dial of the Primum Mobile, so called because it reproduces the diurnal motion of the stars and the annual motion of the sun against the background of stars. Each of the ‘planetary’ dials used complex clockwork to produce reasonably accurate models of the planets’ motion. These agreed reasonably well both with Ptolemaic theory and with observations.^[39][40]

Wallingford’s clock had a large astrolabe-type dial, showing the sun, the moon’s age, phase, and node, a star map, and possibly the planets. In addition, it had a wheel of fortune and an indicator of the state of the tide at London Bridge. Bells rang every hour, the number of strokes indicating the time.^[37] Dondi’s clock was a seven-sided construction, 1 metre high, with dials showing the time of day, including minutes, the motions of all the known planets, an automatic calendar of fixed and movable feasts, and an eclipse prediction hand rotating once every 18 years.^[38] It is not known how accurate or reliable these clocks would have been. They were probably adjusted manually every day to compensate for errors caused by wear and imprecise manufacture. Water clocks are sometimes still used today, and can be examined in places such as ancient castles and museums. The Salisbury Cathedral clock, built in 1386, is considered to be the world’s oldest surviving mechanical clock that strikes the hours.^[41]

Spring-driven

• Examples of spring-driven clocks

Clockmakers developed their art in various ways. Building smaller clocks was a technical challenge, as was improving accuracy and reliability. Clocks could be impressive showpieces to demonstrate skilled craftsmanship, or less expensive, mass-produced items for domestic use. The escapement in particular was an important factor affecting the clock’s accuracy, so many different mechanisms were tried.

Spring-driven clocks appeared during the 15th century,^[42][43][44] although they are often erroneously credited to Nuremberg watchmaker Peter Henlein (or Henle, or Hele) around 1511.^[45][46][47] The earliest existing spring driven clock is the chamber clock given to Phillip the Good, Duke of Burgundy, around 1430, now in the Germanisches Nationalmuseum.^[4] Spring power presented clockmakers with a new problem: how to keep the clock movement running at a constant rate as the spring ran down. This resulted in the invention of the stackfreed and the fusee in the 15th century, and many other innovations, down to the invention of the modern going barrel in 1760.

Early clock dials did not indicate minutes and seconds. A clock with a dial indicating minutes was illustrated in a 1475 manuscript by Paulus Almanus,^[48] and some 15th-century clocks in Germany indicated minutes and seconds.^[49] An early record of a seconds hand on a clock dates back to about 1560 on a clock now in the Fremersdorf collection.^{[50]: 417–418 [51]}

During the 15th and 16th centuries, clockmaking flourished, particularly in the metalworking towns of Nuremberg and Augsburg, and in Blois, France. Some of the more basic table clocks have only one time-keeping hand, with the dial between the hour markers being divided into four equal parts making the clocks readable to the nearest 15 minutes. Other clocks were exhibitions of craftsmanship and skill, incorporating astronomical indicators and musical movements. The cross-beat escapement was invented in 1584 by Jost Bürgi, who also developed the remontoire. Bürgi’s clocks were a great improvement in accuracy as they were correct to within a minute a day.^[52][53] These clocks helped the 16th-century astronomer Tycho Brahe to observe astronomical events with much greater precision than before.^{[citation needed][how?]}

Pendulum

The first pendulum clock, designed by Christiaan Huygens in 1656

The next development in accuracy occurred after 1656 with the invention of the pendulum clock. Galileo had the idea to use a swinging bob to regulate 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 (about 99.4 cm or 39.1 inches for the one second movement) and had the first pendulum-driven clock made. The first model clock was built in 1657 in the Hague, but it was in England that the idea was taken up.^[54] The longcase clock (also known as the grandfather clock) was created to house the pendulum and works by the English clockmaker William Clement in 1670 or 1671. It was also at this time that clock cases began to be made of wood and clock faces to use enamel as well as hand-painted ceramics.

In 1670, William Clement created the anchor escapement,^[55] an improvement over Huygens’ crown escapement. Clement also introduced the pendulum suspension spring in 1671. The concentric minute hand was added to the clock by Daniel Quare, a London clockmaker and others, and the second hand was first introduced.

Hairspring

In 1675, Huygens and Robert Hooke invented the spiral balance spring, or the hairspring, designed to control the oscillating speed of the balance wheel. This crucial advance finally made accurate pocket watches possible. The great English clockmaker Thomas Tompion, was one of the first to use this mechanism successfully in his pocket watches, and he adopted the minute hand which, after a variety of designs were trialled, eventually stabilised into the modern-day configuration.^[56] The rack and snail striking mechanism for striking clocks, was introduced during the 17th century and had distinct advantages over the ‘countwheel’ (or ‘locking plate’) mechanism. During the 20th century there was a common misconception that Edward Barlow invented rack and snail striking. In fact, his invention was connected with a repeating mechanism employing the rack and snail.^[57] The repeating clock, that chimes the number of hours (or even minutes) on demand was invented by either Quare or Barlow in 1676. George Graham invented the deadbeat escapement for clocks in 1720.

Marine chronometer

Main article: Marine chronometer

A major stimulus to improving the accuracy and reliability of clocks was the importance of precise time-keeping for navigation. The position of a ship at sea could be determined with reasonable accuracy if a navigator could refer to a clock that lost or gained less than about 10 seconds per day. This clock could not contain a pendulum, which would be virtually useless on a rocking ship. In 1714, the British government offered large financial rewards to the value of 20,000 pounds^[58] for anyone who could determine longitude accurately. John Harrison, who dedicated his life to improving the accuracy of his clocks, later received considerable sums under the Longitude Act.

In 1735, Harrison built his first chronometer, which he steadily improved on over the next thirty years before submitting it for examination. The clock had many innovations, including the use of bearings to reduce friction, weighted balances to compensate for the ship’s pitch and roll in the sea and the use of two different metals to reduce the problem of expansion from heat. The chronometer was tested in 1761 by Harrison’s son and by the end of 10 weeks the clock was in error by less than 5 seconds.^[59]

Mass production

The British had dominated watch manufacture for much of the 17th and 18th centuries, but maintained a system of production that was geared towards high quality products for the elite.^[60] Although there was an attempt to modernise clock manufacture with mass-production techniques and the application of duplicating tools and machinery by the British Watch Company in 1843, it was in the United States that this system took off. In 1816, Eli Terry and some other Connecticut clockmakers developed a way of mass-producing clocks by using interchangeable parts.^[61] Aaron Lufkin Dennison started a factory in 1851 in Massachusetts that also used interchangeable parts, and by 1861 was running a successful enterprise incorporated as the Waltham Watch Company.^[62][63]

Early electric

Main article: Electric clock

In 1815, the English scientist Francis Ronalds published the first electric clock powered by dry pile batteries.^[64] Alexander Bain, a Scottish clockmaker, patented the electric clock in 1840. The electric clock’s mainspring is wound either with an electric motor or with an electromagnet and armature. In 1841, he first patented the electromagnetic pendulum. By the end of the nineteenth century, the advent of the dry cell battery made it feasible to use electric power in clocks. Spring or weight driven clocks that use electricity, either alternating current (AC) or direct current (DC), to rewind the spring or raise the weight of a mechanical clock would be classified as an electromechanical clock. This classification would also apply to clocks that employ an electrical impulse to propel the pendulum. In electromechanical clocks the electricity serves no time keeping function. These types of clocks were made as individual timepieces but more commonly used in synchronized time installations in schools, businesses, factories, railroads and government facilities as a master clock and slave clocks.

Where an AC electrical supply of stable frequency is available, timekeeping can be maintained very reliably by using a synchronous motor, essentially counting the cycles. The supply current alternates with an accurate frequency of 50 hertz in many countries, and 60 hertz in others. While the frequency may vary slightly during the day as the load changes, generators are designed to maintain an accurate number of cycles over a day, so the clock may be a fraction of a second slow or fast at any time, but will be perfectly accurate over a long time. The rotor of the motor rotates at a speed that is related to the alternation frequency. Appropriate gearing converts this rotation speed to the correct ones for the hands of the analog clock. Time in these cases is measured in several ways, such as by counting the cycles of the AC supply, vibration of a tuning fork, the behaviour of quartz crystals, or the quantum vibrations of atoms. Electronic circuits divide these high-frequency oscillations to slower ones that drive the time display.

Quartz

The piezoelectric properties of crystalline quartz were discovered by Jacques and Pierre Curie in 1880.^[65][66] The first crystal oscillator was invented in 1917 by Alexander M. Nicholson, after which the first quartz crystal oscillator was built by Walter G. Cady in 1921.^[2] In 1927 the first quartz clock was built by Warren Marrison and J.W. Horton at Bell Telephone Laboratories in Canada.^[67][2] The following decades saw the development of quartz clocks as precision time measurement devices in laboratory settings—the bulky and delicate counting electronics, built with vacuum tubes at the time, limited their practical use elsewhere. The National Bureau of Standards (now NIST) based the time standard of the United States on quartz clocks from late 1929 until the 1960s, when it changed to atomic clocks.^[68] In 1969, Seiko produced the world’s first quartz wristwatch, the Astron.^[69] Their inherent accuracy and low cost of production resulted in the subsequent proliferation of quartz clocks and watches.^[65]

Atomic

Currently, atomic clocks are the most accurate clocks in existence. They are considerably more accurate than quartz clocks as they can be accurate to within a few seconds over trillions of years.^[70][71] Atomic clocks were first theorized by Lord Kelvin in 1879.^[72] In the 1930s the development of magnetic resonance created practical method for doing this.^[73] A prototype ammonia maser device was built in 1949 at the U.S. National Bureau of Standards (NBS, now NIST). Although it was less accurate than existing quartz clocks, it served to demonstrate the concept.^[74][75][76] The first accurate atomic clock, a caesium standard based on a certain transition of the caesium-133 atom, was built by Louis Essen in 1955 at the National Physical Laboratory in the UK.^[77] Calibration of the caesium standard atomic clock was carried out by the use of the astronomical time scale ephemeris time (ET).^[78] As of 2013, the most stable atomic clocks are ytterbium clocks, which are stable to within less than two parts in 1 quintillion (2×10⁻¹⁸).^[71]

Operation

The invention of the mechanical clock in the 13th century initiated a change in timekeeping methods from continuous processes, such as the motion of the gnomon‘s shadow on a sundial or the flow of liquid in a water clock, to periodic oscillatory processes, such as the swing of a pendulum or the vibration of a quartz crystal,^[3][79] which had the potential for more accuracy. All modern clocks use oscillation.

Although the mechanisms they use vary, all oscillating clocks, mechanical, electric, and atomic, work similarly and can be divided into analogous parts.^[80][81][82] They consist of an object that repeats the same motion over and over again, an oscillator, with a precisely constant time interval between each repetition, or ‘beat’. Attached to the oscillator is a controller device, which sustains the oscillator’s motion by replacing the energy it loses to friction, and converts its oscillations into a series of pulses. The pulses are then counted by some type of counter, and the number of counts is converted into convenient units, usually seconds, minutes, hours, etc. Finally some kind of indicator displays the result in human readable form.

Power source

• In mechanical clocks, the power source is typically either a weight suspended from a cord or chain wrapped around a pulley, sprocket or drum; or a spiral spring called a mainspring. Mechanical clocks must be wound periodically, usually by turning a knob or key or by pulling on the free end of the chain, to store energy in the weight or spring to keep the clock running.
• In electric clocks, the power source is either a battery or the AC power line. In clocks that use AC power, a small backup battery is often included to keep the clock running if it is unplugged temporarily from the wall or during a power outage. Battery-powered analog wall clocks are available that operate over 15 years between battery changes.

Oscillator

The timekeeping element in every modern clock is a harmonic oscillator, a physical object (resonator) that vibrates or oscillates repetitively at a precisely constant frequency.^{[2][83][84][85]}

• In mechanical clocks, this is either a pendulum or a balance wheel.
• In some early electronic clocks and watches such as the Accutron, they use a tuning fork.
• In quartz clocks and watches, it is a quartz crystal.
• In atomic clocks, it is the vibration of electrons in atoms as they emit microwaves.
• In early mechanical clocks before 1657, it was a crude balance wheel or foliot which was not a harmonic oscillator because it lacked a balance spring. As a result, they were very inaccurate, with errors of perhaps an hour a day.^[86]

The advantage of a harmonic oscillator over other forms of oscillator is that it employs resonance to vibrate at a precise natural resonant frequency or “beat” dependent only on its physical characteristics, and resists vibrating at other rates. The possible precision achievable by a harmonic oscillator is measured by a parameter called its Q,^[87][88] or quality factor, which increases (other things being equal) with its resonant frequency.^[89] This is why there has been a long-term trend toward higher frequency oscillators in clocks. Balance wheels and pendulums always include a means of adjusting the rate of the timepiece. Quartz timepieces sometimes include a rate screw that adjusts a capacitor for that purpose. Atomic clocks are primary standards, and their rate cannot be adjusted.

Synchronized or slave clocks

Some clocks rely for their accuracy on an external oscillator; that is, they are automatically synchronized to a more accurate clock:

• Slave clocks, used in large institutions and schools from the 1860s to the 1970s, kept time with a pendulum, but were wired to a master clock in the building, and periodically received a signal to synchronize them with the master, often on the hour.^[90] Later versions without pendulums were triggered by a pulse from the master clock and certain sequences used to force rapid synchronization following a power failure.

• Synchronous electric clocks do not have an internal oscillator, but count cycles of the 50 or 60 Hz oscillation of the AC power line, which is synchronized by the utility to a precision oscillator. The counting may be done electronically, usually in clocks with digital displays, or, in analog clocks, the AC may drive a synchronous motor which rotates an exact fraction of a revolution for every cycle of the line voltage, and drives the gear train. Although changes in the grid line frequency due to load variations may cause the clock to temporarily gain or lose several seconds during the course of a day, the total number of cycles per 24 hours is maintained extremely accurately by the utility company, so that the clock keeps time accurately over long periods.
• Computer real-time clocks keep time with a quartz crystal, but can be periodically (usually weekly) synchronized over the Internet to atomic clocks (UTC), using the Network Time Protocol (NTP).
• Radio clocks keep time with a quartz crystal, but are periodically synchronized to time signals transmitted from dedicated standard time radio stations or satellite navigation signals, which are set by atomic clocks.

Controller

This has the dual function of keeping the oscillator running by giving it ‘pushes’ to replace the energy lost to friction, and converting its vibrations into a series of pulses that serve to measure the time.

• In mechanical clocks, this is the escapement, which gives precise pushes to the swinging pendulum or balance wheel, and releases one gear tooth of the escape wheel at each swing, allowing all the clock’s wheels to move forward a fixed amount with each swing.
• In electronic clocks this is an electronic oscillator circuit that gives the vibrating quartz crystal or tuning fork tiny ‘pushes’, and generates a series of electrical pulses, one for each vibration of the crystal, which is called the clock signal.
• In atomic clocks the controller is an evacuated microwave cavity attached to a microwave oscillator controlled by a microprocessor. A thin gas of caesium atoms is released into the cavity where they are exposed to microwaves. A laser measures how many atoms have absorbed the microwaves, and an electronic feedback control system called a phase-locked loop tunes the microwave oscillator until it is at the frequency that causes the atoms to vibrate and absorb the microwaves. Then the microwave signal is divided by digital counters to become the clock signal.^[91]

In mechanical clocks, the low Q of the balance wheel or pendulum oscillator made them very sensitive to the disturbing effect of the impulses of the escapement, so the escapement had a great effect on the accuracy of the clock, and many escapement designs were tried. The higher Q of resonators in electronic clocks makes them relatively insensitive to the disturbing effects of the drive power, so the driving oscillator circuit is a much less critical component.^[2]

Counter chain

This counts the pulses and adds them up to get traditional time units of seconds, minutes, hours, etc. It usually has a provision for setting the clock by manually entering the correct time into the counter.

• In mechanical clocks this is done mechanically by a gear train, known as the wheel train. The gear train scales the rotation speed to give a shaft rotating once per hour to which the minute hand of the clock is attached, a shaft rotating once per 12 hours to which the hour hand of the clock is attached, and in some clocks a shaft rotating once per minute, to which the second hand is attached. The gear train also has a second function; to transmit mechanical power from the power source to run the oscillator. There is a friction coupling called the ‘cannon pinion’ between the gears driving the hands and the rest of the clock, allowing the hands to be turned to set the time.^[92]
• In digital clocks a series of integrated circuit counters or dividers add the pulses up digitally, using binary logic. Often pushbuttons on the case allow the hour and minute counters to be incremented and decremented to set the time.

Indicator

Duration: 36 seconds.0:36A cuckoo clock with mechanical automaton and sound producer striking on the eighth hour on the analog dial

This displays the count of seconds, minutes, hours, etc. in a human readable form.

• The earliest mechanical clocks in the 13th century did not have a visual indicator and signalled the time audibly by striking bells. Many clocks to this day are striking clocks which strike the hour.
• Analog clocks display time with an analog clock face, which consists of a dial with the numbers 1 through 12 or 24, the hours in the day, around the outside. The hours are indicated with an hour hand, which makes one or two revolutions in a day, while the minutes are indicated by a minute hand, which makes one revolution per hour. In mechanical clocks a gear train drives the hands; in electronic clocks the circuit produces pulses every second which drive a stepper motor and gear train, which move the hands.
• Digital clocks display the time in periodically changing digits on a digital display. A common misconception is that a digital clock is more accurate than an analog wall clock, but the indicator type is separate and apart from the accuracy of the timing source.
• Talking clocks and the speaking clock services provided by telephone companies speak the time audibly, using either recorded or digitally synthesized voices.

Types

Clocks can be classified by the type of time display, as well as by the method of timekeeping.

Time display methods

Analog

See also: Clock face

Analog clocks usually use a clock face which indicates time using rotating pointers called “hands” on a fixed numbered dial or dials. The standard clock face, known universally throughout the world, has a short “hour hand” which indicates the hour on a circular dial of 12 hours, making two revolutions per day, and a longer “minute hand” which indicates the minutes in the current hour on the same dial, which is also divided into 60 minutes. It may also have a “second hand” which indicates the seconds in the current minute. The only other widely used clock face today is the 24 hour analog dial, because of the use of 24 hour time in military organizations and timetables. Before the modern clock face was standardized during the Industrial Revolution, many other face designs were used throughout the years, including dials divided into 6, 8, 10, and 24 hours. During the French Revolution the French government tried to introduce a 10-hour clock, as part of their decimal-based metric system of measurement, but it did not achieve widespread use. An Italian 6 hour clock was developed in the 18th century, presumably to save power (a clock or watch striking 24 times uses more power).

Another type of analog clock is the sundial, which tracks the sun continuously, registering the time by the shadow position of its gnomon. Because the sun does not adjust to daylight saving time, users must add an hour during that time. Corrections must also be made for the equation of time, and for the difference between the longitudes of the sundial and of the central meridian of the time zone that is being used (i.e. 15 degrees east of the prime meridian for each hour that the time zone is ahead of GMT). Sundials use some or part of the 24 hour analog dial. There also exist clocks which use a digital display despite having an analog mechanism—these are commonly referred to as flip clocks. Alternative systems have been proposed. For example, the “Twelv” clock indicates the current hour using one of twelve colors, and indicates the minute by showing a proportion of a circular disk, similar to a moon phase.^[93]

Digital

Main article: Digital clock

• Examples of digital clocks

Digital clocks display a numeric representation of time. Two numeric display formats are commonly used on digital clocks:

• the 24-hour notation with hours ranging 00–23;
• the 12-hour notation with AM/PM indicator, with hours indicated as 12AM, followed by 1AM–11AM, followed by 12PM, followed by 1PM–11PM (a notation mostly used in domestic environments).

Most digital clocks use electronic mechanisms and LCD, LED, or VFD displays; many other display technologies are used as well (cathode-ray tubes, nixie tubes, etc.). After a reset, battery change or power failure, these clocks without a backup battery or capacitor either start counting from 12:00, or stay at 12:00, often with blinking digits indicating that the time needs to be set. Some newer clocks will reset themselves based on radio or Internet time servers that are tuned to national atomic clocks. Since the introduction of digital clocks in the 1960s, there has been a notable decline in the use of analog clocks.^[94]

Some clocks, called ‘flip clocks‘, have digital displays that work mechanically. The digits are painted on sheets of material which are mounted like the pages of a book. Once a minute, a page is turned over to reveal the next digit. These displays are usually easier to read in brightly lit conditions than LCDs or LEDs. Also, they do not go back to 12:00 after a power interruption. Flip clocks generally do not have electronic mechanisms. Usually, they are driven by AC–synchronous motors.

Hybrid (analog-digital)

Clocks with analog quadrants, with a digital component, usually minutes and hours displayed analogously and seconds displayed in digital mode.

Auditory

Main article: Talking clock

For convenience, distance, telephony or blindness, auditory clocks present the time as sounds. The sound is either spoken natural language, (e.g. “The time is twelve thirty-five”), or as auditory codes (e.g. number of sequential bell rings on the hour represents the number of the hour like the bell, Big Ben). Most telecommunication companies also provide a speaking clock service as well.

Word

Word clocks are clocks that display the time visually using sentences. E.g.: “It’s about three o’clock.” These clocks can be implemented in hardware or software.

Projection

Main article: Projection clock

Some clocks, usually digital ones, include an optical projector that shines a magnified image of the time display onto a screen or onto a surface such as an indoor ceiling or wall. The digits are large enough to be easily read, without using glasses, by persons with moderately imperfect vision, so the clocks are convenient for use in their bedrooms. Usually, the timekeeping circuitry has a battery as a backup source for an uninterrupted power supply to keep the clock on time, while the projection light only works when the unit is connected to an A.C. supply. Completely battery-powered portable versions resembling flashlights are also available.

Tactile

Auditory and projection clocks can be used by people who are blind or have limited vision. There are also clocks for the blind that have displays that can be read by using the sense of touch. Some of these are similar to normal analog displays, but are constructed so the hands can be felt without damaging them. Another type is essentially digital, and uses devices that use a code such as Braille to show the digits so that they can be felt with the fingertips.

Multi-display

Some clocks have several displays driven by a single mechanism, and some others have several completely separate mechanisms in a single case. Clocks in public places often have several faces visible from different directions, so that the clock can be read from anywhere in the vicinity; all the faces show the same time. Other clocks show the current time in several time-zones. Watches that are intended to be carried by travellers often have two displays, one for the local time and the other for the time at home, which is useful for making pre-arranged phone calls. Some equation clocks have two displays, one showing mean time and the other solar time, as would be shown by a sundial. Some clocks have both analog and digital displays. Clocks with Braille displays usually also have conventional digits so they can be read by sighted people.

Purposes

Clocks are in homes, offices and many other places; smaller ones (watches) are carried on the wrist or in a pocket; larger ones are in public places, e.g. a railway station or church. A small clock is often shown in a corner of computer displays, mobile phones and many MP3 players.

The primary purpose of a clock is to display the time. Clocks may also have the facility to make a loud alert signal at a specified time, typically to waken a sleeper at a preset time; they are referred to as alarm clocks. The alarm may start at a low volume and become louder, or have the facility to be switched off for a few minutes then resume. Alarm clocks with visible indicators are sometimes used to indicate to children too young to read the time that the time for sleep has finished; they are sometimes called training clocks.

A clock mechanism may be used to control a device according to time, e.g. a central heating system, a VCR, or a time bomb (see: digital counter). Such mechanisms are usually called timers. Clock mechanisms are also used to drive devices such as solar trackers and astronomical telescopes, which have to turn at accurately controlled speeds to counteract the rotation of the Earth.

Most digital computers depend on an internal signal at constant frequency to synchronize processing; this is referred to as a clock signal. (A few research projects are developing CPUs based on asynchronous circuits.) Some equipment, including computers, also maintains time and date for use as required; this is referred to as time-of-day clock, and is distinct from the system clock signal, although possibly based on counting its cycles.

Time standards

Main articles: Time standard and Atomic clock

For some scientific work timing of the utmost accuracy is essential. It is also necessary to have a standard of the maximum accuracy against which working clocks can be calibrated. An ideal clock would give the time to unlimited accuracy, but this is not realisable. Many physical processes, in particular including some transitions between atomic energy levels, occur at exceedingly stable frequency; counting cycles of such a process can give a very accurate and consistent time—clocks which work this way are usually called atomic clocks. Such clocks are typically large, very expensive, require a controlled environment, and are far more accurate than required for most purposes; they are typically used in a standards laboratory.

Navigation

Until advances in the late twentieth century, navigation depended on the ability to measure latitude and longitude. Latitude can be determined through celestial navigation; the measurement of longitude requires accurate knowledge of time. This need was a major motivation for the development of accurate mechanical clocks. John Harrison created the first highly accurate marine chronometer in the mid-18th century. The Noon gun in Cape Town still fires an accurate signal to allow ships to check their chronometers. Many buildings near major ports used to have (some still do) a large ball mounted on a tower or mast arranged to drop at a pre-determined time, for the same purpose. While satellite navigation systems such as GPS require unprecedentedly accurate knowledge of time, this is supplied by equipment on the satellites; vehicles no longer need timekeeping equipment.

Sports and games

Clocks can be used to measure varying periods of time in games and sports. Stopwatches can be used to time the performance of track athletes. Chess clocks are used to limit the board game players’ time to make a move. In various sports, game clocks measure the duration the game or subdivisions of the game,^[95][96] while other clocks may be used for tracking different durations; these include play clocks, shot clocks, and pitch clocks.

Culture

Folklore and superstition

In the United Kingdom, clocks are associated with various beliefs, many involving death or bad luck. In legends, clocks have reportedly stopped of their own accord upon a nearby person’s death, especially those of monarchs. The clock in the House of Lords supposedly stopped at “nearly” the hour of George III‘s death in 1820, the one at Balmoral Castle stopped during the hour of Queen Victoria‘s death, and similar legends are related about clocks associated with William IV and Elizabeth I.^[97] Many superstitions exist about clocks. One stopping before a person has died may foretell coming death.^[98] Similarly, if a clock strikes during a church hymn or a marriage ceremony, death or calamity is prefigured for the parishioners or a spouse, respectively.^[99] Death or ill events are foreshadowed if a clock strikes the wrong time. It may also be unlucky to have a clock face a fire or to speak while a clock is striking.^[100]

In Chinese culture, giving a clock (traditional Chinese: 送鐘; simplified Chinese: 送钟; pinyin: sòng zhōng) is often taboo, especially to the elderly, as it is a homophone of the act of attending another’s funeral (traditional Chinese: 送終; simplified Chinese: 送终; pinyin: sòngzhōng).^{[101][102][103]}

Specific types

See also: List of clocks

By mechanism	By function	By style
Astronomical clockAtomic clockCandle clockCongreve clockConical pendulum clockDigital clockElectric clockFlip clockFlying pendulum clockHourglassIncense clockLamport clockMechanical watchObservatory chronometerOil-lamp clockPendulum clockProjection clockPulsar clockQuantum clockQuartz clockRadio clockRolling ball clockSpring drive watchSteam clockSundialTorsion pendulum clockAtmos clockWater clock	10-hour clockAlarm clockBinary clockBraille watchChronometer watchCuckoo clockDuodecimal clockEquation clockGame clockJapanese clockMaster clockMusical clockRailroad chronometerSlave clockSpeaking clockStopwatchStriking clockTalking clockTide clockTime ballTime clockWorld clock	American clockAutomaton clockBalloon clockBanjo clockBracket clockCarriage clockCartel clockCat clockChariot clockClock towerCuckoo clockDoll’s head clockFloral clockFrench Empire mantel clockGrandfather clockMora clockLantern clockCorpus ClockLighthouse clockMantel clockSkeleton clockTurret clockWatch

A watch is a timepiece carried or worn by a person. It is designed to keep a consistent movement despite the motions caused by the person’s activities. A wristwatch is designed to be worn around the wrist, attached by a watch strap or other type of bracelet, including metal bands or leather straps. A pocket watch is carried in a pocket, often attached to a chain. A stopwatch is a watch that measures intervals of time.

During most of their history, beginning in the 16th century, watches were mechanical devices, driven by clockwork, powered by winding a mainspring, and keeping time with an oscillating balance wheel. These are called mechanical watches.^[1][2] In the 1960s the electronic quartz watch was invented, powered by a battery and keeping time with a vibrating quartz crystal. By the 1980s it took over most of the watch market, in what was called the quartz revolution (or the quartz crisis in Switzerland, whose renowned watch industry it decimated).^[3][4] In the 2010s, smartwatches emerged, small wrist-worn computers with touchscreens, with functions that go far beyond timekeeping.

Modern watches often display the day, date, month, and year. Mechanical watches may have extra features (“complications“) such as moon-phase displays and different types of tourbillon. Quartz watches often include timers, chronographs, and alarm functions. Smartwatches and more complicated electronic watches may even incorporate calculators, GPS^[5] and Bluetooth technology or have heart-rate monitoring capabilities, and some use radio clock technology to regularly correct the time.

Most watches used mainly for timekeeping have quartz movements. But expensive collectible watches, valued more for their elaborate craftsmanship, aesthetic appeal, and glamorous design than for timekeeping, often have traditional mechanical movements, despite being less accurate and more expensive than their electronic counterparts.^[3][4][6] As of 2019, the most expensive watch ever sold at auction was the Patek Philippe Grandmaster Chime for US$31.2 million.^[7]

History

[edit]

Main article: History of watches

See also: History of timekeeping devices

Origins

[edit]

Watches evolved from portable spring-driven clocks, which first appeared in 15th-century Europe.^{[citation needed]} The first timepieces to be worn, made in the 16th century beginning in the German cities of Nuremberg and Augsburg, were transitional in size between clocks and watches.^[8] Nuremberg clockmaker Peter Henlein (or Henle or Hele) (1485–1542) is often credited as the inventor of the watch.^[9][10] However, other German clockmakers were creating miniature timepieces during this period, and there is no evidence Henlein was the first.^[10][11]

Watches were not widely worn in pockets until the 17th century. One account suggests that the word “watch” came from the Old English word woecce – which meant “watchman” – because town watchmen used the technology to keep track of their shifts at work.^[12] Another says that the term came from 17th-century sailors, who used the new mechanisms to time the length of their shipboard watches (duty shifts).^[13]

Development

[edit]

A rise in accuracy occurred in 1657 with the addition of the balance spring to the balance wheel, an invention disputed both at the time and ever since between Robert Hooke and Christiaan Huygens. This innovation significantly improved the accuracy of watches, reducing errors from several hours a day^[14] to approximately 10 minutes per day,^[15] which led to the introduction of the minute hand on watch faces in Britian around 1680 and in France by 1700.^[16]

The increased accuracy of the balance wheel focused attention on errors caused by other parts of the movement, igniting a two-century wave of watchmaking innovation. The first thing to be improved was the escapement. The verge escapement was replaced in quality watches by the cylinder escapement, invented by Thomas Tompion in 1695 and further developed by George Graham in the 1720s. Improvements in manufacturing – such as the tooth-cutting machine devised by Robert Hooke – allowed some increase in the volume of watch production, although finishing and assembling was still done by hand until well into the 19th century.

A major cause of error in balance-wheel timepieces, caused by changes in elasticity of the balance spring from temperature changes, was solved by the bimetallic temperature-compensated balance wheel invented in 1765 by Pierre Le Roy and improved by Thomas Earnshaw (1749–1829). The lever escapement, the single most important technological breakthrough, though invented by Thomas Mudge in 1754^[17] and improved by Josiah Emery in 1785,^[18] only gradually came into use from about 1800 onwards, chiefly in Britain.^[19]

The British predominated in watch manufacture for much of the 17th and 18th centuries, but maintained a system of production that was geared towards high-quality products for the élite.^[20] The British Watch Company modernized clock manufacture with mass-production techniques and the application of duplicating tools and machinery in 1843. In the United States, Aaron Lufkin Dennison started a factory in 1851 in Massachusetts that used interchangeable parts, and by 1861 a successful enterprise operated, incorporated as the Waltham Watch Company.^[21]

Wristwatches

[edit]

The concept of the wristwatch goes back to the production of the very earliest watches in the 16th century. In 1571, Elizabeth I of England received a wristwatch, described as an “armed watch”, from Robert Dudley. The oldest surviving wristwatch (then described as a “bracelet watch”) is one made in 1806, and given to Joséphine de Beauharnais.^[22] From the beginning, wristwatches were almost exclusively worn by women – men used pocket watches up until the early 20th century.^[23] In 1810, the watch-maker Abraham-Louis Breguet made a wristwatch for the Queen of Naples.^[24] The first Swiss wristwatch was made in the year 1868 by the Swiss watch-maker Patek Philippe for Countess Koscowicz of Hungary.^[25][26]

Wristwatches were first worn by military men towards the end of the 19th century, having increasingly recognized the importance of synchronizing maneuvers during war without potentially revealing plans to the enemy through signaling. The Garstin Company of London patented a “Watch Wristlet” design in 1893, but probably produced similar designs from the 1880s. Officers in the British Army began using wristwatches during colonial military campaigns in the 1880s, such as during the Anglo-Burma War of 1885.^[23] During the First Boer War of 1880–1881, the importance of coordinating troop movements and synchronizing attacks against highly mobile Boer insurgents became paramount, and the use of wristwatches subsequently became widespread among the officer class. The company Mappin & Webb began production of their successful “campaign watch” for soldiers during the campaign in the Sudan in 1898 and accelerated production for the Second Boer War of 1899–1902 a few years later.^[23] In continental Europe, Girard-Perregaux and other Swiss watchmakers began supplying German naval officers with wristwatches in about 1880.^[22]

Early models were essentially standard pocket-watches fitted to a leather strap, but by the early 20th century, manufacturers began producing purpose-built wristwatches. The Swiss company Dimier Frères & Cie patented a wristwatch design with the now standard wire lugs in 1903. In 1904, Louis Cartier produced a wristwatch to allow his friend Alberto Santos-Dumont to check flight performance in his airship while keeping both hands on the controls as this proved difficult with a pocket watch.^[27][28][29] Cartier still markets a line of Santos-Dumont watches and sunglasses.^[30]

In 1905, Hans Wilsdorf moved to London, and set up his own business, Wilsdorf & Davis, with his brother-in-law Alfred Davis, providing quality timepieces at affordable prices; the company became Rolex in 1915.^[31] Wilsdorf was an early convert to the wristwatch, and contracted the Swiss firm Aegler to produce a line of wristwatches.^[32]

The impact of the First World War of 1914–1918 dramatically shifted public perceptions on the propriety of the man’s wristwatch and opened up a mass market in the postwar era.^[33] The creeping barrage artillery tactic, developed during the war, required precise synchronization between the artillery gunners and the infantry advancing behind the barrage. Service watches produced during the war were specially designed for the rigors of trench warfare, with luminous dials and unbreakable glass. The UK War Office began issuing wristwatches to combatants from 1917.^[34] By the end of the war, almost all enlisted men wore a wristwatch (or wristlet), and after they were demobilized, the fashion soon caught on: the British Horological Journal wrote in 1917, that “the wristlet watch was little used by the sterner sex before the war, but now is seen on the wrist of nearly every man in uniform and of many men in civilian attire.”^[35] By 1930, the wristwatch vastly exceeded the pocket watch in market share by a decisive ratio of 50:1.

Automatic watches

[edit]

John Harwood invented the first successful self-winding system in 1923. In anticipation of Harwood’s patent for self-winding mechanisms expiry in 1930, Glycine founder Eugène Meylan started development on a self-winding system as a separate module that could be used with almost any 8.75 ligne (19.74 millimeter) watch movement. Glycine incorporated this module into its watches in October 1930, and began mass-producing automatic watches.^[36]

Electric watches

[edit]

The Elgin National Watch Company and the Hamilton Watch Company pioneered the first electric watch.^[37] The first electric movements used a battery as a power source to oscillate the balance wheel. During the 1950s, Elgin developed the model 725, while Hamilton released two models: the first, the Hamilton 500, released on 3 January 1957, was produced into 1959. This model had problems with the contact wires misaligning, and the watches returned to Hamilton for alignment. The Hamilton 505, an improvement on the 500, proved more reliable: the contact wires were removed and a non-adjustable contact on the balance assembly delivered the power to the balance wheel. Similar designs from many other watch companies followed. Another type of electric watch was developed by the Bulova company that used a tuning-fork resonator instead of a traditional balance wheel to increase timekeeping accuracy, moving from a typical 2.5–4 Hz with a traditional balance wheel to 360 Hz with the tuning-fork design.

Quartz watches

[edit]

The commercial introduction of the quartz watch in 1969 in the form of the Seiko Astron 35SQ, and in 1970 in the form of the Omega Beta 21 was a revolutionary improvement in watch technology. In place of a balance wheel, which oscillated at perhaps 5 or 6 beats per second, these devices used a quartz-crystal resonator, which vibrated at 8,192 Hz, driven by a battery-powered oscillator circuit.^[38] Most quartz-watch oscillators now operate at 32,768 Hz, though quartz movements have been designed with frequencies as high as 262 kHz. Since the 1980s, more quartz watches than mechanical ones have been marketed.^[39]

Smart watches

[edit]

The Timex Datalink wristwatch was introduced in 1994.^[40][41][42] The early Timex Datalink Smartwatches realized a wireless data transfer mode to receive data from a PC. Since then, many companies have released their own iterations of a smartwatch, such as the Apple Watch, Samsung Galaxy Watch, and Huawei Watch.

Hybrid watches

[edit]

A hybrid smartwatch is a fusion between a regular mechanical watch and a smartwatch.^[43]

Parts

[edit]

The movement and case are the basic parts of a watch. A watch band or bracelet is added to form a wristwatch; alternatively, a watch chain is added to form a pocket watch.^[44]

The case is the outer covering of the watch.

The case back is the back portion of the watch’s case. Accessing the movement (such as during battery replacement) depends on the type of case back, which are generally categorized into four types:

• Snap-off case backs (press-on case backs): the watch back pulls straight off and presses straight on.
• Screw-down case backs (threaded case backs): the entire watch back must be rotated to unscrew from the case. Often it has 6 notches on the external part of the case back.
• Screw back cases: tiny screws hold the case back to the case
• Unibody: the only way into the case involves prying the crystal off the front of the watch.

The crystal, also called the window or watch glass, is the transparent part of the case that allows viewing the hands and the dial of the movement. Modern wristwatches almost always use one of 4 materials:^[45]

• Acrylic glass (plexiglass, hesalite glass): the most impact-resistant (“unbreakable”^[46][47]), and therefore used in dive watches and most military watches. Acrylic glass is the lowest cost of these materials, so it is used in practically all low-cost watches.
• Mineral crystal: a tempered glass.
• Sapphire-coated mineral crystal
• Synthetic sapphire crystal: the most scratch-resistant; it is difficult to cut and polish, causing watch crystals made of sapphire to be the most expensive.

The bezel is the ring holding the crystal in place.^[48]

The lugs are small metal projections at both ends of the wristwatch case where the watch band attaches to the watch case.^[48] The case and the lugs are often machined from one solid piece of stainless steel.^[49]

Movement

[edit]

The movement of a watch is the mechanism that measures the passage of time and displays the current time (and possibly other information including date, month, and day).^[51] Movements may be entirely mechanical, entirely electronic (potentially with no moving parts), or they might be a blend of both. Most watches intended mainly for timekeeping today have electronic movements, with mechanical hands on the watch face indicating the time.

Mechanical

[edit]

Main article: Mechanical watch

Compared to electronic movements, mechanical watches are less accurate, often with errors of seconds per day; are sensitive to position, temperature,^[52] and magnetism;^[53] are costly to produce; require regular maintenance and adjustments; and are more prone to failures. Nevertheless, mechanical watches attract interest from consumers, particularly among watch collectors. Skeleton watches are designed to display the mechanism for aesthetic purposes.

A mechanical movement uses an escapement mechanism to control and limit the unwinding and winding parts of a spring, converting what would otherwise be a simple unwinding into a controlled and periodic energy release. The movement also uses a balance wheel, together with the balance spring (also known as a hairspring), to control the gear system’s motion in a manner analogous to the pendulum of a pendulum clock. The tourbillon, an optional part for mechanical movements, is a rotating frame for the escapement, used to cancel out or reduce gravitational bias. Due to the complexity of designing a tourbillon, they are expensive, and typically found in prestigious watches.

The pin-lever escapement (called the Roskopf movement after its inventor, Georges Frederic Roskopf), which is a cheaper version of the fully levered movement, was manufactured in huge quantities by many Swiss manufacturers, as well as by Timex, until it was replaced by quartz movements.^[54][55][56]

Introduced by Bulova in 1960, tuning-fork watches use a type of electromechanical movement with a precise frequency (most often 360 Hz) to drive a mechanical watch. The task of converting electronically pulsed fork vibration into rotary movements is done via two tiny jeweled fingers, called pawls. Tuning-fork watches were rendered obsolete when electronic quartz watches were developed.

Traditional mechanical watch movements use a spiral spring called a mainspring as its power source that must be rewound periodically by the user by turning the watch crown. Antique pocket watches were wound by inserting a key into the back of the watch and turning it. While most modern watches are designed to run 40 hours on a winding, requiring winding daily, some run for several days; a few have 192-hour mainsprings, requiring once-weekly winding.

Automatic watches

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Main article: Automatic watch

A self-winding or automatic watch is one that rewinds the mainspring of a mechanical movement by the natural motions of the wearer’s body. The first self-winding mechanism was invented for pocket watches in 1770 by Abraham-Louis Perrelet,^[57] but the first “self-winding“, or “automatic”, wristwatch was the invention of a British watch repairer named John Harwood in 1923. This type of watch winds itself without requiring any special action by the wearer. It uses an eccentric weight, called a winding rotor, which rotates with the movement of the wearer’s wrist. The back-and-forth motion of the winding rotor couples to a ratchet to wind the mainspring automatically. Self-winding watches usually can also be wound manually to keep them running when not worn or if the wearer’s wrist motions are inadequate to keep the watch wound.

In April 2013, the Swatch Group launched the sistem51 wristwatch. It has a mechanical movement consisting of only 51 parts,^[58] including 19 jewels and a novel self-winding mechanism with a transparent oscillating weight.^[59] Ten years after its introduction, it is still the only mechanical movement manufactured entirely on a fully automated assembly line, including adjustment of the balance wheel and the escapement for accuracy by laser.^[60] The low parts count and the fully automated assembly make it an inexpensive automatic Swiss watch.^[61]

Electronic

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See also: Electric watch and Quartz clock

Electronic movements, also known as quartz movements, have few or no moving parts, except a quartz crystal which is made to vibrate by the piezoelectric effect. A varying electric voltage is applied to the crystal, which responds by changing its shape so, in combination with some electronic components, it functions as an oscillator. It resonates at a specific highly stable frequency, which is used to accurately pace a timekeeping mechanism. Most quartz movements are primarily electronic but are geared to drive mechanical hands on the face of the watch to provide a traditional analog display of the time, a feature most consumers still prefer.^{[citation needed]}

In 1959 Seiko placed an order with Epson (a subsidiary company of Seiko and the ‘brain’ behind the quartz revolution) to start developing a quartz wristwatch. The project was codenamed 59A. By the 1964 Tokyo Summer Olympics, Seiko had a working prototype of a portable quartz watch which was used as the time measurements throughout the event.^{[citation needed]}

The first prototypes of an electronic quartz wristwatch (not just portable quartz watches as the Seiko timekeeping devices at the Tokyo Olympics in 1964) were made by the CEH research laboratory in Neuchâtel, Switzerland. From 1965 through 1967 pioneering development work was done on a miniaturized 8192 Hz quartz oscillator, a thermo-compensation module, and an in-house-made, dedicated integrated circuit (unlike the hybrid circuits used in the later Seiko Astron wristwatch). As a result, the BETA 1 prototype set new timekeeping performance records at the International Chronometric Competition held at the Observatory of Neuchâtel in 1967.^[62] In 1970, 18 manufacturers exhibited production versions of the beta 21 wristwatch, including the Omega Electroquartz as well as Patek Philippe, Rolex Oysterquartz and Piaget.

The first quartz watch to enter production was the Seiko 35 SQ Astron, which hit the shelves on 25 December 1969, swiftly followed by the Swiss Beta 21, and then a year later the prototype of one of the world’s most accurate wristwatches to date: the Omega Marine Chronometer. Since the technology having been developed by contributions from Japanese, American and Swiss,^[63] nobody could patent the whole movement of the quartz wristwatch, thus allowing other manufacturers to participate in the rapid growth and development of the quartz watch market. This ended – in less than a decade – almost 100 years of dominance by the mechanical wristwatch legacy. Modern quartz movements are produced in very large quantities, and even the cheapest wristwatches typically have quartz movements. Whereas mechanical movements can typically be off by several seconds a day, an inexpensive quartz movement in a child’s wristwatch may still be accurate to within half a second per day – ten times more accurate than a mechanical movement.^[64]

After a consolidation of the mechanical watch industry in Switzerland during the 1970s, mass production of quartz wristwatches took off under the leadership of the Swatch Group of companies, a Swiss conglomerate with vertical control of the production of Swiss watches and related products. For quartz wristwatches, subsidiaries of Swatch manufacture watch batteries (Renata), oscillators (Oscilloquartz, now Micro Crystal AG) and integrated circuits (Ebauches Electronic SA, renamed EM Microelectronic-Marin). The launch of the new SWATCH brand in 1983 was marked by bold new styling, design, and marketing. Today, the Swatch Group maintains its position as the world’s largest watch company.

Seiko‘s efforts to combine the quartz and mechanical movements bore fruit after 20 years of research, leading to the introduction of the Seiko Spring Drive, first in a limited domestic market production in 1999 and to the world in September 2005. The Spring Drive keeps time within quartz standards without the use of a battery, using a traditional mechanical gear train powered by a spring, without the need for a balance wheel either.

In 2010, Miyota (Citizen Watch) of Japan introduced a newly developed movement that uses a 3-pronged quartz crystal that was exclusively produced for Bulova to be used in the Precisionist or Accutron II line, a new type of quartz watch with ultra-high frequency (262.144 kHz) which is claimed to be accurate to +/− 10 seconds a year and has a smooth sweeping second hand rather than one that jumps each second.^[65]

Radio time signal watches are a type of electronic quartz watch that synchronizes (time transfers) its time with an external time source such as in atomic clocks, time signals from GPS navigation satellites, the German DCF77 signal in Europe, WWVB in the US, and others. Movements of this type may, among others, synchronize the time of day and the date, the leap-year status and the state of daylight saving time (on or off). However, other than the radio receiver, these watches are normal quartz watches in all other aspects.

Electronic watches require electricity as a power source, and some mechanical movements and hybrid electronic-mechanical movements also require electricity. Usually, the electricity is provided by a replaceable battery. The first use of electrical power in watches was as a substitute for the mainspring, to remove the need for winding. The first electrically powered watch, the Hamilton Electric 500, was released in 1957 by the Hamilton Watch Company of Lancaster, Pennsylvania.

Watch batteries (strictly speaking cells, as a battery is composed of multiple cells) are specially designed for their purpose. They are very small and provide tiny amounts of power continuously for very long periods (several years or more). In most cases, replacing the battery requires a trip to a watch-repair shop or watch dealer; this is especially true for watches that are water-resistant, as special tools and procedures are required for the watch to remain water-resistant after battery replacement. Silver-oxide and lithium batteries are popular today; mercury batteries, formerly quite common, are no longer used, for environmental reasons. Cheap batteries may be alkaline, of the same size as silver-oxide cells but providing shorter life. Rechargeable batteries are used in some solar-powered watches.

Some electronic watches are powered by the movement of the wearer. For instance, Seiko’s kinetic-powered quartz watches use the motion of the wearer’s arm: turning a rotating weight which causes a tiny generator to supply power to charge a rechargeable battery that runs the watch. The concept is similar to that of self-winding spring movements, except that electrical power is generated instead of mechanical spring tension.

Solar powered watches are powered by light. A photovoltaic cell on the face (dial) of the watch converts light to electricity, which is used to charge a rechargeable battery or capacitor. The movement of the watch draws its power from the rechargeable battery or capacitor. As long as the watch is regularly exposed to fairly strong light (such as sunlight), it never needs a battery replacement. Some models need only a few minutes of sunlight to provide weeks of energy (as in the Citizen Eco-Drive). Some of the early solar watches of the 1970s had innovative and unique designs to accommodate the array of solar cells needed to power them (Synchronar, Nepro, Sicura, and some models by Cristalonic, Alba, Seiko, and Citizen). As the decades progressed and the efficiency of the solar cells increased while the power requirements of the movement and display decreased, solar watches began to be designed to look like other conventional watches.^[66]

A rarely used power source is the temperature difference between the wearer’s arm and the surrounding environment (as applied in the Citizen Eco-Drive Thermo).

Display

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Analog

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Traditionally, watches have displayed the time in analog form, with a numbered dial upon which are mounted at least a rotating hour hand and a longer, rotating minute hand. Many watches also incorporate a third hand that shows the current second of the current minute. In quartz watches this second hand typically snaps to the next marker every second. In mechanical watches, the second hand may appear to glide continuously, though in fact it merely moves in smaller steps, typically one-fifth to one-tenth of a second, corresponding to the beat (half period) of the balance wheel. With a duplex escapement, the hand advances every two beats (full period) of the balance wheel, typically ¹⁄₂-second; this happens every four beats (two periods, 1 second), with a double duplex escapement. A truly gliding second hand is achieved with the tri-synchro regulator of Spring Drive watches. All three hands are normally mechanical, physically rotating on the dial, although a few watches have been produced with “hands” simulated by a liquid-crystal display.

Analog display of the time is nearly universal in watches sold as jewelry or collectibles, and in these watches, the range of different styles of hands, numbers, and other aspects of the analog dial is very broad. In watches sold for timekeeping, analog display remains very popular, as many people find it easier to read than digital display; but in timekeeping watches the emphasis is on clarity and accurate reading of the time under all conditions (clearly marked digits, easily visible hands, large watch faces, etc.). They are specifically designed for the left wrist with the stem (the knob used for changing the time) on the right side of the watch; this makes it easy to change the time without removing the watch from the wrist. This is the case if one is right-handed and the watch is worn on the left wrist (as is traditionally done). If one is left-handed and wears the watch on the right wrist, one has to remove the watch from the wrist to reset the time or to wind the watch.

Analog watches, as well as clocks, are often marketed showing a display time of approximately 1:50 or 10:10. This creates a visually pleasing smile-like face on the upper half of the watch, in addition to enclosing the manufacturer’s name. Digital displays often show a time of 12:08, where the increase in the number of active segments or pixels gives a positive feeling.^[67][68]

Tactile

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Tissot, a Swiss luxury watchmaker, makes the Silen-T wristwatch with a touch-sensitive face that vibrates to help the user to tell time eyes-free. The bezel of the watch features raised bumps at each hour mark; after briefly touching the face of the watch, the wearer runs a finger around the bezel clockwise. When the finger reaches the bump indicating the hour, the watch vibrates continuously, and when the finger reaches the bump indicating the minute, the watch vibrates intermittently.^[69]

Eone Timepieces, a Washington D.C.–based company, launched its first tactile analog wristwatch, the “Bradley”, on 11 July 2013 on the Kickstarter website. The device is primarily designed for sight-impaired users, who can use the watch’s two ball bearings to determine the time, but it is also suitable for general use. The watch features raised marks at each hour and two moving, magnetically attached ball bearings. One ball bearing, on the edge of the watch, indicates the hour, while the other, on the face, indicates the minute.^[70][71]

Digital

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A digital display shows the time as a number, e.g., 12:08 instead of a short hand pointing towards the number 12 and a long hand 8/60 of the way around the dial. The digits are usually shown as a seven-segment display.

The first digital mechanical pocket watches appeared in the late 19th century. In the 1920s, the first digital mechanical wristwatches appeared.

The first digital electronic watch, a Pulsar LED prototype in 1970, was developed jointly by Hamilton Watch Company and Electro-Data, founded by George H. Thiess.^[72] John Bergey, the head of Hamilton’s Pulsar division, said that he was inspired to make a digital timepiece by the then-futuristic digital clock that Hamilton themselves made for the 1968 science fiction film 2001: A Space Odyssey. On 4 April 1972, the Pulsar was finally ready, made in an 18-carat gold case and sold for $2,100. It had a red light-emitting diode (LED) display.

Digital LED watches were very expensive and out of reach to the common consumer until 1975, when Texas Instruments started to mass-produce LED watches inside a plastic case. These watches, which first retailed for only $20,^[73] reduced to $10 in 1976, saw Pulsar lose $6 million and the Pulsar brand sold to Seiko.^[74]

An early LED watch that was rather problematic was The Black Watch made and sold by British company Sinclair Radionics in 1975. This was only sold for a few years, as production problems and returned (faulty) product forced the company to cease production.

Most watches with LED displays required that the user press a button to see the time displayed for a few seconds because LEDs used so much power that they could not be kept operating continuously. Usually, the LED display color would be red. Watches with LED displays were popular for a few years, but soon the LED displays were superseded by liquid crystal displays (LCDs), which used less battery power and were much more convenient in use, with the display always visible and eliminating the need to push a button before seeing the time. Only in darkness would a button needed to be pressed to illuminate the display with a tiny light bulb, later illuminating LEDs and electroluminescent backlights.^[75]

The first LCD watch with a six-digit LCD was the 1973 Seiko 06LC, although various forms of early LCD watches with a four-digit display were marketed as early as 1972 including the 1972 Gruen Teletime LCD Watch, and the Cox Electronic Systems Quarza. The Quarza, introduced in 1972 had the first Field Effect LCD readable in direct sunlight and produced by the International Liquid Crystal Corporation of Cleveland, Ohio.^[76] In Switzerland, Ebauches Electronic SA presented a prototype eight-digit LCD wristwatch showing time and date at the MUBA Fair, Basel, in March 1973, using a twisted nematic LCD manufactured by Brown, Boveri & Cie, Switzerland, which became the supplier of LCDs to Casio for the CASIOTRON watch in 1974.^[77]

A problem with LCDs is that they use polarized light. If, for example, the user is wearing polarized sunglasses, the watch may be difficult to read because the plane of polarization of the display is roughly perpendicular to that of the glasses.^[78][79] If the light that illuminates the display is polarized, for example if it comes from a blue sky, the display may be difficult or impossible to read.^[80]

From the 1980s onward, digital watch technology vastly improved. In 1982, Seiko produced the Seiko TV Watch^[81] that had a television screen built-in,^[82] and Casio produced a digital watch with a thermometer (the TS-1000) as well as another that could translate 1,500 Japanese words into English. In 1985, Casio produced the CFX-400 scientific calculator watch. In 1987, Casio produced a watch that could dial telephone numbers (the DBA-800) and Citizen introduced one that would react to voice. In 1995, Timex released a watch that allowed the wearer to download and store data from a computer to their wrist. Some watches, such as the Timex Datalink USB, feature dot matrix displays. Since their apex during the late 1980s to mid-1990s high technology fad, digital watches have mostly become simpler, less expensive timepieces with little variety between models.

• Cortébert digital mechanical pocket watch (1890s)
• Cortébert digital mechanical wristwatch (1920s)
• A silver Pulsar LED watch from 1976
• A Timex digital watch with an always-on display of the time and date
• A digital LCD watch with electroluminescent backlight
• Samsung Galaxy Watch series smartwatches with OLED displays

Illuminated

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This subsection needs additional citations for verification. Please help improve this article by adding citations to reliable sources in this subsection. Unsourced material may be challenged and removed. Find sources: “Watch” – news · newspapers · books · scholar · JSTOR (June 2014) (Learn how and when to remove this message)

Many watches have displays that are illuminated, so they can be used in darkness. Various methods have been used to achieve this.

Mechanical watches often have luminous paint on their hands and hour marks. In the mid-20th century, radioactive material was often incorporated in the paint, so it would continue to glow without any exposure to light. Radium was often used but produced small amounts of radiation outside the watch that might have been hazardous.^[83] Tritium was used as a replacement, since the radiation it produces has such low energy that it cannot penetrate a watch glass. However, tritium is expensive – it has to be made in a nuclear reactor – and it has a half-life of only about 12 years so the paint remains luminous for only a few years. Nowadays, tritium is used in specialized watches, e.g., for military purposes (see Tritium illumination). For other purposes, luminous paint is sometimes used on analog displays, but no radioactive material is contained in it. This means that the display glows soon after being exposed to light and quickly fades.

Watches that incorporate batteries often have electric illumination in their displays. However, lights consume far more power than electronic watch movements. To conserve the battery, the light is activated only when the user presses a button. Usually, the light remains lit for a few seconds after the button is released, which allows the user to move the hand out of the way.

In some early digital watches, LED displays were used, which could be read as easily in darkness as in daylight. The user had to press a button to light up the LEDs, which meant that the watch could not be read without the button being pressed, even in full daylight.

In some types of watches, small incandescent lamps or LEDs illuminate the display, which is not intrinsically luminous. These tend to produce very non-uniform illumination.

Other watches use electroluminescent material to produce uniform illumination of the background of the display, against which the hands or digits can be seen.

Speech synthesis

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Talking watches are available, intended for the blind or visually impaired. They speak the time out loud at the press of a button. This has the disadvantage of disturbing others nearby or at least alerting the non-deaf that the wearer is checking the time. Tactile watches are preferred to avoid this awkwardness, but talking watches are preferred for those who are not confident in their ability to read a tactile watch reliably.

Handedness

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Wristwatches with analog displays generally have a small knob, called the crown, that can be used to adjust the time and, in mechanical watches, wind the spring. Almost always, the crown is located on the right-hand side of the watch so it can be worn of the left wrist for a right-handed individual. This makes it inconvenient to use if the watch is being worn on the right wrist. Some manufacturers offer “left-hand drive”, aka “destro”, configured watches which move the crown to the left side^[84] making wearing the watch easier for left-handed individuals.

A rarer configuration is the bullhead watch. Bullhead watches are generally, but not exclusively, chronographs. The configuration moves the crown and chronograph pushers to the top of the watch. Bullheads are commonly wristwatch chronographs that are intended to be used as stopwatches off the wrist. Examples are the Citizen Bullhead Change Timer^[85] and the Omega Seamaster Bullhead.^[86]

Digital watches generally have push-buttons that can be used to make adjustments. These are usually equally easy to use on either wrist.

Functions

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Customarily, watches provide the time of day, giving at least the hour and minute, and often the second. Many also provide the current date, and some (called “complete calendar” or “triple date” watches) display the day of the week and the month as well. However, many watches also provide a great deal of information beyond the basics of time and date. Some watches include alarms. Other elaborate and more expensive watches, both pocket and wrist models, also incorporate striking mechanisms or repeater functions, so that the wearer could learn the time by the sound emanating from the watch. This announcement or striking feature is an essential characteristic of true clocks and distinguishes such watches from ordinary timepieces. This feature is available on most digital watches.

A complicated watch has one or more functions beyond the basic function of displaying the time and the date; such a functionality is called a complication. Two popular complications are the chronograph complication, which is the ability of the watch movement to function as a stopwatch, and the moonphase complication, which is a display of the lunar phase. Other more expensive complications include Tourbillon, Perpetual calendar, Minute repeater, and Equation of time. A truly complicated watch has many of these complications at once (see Calibre 89 from Patek Philippe for instance). Some watches aimed at Muslims can both indicate the direction of Mecca^[87] and have alarms that can be set for all daily prayer requirements.^[88] Among watch enthusiasts, complicated watches are especially collectible. Some watches include a second 12-hour or 24-hour display for UTC or GMT.

The similar-sounding terms chronograph and chronometer are often confused, although they mean altogether different things. A chronograph is a watch with an added duration timer, often a stopwatch complication (as explained above), while a chronometer watch is a timepiece that has met an industry-standard test for performance under pre-defined conditions: a chronometer is a high quality mechanical or a thermo-compensated movement that has been tested and certified to operate within a certain standard of accuracy by the COSC (Contrôle Officiel Suisse des Chronomètres). The concepts are different but not mutually exclusive; so a watch can be a chronograph, a chronometer, both, or neither.

Electronic sports watches, combining timekeeping with GPS and/or activity tracking, address the general fitness market and have the potential for commercial success (Garmin Forerunner, Garmin Vivofit, Epson,^[5] announced model of Swatch Touch series^[89]).

Braille watches have analog displays with raised bumps around the face to allow blind users to tell the time. Their digital equivalents use synthesised speech to speak the time on command.

Fashion

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Wristwatches and antique pocket watches are often appreciated as jewelry or as collectible works of art rather than just as timepieces.^[90] This has created several different markets for wristwatches, ranging from very inexpensive but accurate watches (intended for no other purpose than telling the correct time) to extremely expensive watches that serve mainly as personal adornment or as examples of high achievement in miniaturization and precision mechanical engineering.

Traditionally, dress watches appropriate for informal (business), semi-formal, and formal attire are gold, thin, simple, and plain, but increasingly rugged, complicated, or sports watches are considered by some to be acceptable for such attire. Some dress watches have a cabochon on the crown or faceted gemstones on the face, bezel, or bracelet. Some are made entirely of faceted sapphire (corundum).

Many fashions and department stores offer a variety of less-expensive, trendy, “costume” watches (usually for women), many of which are similar in quality to basic quartz timepieces but which feature bolder designs. In the 1980s, the Swiss Swatch company hired graphic designers to redesign a new annual collection of non-repairable watches.

Trade in counterfeit watches, which mimic expensive brand-name watches, constitutes an estimated US$1 billion market per year.^[91]

Space

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The zero-gravity environment and other extreme conditions encountered by astronauts in space require the use of specially tested watches.

The first-ever watch to be sent into space was a Russian “Pobeda” watch from the Petrodvorets Watch Factory. It was sent on a single orbit flight on the spaceship Korabl-Sputnik 4 on 9 March 1961. The watch had been attached without authorisation to the wrist of Chernuchka, a dog that successfully did exactly the same trip as Yuri Gagarin, with exactly the same rocket and equipment, just a month before Gagarin’s flight.^[92]

On 12 April 1961, Gagarin wore a Shturmanskie (a transliteration of Штурманские which actually means “navigator’s”) wristwatch during his historic first flight into space. The Shturmanskie was manufactured at the First Moscow Factory. Since 1964, the watches of the First Moscow Factory have been marked by the trademark “Полёт”, transliterated as “POLJOT”, which means “flight” in Russian and is a tribute to the many space trips its watches have accomplished. In the late 1970s, Poljot launched a new chrono movement, the 3133. With a 23 jewel movement and manual winding (43 hours), it was a modified Russian version of the Swiss Valjoux 7734 of the early 1970s. Poljot 3133 were taken into space by astronauts from Russia, France, Germany and Ukraine. On the arm of Valeriy Polyakov, a Poljot 3133 chronograph movement-based watch set a space record for the longest space flight in history.^[93]

Through the 1960s, a large range of watches was tested for durability and precision under extreme temperature changes and vibrations. The Omega Speedmaster Professional was selected by NASA, the U.S. space agency, and it is mostly known thanks to astronaut Buzz Aldrin who wore it during the 1969 Apollo 11 Moon landing. Heuer became the first Swiss watch in space thanks to a Heuer Stopwatch, worn by John Glenn in 1962 when he piloted the Friendship 7 on the first crewed U.S. orbital mission. The Breitling Navitimer Cosmonaute was designed with a 24-hour analog dial to avoid confusion between AM and PM, which are meaningless in space. It was first worn in space by U.S. astronaut Scott Carpenter on 24 May 1962 in the Aurora 7 Mercury capsule.^[94]

Since 1994 Fortis is the exclusive supplier for crewed space missions authorized by the Russian Federal Space Agency. China National Space Administration (CNSA) astronauts wear the Fiyta^[95] spacewatches. At BaselWorld, 2008, Seiko announced the creation of the first watch ever designed specifically for a space walk, Spring Drive Spacewalk. Timex Datalink is flight certified by NASA for space missions and is one of the watches qualified by NASA for space travel. The Casio G-Shock DW-5600C and 5600E, DW 6900, and DW 5900 are Flight-Qualified for NASA space travel.^[96][97]

Various Timex Datalink models were used both by cosmonauts and astronauts.

Scuba diving

[edit]

Main article: Diving watch

Watch construction may be water-resistant. These watches are sometimes called diving watches when they are suitable for scuba diving or saturation diving. The International Organization for Standardization (ISO) issued a standard for water-resistant watches which also prohibits the term “waterproof” to be used with watches, which many countries have adopted. In the United States, advertising a watch as waterproof has been illegal since 1968, per Federal Trade Commission regulations regarding the “misrepresentation of protective features”.^{[98][99][100]}

Water-resistance is achieved by the gaskets which forms a watertight seal, used in conjunction with a sealant applied on the case to help keep water out. The material of the case must also be tested in order to pass as water-resistant.^[101]

None of the tests defined by ISO 2281 for the Water Resistant mark are suitable to qualify a watch for scuba diving. Such watches are designed for everyday life and must be water-resistant during exercises such as swimming. They can be worn in different temperature and pressure conditions but are under no circumstances designed for scuba diving.^{[citation needed][102]}

The standards for diving watches are regulated by the ISO 6425 international standard. The watches are tested in static or still water under 125% of the rated (water) pressure, thus a watch with a 200-metre rating will be water-resistant if it is stationary and under 250 metres of static water. The testing of the water-resistance is fundamentally different from non-dive watches, because every watch has to be fully tested. Besides water resistance standards to a minimum of 100-metre depth rating, ISO 6425 also provides eight minimum requirements for mechanical diver’s watches for scuba diving (quartz and digital watches have slightly differing readability requirements). For diver’s watches for mixed-gas saturation diving two additional ISO 6425 requirements have to be met.

Watches are classified by their degree of water resistance, which roughly translates to the following (1 metre = 3.281 feet):^[103]

Water-resistance rating	Suitability	Remarks
Water Resistant or 30 m	Suitable for everyday use. Splash/rain resistant.	Not suitable for diving, swimming, snorkeling, water-related work, or fishing.
Water Resistant 50 m	Suitable for swimming, white-water rafting, non-snorkeling water related work, and fishing.	Not suitable for diving.
Water Resistant 100 m	Suitable for recreational surfing, swimming, snorkeling, sailing, and water sports.	Not suitable for diving.
Water Resistant 200 m	Suitable for professional marine activity and serious surface water sports.	Suitable for diving.
Diver’s 100 m	Minimum ISO standard for scuba diving at depths not requiring helium gas.	Diver’s 100 m and 150 m watches are generally old(er) watches.
Diver’s 200 m or 300 m	Suitable for scuba diving at depths not requiring helium gas.	Typical ratings for contemporary diver’s watches.
Diver’s 300+ m helium safe	Suitable for saturation diving (helium-enriched environment).	Watches designed for helium mixed-gas diving will have additional markings to indicate this.

Some watches use bar instead of meters, which may then be multiplied by 10, and then subtract 10 to be approximately equal to the rating based on metres. Therefore, a 5 bar watch is equivalent to a 40-metre watch. Some watches are rated in atmospheres (atm), which are roughly equivalent to bar.^{[citation needed]}

Navigation

[edit]

Main article: Direction-finding watch

There is a traditional method by which an analog watch can be used to locate north and south. The Sun appears to move in the sky over a 24-hour period while the hour hand of a 12-hour clock face takes twelve hours to complete one rotation. In the northern hemisphere, if the watch is rotated so that the hour hand points toward the Sun, the point halfway between the hour hand and 12 o’clock will indicate south. For this method to work in the southern hemisphere, the 12 is pointed toward the Sun and the point halfway between the hour hand and 12 o’clock will indicate north. During daylight saving time, the same method can be employed using 1 o’clock instead of 12. This method is accurate enough to be used only at fairly high latitudes.