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Clock

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.

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. 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. 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, so the English word came from the Middle Low German and Middle Dutch Klocke. The word derives from the Middle English clokke, Old North French cloque, or Middle Dutch clocke, all of which mean 'bell'.

Sundials

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. Sundials can be horizontal, vertical, or in other orientations. Sundials were widely used in ancient times. 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.

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

Water clocks, along with sundials, are possibly the oldest time-measuring instruments, with the only exception being the day-counting tally stick. 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.

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. 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.

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 clock. Pope Sylvester II introduced clocks to northern and western Europe around 1000 AD.

Mechanical water clocks
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, 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, who says that some of them work with a chain that turns a gear in the mechanism. Another Greek clock probably constructed at the time of Alexander was in Gaza, as described by Procopius. 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. 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. 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. The Chinese escapement spread west and was the source for Western escapement technology. 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. Knowledge of these mercury escapements may have spread through Europe with translations of Arabic and Spanish texts.

Fully mechanical
The word horologia (from the Greek ὥρα—'hour', and λέγειν—'to tell') was used to describe early mechanical clocks, but the use of this word (still used in several Romance languages) 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', 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. 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. 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.

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, and modern reproductions have been made. 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.

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. 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. 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.

Spring-driven
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, although they are often erroneously credited to Nuremberg watchmaker Peter Henlein (or Henle, or Hele) around 1511. 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. 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, and some 15th-century clocks in Germany indicated minutes and seconds. An early record of a seconds hand on a clock dates back to about 1560 on a clock now in the Fremersdorf collection.

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. These clocks helped the 16th-century astronomer Tycho Brahe to observe astronomical events with much greater precision than before.

Pendulum
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. 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, 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. 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. 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
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 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.

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. 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. 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.

Early electric

In 1815, the English scientist Francis Ronalds published the first electric clock powered by dry pile batteries. 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. 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. In 1927 the first quartz clock was built by Warren Marrison and J.W. Horton at Bell Telephone Laboratories in Canada. 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. In 1969, Seiko produced the world's first quartz wristwatch, the Astron. Their inherent accuracy and low cost of production resulted in the subsequent proliferation of quartz clocks and watches.

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. Atomic clocks were first theorized by Lord Kelvin in 1879. In the 1930s the development of magnetic resonance created practical method for doing this. 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. 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. Calibration of the caesium standard atomic clock was carried out by the use of the astronomical time scale ephemeris time (ET). As of 2013, the most stable atomic clocks are ytterbium clocks, which are stable to within less than two parts in 1 quintillion ($32,768 Hz$).

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, 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. 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.

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. 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, or quality factor, which increases (other things being equal) with its resonant frequency. 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.
 * In mechanical clocks, this is either a pendulum or a balance wheel.
 * In some early electronic clocks and watches such as the Accutron, it is 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.

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. 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, 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.
 * 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.

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 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.
 * 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

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.

Analog

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.

Digital
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.

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
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
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
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 clock measure the duration the game or subdivisions of the game, while other clocks may be used for tracking different durations; these include play clocks, shot clocks, and pitch clocks.

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. Many superstitions exist about clocks. One stopping before a person has died may foretell coming death. 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. 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.

In Chinese culture, giving a clock is often taboo, especially to the elderly, as it is a homophone of the act of attending another's funeral.

Awards

 * Grand Prix d'Horlogerie de Genève (GPHG)
 * Goldene Unruh

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Clock


text:
Charles Proteus Steinmetz

Charles Proteus Steinmetz (born Karl August Rudolph Steinmetz; April 9, 1865 – October 26, 1923) was an American mathematician and electrical engineer and professor at Union College. He fostered the development of alternating current that made possible the expansion of the electric power industry in the United States, formulating mathematical theories for engineers. He made ground-breaking discoveries in the understanding of hysteresis that enabled engineers to design better electromagnetic apparatus equipment, especially electric motors for use in industry.

At the time of his death, Steinmetz held over 200 patents. A genius in both mathematics and electronics, he did work that earned him the nicknames "Forger of Thunderbolts" and "The Wizard of Schenectady". Steinmetz's equation, Steinmetz solids, Steinmetz curves, and Steinmetz equivalent circuit are all named after him, as are numerous honors and scholarships, including the IEEE Charles Proteus Steinmetz Award, one of the highest technical recognitions given by the Institute of Electrical and Electronics Engineers professional society.

Early life and education
Steinmetz was born Karl August Rudolph Steinmetz on April 9, 1865, in Breslau, Province of Silesia, Prussia (now Wrocław, Poland) the son of Caroline (Neubert) and Karl Heinrich Steinmetz. He was baptized as a Lutheran into the Evangelical Church of Prussia. Steinmetz, who stood only 4ft tall as an adult, had dwarfism, hunchback, and hip dysplasia, as did his father and grandfather. Steinmetz graduated with honors from St. John's Gymnasium in 1882.

Following Gymnasium, Steinmetz studied at the University of Breslau to begin work on his undergraduate degree in 1883. Nearing completion of his doctorate in 1888, he was forced to flee to Zürich, Switzerland, as the German government was preparing to prosecute him for his socialist activities.

Political persecution and emigration
As socialist meetings and press had been banned in Germany, Steinmetz fled to Zürich in 1889 to escape possible arrest. Cornell University Professor Ronald R. Kline, author of Steinmetz: Engineer and Socialist, points to other factors which reinforced Steinmetz's decision to leave his homeland such as financial problems and the prospect of a more harmonious life with his socialist friends and supporters than the stressful domestic circumstances of his father's household.

Faced with an expiring visa, he emigrated to the United States in 1889. He changed his first name to "Charles" to sound more American, and chose the middle name "Proteus", a wise hunchbacked character from the Odyssey who knew many secrets, after a epithet bestowed upon him by his college fraternity brothers.

Political activism in the USA
Steinmetz was politically active in the US as a technocratic socialist for over thirty years. Following the Bolshevik introduction of a technocratic plan to electrify Russia, Steinmetz spoke of Lenin alongside Albert Einstein as the "two greatest minds of our time." He believed in a corporatist industrial government also covering its human wellfare function.

A member of the original Technical Alliance, which also included Thorstein Veblen and Leland Olds, Steinmetz had great faith in the ability of machines to eliminate human toil and create abundance for all. He put it this way: "Some day we [will] make the good things of life for everybody."

Electrical engineering
Steinmetz is known for his contribution in three major fields of alternating current (AC) systems theory: hysteresis, steady-state analysis, and transients.

AC hysteresis theory
Shortly after arriving in the United States, Steinmetz went to work for Rudolf Eickemeyer in Yonkers, New York, and published in the field of magnetic hysteresis, earning worldwide professional recognition. Eickemeyer's firm developed transformers for use in the transmission of electrical power among many other mechanical and electrical devices. In 1893 Eickemeyer's company, along with all of its patents and designs, was bought by the newly formed General Electric Company, where Steinmetz quickly became known as the engineering wizard in GE's engineering community.

AC steady state circuit theory
Steinmetz's work revolutionized AC circuit theory and analysis, which had been carried out using complicated, time-consuming calculus-based methods. In the groundbreaking paper, "Complex Quantities and Their Use in Electrical Engineering", presented at a July 1893 meeting published in the American Institute of Electrical Engineers (AIEE), Steinmetz simplified these complicated methods to "a simple problem of algebra". He systematized the use of complex number phasor representation in electrical engineering education texts, whereby the lower-case letter "j" is used to designate the 90-degree rotation operator in AC system analysis. His seminal books and many other AIEE papers "taught a whole generation of engineers how to deal with AC phenomena".

AC transient theory
Steinmetz also greatly advanced the understanding of lightning. His systematic experiments resulted in the first laboratory created "man-made lightning", earning him the nickname the "Forger of Thunderbolts". These were conducted in a football field-sized laboratory at General Electric, using 120,000 volt generators. He also erected a lightning tower to attract natural lightning to study its patterns and effects, which resulted in several theories.

Professional life
Steinmetz acted in the following professional capacities:
 * At Union College, as chair of electrical engineering from 1902 to 1913 and as faculty member thereafter until his death in 1923
 * Board member on the Schenectady Board of Education for six years, including four years as the board's president
 * President of the Common Council of Schenectady
 * President of the American Institute of Electrical Engineers from 1901 to 1902
 * First vice-president of the International Association of Municipal Electricians (IAME) {which later became the International Municipal Signal Association (IMSA)} from 1913 until his death in 1923.

He was granted an honorary degree from Harvard University in 1901 and a doctorate from Union College in 1903.

Steinmetz wrote 13 books and 60 articles, not exclusively about engineering. He was a member and adviser to the fraternity Phi Gamma Delta at Union College, whose chapter house was one of the first electrified residences.

While serving as president of the Schenectady Board of Education, Steinmetz introduced numerous progressive reforms, including extended school hours, school meals, school nurses, special classes for the children of immigrants, and the distribution of free textbooks.

Personal life
Steinmetz was affected by kyphosis, as were his father and grandfather. In spite of his love for children and family life, Steinmetz remained unmarried, to prevent his spinal deformity from being passed to any offspring.

When Joseph LeRoy Hayden, a loyal and hardworking lab assistant, announced that he would marry and look for his own living quarters, Steinmetz made the unusual proposal of opening his large home, complete with research lab, greenhouse, and office to the Haydens and their prospective family. Hayden favored the idea, but his future wife was wary of the unorthodox arrangement. She agreed after Steinmetz's assurance that she could run the house as she saw fit.

After an uneasy start, the arrangement worked well for all parties, especially after three Hayden children were born. Steinmetz legally adopted Joseph Hayden as his son, becoming grandfather to the youngsters, entertaining them with fantastic stories and spectacular scientific demonstrations. The unusual, harmonious living arrangement lasted for the rest of Steinmetz's life.

Steinmetz founded America's first glider club, but none of its prototypes "could be dignified with the term 'flight.

Steinmetz was a lifelong agnostic. He died on October 26, 1923, and was buried in Vale Cemetery in Schenectady.

Legacy
Steinmetz earned wide recognition among the scientific community and numerous awards and honors both during his life and posthumously.

Steinmetz's equation, derived from his experiments, defines the approximate heat energy due to magnetic hysteresis released, per cycle per unit volume of magnetic material. A Steinmetz solid is the solid body generated by the intersection of two or three cylinders of equal radius at right angles. Steinmetz' equivalent circuit is still widely used for the design and testing of induction machines.

One of the highest technical recognitions given by the Institute of Electrical and Electronics Engineers, the "IEEE Charles Proteus Steinmetz Award", is given for major contributions to standardization within the field of electrical and electronics engineering. Other awards include the Certificate of Merit of Franklin Institute, 1908; the Elliott Cresson Medal, 1913; and the Cedergren Medal, 1914. Steinmetz was also an elected member of both the American Academy of Arts and Sciences and the American Philosophical Society.

The Charles P. Steinmetz Memorial Lecture series was begun in his honor in 1925, sponsored by the Schenectady branch of the IEEE. Through 2017 seventy-three gatherings have taken place, held almost exclusively at Union College, featuring notable figures such as Nobel laureate experimental physicist Robert A. Millikan, helicopter inventor Igor Sikorsky, nuclear submarine pioneer Admiral Hyman G. Rickover (1963), Nobel-winning semiconductor inventor William Shockley, and Internet "founding father" Leonard Kleinrock.

Steinmetz's connection to Union is further celebrated with the annual Steinmetz Symposium, a day-long event in which Union undergraduates give presentations on research they have done. Steinmetz Hall, which houses the Union College computer center, is named after him.

The Charles P. Steinmetz Scholarship is awarded annually by the college, underwritten since its inception in 1923 by the General Electric Company. An additional Charles P. Steinmetz Memorial Scholarship was later established at Union by Marjorie Hayden, daughter of Joseph and Corrine Hayden, and is awarded to students majoring in engineering or physics.

A 1914 "Duplex Drive Brougham" Detroit Electric automobile that once belonged to Steinmetz was purchased by Union College in 1971, and restored for use in campus ceremonies. The Steinmetz car is permanent displayed in the first-floor corridor between the Wold Center and F.W. Olin building.

A Chicago public high school, Steinmetz College Prep, is named for him, as well as a Schenectady public school, the Steinmetz Career and Leadership Academy, formerly Steinmetz Middle-School.

A public park in north Schenectady, New York was named for him in 1931.

In 1983, the US Post Office included Steinmetz in a series of postage stamps commemorating American inventors.

In May 2015, a life-size bronze statue of Charles Steinmetz meeting Thomas Edison by sculptor and caster Dexter Benedict was unveiled on a plaza on the corner of Erie Boulevards and South Ferry Street in Schenectady.

Charles Steinmetz's Mohawk River cabin is preserved and on display in the outdoor collection of historic structures in Greenfield Village, part of the Henry Ford Museum complex in Dearborn, Michigan.

In popular culture
Steinmetz is featured in John Dos Passos' U.S.A. trilogy in one of the biographies. He also serves as a major character in Starling Lawrence's The Lightning Keeper.

Steinmetz is a major character in the novel Electric City by Elizabeth Rosner.

In the 1944 Three Stooges short "Busy Buddies", Moe Howard references Steinmetz.

Steinmetz was portrayed in 1959 by the actor Rod Steiger in the CBS television anthology series, The Joseph Cotten Show. The episode focused on his socialist activities in Germany.

A famous anecdote about Steinmetz concerns a troubleshooting consultation at Henry Ford's River Rouge Plant. A humorous aspect of the story is the "itemized bill" he submitted for the work performed.

Patents
At the time of his death, Steinmetz held over 200 patents:

 * , "System of distribution by alternating current" (January 29, 1895)
 * , "Inductor dynamo"
 * , "Three phase induction meter"
 * , "Inductor dynamo"
 * , "Induction motor"
 * , "System of electrical distribution"
 * , "Induction motor"
 * , "Means for producing light" (May 7, 1912)
 * , "Induction furnace"
 * , "Protective device"
 * , "Inductor dynamo"

Works

 * This book's first edition was expanded and updated in many subsequent editions.
 * This book's first edition was expanded and updated in many subsequent editions.
 * This book's first edition was expanded and updated in many subsequent editions.
 * This book's first edition was expanded and updated in many subsequent editions.

title: Charles Proteus Steinmetz


text:
Charles Martel

Charles Martel (c. 688 – 22 October 741), Martel being a sobriquet in Old French for "The Hammer", was a Frankish political and military leader who, as Duke and Prince of the Franks and Mayor of the Palace, was the de facto ruler of the Franks from 718 until his death. He was a son of the Frankish statesman Pepin of Herstal and a noblewoman named Alpaida. Charles successfully asserted his claims to power as successor to his father as the power behind the throne in Frankish politics. Continuing and building on his father's work, he restored centralized government in Francia and began the series of military campaigns that re-established the Franks as the undisputed masters of all Gaul. According to a near-contemporary source, the Liber Historiae Francorum, Charles was "a warrior who was uncommonly ... effective in battle".

Charles gained a very consequential victory against an Umayyad invasion of Aquitaine at the Battle of Tours, at a time when the Umayyad Caliphate controlled most of the Iberian Peninsula. Alongside his military endeavours, Charles has been traditionally credited with an influential role in the development of the Frankish system of feudalism.

At the end of his reign, Charles divided Francia between his sons, Carloman and Pepin. The latter became the first king of the Carolingian dynasty. Pepin's son Charlemagne, grandson of Charles, extended the Frankish realms and became the first emperor in the West since the Fall of the Western Roman Empire.

Background
Charles, nicknamed "Martel" ("the Hammer") in later chronicles, was a son of Pepin of Herstal and his mistress, possible second wife, Alpaida. He had a brother named Childebrand, who later became the Frankish dux (that is, duke) of Burgundy.

Older historiography commonly describes Charles as "illegitimate", but the dividing line between wives and concubines was not clear-cut in eighth-century Francia. It is likely that the accusation of "illegitimacy" derives from the desire of Pepin's first wife Plectrude to see her progeny as heirs to Pepin's throne.

By Charles's lifetime the Merovingians had ceded power to the Mayors of the Palace, who controlled the royal treasury, dispensed patronage, and granted land and privileges in the name of the figurehead king. Charles's father, Pepin of Herstal, had united the Frankish realm by conquering Neustria and Burgundy. Pepin was the first to call himself Duke and Prince of the Franks, a title later taken up by Charles.

Contesting for power

In December 714, Pepin of Herstal died. A few months before his death and shortly after the murder of his son Grimoald the Younger, he had taken the advice of his wife Plectrude to designate as his sole heir Theudoald, his grandson by their deceased son Grimoald. This was immediately opposed by the Austrasian nobles because Theudoald was a child of only eight years of age. To prevent Charles using this unrest to his own advantage, Plectrude had him imprisoned in Cologne, the city which was intended to be her capital. This prevented an uprising on his behalf in Austrasia, but not in Neustria.

Civil war of 715–718
Pepin's death occasioned open conflict between his heirs and the Neustrian nobles who sought political independence from Austrasian control. In 715, Dagobert III named Raganfrid mayor of the palace. On 26 September 715, Raganfrid's Neustrians met the young Theudoald's forces at the Battle of Compiègne. Theudoald was defeated and fled back to Cologne. Before the end of the year, Charles had escaped from prison and been acclaimed mayor by the nobles of Austrasia. That same year, Dagobert III died and the Neustrians proclaimed Chilperic II, the cloistered son of Childeric II, as king.

Battle of Cologne
In 716, Chilperic and Raganfrid together led an army into Austrasia intent on seizing the Pippinid wealth at Cologne. The Neustrians allied with another invading force under Redbad, King of the Frisians and met Charles in battle near Cologne, which was still held by Plectrude. Charles had little time to gather men or prepare and the result was inevitable. The Frisians held off Charles, while the king and his mayor besieged Plectrude at Cologne, where she bought them off with a substantial portion of Pepin's treasure. After that they withdrew. The Battle of Cologne is the only defeat of Charles's career.

Battle of Amblève
Charles retreated to the hills of the Eifel to gather and train men. In April 716, he fell upon the triumphant army near Malmedy as it was returning to Neustria. In the ensuing Battle of Amblève, Charles attacked as the enemy rested at midday. According to one source, he split his forces into several groups which fell at them from many sides. Another suggests that while this was his intention, he then decided, given the enemy's unpreparedness, this was not necessary. In any event, the suddenness of the assault led them to believe they were facing a much larger host. Many of the enemy fled and Charles's troops gathered the spoils of the camp. His reputation increased considerably as a result, and he attracted more followers. This battle is often considered by historians as the turning point in Charles's struggle.

Battle of Vincy
Richard Gerberding points out that up to this time, much of Charles's support was probably from his mother's kindred in the lands around Liege. After Amblève, he seems to have won the backing of the influential Willibrord, founder of the Abbey of Echternach. The abbey had been built on land donated by Plectrude's mother, Irmina of Oeren, but most of Willibrord's missionary work had been carried out in Frisia. In joining Chilperic and Ragqnfrid, Radbod of Frisia sacked Utrecht, burning churches and killing many missionaries. Willibrord and his monks were forced to flee to Echternach. Gerberding suggests that Willibrord had decided that the chances of preserving his life's work were better with a successful field commander like Charles than with Plectrude in Cologne. Willibrord subsequently baptized Charles's son Pepin. Gerberding suggests a likely date of Easter 716. Charles also received support from bishop Pepo of Verdun.

Charles took time to rally more men and prepare. By the following spring, he had attracted enough support to invade Neustria. Charles sent an envoy who proposed a cessation of hostilities if Chilperic would recognize his rights as mayor of the palace in Austrasia. The refusal was not unexpected but served to impress upon Charles's forces the unreasonableness of the Neustrians. They met near Cambrai at the Battle of Vincy on 21 March 717. The victorious Charles pursued the fleeing king and mayor to Paris, but as he was not yet prepared to hold the city, he turned back to deal with Plectrude and Cologne. He took the city and dispersed her adherents. Plectrude was allowed to retire to a convent. Theudoald lived to 741 under his uncle's protection.

Consolidation of power
Upon this success, Charles proclaimed Chlothar IV king in Austrasia in opposition to Chilperic and deposed Rigobert, archbishop of Reims, replacing him with Milo, a lifelong supporter.

In 718, Chilperic responded to Charles's new ascendancy by making an alliance with Odo the Great (or Eudes, as he is sometimes known), the duke of Aquitaine, who had become independent during the civil war in 715, but was again defeated, at the Battle of Soissons, by Charles. Chilperic fled with his ducal ally to the land south of the Loire and Raganfrid fled to Angers. Soon Chlotar IV died and Odo surrendered King Chilperic in exchange for Charles recognizing his dukedom. Charles recognized Chilperic as king of the Franks in return for legitimate royal affirmation of his own mayoralty over all the kingdoms.

Wars of 718–732
Between 718 and 732, Charles secured his power through a series of victories. Having unified the Franks under his banner, Charles was determined to punish the Saxons who had invaded Austrasia. Therefore, late in 718, he laid waste their country to the banks of the Weser, the Lippe, and the Ruhr. He defeated them in the Teutoburg Forest and thus secured the Frankish border.

When the Frisian leader Radbod died in 719, Charles seized West Frisia without any great resistance on the part of the Frisians, who had been subjected to the Franks but had rebelled upon the death of Pippin. When Chilperic II died in 721, Charles appointed as his successor the son of Dagobert III, Theuderic IV, who was still a minor, and who occupied the throne from 721 to 737. Charles was now appointing the kings whom he supposedly served (rois fainéants). By the end of his reign, he didn't appoint any at all. At this time, Charles again marched against the Saxons. Then the Neustrians rebelled under Raganfrid, who had left the county of Anjou. They were easily defeated in 724 but Raganfrid gave up his sons as hostages in turn for keeping his county. This ended the civil wars of Charles' reign.

The next six years were devoted in their entirety to assuring Frankish authority over the neighboring political groups. Between 720 and 723, Charles was fighting in Bavaria, where the Agilolfing dukes had gradually evolved into independent rulers, recently in alliance with Liutprand the Lombard. He forced the Alemanni to accompany him, and Duke Hugbert submitted to Frankish suzerainty. In 725 he brought back the Agilolfing Princess Swanachild as a second wife.

In 725 and 728, he again entered Bavaria but, in 730, he marched against Lantfrid, Duke of Alemannia, who had also become independent, and killed him in battle. He forced the Alemanni to capitulate to Frankish suzerainty and did not appoint a successor to Lantfrid. Thus, southern Germany once more became part of the Frankish kingdom, as had northern Germany during the first years of the reign.

Aquitaine and the Battle of Tours in 732
In 731, after defeating the Saxons, Charles turned his attention to the rival southern realm of Aquitaine, and crossed the Loire, breaking the treaty with Duke Odo. The Franks ransacked Aquitaine twice, and captured Bourges, although Odo retook it. The Continuations of Fredegar allege that Odo called on assistance from the recently established emirate of al-Andalus, but there had been Arab raids into Aquitaine from the 720s onwards. Indeed, the anonymous Chronicle of 754 records a victory for Odo in 721 at the Battle of Toulouse, while the Liber Pontificalis records that Odo had killed 375,000 Saracens. It is more likely that this invasion or raid took place in revenge for Odo's support for a rebel Berber leader named Munnuza.

Whatever the precise circumstances were, it is clear that an army under the leadership of Abd al-Rahman al-Ghafiqi headed north, and after some minor engagements marched on the wealthy city of Tours. According to British medieval historian Paul Fouracre, "Their campaign should perhaps be interpreted as a long-distance raid rather than the beginning of a war". They were, however, defeated by the army of Charles at the Battle of Tours (known in France as the Battle of Poitiers), at a location between the French cities of Tours and Poitiers, in a victory described by the Continuations of Fredegar. According to the historian Bernard Bachrach, the Arab army, mostly mounted, failed to break through the Frankish infantry. News of this battle spread, and may be recorded in Bede's Ecclesiastical History (Book V, ch. 23). However, it is not given prominence in Arabic sources from the period.

Despite his victory, Charles did not gain full control of Aquitaine, and Odo remained duke until 735.

Wars of 732–737

Between his victory of 732 and 735, Charles reorganized the kingdom of Burgundy, replacing the counts and dukes with his loyal supporters, thus strengthening his hold on power. He was forced, by the ventures of Bubo, Duke of the Frisians, to invade independent-minded Frisia again in 734. In that year, he slew the duke at the Battle of the Boarn. Charles ordered the Frisian pagan shrines destroyed, and so wholly subjugated the populace that the region was peaceful for twenty years after.

In 735, Duke Odo of Aquitaine died. Though Charles wished to rule the duchy directly and went there to elicit the submission of the Aquitanians, the aristocracy proclaimed Odo's son, Hunald I of Aquitaine, as duke, and Charles and Hunald eventually recognised each other's position.

Interregnum (737–741)
In 737, at the tail end of his campaigning in Provence and Septimania, the Merovingian king, Theuderic IV, died. Charles, titling himself maior domus and princeps et dux Francorum, did not appoint a new king and nobody acclaimed one. The throne lay vacant until Charles' death. The interregnum, the final four years of Charles' life, was relatively peaceful although in 738 he compelled the Saxons of Westphalia to submit and pay tribute and in 739 he checked an uprising in Provence where some rebels united under the leadership of Maurontus.

Charles used the relative peace to set about integrating the outlying realms of his empire into the Frankish church. He erected four dioceses in Bavaria (Salzburg, Regensburg, Freising, and Passau) and gave them Boniface as archbishop and metropolitan over all Germany east of the Rhine, with his seat at Mainz. Boniface had been under his protection from 723 on. Indeed, the saint himself explained to his old friend, Daniel of Winchester, that without it he could neither administer his church, defend his clergy nor prevent idolatry.

In 739, Pope Gregory III begged Charles for his aid against Liutprand, but Charles was loath to fight his onetime ally and ignored the plea. Nonetheless, the pope's request for Frankish protection showed how far Charles had come from the days when he was tottering on excommunication, and set the stage for his son and grandson to assert themselves in the peninsula.

Death and transition in rule

Charles died on 22 October 741, at Quierzy-sur-Oise in what is today the Aisne département in the Picardy region of France. He was buried at Saint Denis Basilica in Paris.

His territories had been divided among his adult sons a year earlier: to Carloman he gave Austrasia, Alemannia, and Thuringia, and to Pippin the Younger Neustria, Burgundy, Provence, and Metz and Trier in the "Mosel duchy". Grifo was given several lands throughout the kingdom, but at a later date, just before Charles died.

Legacy
Earlier in his life Charles had many internal opponents and felt the need to appoint his own kingly claimant, Chlotar IV. Later, however, the dynamics of rulership in Francia had changed, and no hallowed Merovingian ruler was required. Charles divided his realm among his sons without opposition (though he ignored his young son Bernard). For many historians, Charles laid the foundations for his son Pepin's rise to the Frankish throne in 751, and his grandson Charlemagne's imperial acclamation in 800. However, for Paul Fouracre, while Charles was "the most effective military leader in Francia", his career "finished on a note of unfinished business".

Family and children
Charles married twice, his first wife being Rotrude of Treves, daughter either of Lambert II, Count of Hesbaye, or of Leudwinus, Count of Treves. They had the following children:

 * Hiltrud
 * Carloman
 * Landrade, also rendered as Landres
 * Auda, also rendered as Aldana
 * Pepin the Younger

Most of the children married and had issue. Hiltrud married Odilo I (Duke of Bavaria). Landrade was once believed to have married a Sigrand (Count of Hesbania) but Sigrand's wife was more likely the sister of Rotrude. Auda married Theoderic, Count of Autun.

Charles also married a second time, to Swanhild and they had a child named Grifo.

With Ruodhaid, with whom he had:

 * Bernhard (c. 720–787),
 * Hieronymus (c. 722 – after 782),
 * Remigius (d. 771) archbishop of Rouen.

Military victories
For early medieval authors, Charles was famous for his military victories. Paul the Deacon for instance attributed a victory against the Saracens actually won by Odo of Aquitaine to Charles. However, alongside this there soon developed a darker reputation, for his alleged abuse of church property. A ninth-century text, the Visio Eucherii, possibly written by Hincmar of Reims, portrayed Charles as suffering in hell for this reason. According to British medieval historian Paul Fouracre, this was "the single most important text in the construction of Charles's reputation as a seculariser or despoiler of church lands".

By the eighteenth century, historians such as Edward Gibbon had begun to portray the Frankish leader as the saviour of Christian Europe from a full-scale Islamic invasion.

In the nineteenth century, the German historian Heinrich Brunner argued that Charles had confiscated church lands in order to fund military reforms that allowed him to defeat the Arab conquests, in this way brilliantly combining two traditions about the ruler. However, Fouracre argued that "...there is not enough evidence to show that there was a decisive change either in the way in which the Franks fought, or in the way in which they organised the resources needed to support their warriors."

Many twentieth-century European historians continued to develop Gibbon's perspectives, such as French medievalist Christian Pfister, who wrote in 1911 that

"'Besides establishing a certain unity in Gaul, Charles saved it from a great peril. In 711 the Arabs had conquered Spain. In 720 they crossed the Pyrenees, seized Narbonensis, a dependency of the kingdom of the Visigoths, and advanced on Gaul. By his able policy Odo succeeded in arresting their progress for some years; but a new vali, Abdur Rahman, a member of an extremely fanatical sect, resumed the attack, reached Poitiers, and advanced on Tours, the holy town of Gaul. In October 732—just 100 years after the death of Mahomet—Charles gained a brilliant victory over Abdur Rahman, who was called back to Africa by revolts of the Berbers and had to give up the struggle. ...After his victory, Charles took the offensive'."

Similarly, William E. Watson, who wrote of the battle's importance in Frankish and world history in 1993, suggested that

"'Had Charles Martel suffered at Tours-Poitiers the fate of King Roderick at the Rio Barbate, it is doubtful that a 'do-nothing' sovereign of the Merovingian realm could have later succeeded where his talented major domus had failed. Indeed, as Charles was the progenitor of the Carolingian line of Frankish rulers and grandfather of Charlemagne, one can even say with a degree of certainty that the subsequent history of the West would have proceeded along vastly different currents had 'Abd al-Rahman been victorious at Tours-Poitiers in 732.'"

And in 1993, the influential political scientist Samuel Huntington saw the battle of Tours as marking the end of the "Arab and Moorish surge west and north".

Other recent historians, however, argue that the importance of the battle is dramatically overstated, both for European history in general and for Charles's reign in particular. This view is typified by Alessandro Barbero, who in 2004 wrote,

"'Today, historians tend to play down the significance of the battle of Poitiers, pointing out that the purpose of the Arab force defeated by Charles Martel was not to conquer the Frankish kingdom, but simply to pillage the wealthy monastery of St-Martin of Tours'."

Similarly, in 2002 Tomaž Mastnak wrote: "'The continuators of Fredegar's chronicle, who probably wrote in the mid-eighth century, pictured the battle as just one of many military encounters between Christians and Saracens—moreover, as only one in a series of wars fought by Frankish princes for booty and territory... One of Fredegar's continuators presented the battle of Poitiers as what it really was: an episode in the struggle between Christian princes as the Carolingians strove to bring Aquitaine under their rule.'"

More recently, the memory of Charles has been appropriated by far right and white nationalist groups, such as the 'Charles Martel Group' in France, and by the perpetrator of the Christchurch mosque shootings at Al Noor Mosque and Linwood Islamic Centre in Christchurch, New Zealand, in 2019. The memory of Charles is a topic of debate in contemporary French politics on both the right and the left.

Order of the Genet
In the seventeenth century, a legend emerged that Charles had formed the first regular order of knights in France. In 1620, Andre Favyn stated (without providing a source) that among the spoils Charles's forces captured after the Battle of Tours were many genets (raised for their fur) and several of their pelts. Charles gave these furs to leaders amongst his army, forming the first order of knighthood, the Order of the Genet. Favyn's claim was then repeated and elaborated in later works in English, for instance by Elias Ashmole in 1672, and James Coats in 1725.

title: Charles Martel


text:
Charles Edward Jones

Charles Edward "Chuck" Jones (November 8, 1952 – September 11, 2001) was a United States Air Force officer, an aeronautical engineer, computer programmer, and an astronaut in the USAF Manned Spaceflight Engineer Program. He was killed during the September 11 attacks, aboard American Airlines Flight 11.

Life
Charles Edward Jones was born November 8, 1952, in Clinton, Indiana. He graduated from Wichita East High School in 1970, earned a Bachelor of Science degree in Astronautical Engineering from the United States Air Force Academy in 1974, and received a Master of Science degree in Astronautics from Massachusetts Institute of Technology in 1980. He entered the USAF Manned Spaceflight Engineer program in 1982, and was scheduled to fly on mission STS-71-B in December 1986, but the mission was canceled after the Challenger Disaster in January 1986. He left the Manned Spaceflight Engineer program in 1987.

He later worked for Defense Intelligence Agency, Bolling Air Force Base in Washington, D.C., and was Systems Program Director for Intelligence and Information Systems, Hanscom Air Force Base, Massachusetts. Jones later was the manager of space programs for BAE Systems.

Jones was killed at the age of 48 in the attacks of September 11, 2001, aboard American Airlines Flight 11. Jones was flying that day on a routine business trip for BAE Systems, and had been living as a retired U.S. Air Force colonel in Bedford, Massachusetts, at the time of his death. He was survived by his wife Jeanette.

At the National 9/11 Memorial, Jones is memorialized at the North Pool, on Panel N-74.

Military decorations
His awards include:

 * Senior Missile Badge

title: Charles Edward Jones