History of timing devices

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The history of timing devices can be traced back to the Sumerians and Egyptians who lived around 3000 BC. Knew sundials based on simple shadow rods. The shadow staff has been around since 2400 BC. Also known from China. The Greeks later called him " Gnomon ".

Around 2000 BC The Babylonians used the sexagesimal system with the base number 60, from which the twelve system ( duodecimal system ) for the division of hours later developed. The ancient Egyptians divided the day into two twelve-hour periods and used large obelisks on which the movement of the sun could be followed. Water clocks were among the first timekeepers that were not based on observations of the heavenly bodies. One of the oldest was found in the tomb of the Egyptian pharaoh Amenhotep I , around 1500 BC. Found. About 325 BC The water clock came to the Greeks, who called them Klepsydra ("water thief"). Other ancient timing devices are the candle clocks that were used in China , Japan , England and Iraq . In India and Tibet , the so-called timesticks (incense stick clock ) were widespread, as were the hourglasses in some parts of Europe.

The oldest clocks used the shade of the sun - that is, they failed in cloudy weather or at night - and only showed the time very imprecisely. More precise sundials required the seasons to be taken into account, which was difficult with the Gnomon and later led to the alignment of the shadow pointer to the celestial axis . The first clock with an escapement mechanism that converted the rotational energy into vibrations was developed by a Greek in the 3rd century BC. In the 11th century, Arab engineers invented clocks whose gears and weights were driven by water.

A clock in the Musee d'Art et d'Histoire de Neuchatel

Mechanical clocks with a spindle escapement emerged around 1300 in Europe and became the standard timekeeping device until spring-driven and pocket watches followed in the 16th century, and the pendulum clock around 1650 . Quartz watches were invented in the 20th century , followed by atomic clocks . Although the first quartz oscillators were designed for laboratories because of their accuracy, they soon became easy to manufacture and incorporate into wristwatches. Atomic clocks are by far the most accurate of the previous time measuring devices. In order to calibrate other clocks and to define a standard time for the earth, the system of " Coordinated Universal Time " on an atomic basis was finally introduced in 1968 .

Early timing devices

Many ancient civilizations observed the heavenly bodies, especially the sun and moon, to determine the times, dates, and the seasons. Sexagesimal timekeeping methods, widely used today in Western society, first emerged almost 4000 years ago in Mesopotamia and Egypt , and a similar system was later developed in Central America. The first calendars may have been created by hunters and gatherers during the last ice age . They had used sticks and bones that corresponded to the phase lengths of the moon or the seasons. Stone circles, such as Stonehenge in England, were mainly built in prehistoric Europe and in various parts of the world. It is believed that they were used to predict seasonal and annual events such as the equinox or the solstice. Since these megalithic cultures left no record, little is known of their calendars or timekeeping methods.

3500 BC Until 500 BC Chr.

Byzantine sundial with inscription

Sundials have their origins in the shadow clocks , they were the first devices to be used to measure the parts of a day. The oldest shadow clock comes from Egypt and was made from green slate. Egyptian obelisks were built around 3500 BC. They are also among the first shadow clocks.

obelisk

During the day, Egyptian shadow clocks were divided into ten parts, with an additional four "twilight hours" - two in the morning and two in the evening. One type of shadow clock consisted of a long stem with five variable marks and a raised bar that cast a shadow on these marks. It was positioned to the east in the morning and to the west at noon. Obelisks worked the same way, the shadows on the markers allowed the Egyptians to calculate the time. The obelisk also made it possible to determine the summer and winter solstices. The Egyptians also discovered the meridian , realizing that an obelisk's shadow, when it is shortest, always falls in the same direction regardless of the season. Around 1500 BC A shadow clock was developed similar to a curved T-bar. The T-bar was oriented to the east in the morning and turned around at noon so that its shadow was cast in the opposite direction. The Egyptians developed a number of alternative timekeeping devices, including water clocks and a system for tracking the movements of the stars . The oldest description of a water clock comes from the 16th century BC. And was found in the tomb of the Egyptian court official Amenemhet . There were several types of water clocks, ranging from simple to complex. One type of water clock was the so-called inlet clock, it consisted of a bowl with small holes in the bottom. The bowl floated on the water and the holes allowed the bowl to fill at a nearly constant rate. There were markings on the inside of the bowl that indicated the elapsed time due to the rising water level. In the case of the outlet clocks , a falling water level indicated that time was "running out". The oldest water clock was found in the tomb of Pharaoh Amenhotep I , suggesting that it was first used in ancient Egypt. In addition, the Chaldeans proved as early as the 1st millennium BC That water clocks were multifunctional - they developed a closed system of measurements in the form of a water-filled cube that combined time, weight and length measurement. Another Egyptian method of telling the time at night was done with plumb lines (Merkhet). This method has been around since at least 600 BC. Chr. In use. Two merkhets aligned with the pole star were used to create a north-south line (or meridian). By observing certain stars, the exact night hour when crossing the meridian could be measured.

500 BC BC to 1 BC Chr.

About 425 BC The water clock came to the Greeks, who called them Klepsydra ("water thief"). After their introduction, Plato invented a water-based alarm clock. Plato's water alarm clock was dependent on the nocturnal overflow of a vessel filled with lead balls that floated on a column and was constantly supplied with water from a cistern. As a result, the vessel rose up the pillar until it struck the end of the pillar in the morning and tipped over, so that the lead balls pelted a copper plate. Plato's students at the Academy were awakened by the sound of the lead bullets. Another version of the water alarm clock is based on two jugs connected next to a siphon . One jug was filled with water until it overflowed and the water ran through the siphon into the other empty jug. The rising water forced the air out of the empty vessel, which produced a loud whistle. The Greeks and Chaldeans regularly used their timekeeping records as an integral part of their astronomical observations. The Greek astronomer Andronikos from Kyrrhos built in 50 BC In Athens the "Tower of the Winds", with a water clock inside the tower and several sundials on the outer walls.

Functional diagram of a Klepsydre

In the Greek tradition, Socrates' water clocks (Klepsydren) were already used during his lifetime to limit speaking time in court; the Romans later adopted this practice. There are several references to this in the historical records and literature of the period. For example in Theaetetus Plato says that “the men on the other side always speak in a hurry because the running water prompts them to”. Another mention is made in Lucius Apuleius' “Golden Donkey”: “The secretary of the court called on the summoned witness for the prosecution. Thereupon an old man whom I did not know stepped forward. He was invited to speak as long as there was water in the hollow sphere. The water was poured through a funnel into the neck of the hollow ball and flowed out through the fine perforation at the bottom of the ball. ”The clock in Apuleius' calculation was only one of several types of water clocks used.

Klepsydrons were more useful than sundials because they could be used indoors, during the night, and when the sky was cloudy. Since they weren't as accurate as sundials, the Greeks looked for a way to improve their water clocks. About 325 BC The Greek water clock was adapted, it got a face on which exactly one hour could be read. This made reading the water clock more precise and convenient. One of the most common problems in most types of klepsydrene has been caused by water pressure. When the container is full, the water flowed out faster due to the higher pressure. As a result, the water had a different flow rate depending on the level. This problem was posed by the Greek and Roman watchmakers from 100 BC onwards. Chr. Treated. In order to counteract the increased water pressure, the water clocks were given a conical shape. The thin drain made it possible for the water to drip off consistently, regardless of the water surface in the clock. In the centuries that followed, further improvements were made to the water clock. The clocks were more elegant in their design and provided with gongs in order to notify the full hours noisily. Other water clocks were equipped with miniature figures, or movable mechanisms opened a door or rang a bell every full hour. There were still unsolved problems, such as the effect of temperature. Cold water has a greater density than warm water, which results in a different flow rate. Furthermore, the water meter could not be used in frost.

Although the Greeks and Romans were way ahead in water clock technology, the shadow clocks continued to be used. The mathematician and astronomer Theodosius of Bithynia is said to have invented a universal sundial that showed the correct time everywhere on earth. Other contemporaries wrote about the sundial in mathematics and in the literature of the time. The Roman builder and chronicler Marcus Vitruvius Pollio described the mathematics of the Gnomones (shadow pointer) in his standard work De Architectura and already described 13 different types of sundials. When it came to timekeeping, the Romans shone less through innovation than through conquest and written fixation. This is surprising insofar as their precise language and jurisprudence suggests that precise time measurement and division were essential, especially due to the size of the Roman Empire. Due to the significantly longer shifts than in the south of the empire, the Roman legionaries stationed in Britain complained to their commanders. In 55 BC During a personal stay in Britain, Julius Caesar noticed that British summer nights are shorter than Italians. Probably the oldest Roman sundial that was made in the 3rd century BC. BC was built in front of the Temple of Quirinus, according to tradition, it was a booty from the First Punic War . Due to the change of location in 262 BC It displayed the wrong time for 100 years until it was noticed and the marks and angles for Rome's longitude were adjusted.

1 AD to 1500 AD

Water clocks

(1) water; (2) timing ruler; (3) drain hole; (4) Water collecting tank

Joseph Needham speculates that the introduction of the spout water clock in China dates back to the 2nd millennium BC. BC, during the Shang Dynasty , and no later than the 1st millennium BC. With the beginning of the Han dynasty in 202 BC. Chr. The outlet water meter was gradually replaced by the inlet water meter. The inlet water meter had an indicator stick on which a float weight was placed. To compensate for the falling pressure head in the container, Zhang Heng installed an additional tank between the reservoir and the inflow. This adjusted the flow rate of the water to the time measurement. Around 550 AD, Yin Gui described the first water clock operated in China with a constant liquid level. The details of this water clock were later described by the inventor Shen Kuo. In AD 610, during the Sui Dynasty, the equilibrium water clock was invented by two inventors, Geng Xun and Yuwen Kai. By shifting the weight of the float on the float arm, the pressure on the water surface in the expansion tank was changed. Markings of standard positions on the float arm made it possible to regulate the different lengths of day and night due to the flow speed of the water. So this equilibrium water clock could be used in all seasons.

Water clock with float, counterweight and dial to display the time

Between 270 BC BC and AD 500, Greek and Roman watchmakers as well as astronomers were busy developing complex mechanized water clocks. This was only made possible by the inventions of Euclid , who founded the theorems of geometry, and Archimedes , who taught the laws of the lever and pulley, the cogwheel and the endless screw, as well as the fundamental laws of hydraulics. A student of Archimedes', a barber by the name of Ktesibios, who applied the laws of hydraulics and mechanics to the water clocks, built a water clock with a dial and pointer. In addition, the regulation of the water flow has been adjusted, which significantly improves the accuracy of the water clocks. Various water clocks were built. For example, there were water clocks with bells and gong striking, while others opened windows and doors, behind which figures emerged. Still others showed astrological models of the universe. The monastery water clock works in a similar way to the hourglass: water flows from an upper ball through a tube into a lower ball and is turned around after a calibrated unit. The water pendulum clock makes use of the properties of the pendulum. The compensation water clock of the Greek Pyrlas worked in conjunction with mercury and compensated for temperature fluctuations. Finally, there is the whale clock, which consists of a frame in which a drum can move up and down depending on the water level in the container. An axis rod goes through the center of the drum and moves over a time scale so that the time can be read.

Elephant watch from Al-jazari

Some of the most elaborate water clocks were designed by Muslim engineers. In particular, these are the Al-Jazari water clocks, which were built in 1206, or the so-called elephant clock. This water clock recorded the position of the hours, which meant that the flow rate of the water could be changed. This enabled it to be adjusted daily to the unequal length of the days throughout the year. To achieve this, the clock had two tanks, the upper tank telling the time. This was connected to mechanisms via a flow rate regulator and the lower tank. At daybreak, the upper tank was opened and the water flowed into the lower tank via a float so that a constant pressure was maintained in the receiving container.

Water clocks with gears and escapement

The earliest example of a fluid-powered escapement was described by the Greek engineer Philon of Byzantium (3rd century BC) in his technical treatise Pneumatics (Chapter 31). Another early escapement clock was built in Chang'an by tantric monk and mathematician Xing Yi and government official Liang Lingzan. It was an astronomical instrument that was also used as a clock. This water clock was created as an image of a celestial sphere and showed the equator and the lunar orbits in their order. The water flowed in balls and automatically turned a wheel. One full turn of the wheel corresponded to a day and a night. Two rings were attached to the outside of the celestial sphere. On these rings the model of the sun was mounted on one and a model of the moon on the other. These rings orbited the celestial sphere as the so-called orbit of these two planets. Half of the celestial sphere was sunk into a wooden case, the surface of which represented the horizon. This astronomical instrument allowed the exact determination of time, sunrises and sunsets as well as the full and new moon. In addition, there were two wooden bushings attached to the horizon surface. The first wooden socket struck a bell and indicated the full hours by striking the bell, the second struck a drum, which announced a new quarter. All tasks were handled by machines inside the housing, which were dependent on wheels and shafts, hooks, pins and locking bars as well as braking devices.

Use of the Xing Yi water clock was impaired by the temperature fluctuations in the water. This problem was solved by Zhang Sixun in AD 976 by replacing the water with mercury, as mercury remains liquid down to minus 39 ° C. Zhang Sixun implemented this change in a tower clock about ten meters tall, which was fitted with an escapement and sounded a bell every quarter of an hour. The Chinese mathematician and engineer Han Kung-Lien also built a water clock with an escapement in 1088 AD. A wheel with scooping chambers was built into a wooden frame. A pumping chamber was filled with water every 24 seconds. The weight of the filled water scoop depressed a trigger. This pulled on a chain that released the escapement and let the wheel advance by a notch before the lock re-engaged. A Chinese manuscript from 1090 AD, kept in the Beijing National Library, tells of a water clock that Su Song built for the palace gardens in Kai-Feng. The "heaven machine", which was built in 1088 AD, was ten meters high. The cladding of the cylindrical building had five openings in which tablets and figures with cymbals and gongs indicated the time. The mechanism of this clock worked as follows: A wheel about four meters in diameter was driven by a steadily flowing jet of water so that containers attached to the circumference of the wheel were filled. When a container had reached a certain weight, an inhibition was released by a device until the next cup was under the water jet; then the wheel was locked again. This regulating mechanism already anticipated the mechanical escapements, as they were later implemented in the wheel clocks. A lever mechanism moved the figures and panels that indicated the time. This water clock had the first known endlessly power-transmitting chain drive in watchmaking. This clock was originally located in the capital of Kai-Feng. There it was dismantled by the Jin Army and taken to the capital Yanjing (now Beijing), where it could not be put back together. As a result, Su Song's son So Xie was ordered to make a replica.

Tower clock from Su Song's book

The bell towers of Zhang Sixun and Su Song, built in the 10th and 11th centuries, were the first clocks to have a striking mechanism. This mechanism made it possible to produce a percussion sound every hour using jacks. The first chiming clock outside of China was the bell tower near the Umayyad Mosque in Damascus . It was built by the Arab engineer al-Kaysarani in 1154 and announced the full hour with a chime.

The first clock with a gear was invented in the 11th century by the Arab engineer Ibn Khalaf al-Muradi in Islamic Iberia. It was a water clock that worked with range and planetary gears. Other monumental water clocks with complex gear trains and areas of automatons were built by Muslim engineers. Like the Greeks and Chinese, Arab engineers also built water clocks with an escapement powered by liquids. Heavy swimmers were used as weights. The constant head system of the watch was used with an escapement mechanism. This hydraulic control is still used today to lift heavy loads slowly and steadily.

The water clock was considered a royal gift for centuries. As early as 507 AD, Theodoric, the then ruler over Italy, gave Sigmund, King of Burgundy, a shadow clock and a water clock. In Baghdad , the Muslim culture had reached its apex when the caliph Hārūn ar-Rashīd presented Charlemagne as a gift on his coronation with an ore water clock with damascene gold. It was the most magnificent water clock with automatons and carillon that was ever known.

Mercury clocks

In 1277 a mercury clock was described for the first time in the Libros del saber de Astronomia , a Spanish work consisting of scientific translations of Arabic and Jewish texts. This mercury watch already had the essential characteristics of a mechanical watch. She was propelled by weights. A rope moved a drum that contained mercury. Mercury is a viscous substance whose inert property was used as an inhibitor. The rotating drum was divided into sectors by built-in perforated sheets. When the drum was rotating, the mercury flowed from one chamber through the perforation into the next chamber. Due to its inertia, it slowed down the rotation of the drum. By appropriately adjusting the driving weights, the drum made one revolution in four hours. A reduction in the ratio 6: 1 enabled the drum to cover one revolution in 24 hours. Thus, the time and other astronomical data could be read directly on the display panel.

Fire watches

A stick coated with pitch and sawdust was cut to a specific length. Small metal balls were attached to the rod with threads at regular intervals. The staff protruded over a gong. If the stick was lit at sunrise, the flame would eat its way along the stick.

In the process, she burned off the threads from which the metal balls were attached. They fell down on the gong, struck it and people could hear that a unit of time had passed again.

Candle clocks
Candle clock

It is not known where or when candle clocks were first used, their earliest mention is from a Chinese poem written by Jianfu in AD 520. According to the poem, the candle was a means of determining the time of night. Similar candles were used in Japan until the beginning of the 10th century. It was mentioned in history that King Alfred the Great of England invented the candle clock in Europe in the 9th century. It consisted of six wax candles that were 30 centimeters high and an even thickness of 2.5 centimeters. A wax candle burned for four hours. His chronicler reported that he spent exactly eight hours on public duties, eight hours on studying, eating and sleeping, and eight hours on prayer. In order to be able to keep up his structured daily routine, he needed six wax candles a day, which he kept in a lantern in order to optimize the evenness of the burning.

The most modern candle clocks of their time were those from Al-Jazari in 1206. One of his candle clocks contained a dial with a time display, which was held by a bayonet lock for the first time. This fastening mechanism was still used in modern times. Donald Routledge Hill described the Al-Jazari candle clocks as follows:

The candle, whose burning speed was known, had a hole on the underside of the cap through which the wick was passed. The burned wax was collected in the indentation and could be removed periodically so that it did not come into contact with the constantly burning candle. The lower part of the candle lay in a shallow bowl, which was connected to a counterweight by a ring on its side with rollers. As the candle burned down, the weight pushed up at a constant speed. The time display was operated from the bowl at the bottom of the candle.

Oil lamp clocks
Oil lamp clock

The oil lamp clocks were also a variation of the early timing devices. These consisted of a stepped glass room with a vertical scale. This glass space served as a storage container for the fuel supply for the lamp installed on the side of the storage container. Oil or oil served as fuel. Tran was typically used because it burned cleaner and more evenly than oil. Due to the fuel consumption of the lamp, the oil or transparent level in the glass reservoir sank, whereby the time was read off on the scale. With the oil lamp clock, a rough time measurement was possible at night.

Incense clocks
Chinese incense stick clock in the shape of a dragon, with bell alarm

In the Far East - in addition to water clocks, mechanical clocks and candle clocks - incense clocks in various forms were also used. Incense clocks were first used in China around the 6th century. In Japan the incense clocks are still used in the Shōsōin (treasury of the Tōdai-ji ), although the characters are not Chinese, but Devanagari. Due to their frequent use of Devanagari signs and their use in Buddhist ceremonies, Edward H. Schäfer speculates that incense clocks were invented in India. Although similar to the candle clock, the incense clock burned evenly and without a flame, making it more accurate and safer for indoor use.

Various types of incense clocks have been found; the most common forms are the incense sticks and incense seals. One type of incense clock was equipped with calibrated incense sticks, while others had an elaborate mechanism. For example, weights were attached at regular intervals with a thread. When the incense sticks burned off, the weight fell on a gong after a certain time. Some incense clocks were installed in elegant bowls, in which the weights fell into a decorative compartment through an open base plate. There were incense sticks with different scents, so that the hours were marked by a change in the scent note. The incense sticks were used in stick form or as spirals. The spiral shape was often hung on the roofs of houses and temples and had a longer burning time compared to the bars. Up until 1924, incense sticks were a special type of timepiece used exclusively in Japanese geisha (okiya) houses. The geisha was paid for their entertainment according to the number of burned Senkodokei (incense sticks for a fee). Incense seal clocks were used for official occasions and events and were of primary importance for religious purposes. The seal was etched out of wood or a stone slab with one or more grooves. It was filled with incense and used mainly by Chinese scholars and intellectuals. These clocks were common in China, but smaller numbers were also made in Japan. To mark the transition from a certain hour, various resins or fragrant incense sticks as well as incense powder were applied to the clock surface. This resulted in a variety of incense clocks, depending on the fragrance used. The length of the incense line directly determined the burning time of the clock. There were incense clocks for short periods of time and those that burned between twelve hours and a month.

While the incense holders were initially made of wood or stone, the Chinese gradually introduced metal plates. This enabled artisans to make the incense clocks easier and better to decorate them. Another benefit was the ability to vary the paths of the grooves to accommodate the changing length of days in the year. As smaller mounts became available, the watch grew in popularity with the Chinese and was often given as gifts. Incense stick seal watches are often sought after by today's watch collectors, but few are available, either they have already been sold or are owned by museums or temples.

Astronomical clocks

Arabic astrolabe around 1208

An astrolabe is a scientific astronomical device that was also used by Muslims to establish the time of prayer, for simple surveying purposes, and for navigation. Among other things, it provided the Arab and European astronomers with the exact time until the 17th century. The astrolabe consisted of a ring in which a disc with a rotating radius was suspended. Contemporary Muslim astronomers used a variety of very accurate astronomical clocks for use in their mosques and observatories, such as the Al-Jazari water-powered astronomical clock from 1206 and the Ibn al-Shatir astronomical clock in the early 14th century. The most modern astrolabes for timekeeping were the aligned astrolabes of Al-Biruni in the 11th century and of Muhammad ibn Abi Bakr in the 13th century. These were used as timing devices and as calendars. Al-Jazari's castle clock from 1206 was the most modern water-powered astronomical clock. It is considered an early example of a programmable analog computer. This clock was a complex device that was about 11 meters high and had several functions besides measuring time. It contained a representation of the zodiac and the solar and lunar orbits and had a pointer shaped as a crescent moon. The point of this pointer passed over a gate that opened automatically every hour and let a figure emerge. The length of the days and nights could be reprogrammed according to the seasons. In the front stood five musicians who were connected to a lever by a hidden camshaft. This lever was moved by the rotating water wheel, which automatically played music at a certain time. Other components of the castle clock were: a storage container with a float device, a float chamber and a flow regulator as well as two machines from which balls fell into vases to serve as an alarm clock.

Modern timing devices

Modern equipment of ancient origin

Sundial in Carcassonne (Aude, France); 1961 manufactured by René RJ Rohr (1905-2000)

With sundials, the shadow of a point-shaped body ( nodus ) is read on a dial. The temporal hours of the day used in antiquity depend on the season. The day was divided into two parts of twelve hours: the light day, which goes from sunrise to sunset, and the night from sunset to sunrise. In summer the daytime hours were longer than the nighttime hours, in winter it was the other way around. The idea of ​​using hours of equal length all year round was applied by Abul-Hasan Ibn al-Shatir in 1371. His idea was based on earlier developments in trigonometry by Muhammad ibn al-Jabir al-Harrānī Battani (Albategni), who was known as Ibn al-Shatir. The gnomon (shadow pointer) was aligned parallel to the earth's axis, so the hour lines indicated the same time on every day of the year. His sundial is the oldest extant sundial that is aligned with the earth's axis. This concept was used in western sundials from 1446 onwards.

After the adoption of heliocentrism and equal hours, as well as advances in trigonometry, sundials in their current form were built in large numbers during the Renaissance . In 1524, the French astronomer Oronce Finé built an ivory sundial that still exists today. In 1570, the Italian astronomer Giovanni Padovani published a treatise, including instructions for making and laying wall paintings of the vertical and horizontal sundials. Around 1620 Giuseppe Biancani also describes how sundials are to be constructed in Constructio instrumenti ad horologia solariums . During his circumnavigation in 1522, the Portuguese navigator Ferdinand Magellan used 18 hourglasses on each of his ships. Since the hourglass was one of the few reliable methods of measuring time at sea, it is speculated that it was used on board ships as a supplementary aid to navigation as early as the 11th century. However, the earliest evidence of its use in painting appears in 1338 (Allegory of the Good Government by Ambrogio Lorenzetti). As today, hourglasses were based on the sand flowing through a narrow chamber from an upper to a lower chamber. Usually the elapsed time was limited to half an hour. From the 15th century onwards, hourglasses were used in a wide range, mainly for measuring short periods of time, for example as a pulpit clock to determine the duration of a sermon or even the speaking time in court. In the seafaring, they determined the watch sequence in four hours of watch at eight glasses. A cabin boy had to turn the hourglass every half hour. The hourglass was also used in industry and in the kitchen. They were the first reliable, reusable, sufficiently accurate and easy to build timing devices. In the Middle Ages, the hourglass was seen as a symbol of the passing of time and human transience. Although the hourglass was also used in China, it is not known how long it was used there.

Western European mechanical watches

The earliest medieval European clockmakers were Christian monks. Medieval monasteries and educational institutions needed clocks because daily prayer and work schedules were regulated exclusively according to them. This was done with different types of timing devices, such as the sundial, the water clock, or the candle clock. These types of clocks were also used in combination. When mechanical clocks were used, they had to be readjusted twice a day to ensure accuracy. Important times were announced by the sound of bells or a mechanical device such as a falling weight or a rotating knocker. The necessities of piety and the technical skills of medieval monks were crucial factors in the development of clocks. There were also talented watchmakers among the monks. In 996 AD the future Pope Sylvester II erected the first noted clock in the city of Magdeburg . Peter Lightfoot, a 14th century monk from Glastonbury, built one of the oldest clocks that can still be seen in the Science Museum in London . The mention of clocks in the 11th century writings suggests that they were well known in Europe at that time. In the early 14th century, the Florentine poet Dante Alighieri referred to a clock in his Paradiso that contained the first literary reference to an hour-bell movement. The earliest detailed description of the movement was given by Giovanni Da Dondi, professor of astronomy in Padua , in his 1364 treatise by IL Tractatus Astrarii . This movement featured some modern replicas. Other notable examples during this period were set up in Milan (1335), Strasbourg (1354), Lund (1380), Rouen (1389), and Prague (1410).

The clock in Salisbury Cathedral ( Wiltshire , England) from 1386 is the oldest clock in the world, made almost entirely of original components. This watch has no dial as it only strikes a bell at the precise times. The wheels and gears were placed in an open, box-like iron frame with a side length of 1.20 meters. The frame is held together with metal dowels and plugs. It is driven by the force of gravity of two large stones that are suspended from a belt pulley. As the weights fall, ropes unwind from the wooden barrels. One barrel drives the drive wheel, which is regulated by the escapement, and the other drives the striking mechanism and pneumatic brake. Peter Lightfoot's cathedral clock, built in 1390, works on the same system. By setting the dial, the view of the medieval universe was shown with its sun and moon orbit, which rotate around the centrally located globe. Figures are placed above the clock that strike the bell while a set of tournament knights turn on a rail every 15 minutes. This clock was converted in the 17th century with a pendulum and an anchor escapement. It was moved to the London Science Museum in 1884, where it still works today. Similar astronomical clocks can still be seen today at the cathedrals of Exeter , Ottery Saint Mary, and Wimborne Minster .

Richard Wallingford

A clock that no longer exists today was built in the 14th century by Abbot Richard of Wallingford at Saint Albans Abbey. When Henry VIII dissolved the monasteries, this clock was destroyed, but records made a complete reconstruction possible. In addition to the time, this watch could also accurately predict the phases of the sun and moon as well as the position of the stars and planets. A display made it possible to read the current tide on London Bridge . The clockmaker Giovanni de Dondi created an astronomical clock (astrarium) between 1348 and 1364, which was unparalleled from a technical point of view over the next two centuries. This clock also no longer exists today, but was recreated based on drawings by Leonardo da Vinci and, above all, on the basis of precise technical drawings and descriptions that de Dondi wrote down during construction. In contrast to many other astronomical clocks, this clock was only small in size and was made entirely of brass in 107 individual parts. De Dondi's clock had seven faces which, in addition to the time, also indicated the positions of the sun, moon and five other planets as well as all religious feast days. The accuracy and versatility of this work was previously unknown. The reconstructions can be seen today in the National Museum of American History at the Smithsonian Institution in Washington DC, in the Paris Observatory, in the Science Museum in London and in the Beyer Watch Museum in Zurich.

Medieval life was regulated by a multitude of bells from the church and city towers. Prayer times of the monasteries, opening times of city gates, court and market times and other important times were heralded by the towers. A reliable time display was required for this; a necessity that the sundials and water clocks did not meet.

While clocks were mainly used for religious purposes in the Middle Ages, they were also used for secular time measurements from the 15th century. Official timekeeping became a local custom in Dublin , with a general clock on the City Court and Town Hall until 1466. This clock was the first of its kind in Ireland and had only an hour hand. The increasing pomp in the castles led to the construction of large tower clocks. A clock tower has been preserved from Leeds Castle. The clock from 1435 was decorated with pictures of the crucifixion of Jesus as well as pictures of Mary and St. George.

In the Middle Ages, mechanical clocks were used in many bell towers in Western Europe. The clock tower of Saint Mark in Venice was assembled in 1493 by the clockmaker Gian Carlo Rainieri from Reggio Emilia. In 1497 Simone Campanato formed a large bell, also called Marangona, for the bell tower of Saint Mark. This bell was installed on December 1, 1497 and had a diameter of 1.27 meters and a height of 1.56 meters. The beginning and the end of a working day are announced by two mechanical bronze statues 2.60 meters high, which strike the bell with a hammer. In 1410, the two clockmakers Mikulas von Kadan and Jan Šindel designed the Prague astronomical clock . It consists of three main components: 1. the astronomical pointer, which represents the position of the sun and moon in the sky and shows other astronomical details; 2. the clockwork called “The Walk of the Apostles”, which lets figures of the apostles and some other sculptures appear every hour on the hour; and 3. the calendar hand, which shows the months with medallions. Around 1490, the remaining hands were added by the clockmaker Jan Růže, and the clock received its Gothic design. The Prague astronomical clock was the third of its kind. The first was made in Padua, Italy in 1344.

Early mechanical watches did not use minutes and seconds displays. A minute indicator is mentioned for the first time in a manuscript from 1475. Clocks with minute and second displays have existed in Germany since the 15th century. Clocks with minutes and seconds were still in the minority and their displays were inaccurate. It was only with the development of the pendulum that greater accuracy of the display became possible. In the 16th century, the astronomer Tycho Brahe used clocks with minutes and seconds to observe stellar positions.

Decimal clock face (from the time of the French Revolution)

Between 1794 and 1795, the French government requested the introduction of decimal clocks. A day was divided into ten hours and the hour was 100 minutes. The astronomer and mathematician Pierre-Simon Laplace and other intellectuals then changed the clock setting to decimal time. A clock in the Palais des Tuileries showed the decimal time until 1801. The cost of replacing all clocks in France prevented the decimal clocks from spreading. Because decimal clocks were only helping astronomers instead of ordinary citizens, it was one of the most unpopular changes associated with the metric system, and so it was discarded.

Ottoman mechanical clocks

In 1565, the Ottoman engineer Taqi ad-Din described a weight-driven mechanical clock in his book The Brightest Stars for the Construction of Mechanical Clocks (al-Kawākib ad-durriyya fī waḍʿ al-bankāmat ad-dauriyya). This had a Foliot (German: Waag, Balkenwaag or spoon balance) with escapement, cogwheels, a wake-up device and a representation of the moon phase. Similar to the European mechanical alarm clocks of the 15th century, the alarm time was set by moving a plug. The clock had three displays, for the hours, the minutes and the degree. Taqi al-Din later constructed a mechanical clock for the Istanbul Observatory, which he used to observe the right ascension . In astronomy, the right ascension is the angle between the longitude of the vernal equinox and the longitude above which the observed object is measured on the equatorial plane. It is the equivalent on the (imaginary) celestial sphere to the geographic longitude on earth. This clock had an hour, minute and second display. Each minute was divided into five seconds. This was an important innovation in practical astronomy in the 16th century, as mechanical clocks at the beginning of the century were not accurate enough for astronomical purposes.

Watch development in Japan

Japanese clocks (Clock and Jewelry Museum Frankfurt)
The "10,000 years clock" (example of a Wadokei clock from 1851)

Mechanical clocks made of brass or iron with a verge escapement were introduced to Japan by Jesuit missionaries in the 16th century. They founded a missionary school in Nagasaki Prefecture to provide general and vocational education. There the students learned to build clocks, organs and astronomical devices. From 1635, Japan began to isolate itself from foreign influence ( sakoku ), and foreign travel was also prohibited by the Tokugawa shogunate . But as the country became more and more isolated from the outside world, Japanese watchmaking flourished for three hundred years. The royal seat of Edo (today's Tokyo ) became the center of Japanese watchmaking. Soon after came the first Japanese timepiece, called Wadokei that of western watches is distinguished in that they are up to the second half of the 19th century temporal hours anzeigten. For the time measurement, each day from sunrise to sunset was divided into a daytime and a nighttime. The day and night were each divided into six periods. Since the length of day and night varied continuously throughout the year, the lengths of these periods also changed daily. The Wadokei clocks had to cope with these daily variations. That worked well; later versions were equipped with alarm mechanisms. The Wadokei clocks were made until 1872, when the Japanese cabinet decided to introduce the equinox at the same time as the Gregorian calendar was introduced . The old Japanese time system was abandoned, the wadokei clocks lost their use, and from then on the Japanese clockmakers built clocks according to the western system.

As there was a lack of experience in Japan with clocks for the new time system, clocks were initially imported from the West. Western technologies were initially used in the construction of wall clocks. The complex Japanese technology reached its climax in 1850 in the "10,000 year clock" of Tanaka Hisashige, who later founded the Toshiba group. In 1881, Hattori Kintarō founded a watch and jewelry business (today the Seiko Group) and later his own watch manufacturer Seikōsha , thus giving the go-ahead for the development of a Japanese watch industry. Seikōsha became one of the most important watch factories in the world and is significantly involved in many technical developments, such as the quartz movement.

In the 1970s, a new wristwatch came onto the market from Japan that had no mechanical movement but computerized control. The range of services of this wristwatch included not only precise timekeeping, but also displays for the date and the day of the week and also took leap years into account.

Watch types

Clocks were built for a wide variety of uses, ranging from wristwatches to atomic clocks. Throughout the history of timepieces, clocks have used a variety of energy sources, such as the sun, water, gravity, electricity including the atom. The Chinese official Liang Lingzan and the monk Yi Xing are credited with inventing the mechanical clockwork. However, mechanical clocks were not used in the western world until the 14th century. From the year 1550 the precision of the watch mechanics reached a remarkable level. Inspired by the zeitgeist of the Renaissance, mechanical clocks with striking mechanisms and astronomical information about periods of up to 20 years were created. However, gear differences of up to one hour a day had to be accepted.

Pendulum clocks

Early pendulum clock from Christian Huygens

With the miniaturization of clocks in the 15th century and the manufacture of personal clocks in the 16th century, the innovations in mechanical clocks continued. In 1581 the famous astronomer and physicist Galileo Galilei proposed his pendulum theory. It says that the oscillation time of a pendulum is hardly determined by the oscillation amplitude, but primarily by its length. Although Galileo studied the pendulum, he never designed a clock based on this principle. The first pendulum clock was designed and built by the Dutch scientist Christiaan Huygens in 1656 . Early versions had a time deviation of less than a minute per day, which was soon improved to a few seconds.

In the 17th and 18th centuries, the Jesuits also contributed to the development of the pendulum clock because they had an unusually keen understanding of the importance of accuracy. The Italian Father Giovanni Battista Riccioli developed an accurate one-second pendulum that ideally generated 86,400 oscillations per day. Jesuits played a vital role in spreading scientific ideas and collaborated with contemporary scholars such as Huygens.

The invention of the lever escapement in 1670 made the development of modern pendulum clocks possible. The previous long pendulum clocks had used the verge escapement, which required a very large pendulum swing of about 100 degrees (?). To reduce this large pendulum swing, most pendulum clocks with a verge escapement used a short pendulum. However, these short pendulums had the disadvantage of inaccurate time measurement, required more kinetic energy and caused more friction and wear than the long pendulums. By using the anchor escapement, the swing of the pendulum could be reduced to four to six degrees, which meant that a long pendulum could be used again. Most pendulum clocks were built in such a way that the pendulums were tuned to a time interval of one second per pendulum oscillation, whereby the length of the pendulum was about one meter. Due to the length of the pendulum and the long drop space of the drive weights, tall and narrow pendulum clocks had to be made.

The accuracy of astronomical time determination with second pendulums reached a tenth of a second as early as the 18th century , which stimulated the construction of temperature-compensated pendulum rods. The Riefler pendulum , developed around 1880, improved the time systems of the observatories even further in the range of a few 0.01 seconds and in 1921 the Shortt clock in milliseconds. These precision pendulum clocks served as the basis of time services until around 1960 (and were then replaced by high-precision quartz clocks and later atomic clocks ).

Since the pendulum clocks had to be set up permanently, marine chronometers were often used as work clocks on the telescope . The synchronization was initially carried out using electrical contacts and later using radio technology or time signal transmitters .

Pocket watches

Pocket watch with spring cover

A further technical refinement was brought about in 1676 by the English philosopher Robert Hooke, which was devised by the English philosopher Robert Hooke and used in particular on grandfather clocks. This invention made it possible for Christiaan Huygens to insert a spiral spring (balance wheel) into the regulators of conventional watches, which made them capable of natural oscillation. This made it possible to reduce the disturbances caused by the uneven drive and by external influences when wearing the pocket watches, at the same time a great advance in the accuracy of the pocket watches was achieved. Huygens' contributions to improving the reliability of timepieces were critical to the mass production of watches.

Wrist watches

Wrist watch showing the moon phase

In 1904, the pilot Alberto Santos-Dumont asked his friend Louis Cartier , a French watchmaker, to design a watch that could be useful during his flights. In 1868, Patek Philippe invented a wristwatch, but it was intended more as a piece of jewelry for women. Since pocket watches were unsuitable for pilots, Louis Cartier made the Santos wristwatch. This was the first men's wristwatch that was intended for practical use and is still in production today. The wristwatch gained popularity during the First World War. Since wristwatches were more comfortable than pocket watches in warfare, they were particularly preferred by officers. Artillery and infantry officers were dependent on their watches as coordinated operations were necessary during the fighting. The so-called trench clock was created during the First World War. In this watch, the glass was protected by a steel grille to prevent the glass from breaking. To make reading the time as easy as possible, these early military watches had particularly large numbers of hours on the dial and very large hands that were additionally provided with a luminous material made of radium so that the soldiers could read the time even in the dark.

In the 1920s, the method developed by Abraham-Louis Perrelet around 1770 with a rotating flywheel, which enabled the automatic winding of a clock, became established. In the period between 1770 and the beginning of the 20th century, this technology could not prevail because it was mainly used in pocket watches and these were not moved enough. It was not until the wristwatch that the process developed by Perrelet achieved its breakthrough, as the arm movements of the watch wearer were sufficient to operate the automatic winding mechanism. Due to the changed wearing habits of the wristwatches, shocks, vibrations and temperature fluctuations had to be taken into account during production in order to guarantee a long service life for the wristwatch. A pioneer in this field was the German watchmaker Hans Wilsdorf , who already subjected some of his watch creations to very special tests at the beginning of the century. A decisive innovation in the wristwatch sector in the 1930s was the Nivarox spiral developed by Reinhard Straumann. It consisted of a special alloy, was independent of temperature, elastic, non-magnetic and rust-free. In 1931 a company in La Chaux-de-Fonds, Switzerland, developed the so-called Incabloc system, in which bumps and blows were converted into a controlled mechanical movement. This system is still used today. The German watchmaker Helmut Sinn has also been making wristwatches for the blind since the 1950s .

Marine chronometer

A marine chronometer is a precise time measuring device that is used in seafaring to determine the longitude and the astronomical location. Marine chronometers were first developed in 1759 by the English watchmaker John Harrison . In 1761, John Harrison won the price of £ 20,000 offered by the British Parliament in 1741 for the solution of the longitude problem with the clock he had developed . This chronometer, known as the H.4, achieved an accuracy of 5.1 seconds on the journey to Jamaica and back in stormy seas in five months. The Swiss watchmaker Louis Berthoud (1753–1813) manufactured a precision pocket chronometer that Alexander von Humboldt tested in 1799 on his voyages. With this marine chronometer it was possible to determine the length very precisely. As a result, Humboldt was able to make exact descriptions of the ocean currents and, by comparing them with the displacement of the ship, calculate their direction and strength using this specific information. Marine chronometers continued to be used in the navy after the Second World War. The decline of the chronometer came only in the second half of the 20th century with the invention of the quartz watch, the accuracy of which improved by three powers of ten. There was no longer any need for chronometers as navigation instruments.

Modern chronometer

Chronometers are particularly precise mechanical watches that were previously required for time determination and navigation in sea and aviation. Mechanical chronometers are still made today for collectors and enthusiasts. A mechanical watch is called an official chronometer if the movement meets certain precision standards. Every single movement is subjected to a precisely defined test and individually certified. Worldwide, this test may only be carried out by the independent Swiss observatory Contrôle officiel suisse des chronomètres (COSC). Every year over a million chronometers are checked and certified with a serial number.

Quartz watches

In 1880 the piezoelectric properties of crystal quartz were discovered by Jacques and Pierre Curie . In 1921 the first quartz oscillator was built by Walter Guyton Cady . Warren Marrison and JW Horton built the first quartz watch at the Bell Telephone Laboratories in Canada in 1927 . The following decades saw the development of quartz clocks as precision time measuring devices in laboratories; their practical use was limited to the calibration of sensitive counting electronics. It was not until 1932 that the German physicists Adolf Scheibe and Udo Adelsberger developed a quartz watch that was able to measure small weekly fluctuations in the rate of rotation of the earth. In the mid-1930s, the quartz watch was developed for series production by the German company Rohde & Schwarz and manufactured in 1938 as the world's first portable quartz watch. In 1969, the Seiko company in Japan produced the first quartz wristwatch, called the "Astron", for the mass market. The “Astron” had a battery capacity of one year, its accuracy and low manufacturing costs resulted in the proliferation of quartz wristwatches.

Digital clocks

Digital technology was used to measure time as early as the 19th century. The display variants used up to then, such as "falling leaves", "discs" or "rollers" with printed numbers to indicate the time, were replaced by light-emitting diodes ( LED ) and liquid crystal elements ( LCD ) for the digital clocks used today. The so-called seven - segment display and the matrix display are usually used to display the numbers . For the function of LED displays, driver modules are required that control individual light emitting diodes or seven-segment displays. The display data are transferred to the module via a serial three-wire interface; a decoding mode can also be activated for convenient control of seven-segment displays. Oscillating crystals are mainly used to control the clock frequency of the digital clocks.

In 1972, the Swiss company Longines developed the prototype of a digital watch, called “Clepsydre”, which was equipped with a liquid crystal element display (LCD). This watch consumed up to 30,000 times less electricity than the LED watches and had a service life of more than a year thanks to the use of mercury batteries. Due to the drop in the price of LCD elements, Japanese watch manufacturers turned what was once high technology into a cheap mass product. Later, in the history of the digital watch, additional options such as computers, databases, heart rate monitors, cameras, compasses and TV reception were brought about further technical refinements. In the meantime, digital wristwatches are being replaced by so-called smartwatches , watches that have LCD displays and can communicate with the Internet.

Atomic clocks

Atomic clocks are the most accurate time measuring devices known. Because of their time deviation of only a few seconds over many thousands of years, they are used to calibrate other clocks and chronometric instruments. The foundations of the atomic clock were developed by the American physicist Isidor Isaac Rabi at Columbia University, who received the Nobel Prize in Physics for this in 1944. The first atomic clock was invented in 1949 and is located in the Smithsonian Institution (largest museum complex in the world). It was based on the absorption line in the ammonia molecule, but most atomic clocks today are based on the cesium atom's own spin. The International System of Units standardized its unit of time for the second time in 1967, based on the properties of the isotope Cs-133. Due to the excellent rate results of these clocks, atomic time was defined as the international standard for the second. One application is cesium atomic clocks, in which the oscillation of the cesium atom is used as a very precise timekeeper. Atomic clocks also work with other elements, such as hydrogen and rubidium vapor. The hydrogen atomic clock has great advantages over the rubidium clock , such as greater stability, small size, low power consumption and consequently it is cheaper.

Researchers at the National Institute of Standards and Technology (NIST) in Boulder (USA) developed the optical atomic clocks. These are considered the successors to the 50-year-old cesium clocks that set the time all over the world. The mercury atomic clock was first introduced in 2000 and has been continuously improved since then. This optical atomic clock uses the rapid oscillations of a mercury ion that sits in an ultra-cold magnetic trap. The excited mercury ion emits a light pulse with a frequency of more than one quadrillion oscillations per second. The second optical atomic clock works with an aluminum ion. Since it is hardly influenced by electric and magnetic fields as well as temperature fluctuations, it is extremely accurate . The cesium atomic clock has an accuracy of one femtosecond , 15 decimal places behind the comma. In the experiments at the National Institute of Standards and Technology (NIST), the time of the optical atomic clocks could be measured to within a few attoseconds (17 decimal places behind the decimal point). These experiments prove that both the mercury atomic clock and the newly developed aluminum ion clock are ten times more accurate than the best cesium-based atomic clocks in the world.

Radio controlled clocks

Radio clock with displays: time, date, weekday, temperature

A radio clock is a clock that is synchronized by a bit stream of the time code and is transmitted by a signal transmitter that is connected to a time specification such as an atomic clock. This method of transmitting time by radio was invented in 1967 by the Telefunken company and a patent has been applied for. A radio clock can be synchronized with national or regional signal transmitters, or it uses a multiple signal transmitter such as the global positioning system . Radio-controlled clocks have been widely used as wall clocks and wristwatches in Europe since the 1980s.

Global Positioning System

The Global Positioning System (GPS), in coordination with the Network Time Protocol, is a radio navigation system used to synchronize timekeeping systems across the globe. The GPS was developed by the US Department of Defense to provide constant all-weather navigation capabilities for the Army , Navy and Air Force . Between February 22, 1978 and October 9, 1985, the first generation of 24 satellites that make up the global positioning system was launched from Vandenberg Air Force Base in California . In 1983, after Korean Air Lines Flight 007 was shot down while crossing Soviet airspace, President Ronald Reagan issued a guideline allowing free commercial use of GPS to prevent further navigation incidents. The GPS time cannot be correctly matched with the rotation of the earth, so it does not take into account leap seconds or other corrections that are regularly applied to the systems such as the coordinated universal time (UTC). This is the reason why the connection between the GPS time and UTC has diverged. The GPS time is therefore stuck to a constant offset of 19 seconds from International Atomic Time (TAI). The satellite clocks of the GPS system are regularly synchronized with the atomic clocks on earth in order to correct relativistic effects. Since 2007, the time difference between GPS time and UTC is only 14 seconds, which are taken into account by GPS navigation. Receivers subtract this offset from the GPS time, so specific UTC time zone values ​​can be calculated. In the United States, the Navstar-GPS system is maintained by 24 satellites orbiting the earth in six orbits every twelve hours. Russia operates a system known as GLONASS (Global Navigation Satellite System). In 2007 the European Community approved funding for the Galileo navigation system . This navigation system consists of 30 satellites that should be operational by 2018. China has two orbiting satellites of the planned 35 for its Beidou navigation system in space.

Watchmaking

The first watchmakers were blacksmiths, cannon founders, locksmiths, goldsmiths and silversmiths. Craftsmen who could make clocks were travelers in the Middle Ages, moving from town to town taking on orders. Over the years the watchmaking trade has evolved from a skilled craft into a mass production industry. Paris and Blois were the early centers of watchmaking in France . Further watchmaking centers were Augsburg and Nuremberg in Germany , Geneva in Switzerland and London in England. French watchmakers like Julien Le Roy of Versailles were leaders in the design of decorative clocks. Le Roy belonged to the fifth generation of a family of watchmakers and was described by his contemporaries as "the most talented watchmaker in France". He invented a special repeating mechanism that improved the precision of the clocks. He built for Louis XV. two clocks whose dial could be opened and thus made the internal clockwork visible. During his life he made over 3,500 clocks in his workshop, that is an average of 100 pieces per year. For comparison: other watchmakers produced around 30–50 pieces a year. The competition and scientific rivalry that resulted from his discoveries further stimulated researchers to search for new methods of accurately measuring time.

In Germany, Nuremberg and Augsburg were the early centers of watchmaking. In the first half of the 19th century, lacquer shield clocks were manufactured in the Black Forest . Lacquer shield clocks get their name from their shield-shaped, painted and lacquered dial that covers everything else. The majority of clockmakers in the 17th and 18th centuries came from England. Switzerland founded its own watchmaking center in Geneva in the 19th century. The influx of Huguenot artisans made it possible for Switzerland to manufacture clocks by machine, which is why Swiss industry gained worldwide dominance in the manufacture of high-quality machine-made clocks. The leading company at that time was Patek Philippe . It was founded by Antoni Patek from Warsaw and Adrien Philippe from Bern.

literature

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