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121-445: An alarm clock or alarm is a clock that is designed to alert an individual or group of people at a specified time. The primary function of these clocks is to awaken people from their night's sleep or short naps; they can sometimes be used for other reminders as well. Most alarm clocks make sounds; some make light or vibration. Some have sensors to identify when a person is in a light stage of sleep, in order to avoid waking someone who
242-481: 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
363-528: 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
484-400: A "particularly elaborate example" of a water clock. Pope Sylvester II introduced clocks to northern and western Europe around 1000 AD. 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
605-570: 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. An elaborate water clock,
726-478: 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
847-532: 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,
968-477: A complex public striking clock in his home town Gaza which featured an hourly gong and figures moving mechanically day and night. In China, a striking clock was devised by the Buddhist monk and inventor Yi Xing (683–727). The Chinese engineers Zhang Sixun and Su Song integrated striking clock mechanisms in astronomical clocks in the 10th and 11th centuries, respectively. A striking clock outside of China
1089-401: 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
1210-555: A feature which sets the time automatically using signals from atomic clock -synced time signal radio stations such as WWV , making the clock accurate and immune to time reset due to power interruptions. Alarm clock software programs have been developed for personal computers . There are Web-based alarm clocks, some of which may allow a virtually unlimited number of alarm times (i.e. Personal information manager ) and personalized tones. However, unlike mobile phone alarms, online alarm clocks have some limitations. They do not work when
1331-400: 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
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#17327930761101452-416: 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
1573-414: A gong, or blow trumpets (by forcing bell-jars down into water and taking the compressed air through a beating reed) at pre-set times" ( Vitruv 11.11). The late Roman statesman Cassiodorus (c. 485–585) advocated in his rulebook for monastic life the water clock as a useful alarm for the "soldiers of Christ " (Cassiod. Inst. 30.4 f.). The Christian rhetorician Procopius described in detail prior to 529
1694-512: A hammer. User-settable mechanical alarm clocks date back at least to 15th-century Europe. These early alarm clocks had a ring of holes in the clock dial and were set by placing a pin in the appropriate hole. The first American alarm clock was created in 1787 by Levi Hutchins in Concord, New Hampshire . This device he made only for himself, however, and it only rang at 4 am, in order to wake him for his job. The French inventor Antoine Redier
1815-498: 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
1936-401: 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,
2057-413: A large button on the top that silences the alarm and sets it to resume sounding a few minutes later. Some clock radios also have a "sleep" timer, which turns the radio on for a set amount of time (usually around one hour). This is useful for people who like to fall asleep while listening to the radio. Newer clock radios are available with other music sources such as iPod , iPhone , and/or audio CD . When
2178-564: A later inscription about the Ottoman Sultan Abd al-Aziz . There's evidence that suggests that in 1235, the madrasa contained an example of an early monumental water-powered alarm clock that announced the appointed hours of prayer and the time both by day and by night in the entrance hall as the Abbasids had many of these water-powered clocks at the time. The clock was said to be built by a man named "Ali Ibn Tha’lab" and based on
2299-552: A monthly stipend for its students. Its library had an initial collection of 80,000 volumes, given by the Caliph. The collection was said to have grown to 400,000 volumes, although the reports of both these figures may have been exaggerated. Even though the libraries’ collection survived the Mongol sack of 1258 CE, it was merged with that of al-Nizamiyah Madrasa in 1393 CE, whose collection had subsequently been dispersed or disappeared. As
2420-403: A more accurate clock: 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
2541-578: 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
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#17327930761102662-554: 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
2783-488: 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
2904-652: A provision for setting the clock by manually entering the correct time into the counter. Mustansiriya Madrasah Al-Mustansiriya Madrasa ( Arabic : المدرسة المستنصرية ) was a medieval-era scholarly complex that provided a universal system of higher education. It was established in 1227 CE and was named after and built by the Abbasid Caliph al-Mustansir in Baghdad, Iraq . The Madrasa taught many different subjects, including medicine, math, literature, grammar, philosophy, and Islamic religious studies. However,
3025-630: A result of the Ottoman invasion and capture of Baghdad in 1534 CE, books from the palaces and libraries were taken as the spoils of war and became an important part of the royal library in Istanbul. After the 13th century, the Madrasa experienced a period of decline in prominence, followed by fluctuating centuries of purpose and power. The widespread annihilation and conquest of the Mongols throughout
3146-517: 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
3267-471: 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,
3388-579: 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
3509-433: A two-story rectangular building with a large courtyard. Each school of Islamic law was designated to a separate corner of the building. Some of the main decorative features includes muqarnas ; series of interconnected vaults used to highlight squinch zones of domes or exterior of minarets and domes. Al-Mustansiriya incorporates arabesque and carved brick decoration in an exterior tripartite facade. The main entrance
3630-652: 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 . In 1815, the English scientist Francis Ronalds published the first electric clock powered by dry pile batteries. Alexander Bain ,
3751-421: 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
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3872-436: 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
3993-584: Is also derived from the Middle English clokke , Old North French cloque , or Middle Dutch clocke , all of which mean 'bell'. 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
4114-431: Is considered to be the world's oldest surviving mechanical clock that strikes the hours. 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
4235-747: Is deeply asleep, which causes tiredness, even if the person has had adequate sleep. To turn off the sound or light, a button or handle on the clock is pressed; most clocks automatically turn off the alarm if left unattended long enough. A classic analog alarm clock has an extra hand or inset dial that is used to show the time at which the alarm will ring. Alarm clock functions are also used in mobile phones, watches, and computers. Many alarm clocks have radio receivers that can be set to start playing at specified times, and are known as clock radios . Additionally, some alarm clocks can set multiple alarms. A progressive alarm clock can have different alarms for different times (see next-generation alarms ) and play music of
4356-436: Is made up of three conical archways, star and polygon figures, and an inscription describing the patron of the building, Al-Mustansir. Earlier Umayyad and Abbasid themes of foliage and greenery are also evoked in the exterior facade of the entrance archways. The other entrances are ornately decorated with geometric patterns of zig-zags, square designs, and ornamentation centered around water. The southwestern entrance also includes
4477-459: 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. Some clocks rely for their accuracy on an external oscillator; that is, they are automatically synchronized to
4598-619: The Abbasid Palace , and Caliph's Street. The madrasa was established by Caliph al-Mustansir and its cost amounted to 700 thousand dinars, and it was opened for study on the 6th of April, 1233, and a large celebration and feast was held in its opening. It was the first Islamic university in which the study of jurisprudence based on the four schools of thought; Hanafi , Shafi’i , Maliki , and Hanbali and all were combined into “one school.” This inspired al-Salihiyya Madrasa in Cairo which
4719-608: 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. The word horologia (from
4840-512: The Levant and Egypt who were known for their deep research and study. Some of the teachers were also assisted by higher teachers. Employees of the Madrasa also had a salary. In 1235, an early monumental water-powered alarm clock that announced the appointed hours of prayer and the time both by day and by night was completed in the entrance hall of al-Mustansiriya Madrasa in Baghdad. Within
4961-596: The Middle East resulted in the first stages of transformation for the complex. The Mongol Sack of 1258 devastated parts of the Madrasa that were later restored. After the initial attack, the Mongols settled in Baghdad under the emperors of the Il-Khanids . Among the notables of the madrasa during this period was the librarian and historian Ibn al-Fuwati who returned to Baghdad in 1281 and was appointed director of
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5082-499: 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
5203-419: 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. In 1675, Huygens and Robert Hooke invented the spiral balance spring , or the hairspring, designed to control the oscillating speed of
5324-415: 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 ,
5445-412: The computer is shut off or in sleep mode . Native applications, however, can wake the computer up from sleep using the built-in real-time clock alarm chip or even power it back on after it had been shut down. Many modern mobile phones feature built-in alarm clocks that do not need the phone to be switched on for the alarm to ring off. Some of these mobile phones feature the ability for the user to set
5566-511: 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
5687-459: 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
5808-575: 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
5929-400: The 1830s, when the use of the telegraph and trains standardized time and time zones between cities. 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
6050-476: 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. 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
6171-524: 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
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#17327930761106292-581: The Levant, and other Islamic countries at the time. Two centuries after Tamerlane's destruction, there was an attempt at revival in 1589 but it closed its doors in 1638. In its place, the Mosque-Madrasa of al-Asifyah was established and connected to the Madrasa. In 1534, the Ottoman Turks seized control, maintaining a stable reign until the British accession in the early 20th century. During
6413-537: 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
6534-620: The Madrasa is now part of al-Mustansiriya University . Currently, the Minister of Culture takes care of the complex of the madrasa. Al-Mustansiriya Madrasa was included on the list of the Islamic World Educational, Scientific and Cultural Organization (ISESCO) in 2013, due to its great importance and significance in Islamic history. Generally, al-Mustansiriya Madrasa is considered the first university of its time. In 2020,
6655-705: The Madrasa's architecture and position within Baghdad was the Mongol Siege of Baghdad (1258) . Today, the Madrasa is in a state of restoration as is it being overseen by the Directorate of Antiquities in Iraq. It is currently a part of al-Mustansiriya University , and is located on the left bank of the Tigris River. Adjacent landmarks include Souk al-Sarai , the Baghdadi Museum , Mutanabbi Street ,
6776-408: The Madrasa. Under Tamerlane , the madrasas of Baghdad, including this one, suffered greatly and studies in them were suspended. He had destroyed Baghdad twice, first in 1392 and second in 1400, and destroyed its schools; he took many of its writers, engineers, and architects to Samarkand . The Madrasa's library has also lost thousands of books and a large number of its scholars left Baghdad to Egypt,
6897-554: The Office of Price Administration. The first radio alarm clock was invented by James F. Reynolds, in the 1940s and another design was also invented by Paul L. Schroth Sr. A clock radio is an alarm clock and radio receiver integrated in one device. The clock may turn on the radio at a designated time to wake the user, and usually includes a buzzer alarm. Typically, clock radios are placed on the bedside stand. Some models offer dual alarm for awakening at different times and "snooze", usually
7018-445: The alarm is triggered, it can play a set radio station or the music from a selected music source to awaken the sleeper. Some models come with a dock for iPod/iPhone that also charges the device while it is docked. They can play AM/FM radio, iPod/iPhone or CD like a typical music player as well (without being triggered by the alarm function). A few popular models offer "nature sounds" like rain, forest, wind, sea, waterfall etc., in place of
7139-549: The alarm's ringtone , and in some cases music can be downloaded to the phone and then chosen to play for waking. Scientific studies on sleep having shown that sleep stage at awakening is an important factor in amplifying sleep inertia . Alarm clocks involving sleep stage monitoring appeared on the market in 2005. The alarm clocks use sensing technologies such as EEG electrodes and accelerometers to wake people from sleep. Dawn simulators are another technology meant to mediate these effects. Sleepers can become accustomed to
7260-426: 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
7381-453: The bed) also exist. Time switches can be used to turn on anything that will awaken a sleeper, and can therefore be used as alarms. Lights, bells, and radio and TV sets can easily be used. More elaborate devices have also been used, such as machines that automatically prepare tea or coffee. A sound is produced when the drink is ready, so the sleeper awakes to find the freshly brewed drink waiting. Clock A clock or chronometer
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#17327930761107502-573: 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. 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
7623-475: The building was lost until 1960 when the Iraqi government restored the Madrasa's complex and opened it for visits and tourists as a historic monument. Al-Mustansiriya Madrasa is one of the only buildings still standing that provides evidence for Baghdad's role as a center for Islamic Art and for the city's role in the development of geometric ornaments. The layout of the Madrasa is a basic four-iwan plan fit into
7744-504: The buzzer. Clock radios are powered by AC power from the wall socket. In the event of a power interruption, older electronic digital models used to reset the time to midnight (00:00) and lose alarm settings. This would cause failure to trigger the alarm even if the power is restored, such as in the event of a power outage . Many newer clock radios feature a battery backup to maintain the time and alarm settings. Some advanced radio clocks (not to be confused with clocks with AM/FM radios) have
7865-420: The circle were two model falcons, made of gold, each inside a golden bowl. Two bronze ball bearings were positioned behind each falcon so that they were not visible to the observer. At the moment of the elapsing of an hour, the mouth of each falcon opened, and out fell the ball bearings. Each time a ball bearing fell, one of the doors inside the arches opened. The doors were golden, but they then became silver (i.e.
7986-580: 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
8107-547: 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
8228-565: 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. The next development in accuracy occurred after 1656 with
8349-542: The complex. All students, including the orphans, were designated an equal wage, bread, and stew. The Dar al-Hadith was dedicated to the study of the sayings and traditions of the Prophet Muhammad. Within this school, there was a senior scholar, or shaykh, who held the highest position of education within the school. Additionally, the School of Medicine was housed in al-Mustansiriya Madrasa. The School of Medicine
8470-637: 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 ( 2 × 10 ). The invention of
8591-469: 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
8712-471: 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
8833-399: 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
8954-563: 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
9075-472: 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. The timekeeping element in every modern clock is a harmonic oscillator , a physical object ( resonator ) that vibrates or oscillates repetitively at
9196-679: The entrance hall of the Mustansiriya Madrasah in Baghdad . From the 14th century, some clock towers in Western Europe were also capable of chiming at a fixed time every day; the earliest of these was described by the Florentine writer Dante Alighieri in 1319. The most famous original striking clock tower still standing is possibly the one in St Mark's Clocktower in St Mark's Square , Venice . The St Mark's Clock
9317-421: 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. This counts the pulses and adds them up to get traditional time units of seconds, minutes, hours, etc. It usually has
9438-459: 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
9559-547: 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
9680-417: The golden door was replaced by a silver one). When the ball bearings fall into the bowls below they then run back to their original positions. Then golden planets ascend into the azure sky within this depiction of the heavens simultaneously with the rising of the real sun in the sky. They move [on the clock face] mirroring the movement of the sun across the sky [so that they eventually] descend and disappear with
9801-404: 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, along with sundials, are possibly
9922-402: 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
10043-441: 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
10164-436: The late 18th to early 20th century, al-Mustansiriya Madrasa was used largely for military purposes such as serving as a place of rest and resource as well as a storage house for soldier uniforms. This multipurpose building also became known as the K han al-Muwasilah in the 18th century specifically, which served as a caravanserai for traders passing through Baghdad. Over the years, the madrasa suffered from neglect, and much of
10285-559: The major focus of education was Islamic law. It became the most prominent and high-ranking center for Islamic studies in all of Baghdad. Madrasas during the Abbasid period were used as the predominant instrument to foster the spread of Sunni thought as well as a way to extend the founder's pious ideals. The architecture of the Madrasa was also an important example of Islamic architectural development in Baghdad. The Madrasa has experienced several periods of decline and reemergence throughout its history. The most significant degradation to
10406-404: 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
10527-422: 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
10648-526: The metal cover at back of the clock itself also functions as the bell. In an electronically operated bell-type alarm clock, the bell is rung by an electromagnetic circuit with an armature that turns the circuit on and off repeatedly. Digital alarm clocks can make other noises. Simple battery -powered alarm clocks make a loud buzzing, ringing or beeping sound to wake a sleeper, while novelty alarm clocks can speak, laugh, sing, or play sounds from nature. The ancient Greek philosopher Plato (428–348 BCE)
10769-456: 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
10890-497: 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,
11011-482: 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. The British had dominated watch manufacture for much of
11132-501: 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
11253-463: The period of Iraq before the Mongol invasion. It is safe to assume that since Ibn al-Fuwati was a native of Baghdad, the following description he gave on the clock was either his eyewitness account or one that he heard firsthand from another person. Ibn al-Fuwati recounts: “On the outside wall of this counter was a circle on which there was a depiction of the heavens, and on it were many finely decorated bronze arches housing finely decorated doors. Within
11374-421: 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
11495-420: 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
11616-471: 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
11737-605: The school of Islamic studies, there were specific divisions of Islamic knowledge. The divisions included the Dar al-Qur'an and the Dar al-Hadith. The Dar al-Qur’an, or the House of Qur’an, was dedicated to the study and recitation of the Qur’an. There was a designated reciter of the Qur'an and a fellow aid to help teach the students. Along with the students, there were thirty orphans who were housed in
11858-435: The setting of the sun. When night comes then there are planets that gradually emerge [to the observer] because of a light glowing from behind them. The [strength of the] light emitting from the discs of the planets [grows gradually and] reaches its fullest intensity on the completion of a full hour. Then this process begins in the next planet-disc and so on until the night ends and the sun begins to rise. In this way, you can know
11979-592: The sound of their alarm clock if it has been used for a period of time, making it less effective. Due to progressive alarm clocks' complex waking procedure, they can deter this adaptation due to the body needing to adapt to more stimuli than just a simple sound alert. The deaf and hard of hearing are often unable to perceive auditory alarms when asleep. They may use specialized alarms, including alarms with flashing lights instead of or in addition to noise. Alarms which can connect to vibrating devices (small ones inserted into pillows, or larger ones placed under bedposts to shake
12100-476: 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
12221-460: 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
12342-509: 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),
12463-488: 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
12584-540: 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. 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
12705-479: The times of the prayers.” In 1973, al-Mustansiriya Madrasa was overseen by the Directorate of Antiquities in Iraq. Since then, the complex has been in a consistent state of reconstruction. Recently, the modern businesses surrounding the Madrasa have been demolished with the intention of restoring the original perimeters of the complex. As a result of the reconstruction and conservation of this complex, al-Mustansiriya Madrasa still plays an important role in Baghdad as
12826-427: 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
12947-521: The traditional clocks found in Damascus at the time. The clock included metallic and golden doors; bird figurines dropping metal balls into vessels that told the elapsing of an hour during the day as well as functions and lighting to announce the night which mirrored the movements of celestial objects. Furthermore, the clock was mentioned with great detail in aI-Hawadith al-Jami'a Wal-Tajarub al-Nafi'a Fi al-Mi'a al-Sabi'a by Ibn al-Fuwati which dealt with
13068-417: The user's choice. Most modern televisions, computers, mobile phones and digital watches have alarm functions that automatically turn on or sound alerts at a specific time. Traditional mechanical alarm clocks have one or two bells that ring by means of a mainspring that powers a gear to quickly move a hammer back and forth between the two bells, or between the internal sides of a single bell. In some models,
13189-477: The war effort. In a pooling arrangement overseen by the Office of Price Administration , several clock companies were allowed to start producing new clocks, some of which were continuations of pre-war designs, and some of which were new designs, thus becoming among the first "postwar" consumer goods to be made, before the war had even ended. The price of these "emergency" clocks was, however, still strictly regulated by
13310-467: Was assembled in 1493, by the famous clockmaker Gian Carlo Rainieri from Reggio Emilia , where his father Gian Paolo Rainieri had already constructed another famous device in 1481. In 1497, Simone Campanato moulded the great bell (h. 1,56 m., diameter m. 1,27), which was put on the top of the tower where it was alternatively beaten by the Due Mori ( Two Moors ), two bronze statues (h. 2,60) handling
13431-470: 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
13552-554: 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.,
13673-475: Was established almost a decade after al-Mustansiriya Madrasa and also taught four schools of thought into one. The management of the Madrasa was carried out by a headmaster who was chosen by the senior state employees. The headmaster was assisted by a number of assistants, led by the supervisor, who was like the financial inspector. A number of employees were also hired to serve the teachers and students. Teachers usually consisted of senior Sheikhs and Imams from Iraq,
13794-414: 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
13915-446: Was invented by either Quare or Barlow in 1676. George Graham invented the deadbeat escapement for clocks in 1720. 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
14036-467: Was led by a senior Muslim physician who was required to have ten students employed to him. There was also a hospital located in the Madrasa, allowing medical students to learn and practice medicine within the same complex. Al-Mustansiriya Madrasa included a variety of buildings such as a hammam , public hospital, pharmacy, food storage site, and kitchen. There was also space designated for student residences. The Madrasa provided food, lodging, clothing, and
14157-404: 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 ,
14278-435: Was said to possess a large water clock with an unspecified alarm signal similar to the sound of a water organ ; he used it at night, possibly for signaling the beginning of his lectures at dawn ( Athenaeus 4.174c). The Hellenistic engineer and inventor Ctesibius ( fl. 285–222 BCE) fitted his clepsydras with dial and pointer for indicating the time, and added elaborate "alarm systems, which could be made to drop pebbles on
14399-636: Was the first to patent an adjustable mechanical alarm clock, in 1847. Alarm clocks, like almost all other consumer goods in the United States, ceased production in the spring of 1942, as the factories which made them were converted over to war work during World War II , but they were one of the first consumer items to resume manufacture for civilian use, in November 1944. By that time, a critical shortage of alarm clocks had developed due to older clocks wearing out or breaking down. Workers were late for, or missed completely, their scheduled shifts in jobs critical to
14520-584: Was the water-powered clock tower near the Umayyad Mosque in Damascus , Syria , which struck once every hour. It is the subject of a book, On the Construction of Clocks and their Use (1203), by Riḍwān ibn al-Sāʿātī , the son of clockmaker. In 1235, an early monumental water-powered alarm clock that "announced the appointed hours of prayer and the time both by day and by night" was completed in
14641-420: 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
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