I walk in the parking lot of a strip center and see the Heritage House Clocks store sign. I did not go in, but imagine it specializes in more expensive clocks like antiques or grandfather clocks. It probably would not be worth the money for most people to have a bedroom or kitchen clock repaired unless they paid a lot of money for it. In fact, the store seems rather anachronistic. Since the invention of cell phones, who uses clocks any more? I still wear a watch, although it is an Apple watch. Many people just look up the time on their phones. When my father got macular degeneration, we got him a watch that talked to him, telling him the time every hour. I have been fascinated by the clocks in my car — a digital and an analog. Every year when daylight saving starts or ends, I punch a button on my dash and the arms of the analog clock spin forward or backward. There was also a James Bond movie where he took some drugs to make it look like he was dead, but at a certain prescribed time, a small metal bar poked out of the watch on his wrist and woke him up. Now that’s what you call a valuable timepiece. Let’s learn more about clocks.
According to Wikipedia, a clock is a device used to measure, keep and indicate time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units: the day, lunar month and year. Devices operating on several physical processes have been used over the millennia.
Some predecessors to the modern clock may be considered as "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 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 no longer made. 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 pendlum 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, tuning fork, quartz crystal or vibration of electrons in atoms as they emit microwaves.
Clocks have different ways of displaying the time. Analog clocks indicate time with a traditional clock face, with moving hands. Digital clocks display a numeric representation of time. Two numbering systems are in use; 24-hour time notation and 12-hour notation. Most digital clocks use electronic mechanisms and LCD, LED or VFD displays. For the blind and 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. The study of timekeeping is known as horology.
Etymology
The word “clock” derives from the medieval Latin word for “bell” or “clogga” and has cognates in many European languages. Clocks spread to England from the Low Countries, a coastal lowland region in northwestern Europe forming the lower basin of the Rhine-Meuse-Scheldt delta and consisting of Belgium, the Netherlands and Luxembourg. So, the English word came from the Middle Low German and Middle Dutch “klocke.”
Sundials
The apparent position of the sun in the sky moves over the course of each day, reflecting the rotation of 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, which has markings that correspond to the hours. Sundials can be horizontal, vertical or in other orientations. Sundials were widely used in ancient times. With the 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, with the use of the telegraph and train to standardize time and time zones between cities.
Candle clocks, incense clocks and hourglasses
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 hourglasses. 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 hourglasses, 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 the sundials, are possibly the oldest time-measuring instruments, with the only exceptions being the day counting tally stick. Given their great antiquity, where and when they first existed is not known and perhaps unknowable. The bowl-shaped outflow is the simplest form of a water clock and is known to have existed in Babylon and in 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.
Greek astronomer Andronicus of Cyrrhus supervised the construction of the Tower of the Winds in Athens in the 1st century B.C., an octagonal marble clocktower that functioned as a horologion or "timepiece." It is considered the world's first meterological station. The Greek and Roman civilizations advanced water clock design with improved accuracy. These advances were passed on through Byzantium and Islamic times, eventually making their way back to Europe. Independently, the Chinese developed their own advanced water clocks in 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 with 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. He created his astronomical clock that was also a cuckoo clock with birds singing and moving every hour. It is the first carillon clock as it plays music and simultaneously with a person blinking his eyes surprised by the singing birds. 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 of the mechanism. Another Greek clock probably constructed at the time of Alexander was in Gaza, described by Procopius. The Gaza clock was probably a Meteoroskopeion, i.e. a building showing the celestial phenomena and the time. It had 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.
Another geared clock was developed in the 11th century by the Arab engineer Ibn Khalaf al-Muradi in Islamic Iberia; it was a water clock that employed a complex gear train mechanism, including both segmental and epicyclic gearing, capable of transmitting high torque. The clock was unrivalled in its use of sophisticated complex gearing, until the mechanical clocks of the mid-14th century. Al-Muradi's clock also employed the use of mercury in its hydraulic linkages, which could function mechanical automata. Al-Muradi's work was known to scholars working under alfonso X of Castile, hence the mechanism may have played a role in the development of the European mechanical clocks. Other monumental water clocks constructed by medieval Muslim engineers also employed complex gear trains and arrays of automata. Arab engineers at the time also developed a liquid-driven escapement mechanism which they employed in some of their water clocks. Heavy floats were used as weights and a constant-head system was used as an escapement mechanism, which was present in the hydraulic controls they used to make heavy floats descend at a slow and steady rate.
A water-powered cogwheel clock was created in China by Yi Xing and Liang Lingzan. This is not considered an escapement mechanism clock as it was unidirectional, 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, along with liquid mercury during the freezing temperature of winter i.e., hydraulics. A mercury clock, described in the “Libros del saber,” a Spanish work from 1277 consisting of translations and paraphrases of Arabic works, is sometimes quoted as evidence for Muslim knowledge of a mechanical clock. A mercury-powered cogwheel clock was created by Ibn Khalaf al-Muradi.
In the 13th century, Badīʿ az-Zaman Abu l-ʿIzz ibn Ismāʿīl ibn ar-Razāz al-Jazarī, an engineer from Mesopotamia who lived from 1136 to 1206 and worked for Artugid king of Diyar-Bakr, Nasir al-Din, made numerous clocks of all shapes and sizes. A book on his work described 50 mechanical devices in six categories, including water clocks. The most reputed clocks included the elephant scribe and castle clocks, all of which have been successfully reconstructed. As well as telling the time, these grand clocks were symbols of status, grandeur and wealth of the Urtuq State.
Fully mechanical clocks
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. Verge escapement mechanism derived in the surge of true mechanical clocks, which didn't need any kind of fluid power like water or mercury to work.
These mechanical clocks were intended for two main purposes: for signaling 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, 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 clock started acquiring extravagant features such as automata.
In 1283, a large clock was installed at Dunstable Priory; 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 are 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 astronomical dial with automata and bells. The costs of the installation included the full-time employment of two clockkeepers for two years.
Astronomical clocks
Besides the Chinese astronomical clock of Su Song in 1088 mentioned above, contemporary Muslim astronomers also constructed a variety of highly accurate astronomical clocks for use in their mosques and observatories, such as the water-powered astronomical clock by Al-Jazari in 1206 and the astrolabic clock by Ibn al-Shatir in the early 14th century. The most sophisticated timekeeping astrolabes were the geared astrolabe mechanisms designed by Abū Rayhān al-Bīrūnī in the 11th century and by Muhammad ibn Abi Bakr in the 13th century. These devices functioned as timekeeping devices and also as calendars.
A sophisticated water-powered astronomical clock was built by al-Jazarī in 1206. This castle clock was a complex device that was about 11 feet high and had multiple functions alongside timekeeping. It included a display of the zodiac and the solar and lunar paths, and a pointer in the shape of the crescent moon which traveled across the top of a gateway, moved by a hidden cart and causing doors to open, each revealing a mannequin, every hour. It was possible to reset the length of day and night in order to account for the changing lengths of day and night throughout the year. This clock also featured a number of automata including falcons and musicians who automatically played music when moved by levers operated by a hidden camshaft attached to a water wheel.
In Europe, there were the clocks constructed by Richard Wallingford in St. Albans, England in 1336 and by Giovanni de’ Dondi in Padua, Italy 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.
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. Giovanni de’ Dondi's clock was a seven-sided construction, one-meter high, with dials showing the time of day, including minutes, the motions of all the known planets, an automatic calendar of fixed and moveable 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 clocks
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 clocks
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 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 utilize 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.
Marine chronometer
A major stimulus to improving the accuracy and reliability of clocks was the importance of precise timekeeping 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 30 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.
Early electric clocks
In 1815, Francis Ronalds published the first electric clock powered by dry pile batteries. Alexander Bain, 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 timekeeping 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 behavior 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 clocks
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, limited their practical use elsewhere. The National Bureau of Standards — now National Institute of Standards and Technology — 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 clocks
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 a practical method for doing this. A prototype ammonia maser device was built in 1949 at the U.S. National Bureau of Standards, now National Institute of Standards and Technology. 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. Chip-scale atomic clocks, such as the one in the photo above which was unveiled in 2004, are expected to greatly improve GPS location. As of 2013, the most stable atomic clocks are those made with the chemical element ytterbium, which are stable to within less than two parts in 1 quintillion (2×10−18).
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