189-463: A clock or chronometer is a device that measures and displays time . The clock is one of the oldest human inventions , meeting the need to measure intervals of time shorter than the natural units such as the day , the lunar month , and the year . Devices operating on several physical processes have been used over the millennia . Some predecessors to the modern clock may be considered "clocks" that are based on movement in nature: A sundial shows
378-584: 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
567-529: A causal relation . General relativity does not address the nature of time for extremely small intervals where quantum mechanics holds. In quantum mechanics, time is treated as a universal and absolute parameter, differing from general relativity's notion of independent clocks. The problem of time consists of reconciling these two theories. As of 2024, there is no generally accepted theory of quantum general relativity. Generally speaking, methods of temporal measurement, or chronometry , take two distinct forms:
756-481: 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
945-528: 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
1134-459: 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 the first carillon clock as it plays music simultaneously with
1323-569: 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,
1512-478: 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
1701-617: A calendar based solely on twelve lunar months. Lunisolar calendars have a thirteenth month added to some years to make up for the difference between a full year (now known to be about 365.24 days) and a year of just twelve lunar months. The numbers twelve and thirteen came to feature prominently in many cultures, at least partly due to this relationship of months to years. Other early forms of calendars originated in Mesoamerica, particularly in ancient Mayan civilization. These calendars were religiously and astronomically based, with 18 months in
1890-401: 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
2079-620: A dimension. Isaac Newton said that we are merely occupying time, he also says that humans can only understand relative time . Relative time is a measurement of objects in motion. The anti-realists believed that time is merely a convenient intellectual concept for humans to understand events. This means that time was useless unless there were objects that it could interact with, this was called relational time . René Descartes , John Locke , and David Hume said that one's mind needs to acknowledge time, in order to understand what time is. Immanuel Kant believed that we can not know what something
SECTION 10
#17327651051192268-442: A few seconds over trillions of years. Atomic clocks were first theorized by Lord Kelvin in 1879. In the 1930s the development of magnetic resonance created practical method for doing this. A prototype ammonia maser device was built in 1949 at the U.S. National Bureau of Standards (NBS, now NIST ). Although it was less accurate than existing quartz clocks , it served to demonstrate the concept. The first accurate atomic clock,
2457-415: 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
2646-511: 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,
2835-479: A half millennia . It began with the incipient unification of Nile Valley polities around 3100 BC, traditionally under Menes . The civilisation of ancient Egypt was characterised primarily by intensive agricultural use of the fertile Nile Valley; the use of the Nile itself for transportation; the development of writing systems – first hieroglyphs and then later hieratic and other derived scripts – and literature ;
3024-403: A head in the famous Leibniz–Clarke correspondence . Philosophers in the 17th and 18th century questioned if time was real and absolute, or if it was an intellectual concept that humans use to understand and sequence events. These questions lead to realism vs anti-realism; the realists believed that time is a fundamental part of the universe, and be perceived by events happening in a sequence, in
3213-407: A hundred minutes of a hundred seconds, which marked a deviation from the base 12 ( duodecimal ) system used in many other devices by many cultures. The system was abolished in 1806. A large variety of devices have been invented to measure time. The study of these devices is called horology . An Egyptian device that dates to c. 1500 BC , similar in shape to a bent T-square , measured
3402-496: 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
3591-400: 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,
3780-496: A large kingdom at three different times in history. These are called the Old (20th to 18th centuries BC), Middle (14th to 11th centuries BC), and Neo-Assyrian (9th to 7th centuries BC) kingdoms, or periods. Mitanni was a Hurrian empire in northern Mesopotamia founded around 1500 BC. The Mitanians conquered and controlled Assyria until the 14th century BC while contending with Egypt for control of parts of modern Syria. Its capital
3969-589: A later emperor, Darius the Great , expanded the empire to the Indus River , creating the largest empire in the world to that date. But Darius and his son Xerxes I failed to expand into Greece , with expeditions in 490 and 480 BC eventually failing. The Achaemenid dynasty and empire fell to Alexander the Great by 330 BC, and after Alexander's death, much of the area previously ruled by the Cyrus and his successors
SECTION 20
#17327651051194158-403: 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
4347-576: 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
4536-451: A number of dynasties that peaked in power under the reign of Ashoka Maurya, one of India's most legendary and famous emperors. During the reign of Ashoka, the four dynasties of Chola , Chera , and Pandya were ruling in the South, while Devanampiya Tissa (250–210 BC) controlled Anuradhapura (now Sri Lanka ). These kingdoms, while not part of Ashoka's empire, were in friendly terms with
4725-577: A number or calendar date to an instant (point in time), quantifying the duration of a time interval, and establishing a chronology (ordering of events). In modern times, several time specifications have been officially recognized as standards, where formerly they were matters of custom and practice. The invention in 1955 of the caesium atomic clock has led to the replacement of older and purely astronomical time standards such as sidereal time and ephemeris time , for most practical purposes, by newer time standards based wholly or partly on atomic time using
4914-553: 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
5103-522: A period often known as the Vedic period . Between 1500 and 500 BC these peoples spread throughout most of India and had begun to found small cities. Vedic society was characterized by the varna system which divided society into four broad castes, which were later elaborated. By the end of the Vedic period, this way of organizing society had become central to Indian society. Religion in the late Vedic period
5292-414: A person blinking his eyes, surprised by the singing birds. The Archimedes clock works with a system of four weights, counterweights, and strings regulated by a system of floats in a water container with siphons that regulate the automatic continuation of the clock. The principles of this type of clock are described by the mathematician and physicist Hero, who says that some of them work with a chain that turns
5481-481: 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
5670-488: A prime motivation in navigation and astronomy . Time is also of significant social importance, having economic value (" time is money ") as well as personal value, due to an awareness of the limited time in each day and in human life spans . The concept of time can be complex. Multiple notions exist and defining time in a manner applicable to all fields without circularity has consistently eluded scholars. Nevertheless, diverse fields such as business, industry, sports,
5859-409: A provision for setting the clock by manually entering the correct time into the counter. Time Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past , through the present , and into the future . It is a component quantity of various measurements used to sequence events, to compare the duration of events or
Clock - Misplaced Pages Continue
6048-486: A recurring pattern of ages or cycles, where events and phenomena repeated themselves in a predictable manner. One of the most famous examples of this concept is found in Hindu philosophy , where time is depicted as a wheel called the " Kalachakra " or "Wheel of Time." According to this belief, the universe undergoes endless cycles of creation, preservation, and destruction. Similarly, in other ancient cultures such as those of
6237-514: 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
6426-471: 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,
6615-579: 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
6804-456: A tradition of bronze production and the manufacture of evermore refined bronze and iron objects, such as plows, axes and sickles with shaft holes, socketed arrows and spearheads and small ornamented items. By about 500 BCE, large and delicately decorated bronze drums of remarkable quality, weighing more than 70 kg (150 lb), were produced in the laborious lost-wax casting process. This industry of highly sophisticated metal processing
6993-648: 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 ,
7182-421: 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
7371-525: A year and 20 days in a month, plus five epagomenal days at the end of the year. The reforms of Julius Caesar in 45 BC put the Roman world on a solar calendar . This Julian calendar was faulty in that its intercalation still allowed the astronomical solstices and equinoxes to advance against it by about 11 minutes per year. Pope Gregory XIII introduced a correction in 1582; the Gregorian calendar
7560-528: Is Harappan, after the first of its cities to be excavated, Harappa in the Pakistani province of Punjab . Harappan civilization grew out of the earlier agricultural communities as they evolved into cities. These communities created and traded jewelry, figurines, and seals that appear widely scattered throughout Mesopotamia, Afghanistan, and Iran. Chickens were domesticated in addition to the earlier crops and animals. They developed their own writing system,
7749-444: Is a time period from the beginning of writing and recorded human history through late antiquity . The span of recorded history is roughly 5,000 years, beginning with the development of Sumerian cuneiform script. Ancient history covers all continents inhabited by humans in the period 3000 BC – AD 500, ending with the expansion of Islam in late antiquity. The three-age system periodizes ancient history into
Clock - Misplaced Pages Continue
7938-768: Is a fundamental concept to define other quantities, such as velocity . To avoid a circular definition, time in physics is operationally defined as "what a clock reads", specifically a count of repeating events such as the SI second . Although this aids in practical measurements, it does not address the essence of time. Physicists developed the concept of the spacetime continuum, where events are assigned four coordinates: three for space and one for time. Events like particle collisions , supernovas , or rocket launches have coordinates that may vary for different observers, making concepts like "now" and "here" relative. In general relativity , these coordinates do not directly correspond to
8127-458: Is a theoretical ideal scale realized by TAI. Geocentric Coordinate Time and Barycentric Coordinate Time are scales defined as coordinate times in the context of the general theory of relativity. Barycentric Dynamical Time is an older relativistic scale that is still in use. Many ancient cultures, particularly in the East, had a cyclical view of time. In these traditions, time was often seen as
8316-584: 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
8505-430: 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
8694-430: Is credited to Egyptians because of their sundials, which operated on a duodecimal system. The importance of the number 12 is due to the number of lunar cycles in a year and the number of stars used to count the passage of night. The most precise timekeeping device of the ancient world was the water clock , or clepsydra , one of which was found in the tomb of Egyptian pharaoh Amenhotep I . They could be used to measure
8883-500: Is dominated by temporality ( kala ), everything within time is subject to change and decay. Overcoming pain and death requires knowledge that transcends temporal existence and reveals its eternal foundation. Two contrasting viewpoints on time divide prominent philosophers. One view is that time is part of the fundamental structure of the universe – a dimension independent of events, in which events occur in sequence . Isaac Newton subscribed to this realist view, and hence it
9072-504: Is in Byrhtferth 's Enchiridion (a science text) of 1010–1012, where it was defined as 1/564 of a momentum (1 1 ⁄ 2 minutes), and thus equal to 15/94 of a second. It was used in the computus , the process of calculating the date of Easter. As of May 2010 , the smallest time interval uncertainty in direct measurements is on the order of 12 attoseconds (1.2 × 10 seconds), about 3.7 × 10 Planck times . The second (s)
9261-764: Is kept within 0.9 second of UT1 by the introduction of one-second steps to UTC, the leap second . The Global Positioning System broadcasts a very precise time signal based on UTC time. The surface of the Earth is split into a number of time zones . Standard time or civil time in a time zone deviates a fixed, round amount, usually a whole number of hours, from some form of Universal Time, usually UTC. Most time zones are exactly one hour apart, and by convention compute their local time as an offset from UTC. For example, time zones at sea are based on UTC. In many locations (but not at sea) these offsets vary twice yearly due to daylight saving time transitions. Some other time standards are used mainly for scientific work. Terrestrial Time
9450-411: Is neither an event nor a thing, and thus is not itself measurable nor can it be travelled. Furthermore, it may be that there is a subjective component to time, but whether or not time itself is "felt", as a sensation, or is a judgment, is a matter of debate. In Philosophy, time was questioned throughout the centuries; what time is and if it is real or not. Ancient Greek philosophers asked if time
9639-483: Is not rather than what it is, an approach similar to that taken in other negative definitions . However, Augustine ends up calling time a "distention" of the mind (Confessions 11.26) by which we simultaneously grasp the past in memory, the present by attention, and the future by expectation. Isaac Newton believed in absolute space and absolute time; Leibniz believed that time and space are relational. The differences between Leibniz's and Newton's interpretations came to
SECTION 50
#17327651051199828-666: Is qualitative, as opposed to quantitative. In Greek mythology, Chronos (ancient Greek: Χρόνος) is identified as the Personification of Time. His name in Greek means "time" and is alternatively spelled Chronus (Latin spelling) or Khronos. Chronos is usually portrayed as an old, wise man with a long, gray beard, such as "Father Time". Some English words whose etymological root is khronos/chronos include chronology , chronometer , chronic , anachronism , synchronise , and chronicle . Rabbis sometimes saw time like "an accordion that
10017-600: Is seen as progressing in a straight line from past to future without repetition. In general, the Islamic and Judeo-Christian world-view regards time as linear and directional , beginning with the act of creation by God. The traditional Christian view sees time ending, teleologically, with the eschatological end of the present order of things, the " end time ". In the Old Testament book Ecclesiastes , traditionally ascribed to Solomon (970–928 BC), time (as
10206-447: Is sometimes referred to as Newtonian time . The opposing view is that time does not refer to any kind of "container" that events and objects "move through", nor to any entity that "flows", but that it is instead part of a fundamental intellectual structure (together with space and number) within which humans sequence and compare events. This second view, in the tradition of Gottfried Leibniz and Immanuel Kant , holds that time
10395-402: Is the SI base unit. A minute (min) is 60 seconds in length (or, rarely, 59 or 61 seconds when leap seconds are employed), and an hour is 60 minutes or 3600 seconds in length. A day is usually 24 hours or 86,400 seconds in length; however, the duration of a calendar day can vary due to Daylight saving time and Leap seconds . A time standard is a specification for measuring time: assigning
10584-561: Is the second , which is defined by measuring the electronic transition frequency of caesium atoms. General relativity is the primary framework for understanding how spacetime works. Through advances in both theoretical and experimental investigations of spacetime, it has been shown that time can be distorted and dilated , particularly at the edges of black holes . Throughout history, time has been an important subject of study in religion, philosophy, and science. Temporal measurement has occupied scientists and technologists and has been
10773-442: Is unless we experience it first hand. Time is not an empirical concept. For neither co-existence nor succession would be perceived by us, if the representation of time did not exist as a foundation a priori . Without this presupposition, we could not represent to ourselves that things exist together at one and the same time, or at different times, that is, contemporaneously, or in succession. Ancient times Ancient history
10962-459: 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
11151-520: Is yet to be confirmed with extensive survey work. With the help of archaeological excavations mainly by Susan and Roderick McIntosh , the site is known to have been occupied from 250 BC to AD 900. The city is believed to have been abandoned and moved where the current city is located due to the spread of Islam and the building of the Great Mosque of Djenné . Previously, it was assumed that advanced trade networks and complex societies did not exist in
11340-605: 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
11529-569: The Chaldeans in 614 BC. The Achaemenid Empire was founded by Cyrus the Great , who first became king of the Persians, then conquered the Medes, Lydia , and Babylon by 539 BC. The empire built on earlier Mesopotamian systems of government to govern their large empire. By building roads, they improved both the ability to send governmental instructions throughout their lands as well as improving
SECTION 60
#173276510511911718-578: The Clock of the Long Now . They can be driven by a variety of means, including gravity, springs, and various forms of electrical power, and regulated by a variety of means such as a pendulum . Alarm clocks first appeared in ancient Greece around 250 BC with a water clock that would set off a whistle. This idea was later mechanized by Levi Hutchins and Seth E. Thomas . A chronometer is a portable timekeeper that meets certain precision standards. Initially,
11907-763: The Congo River and into the Great Lakes area. By AD 1000 these groups had spread throughout all of southern Africa south of the equator. Iron metallurgy and agriculture spread along with these peoples, with the cultivation of millet, oil palms, sorghum, and yams as well as the use of domesticated cattle, pigs, and sheep. These technologies helped increase population, and settled communities became common in sub-Saharan Africa except in deserts or heavy forests. Paleolithic tools have been discovered in India dating to 200,000 years ago, and Neolithic sites are known from near
12096-681: The Indus Valley dating to around 8000 BC. Agriculture began in the Indus Valley around 7000 BC, and reached the Ganges Valley by 3000 BC. Barley , cotton , and wheat were grown and the population had domesticated cattle, goats, and sheep. The Indus Valley Civilisation developed around 3000 BC in the Indus and Ghaggar-Hakra river valleys of eastern Afghanistan , Pakistan, and western India. Another name for this civilisation
12285-495: The Indus Valley script , which is still mostly undeciphered. The exact structure of society and the way the cities were governed is not known. By about 1600 BC, the Indus Valley culture had abandoned many of their cities, including Mohenjo-Daro . The exact reason for this decline is not known. Indo-European speaking peoples began to spread into India about 1500 BC. The Rigveda , in Sanskrit , dates to this period and begins
12474-587: The Maccabean revolt led to independence during Hellenistic period until Roman conquest . Phoenicia was an ancient civilisation centered in the north of ancient Canaan , with its heartland along the coastal regions of modern-day Lebanon , Syria and Israel. Phoenician civilisation was an enterprising maritime trading culture that spread across the Mediterranean between the period of 1550 to 300 BC. One Phoenician colony, Carthage , ruled an empire in
12663-802: The Maritime Jade Road , a jade trade network, in Southeast Asia which existed in Taiwan and the Philippines for 3,000 years from 2000 BCE to 1000 CE. The trade was established by links between the indigenous peoples of Taiwan and the Philippines, and later included parts of Vietnam, Malaysia, Indonesia, Thailand, and other areas in Southeast Asia (known as the Sa Huynh - Kalanay Interaction Sphere). Lingling-o artifacts are one of
12852-603: The Maurya Empire . An alliance existed between Devanampiya Tissa and Ashoka of India, who sent Buddhist missionaries to Sri Lanka. Most of North India was reunited under the Gupta Empire beginning under Chandragupta I around AD 320. Under his successors the empire spread to include much of India except for the Deccan Plateau and the very south of the peninsula. This was a period of relative peace, and
13041-778: The Nile Delta in the north, as far south as Jebel Barkal at the Fourth Cataract of the Nile. Extensions to the geographical range of ancient Egyptian civilisation included, at different times, areas of the southern Levant , the Eastern Desert and the Red Sea coastline, the Sinai Peninsula , and the Western Desert (focused on the several oases ). Ancient Egypt developed over at least three and
13230-688: The Old Kingdom , which saw pyramid building on a large scale. After 2100 BC, the Old Kingdom dissolved into smaller states during the First Intermediate Period , which lasted about 100 years. The Middle Kingdom began around 2000 BC with the reunification of Egypt under pharoes ruling from Thebes . The Middle Kingdom ended with the conquest of northern Egypt by the Hyksos around 1650 BC. The Hyksos were expelled from Egypt and
13419-827: The Pitcairns , the Kermadec Islands , and the Norfolk Islands were also formerly settled by Austronesians but later abandoned. There is also putative evidence, based in the spread of the sweet potato , that Austronesians may have reached South America from Polynesia, where they might have traded with the Indigenous peoples of the Americas . Austronesians established prehistoric maritime trade networks in Island Southeast Asia, including
13608-497: 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
13797-845: The Seleucid Empire . Parthia had many wars with the Romans, but it was rebellions within the empire that ended it in the 3rd century AD. The Sasanian Empire began when the Parthian Empire ended in AD 224. Their rulers claimed the Achaemenids as ancestors and set up their capital at Ctesiphon in Mesopotamia. Their period of greatest military expansion occurred under Shapur I , who by the time of his death in AD 272 had defeated Roman imperial armies and set up buffer states between
13986-713: The Stone Age , the Bronze Age , and the Iron Age , with recorded history generally considered to begin with the Bronze Age. The start and end of the three ages vary between world regions. In many regions the Bronze Age is generally considered to begin a few centuries prior to 3000 BC, while the end of the Iron Age varies from the early first millennium BC in some regions to the late first millennium AD in others. During
14175-496: The Zapotec civilization . The ancient Near East is considered the cradle of civilization . It was the first to practice intensive year-round agriculture; created one of the first coherent writing systems , invented the potter's wheel and then the vehicular wheel , created the first centralized governments , law codes and empires, as well as displaying social stratification , slavery, and organized warfare. It began
14364-418: 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
14553-414: 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 ,
14742-425: The calendar , a mathematical tool for organising intervals of time, and the clock , a physical mechanism that counts the passage of time. In day-to-day life, the clock is consulted for periods less than a day, whereas the calendar is consulted for periods longer than a day. Increasingly, personal electronic devices display both calendars and clocks simultaneously. The number (as on a clock dial or calendar) that marks
14931-511: 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
15120-459: 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
15309-574: 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
15498-399: 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
15687-474: 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
15876-575: The Assyrians, who conquered Israel in 722 BC. The Neo-Babylonian Empire did the same to Judah in 586. After both conquests, the conquering forces deported many of the inhabitants to other regions of their respective empires. Following the fall of Babylon to the Persian Empire, Cyrus the Great allowed the rebuilding of the temple at Jerusalem , and some of the exiles from Judah returned to Judea , where they remained under Persian rule until
16065-650: The Egyptians as a possible challenge to their hegemony , but an ethnic group rather than an organised state. Israel had emerged by the middle of the 9th century BC, when the Assyrian King Shalmaneser III named " Ahab the Israelite" among his enemies at the battle of Qarqar (853). Judah emerged somewhat later than Israel, probably during the 9th century BC, but the subject is one of considerable controversy. Israel came into conflict with
16254-518: The Fertile Crescent, alongside the first evidence for agriculture. Other animals, such as pigs and poultry , were later domesticated and used as food sources. Cattle and water buffalo were domesticated around 7000 BC and horses , donkeys , and camels were domesticated by about 4000 BC. All of these animals were used not only for food, but to carry and pull people and loads, greatly increasing human ability to do work. The invention of
16443-468: 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
16632-613: The Gupta rulers generally left administration in local rulers. The Gupta Empire was weakened and ultimately ruined by the raids of Hunas (a branch of the Hephthalites emanating from Central Asia), and the empire broke up into smaller regional kingdoms by the end of the fifth century AD. India would remain fragmented into smaller states until the rise of the Mughal Empire in the 1500s. The Neolithic period of Southeast Asia
16821-622: The Hebrew word עידן, זמן iddan (age, as in "Ice age") zĕman(time) is often translated) is a medium for the passage of predestined events. (Another word, زمان" זמן" zamān , meant time fit for an event , and is used as the modern Arabic , Persian , and Hebrew equivalent to the English word "time".) The Greek language denotes two distinct principles, Chronos and Kairos . The former refers to numeric, or chronological, time. The latter, literally "the right or opportune moment", relates specifically to metaphysical or Divine time. In theology, Kairos
17010-535: 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
17199-889: The Malayan-Indonesian " thalassian " zone shared these characteristics with Indochinese polities like the Pyu city-states in the Irrawaddy River valley, the Văn Lang kingdom in the Red River Delta and Funan around the lower Mekong . Văn Lang, founded in the 7th century BCE, endured until 258 BCE under the Hồng Bàng dynasty , as part of the Đông Sơn culture that sustained a dense and organised population that produced an elaborate Bronze Age industry. Intensive wet-rice cultivation in an ideal climate enabled
17388-529: The Mayans, Aztecs, and Chinese, there were also beliefs in cyclical time, often associated with astronomical observations and calendars. These cultures developed complex systems to track time, seasons, and celestial movements, reflecting their understanding of cyclical patterns in nature and the universe. The cyclical view of time contrasts with the linear concept of time more common in Western thought, where time
17577-480: The Middle Dutch word klocke which, in turn, derives from the medieval Latin word clocca , which ultimately derives from Celtic and is cognate with French, Latin, and German words that mean bell . The passage of the hours at sea was marked by bells and denoted the time (see ship's bell ). The hours were marked by bells in abbeys as well as at sea. Clocks can range from watches to more exotic varieties such as
17766-656: The Middle East. Egypt developed its own system of hieroglyphs by about 3200 BC. By 2800 BC the Indus Valley Civilization had developed its Indus script , which remains undeciphered. Chinese Characters were independently developed in China during the Shang dynasty in the form of the Oracle Bone Script dating to the period 1600 to 1100 BC. Writing in Mesoamerica dates to 600 BC with
17955-588: The Nubians had created a new kingdom further south, known as the Kingdom of Kush , centred on the upper Nile with a capital at Kerma . In the Egyptian New Kingdom period, Kush once more was conquered by Egypt. However, by 1100 BC a new kingdom of Kush had formed, with a capital at Napata . Nubian rulers conquered Egypt around 760 BC and retained control for about a century. The Kingdom of Aksum
18144-653: The Pacific Islands to successfully retain rice cultivation. Palau and Yap were settled by separate voyages by 1000 BCE. Another important migration branch was by the Lapita culture , which rapidly spread into the islands off the coast of northern New Guinea and into the Solomon Islands and other parts of coastal New Guinea and Island Melanesia by 1200 BCE. They reached the islands of Fiji , Samoa , and Tonga by around 900 to 800 BCE. This remained
18333-517: The SI second. International Atomic Time (TAI) is the primary international time standard from which other time standards are calculated. Universal Time (UT1) is mean solar time at 0° longitude, computed from astronomical observations. It varies from TAI because of the irregularities in Earth's rotation. Coordinated Universal Time (UTC) is an atomic time scale designed to approximate Universal Time. UTC differs from TAI by an integral number of seconds. UTC
18522-620: The Sasanians and Roman Empires. After Shapur, the Sasanians were under more pressure from the Kushans to their east as well as the Roman then Byzantine Empire to its west. However, the Sasanians rebuilt and founded numerous cities and their merchants traveled widely and introduced crops such as sugar, rice, and cotton into the Iranian plateau. But in AD 651, the last Sassanid emperor was killed by
18711-667: The Western Mediterranean until being defeated by Rome in the Punic Wars . The Phoenicians invented the Phoenician alphabet , the forerunner of the modern alphabet still in use today. The history of Pre-Islamic Arabia before the rise of Islam in the AD 630s is not known in great detail. Archaeological exploration in the Arabian Peninsula has been sparse; indigenous written sources are limited to
18900-492: The ability of their military forces to be deployed rapidly. Increased trade and upgraded farming techniques increased wealth, but also exacerbated inequalities between social classes. The empire's location at the centre of trading networks spread its intellectual and philosophical ideas throughout a wide area, and its religion, while not itself spreading far, had an impact on later religions such as Christianity , Islam , and Judaism . Cyrus' son Cambyses II conquered Egypt, while
19089-492: The archipelago of the Philippines , intermingling with the earlier Australo-Melanesian population who had inhabited the islands since about 23,000 years earlier. Over the next thousand years, Austronesian peoples migrated southeast to the rest of the Philippines, and into the islands of the Celebes Sea and Borneo. From southwestern Borneo, Austronesians spread further west in a single migration event to both Sumatra and
19278-423: 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
19467-571: 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
19656-527: The capital of the Akkadian Empire. Despite an extensive search, the precise site has never been found. Akkad reached the height of its power between about 2330 and 2150 BC, following the conquests of King Sargon of Akkad . Through the spread of Sargon's empire, the language of Akkad, known as Akkadian from the city, spread and replaced the Sumerian language in Mesopotamia and eventually by 1450 BC
19845-570: The casting of iron with molds and then hammering it which enabled weapons and tools to be made stronger and also cheaper. Although chariots had been used previously, the use of spoked wheels allowed the chariots to be much lighter and more maneuverable. In 1274 BC the Hittites clashed with the Egyptians at the Battle of Kadesh , where both sides claimed victory. In 1207 the Hittite capital of Hattusa
20034-523: The causal structure of events. Instead, the spacetime interval is calculated and classified as either space-like or time-like, depending on whether an observer exists that would say the events are separated by space or by time. Since the time required for light to travel a specific distance is the same for all observers—a fact first publicly demonstrated by the Michelson–Morley experiment —all observers will consistently agree on this definition of time as
20223-573: 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
20412-544: 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
20601-561: 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
20790-614: The coastal regions of southern Vietnam, becoming the ancestors of the speakers of the Malayic and Chamic branches of the Austronesian language family. Soon after reaching the Philippines, Austronesians colonized the Northern Mariana Islands by 1500 BCE or even earlier, becoming the first humans to reach Remote Oceania . The Chamorro migration was also unique in that it was the only Austronesian migration to
20979-469: 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
21168-471: 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
21357-399: 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
21546-562: 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
21735-538: The empire was Aksum , now in northern Ethiopia. The Nok culture appeared in Nigeria around 1000 BC and mysteriously vanished around AD 200. The civilisation's social system is thought to have been highly advanced. The Nok civilisation was considered to be the earliest sub-Saharan producer of life-sized Terracotta which have been discovered by archaeologists. The Nok also used iron smelting that may have been independently developed. The civilisation of Djenné-Djenno
21924-472: 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
22113-498: The entire territory. Among large, thin-walled terracotta jars, ornamented and colorized cooking pots, glass items, jade earrings and metal objects were deposited near the rivers and along the coast. Around 3000 to 1500 BCE, a large-scale migration of Austronesians , known as the Austronesian expansion began from Taiwan . Population growth primarily fueled this migration. These first settlers settled in northern Luzon , in
22302-420: 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
22491-523: The events of the abbeys and monasteries of the Middle Ages. Richard of Wallingford (1292–1336), abbot of St. Alban's abbey, famously built a mechanical clock as an astronomical orrery about 1330. Great advances in accurate time-keeping were made by Galileo Galilei and especially Christiaan Huygens with the invention of pendulum-driven clocks along with the invention of the minute hand by Jost Burgi. The English word clock probably comes from
22680-486: The expanding Islamic Arabs. The Hittites first came to Anatolia about 1900 BC and during the period 1600-1500 they expanded into Mesopotamia where they adopted the cuneiform script to their Indo-European language. By 1200 their empire stretched to Phoenicia and eastern Anatolia . They improved two earlier technologies from Mesopotamia and spread these new techniques widely – improved iron working and light chariots with spoked wheels in warfare. The Hittites introduced
22869-521: The farming communities to produce a regular crop surplus that was used by the ruling elite to raise, command and pay work forces for public construction and maintenance projects such as canals and fortifications. The earliest known evidence of copper and bronze production in Southeast Asia was found at Ban Chiang in north-east Thailand and among the Phùng Nguyên culture of northern Vietnam around 2000 BCE. The Đông Sơn culture established
23058-439: The first mechanical clocks driven by an escapement mechanism. The hourglass uses the flow of sand to measure the flow of time. They were used in navigation. Ferdinand Magellan used 18 glasses on each ship for his circumnavigation of the globe (1522). Incense sticks and candles were, and are, commonly used to measure time in temples and churches across the globe. Water clocks, and, later, mechanical clocks, were used to mark
23247-544: 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
23436-481: The frequency of electronic transitions in certain atoms to measure the second. One of the atoms used is caesium ; most modern atomic clocks probe caesium with microwaves to determine the frequency of these electron vibrations. Since 1967, the International System of Measurements bases its unit of time, the second, on the properties of caesium atoms. SI defines the second as 9,192,631,770 cycles of
23625-687: The furthest extent of the Austronesian expansion into Polynesia until around 700 CE, when there was another surge of island colonization. It reached the Cook Islands , Tahiti , and the Marquesas by 700 CE; Hawaii by 900 CE; Rapa Nui by 1000 CE; and New Zealand by 1200 CE. For a few centuries, the Polynesian islands were connected by bidirectional long-distance sailing, with the exception of Rapa Nui, which had limited further contact due to its isolated geographical location. Island groups like
23814-438: The hours even at night but required manual upkeep to replenish the flow of water. The ancient Greeks and the people from Chaldea (southeastern Mesopotamia) regularly maintained timekeeping records as an essential part of their astronomical observations. Arab inventors and engineers, in particular, made improvements on the use of water clocks up to the Middle Ages. In the 11th century, Chinese inventors and engineers invented
24003-404: 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
24192-482: The intervals between them, and to quantify rates of change of quantities in material reality or in the conscious experience . Time is often referred to as a fourth dimension , along with three spatial dimensions . Time is one of the seven fundamental physical quantities in both the International System of Units (SI) and International System of Quantities . The SI base unit of time
24381-402: 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
24570-441: 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
24759-555: The land was reunited in the New Kingdom around 1550 BC. This period lasted until about 1000 BC, and saw Egypt expand its borders into Palestine and Syria. The Third Intermediate Period was marked by the rule of priests as well as the conquest of Egypt by Nubian kings and then later Assyria, Persia, and Macedonians. The Ta-Seti kingdom in Nubia to the south of Egypt was conquered by Egyptian rulers around 3100 BC, but by 2500 BC
24948-467: The many inscriptions and coins from southern Arabia. Existing material consists primarily of written sources from other traditions (such as Egyptians, Greeks, Persians, Romans, etc.) and oral traditions later recorded by Islamic scholars. A number of small kingdoms existed in Arabia from around AD 100 to perhaps about AD 400. Carthage was founded around 814 BC by Phoenician settlers. Ancient Carthage
25137-402: 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
25326-419: 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
25515-454: 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
25704-496: 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,
25893-583: The nature of time. Plato , in the Timaeus , identified time with the period of motion of the heavenly bodies. Aristotle , in Book IV of his Physica defined time as 'number of movement in respect of the before and after'. In Book 11 of his Confessions , St. Augustine of Hippo ruminates on the nature of time, asking, "What then is time? If no one asks me, I know: if I wish to explain it to one that asketh, I know not." He begins to define time by what it
26082-481: 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
26271-511: The occurrence of a specified event as to hour or date is obtained by counting from a fiducial epoch – a central reference point. Artifacts from the Paleolithic suggest that the moon was used to reckon time as early as 6,000 years ago. Lunar calendars were among the first to appear, with years of either 12 or 13 lunar months (either 354 or 384 days). Without intercalation to add days or months to some years, seasons quickly drift in
26460-500: 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
26649-442: The organisation of collective projects such as the pyramids ; trade with surrounding regions; and a polytheistic religious tradition that included elaborate funeral customs including mummification . Overseeing these activities were a socio-political and economic elite under the figure of a (semi)-divine ruler from a succession of ruling dynasties . Ancient Egyptian history is divided across various periods, beginning with
26838-419: The passage of time from the shadow cast by its crossbar on a nonlinear rule. The T was oriented eastward in the mornings. At noon, the device was turned around so that it could cast its shadow in the evening direction. A sundial uses a gnomon to cast a shadow on a set of markings calibrated to the hour. The position of the shadow marks the hour in local time . The idea to separate the day into smaller parts
27027-472: The population to settle in one place instead of migrating after crops and herds. It also allowed for a much greater population density, and in turn required an extensive labour force and division of labour. This organization led to the necessity of record keeping and the development of writing. Babylonia was an Amorite state in lower Mesopotamia (modern southern Iraq ), with Babylon as its capital. Babylonia emerged when Hammurabi created an empire out of
27216-419: 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
27405-420: 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
27594-471: 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
27783-641: The radiation that corresponds to the transition between two electron spin energy levels of the ground state of the Cs atom. Today, the Global Positioning System in coordination with the Network Time Protocol can be used to synchronize timekeeping systems across the globe. In medieval philosophical writings, the atom was a unit of time referred to as the smallest possible division of time. The earliest known occurrence in English
27972-567: The region in the former savannah of the Sahara. Its inhabitants fished and grew millet. It has been found that the Soninke of the Mandé peoples were responsible for constructing such settlements. Around 300 BC, the region became more desiccated and the settlements began to decline, most likely relocating to Koumbi Saleh. From the type of architecture and pottery, it is believed that Tichit was related to
28161-465: The region until the arrival of traders from Southwest Asia . However, sites such as Djenné-Djenno disprove this, as these traditions in West Africa flourished long before. Towns similar to that at Djenne-Jeno also developed at the site of Dia, also in Mali along the Niger River , from around 900 BC. Dhar Tichitt and Oualata were prominent among the early urban centres, dated to 2000 BC, in present-day Mauritania. About 500 stone settlements littered
28350-420: The same time period. Cultivation of millet, rice , and legumes began around 7000 BC in China . Taro cultivation in New Guinea dates to about 7000 BC also with squash cultivation in Mesoamerica perhaps sharing that date. Animal domestication began with the domestication of dogs , which dates to at least 15,000 years ago, and perhaps even earlier. Sheep and goats were domesticated around 9000 BC in
28539-554: The same time, southeastern Europe and Siberia around 40,000 years ago, and Japan about 30,000 years ago. Humans migrated to the Americas about 15,000 years ago. Evidence for agriculture emerges in about 9000 BC in what is now eastern Turkey and spread through the Fertile Crescent . Settlement at Göbekli Tepe began around 9500 BC and may have the world's oldest temple. The Nile River Valley has evidence of sorghum and millet cultivation starting around 8000 BC and agricultural use of yams in Western Africa perhaps dates to
28728-576: The sciences, and the performing arts all incorporate some notion of time into their respective measuring systems . Traditional definitions of time involved the observation of periodic motion such as the apparent motion of the sun across the sky, the phases of the moon, and the passage of a free-swinging pendulum. More modern systems include the Global Positioning System , other satellite systems, Coordinated Universal Time and mean solar time . Although these systems differ from one another, with careful measurements they can be synchronized. In physics, time
28917-412: The simple plough by 6000 BC further increased agricultural efficiency. Metal use in the form of hammered copper items predates the discovery of smelting of copper ores , which happened around 6000 BC in western Asia and independently in eastern Asia before 2000 BC. Gold and silver use dates to between 6000 and 5000 BC. Alloy metallurgy began with bronze in about 3500 BC in Mesopotamia and
29106-476: 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
29295-525: The study of the stars and the sciences of astronomy and mathematics. Mesopotamia is the site of some of the earliest known civilisations in the world. Agricultural communities emerged in the area with the Halaf culture around 8000 BC and continued to expand through the Ubaid period around 6000 BC. Cities began in the Uruk period (4000–3100 BC) and expanded during the Jemdet Nasr (3100–2900 BC) and Early Dynastic (2900–2350 BC) periods. The surplus of storable foodstuffs created by this economy allowed
29484-439: The subsequent Ghana Empire. Old Jenne (Djenne) began to be settled around 300 BC, producing iron and with sizeable population, evidenced in crowded cemeteries. The inhabitants and creators of these settlements during these periods are thought to have been ancestors of the Soninke people. Peoples speaking precursors to the modern-day Bantu languages began to spread throughout southern Africa, and by 2000 BC they were expanding past
29673-459: 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
29862-532: The term was used to refer to the marine chronometer , a timepiece used to determine longitude by means of celestial navigation , a precision first achieved by John Harrison . More recently, the term has also been applied to the chronometer watch , a watch that meets precision standards set by the Swiss agency COSC . The most accurate timekeeping devices are atomic clocks , which are accurate to seconds in many millions of years, and are used to calibrate other clocks and timekeeping instruments. Atomic clocks use
30051-460: The territories of the former kingdoms of Sumer and Akkad . The Neo-Babylonian Empire , or Chaldea , was Babylonia from the 7th and 6th centuries BC. Under the reign of Nebuchadnezzar II , it conquered Jerusalem . This empire also created the Hanging Gardens of Babylon and the still-surviving Ishtar Gate as architectural embellishments of its capital at Babylon. Akkad was a city and its surrounding region near Babylon. Akkad also became
30240-505: 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),
30429-427: 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
30618-446: The time period of ancient history, the world population was already exponentially increasing due to the Neolithic Revolution , which was in full progress. While in 10,000 BC, the world population stood at 2 million, it rose to 45 million by 3000 BC. By the Iron Age in 1000 BC, the population had risen to 72 million. By the end of the ancient period in AD 500, the world population is thought to have stood at 209 million. In 10,500 years,
30807-485: 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
30996-427: 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
31185-568: The use of fire has been dated as early as 1.8 million years ago, a date which is contested, with generally accepted evidence for the controlled use of fire dating to 780,000 years ago. Actual use of hearths first appears 400,000 years ago. Dates for the emergence of Homo sapiens (modern humans) range from 250,000 to 160,000 years ago, with the varying dates being based on DNA studies and fossils respectively. Some 50,000 years ago, Homo sapiens migrated out of Africa . They reached Australia about 45,000 years ago, southwestern Europe about
31374-443: The world population increased by 100 times. Prehistory is the period before written history. Most of our knowledge of that period comes from the work of archaeologists. Prehistory is often known as the Stone Age , and is divided into the Paleolithic (earliest), Mesolithic , and Neolithic . The early human migrations in the Lower Paleolithic saw Homo erectus spread across Eurasia 1.8 million years ago. Evidence for
31563-414: Was Washukanni , whose precise location has not been determined by archaeologists. The Medes and Persians were peoples who had appeared in the Iranian plateau around 1500 BC. Both peoples spoke Indo-European languages and were mostly pastoralists with a tradition of horse archery. The Medes established their own Median Empire by the 6th century BC, having defeated the Neo-Assyrian Empire with
31752-414: Was a city-state that ruled an empire through alliances and trade influence that stretched throughout North Africa and modern Spain . At the height of the city's influence, its empire included most of the western Mediterranean. The empire was in a constant state of struggle with the Roman Republic , which led to a series of conflicts known as the Punic Wars . After the third and final Punic War , Carthage
31941-430: Was an illusion to humans. Plato believed that time was made by the Creator at the same instant as the heavens. He also says that time is a period of motion of the heavenly bodies . Aristotle believed that time correlated to movement, that time did not exist on its own but was relative to motion of objects. He also believed that time was related to the motion of celestial bodies ; the reason that humans can tell time
32130-438: Was an important trading nation in northeastern Africa centered in present-day Eritrea and northern Ethiopia , it existed from approximately AD 100 to 940, growing from the Iron Age proto-Aksumite period around the 4th century BC to achieve prominence by the 1st century AD. The Kingdom of Aksum at its height by the early 6th-century AD extended through much of modern Ethiopia and across the Red Sea to Arabia. The capital city of
32319-466: Was because of orbital periods and therefore there was a duration on time. The Vedas , the earliest texts on Indian philosophy and Hindu philosophy dating to the late 2nd millennium BC , describe ancient Hindu cosmology , in which the universe goes through repeated cycles of creation, destruction and rebirth, with each cycle lasting 4,320 million years. Ancient Greek philosophers , including Parmenides and Heraclitus , wrote essays on
32508-417: 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
32697-445: Was characterized by several migrations into Mainland and Island Southeast Asia from southern China by Austronesian , Austroasiatic , Kra-Dai and Hmong-Mien -speakers. Territorial principalities in both Insular and Mainland Southeast Asia, characterized as "agrarian kingdoms", developed an economy by around 500 BCE based on surplus crop cultivation and moderate coastal trade of domestic natural products. Several states of
32886-554: 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.,
33075-422: Was destroyed and then occupied by Roman forces. Nearly all of the territory held by Carthage fell into Roman hands. Ancient Egypt was a long-lived civilisation geographically located in north-eastern Africa. It was concentrated along the middle to lower reaches of the Nile River, reaching its greatest extent during the 2nd millennium BC, which is referred to as the New Kingdom period. It reached broadly from
33264-405: Was developed independent of Chinese or Indian influence. Historians relate these achievements to the presence of organized, centralized and hierarchical communities and a large population. Between 1000 BCE and 100 CE, the Sa Huỳnh culture flourished along the south-central coast of Vietnam . Ceramic jar burial sites that included grave goods have been discovered at various sites along
33453-609: Was developed independently in China by 2000 BC. Pottery developed independently throughout the world, with fired pots appearing first among the Jomon of Japan and in West Africa at Mali . Sometime between 5000 and 4000 BC the potter's wheel was invented. By 3000 BC, the pottery wheel was adapted into wheeled vehicles which could be used to carry loads further and easier than with human or animal power alone. Writing developed separately in five different locations in human history: Mesopotamia, Egypt, India, China, and Mesoamerica. By 3400 BC, "proto-literate" cuneiform spread in
33642-421: Was evolving into Hinduism , which spread throughout Southeast Asia. Siddhartha Gautama , born around 560 BC in northern India, went on to found a new religion based on his ascetic life – Buddhism . This faith also spread throughout Eastern and Southeastern Asia after his death. This period also saw the composition of the epics Ramayana and Mahabharata . The kingdom of Magadha rose to prominence under
33831-480: Was expanded and collapsed at will." According to Kabbalists , "time" is a paradox and an illusion . According to Advaita Vedanta , time is integral to the phenomenal world, which lacks independent reality. Time and the phenomenal world are products of maya , influenced by our senses, concepts, and imaginations. The phenomenal world, including time, is seen as impermanent and characterized by plurality, suffering, conflict, and division. Since phenomenal existence
34020-413: 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
34209-446: 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
34398-415: Was linear or cyclical and if time was endless or finite . These philosophers had different ways of explaining time; for instance, ancient Indian philosophers had something called the Wheel of Time. It is believed that there was repeating ages over the lifespan of the universe. This led to beliefs like cycles of rebirth and reincarnation . The Greek philosophers believe that the universe was infinite, and
34587-455: Was located in the Niger River Valley in the country of Mali and is considered to be among the oldest urbanized centers and the best-known archaeology site in sub-Saharan Africa . This archaeological site is located about 3 kilometers (1.9 miles) away from the modern town and is believed to have been involved in long-distance trade and possibly the domestication of African rice. The site is believed to exceed 33 hectares (82 acres); however, this
34776-409: Was only slowly adopted by different nations over a period of centuries, but it is now by far the most commonly used calendar around the world. During the French Revolution , a new clock and calendar were invented as part of the dechristianization of France and to create a more rational system in order to replace the Gregorian calendar. The French Republican Calendar 's days consisted of ten hours of
34965-403: 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 ,
35154-403: Was ruled by the Seleucid dynasty . Parthia was an Iranian civilisation situated in the northeastern part of modern Iran. Their power was based on a combination of military power based on heavy cavalry with a decentralised governing structure based on a federated system . The Parthian Empire was led by the Arsacid dynasty , which by around 155 BC under Mithradates I had mostly conquered
35343-442: Was sacked, ending the Hittite Empire . Israel and Judah were related Iron Age kingdoms of the ancient Levant and had existed during the Iron Ages and the Neo-Babylonian, Persian and Hellenistic periods. The name Israel first appears in the stele of the Egyptian pharaoh Merneptah around 1209 BC. This "Israel" was a cultural and probably political entity of the central highlands, well enough established to be perceived by
35532-516: Was the main language of diplomacy in the Near East. Assyria was originally a region on the Upper Tigris , where a small state was created in the 19th century BC. The capital was at Assur , which gave the state its name. Later, as a nation and empire that came to control all of the Fertile Crescent, Egypt and much of Anatolia , the term "Assyria proper" referred to roughly the northern half of Mesopotamia (the southern half being Babylonia), with Nineveh as its capital. The Assyrian kings controlled
35721-420: 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
#118881