1.
Clock
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A clock is an instrument to measure, keep, and indicate time. The word clock is derived from the Celtic words clagan and clocca meaning bell, a silent instrument missing such a striking mechanism has traditionally been known as a timepiece. In general usage today a clock refers to any device for measuring and displaying the time, Watches and other timepieces that can be carried on ones person are often distinguished from clocks. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units, the day, the lunar month. Devices operating on several physical processes have been used over the millennia, a sundial shows the time by displaying the position of a shadow on a flat surface. There is a range of duration timers, an example being the hourglass. Water clocks, along with the sundials, are possibly the oldest time-measuring instruments, spring-driven clocks appeared during the 15th century. During the 15th and 16th centuries, clockmaking flourished, the next development in accuracy occurred after 1656 with the invention of the pendulum clock. A major stimulus to improving the accuracy and reliability of clocks was the importance of precise time-keeping for navigation, the electric clock was patented in 1840. The development of electronics in the 20th century led to clocks with no clockwork parts at all, the timekeeping element in every modern clock is a harmonic oscillator, a physical object that vibrates or oscillates at a particular frequency. This object can be a pendulum, a fork, a quartz crystal. Analog clocks usually indicate time using angles, Digital clocks display a numeric representation of time. Two numeric display formats are used on digital clocks, 24-hour notation. Most digital clocks use electronic mechanisms and LCD, LED, or VFD displays, for convenience, distance, telephony or blindness, auditory clocks present the time as sounds. There are also clocks for the blind that have displays that can be read by using the sense of touch, some of these are similar to normal analog displays, but are constructed so the hands can be felt without damaging them. The evolution of the technology of clocks continues today, the study of timekeeping is known as horology. The apparent position of the Sun in the sky moves over the course of a day, shadows cast by stationary objects move correspondingly, so their positions can be used to indicate the time of day. A sundial shows the time by displaying the position of a shadow on a flat surface, sundials can be horizontal, vertical, or in other orientations
2.
Watch
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A watch is a small timepiece intended to be carried or worn by a person. It is designed to keep working despite the motions caused by the persons activities, a wristwatch is designed to be worn around the wrist, attached by a watch strap or other type of bracelet. A pocket watch is designed for a person to carry in a pocket, watches evolved in the 17th century from spring-powered clocks, which appeared as early as the 14th century. During most of its history the watch was a device, driven by clockwork, powered by winding a mainspring. In the 1960s the electronic quartz watch was invented, which was powered by a battery, by the 1980s the quartz watch had taken over most of the market from the mechanical watch. Today most inexpensive and medium-priced watches, used mainly for timekeeping, have quartz movements, various extra features, called complications, such as moon-phase displays and the different types of tourbillon, are sometimes included. Modern watches often display the day, date, month and year, time-related features such as timers, chronographs and alarm functions are common. Some modern designs incorporate calculators, GPS and Bluetooth technology or have heart-rate monitoring capabilities, some watches use radio clock technology to regularly correct the time. Developments in the 2010s include smartwatches, which are elaborate computer-like electronic devices designed to be worn on a wrist and they generally incorporate timekeeping functions, but these are only small fractions of what the smartwatch can do. The study of timekeeping is known as horology, watches evolved from portable spring-driven clocks, which first appeared in 15th century Europe. Watches werent widely worn in pockets until the 17th century, one account says that the word watch came from the Old English word woecce which meant watchman, because it was used by town watchmen to keep track of their shifts at work. Another says that the term came from 17th century sailors, who used the new mechanisms to time the length of their shipboard watches, the increased accuracy of the balance wheel focused attention on errors caused by other parts of the movement, igniting a two-century wave of watchmaking innovation. The first thing to be improved was the escapement, the verge escapement was replaced in quality watches by the cylinder escapement, invented by Thomas Tompion in 1695 and further developed by George Graham in the 1720s. The British had predominated in watch manufacture for much of the 17th and 18th centuries, aaron Lufkin Dennison started a factory in 1851 in Massachusetts that used interchangeable parts, and by 1861 it was running a successful enterprise incorporated as the Waltham Watch Company. The concept of the wristwatch goes back to the production of the very earliest watches in the 16th century, elizabeth I of England received a wristwatch from Robert Dudley in 1571, described as an arm watch. The oldest surviving wristwatch is one made in 1806 and given to Joséphine de Beauharnais, from the beginning, wrist watches were almost exclusively worn by women, while men used pocket-watches up until the early 20th century. The Garstin Company of London patented a Watch Wristlet design in 1893, officers in the British Army began using wristwatches during colonial military campaigns in the 1880s, such as during the Anglo-Burma War of 1885. In continental Europe Girard-Perregaux and other Swiss watch makers began supplying German naval officers with wrist watches in about 1880 and these early models were essentially standard pocket-watches fitted to a leather strap but, by the early 20th century, manufacturers began producing purpose-built wristwatches
3.
Hour
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An hour is a unit of time conventionally reckoned as 1⁄24 of a day and scientifically reckoned as 3, 599–3,601 seconds, depending on conditions. The seasonal, temporal, or unequal hour was established in the ancient Near East as 1⁄12 of the night or daytime, such hours varied by season, latitude, and weather. It was subsequently divided into 60 minutes, each of 60 seconds, the modern English word hour is a development of the Anglo-Norman houre and Middle English ure, first attested in the 13th century. It displaced the Old English tide and stound, the Anglo-Norman term was a borrowing of Old French ure, a variant of ore, which derived from Latin hōra and Greek hṓrā. Like Old English tīd and stund, hṓrā was originally a word for any span of time, including seasons. Its Proto-Indo-European root has been reconstructed as *yeh₁-, making hour distantly cognate with year, the time of day is typically expressed in English in terms of hours. Whole hours on a 12-hour clock are expressed using the contracted phrase oclock, Hours on a 24-hour clock are expressed as hundred or hundred hours. Fifteen and thirty minutes past the hour is expressed as a quarter past or after and half past, respectively, fifteen minutes before the hour may be expressed as a quarter to, of, till, or before the hour. Sumerian and Babylonian hours divided the day and night into 24 equal hours, the ancient Egyptians began dividing the night into wnwt at some time before the compilation of the Dynasty V Pyramid Texts in the 24th century BC. By 2150 BC, diagrams of stars inside Egyptian coffin lids—variously known as diagonal calendars or star clocks—attest that there were exactly 12 of these. The coffin diagrams show that the Egyptians took note of the risings of 36 stars or constellations. Each night, the rising of eleven of these decans were noted, the original decans used by the Egyptians would have fallen noticeably out of their proper places over a span of several centuries. By the time of Amenhotep III, the priests at Karnak were using water clocks to determine the hours and these were filled to the brim at sunset and the hour determined by comparing the water level against one of its twelve gauges, one for each month of the year. During the New Kingdom, another system of decans was used, the later division of the day into 12 hours was accomplished by sundials marked with ten equal divisions. The morning and evening periods when the failed to note time were observed as the first and last hours. The Egyptian hours were closely connected both with the priesthood of the gods and with their divine services, by the New Kingdom, each hour was conceived as a specific region of the sky or underworld through which Ras solar bark travelled. Protective deities were assigned to each and were used as the names of the hours, as the protectors and resurrectors of the sun, the goddesses of the night hours were considered to hold power over all lifespans and thus became part of Egyptian funerary rituals. The Egyptian for astronomer, used as a synonym for priest, was wnwty, the earliest forms of wnwt include one or three stars, with the later solar hours including the determinative hieroglyph for sun
4.
Digital clock
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A digital clock is a type of clock that displays the time digitally, as opposed to an analog clock, where the time is indicated by the positions of rotating hands. Digital clocks are often associated with electronic drives, but the description refers only to the display. The biggest digital clock is the Lichtzelt Pegel on the television tower Rheinturm Düsseldorf, the first digital pocket watch was the invention of Austrian engineer Josef Pallweber who created his jump-hour mechanism in 1883. Instead of a dial, the jump-hour featured two windows in an enamel dial, through which the hours and minutes are visible on rotating discs. By 1885 Pallweber mechanism was already on the market in pocket watches by Cortébert and IWC, arguably contributing to the subsequent rise, the principles of Pallweber jump-hour movement had appeared in wristwatches by the 1920s and are still used today. While the original inventor didnt have a brand at the time. Plato clocks used an idea but a different layout. These spring-wound pieces consisted of a cylinder with a column inside, affixed to which were small digital cards with numbers printed on them. The Plato clocks were introduced at the St. Louis World Fair in 1904, eugene Fitch of New York patented the clock design in 1903. 13 years earlier Josef Pallweber had patented the same invention using digital cards in Germany, the German factory Aktiengesellschaft für Uhrenfabrikation Lenzkirch made such digital clocks in 1893 and 1894. The earliest patent for an alarm clock was registered by D. E Protzmann and others on October 23,1956. Protzmann and his associates also patented another digital clock in 1970, two side-plates held digital numerals between them, while an electric motor and cam gear outside controlled movement. In 1970, the first digital wristwatch with an LED display was mass-produced, called the Pulsar, and produced by the Hamilton Watch Company, this watch was hinted at two years prior when the same company created a prototype digital watch for Kubricks 2001, A Space Odyssey. Throughout the 1970s, despite the initial hefty cost of digital watches, over the years, many different types of digital alarm clocks have been developed. In Soviet Russia, the 7-segment digital clocks were known as Elektronika 7, Digital clocks typically use the 50 or 60 hertz oscillation of AC power or a 32,768 hertz crystal oscillator as in a quartz clock to keep time. Most digital clocks display the hour of the day in 24-hour format, in the United States and a few other countries, emulations of analog-style faces often use an LCD screen, and these are also sometimes described as digital. To represent the time, most digital clocks use a seven-segment LED, VFD and they generally also include other elements to indicate whether the time is AM or PM, whether or not an alarm is set, and so on. Digital clocks that run on electricity and have no battery must be reset every time the power is cut off or if they are moved
5.
24-hour analog dial
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Clocks and watches with a 24-hour analog dial have an hour hand that makes one complete revolution, 360°, in a day. The more familiar 12-hour analog dial has a hand that makes two complete revolutions in a day. Twenty-four-hour analog clocks and watches are used today by pilots, scientists, and the military, note that this definition refers to the use of a complete circular dial to represent a 24-hour day. Using the numbers from 0 to 23 to mark the day is the 24-hour clock system, sundials use 24-hour analog dials—the shadow traces a path that repeats approximately once per day. Many sundials are marked with the double-XII or double-12 system, in which the numbers I to XII are used twice, once for the morning hours, so VI appears twice on many dials, once near sunrise and once near sunset. Modern 24-hour analog dials—other than sundials—are almost always marked with 24 numbers or hour marks around the edge and these dials do not need to indicate AM or PM. The ancient Egyptians divided the day into 24 hours, there are diagrams of circles divided into 24 sections in the astronomical ceiling in the tomb of Senemut. Sundials use some or all of the 24-hour dial, because they show the position of the sun in the sky, sometimes, for aesthetic rather than practical reasons, all the 24 hour marks are shown. Medieval clocks often used the 24-hour analog dial, influenced by the example of the astrolabe. In Italy, the numbers from 1 to 24 were used, on Italian clocks, though, the I was often shown at the right side of the dial, rather than the top. This probably reflects the influence of the Italian timekeeping system, which started counting the hours of the day at sunset or twilight. In northern Europe, the double XII system was superseded during the 14th and 15th centuries by the single XII. The 24-hour analog dial continued to be used, but primarily by technicians, astronomers, scientists, john Harrison, Thomas Tompion, and Mudge built a number of clocks with 24-hour analog dials, particularly when building astronomical and nautical instruments. In the 20th century, the 24-hour analog dial was adopted by radio amateurs, pilots, submariners, 24-hour analog watches and clocks are still being manufactured today, and are sought after by collectors and enthusiasts. A famous brand is the Glycine Airman watch, other manufacturers who make 24-hour analog watches include Breitling, Raketa, Vostok, Fortis, Poljot, Swatch, and many others. The major variation in the design of 24-hour analog dials is the location of midnight, although always opposite each other, 180° apart, noon is sometimes at the top, sometimes at the bottom. A few rare variants place noon and midnight at the right, there is no ambiguity if the 24-hour numbering is used. In the United States, the government and military commonly use 24-hour clocks having noon at the bottom, the Chinese traditional shi-ke system may be an optimum design of 24-hour clock
6.
Military
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The armed forces of a country are its government-sponsored defense, fighting forces, and organizations. They exist to further the foreign and domestic policies of their body and to defend that body. Armed force is the use of armed forces to achieve political objectives, the study of the use of armed forces is called military science. Broadly speaking, this involves considering offense and defense at three levels, strategy, operational art, and tactics, all three levels study the application of the use of force in order to achieve a desired objective. In most countries the basis of the forces is the military. However, armed forces can include other paramilitary structures, the obvious benefit to a country in maintaining armed forces is in providing protection from foreign threats and from internal conflict. In recent decades armed forces personnel have also used as emergency civil support roles in post-disaster situations. On the other hand, they may harm a society by engaging in counter-productive warfare. Expenditure on science and technology to develop weapons and systems sometimes produces side benefits, although some claim that greater benefits could come from targeting the money directly
7.
24-hour clock
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The 24-hour clock is the convention of time keeping in which the day runs from midnight to midnight and is divided into 24 hours, indicated by the hours passed since midnight, from 0 to 23. This system is the most commonly used time notation in the world today, in the practice of medicine, the 24-hour clock is generally used in documentation of care as it prevents any ambiguity as to when events occurred in a patients medical history. It is popularly referred to as time in the United States. In the case of a second, the value of ss may extend to 60. A leading zero is added for numbers under 10 and this zero is optional for the hours, but very commonly used in computer applications, where many specifications require it. Where subsecond resolution is required, the seconds can be a fraction, that is. The most commonly used separator symbol between hours, minutes and seconds is the colon, which is also the used in ISO8601. In the past, some European countries used the dot on the line as a separator, in some contexts, no separator is used and times are written as, for example,2359. In East Asia, time notation was 24-hour before westernization in modern times, the clocks were changed into 12 dual-hours style when they were shipped to China in the Qing dynasty. In the 24-hour time notation, the day begins at midnight,00,00, and the last minute of the day begins at 23,59. Where convenient, the notation 24,00 may also be used to refer to midnight at the end of a given date – that is,24,00 of one day is the time as 00,00 of the following day. The notation 24,00 mainly serves to refer to the end of a day in a time interval. A typical usage is giving opening hours ending at midnight, similarly, some railway timetables show 00,00 as departure time and 24,00 as arrival time. Legal contracts often run from the date at 00,00 until the end date at 24,00. While the 24-hour notation unambiguously distinguishes between midnight at the start and end of any date, there is no commonly accepted distinction among users of the 12-hour notation. Sometimes the use of 00,00 is also avoided, in variance with this, the correspondence manual for the U. S. Navy and U. S. Marine Corps formerly specified 0001 to 2400. The manual was updated in June 2015 to use 0000 to 2359, time-of-day notations beyond 24,00 are not commonly used and not covered by the relevant standards. In most countries, computers by default show the time in 24-hour notation, for example, Microsoft Windows and macOS activate the 12-hour notation by default only if a computer is in a handful of specific language and region settings
8.
Timer
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A timer is a specialized type of clock for measuring time intervals. By function timers can be categorized to two main types, a simple example for this type is an hourglass. By working method timers have two groups, Hardware and Software timers. Some timers sound an audible indication that the interval has expired. Time switches, timing mechanisms which activate a switch, are also called timers. Mechanical timers use clockwork to measure time, manual timers are typically set by turning a dial to the time interval desired, turning the dial stores energy in a mainspring to run the mechanism. They function similarly to an alarm clock, the energy in the mainspring causes a balance wheel to rotate back. Each swing of the releases the gear train to move forward by a small fixed amount, causing the dial to move steadily backward until it reaches zero. The mechanical kitchen timer was invented in 1926 by Thomas Norman Hicks, some less accurate, cheaper mechanisms use a flat paddle called a fan fly that spins against air resistance, low-precision mechanical egg-timers are sometimes of this type. The simplest and oldest type of mechanical timer is the hourglass, the most common use of this type is in the flasher units that flash turn signals in automobiles, and sometimes in Christmas lights. This is a type of multivibrator. An electromechanical cam timer uses a small synchronous AC motor turning a cam against a comb of switch contacts, the AC motor is turned at an accurate rate by the alternating current, which power companies carefully regulate. Gears drive a shaft at the rate, and turn the cam. The most common application of this now is in washers, driers and dishwashers. This type of timer often has a clutch between the gear train and the cam, so that the cam can be turned to reset the time. In the past, these timers were often combined with electrical relays to create electro-mechanical controllers. Electromechanical timers reached a state of development in the 1950s and 1960s because of their extensive use in aerospace. Programmable electromechanical timers controlled launch sequence events in early rockets and ballistic missiles, as digital electronics has progressed and dropped in price, electronic timers have become more advantageous
9.
Roman numerals
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The numeric system represented by Roman numerals originated in ancient Rome and remained the usual way of writing numbers throughout Europe well into the Late Middle Ages. Numbers in this system are represented by combinations of letters from the Latin alphabet, Roman numerals, as used today, are based on seven symbols, The use of Roman numerals continued long after the decline of the Roman Empire. The numbers 1 to 10 are usually expressed in Roman numerals as follows, I, II, III, IV, V, VI, VII, VIII, IX, Numbers are formed by combining symbols and adding the values, so II is two and XIII is thirteen. Symbols are placed left to right in order of value. Named after the year of its release,2014 as MMXIV, the year of the games of the XXII Olympic Winter Games The standard forms described above reflect typical modern usage rather than a universally accepted convention. Usage in ancient Rome varied greatly and remained inconsistent in medieval, Roman inscriptions, especially in official contexts, seem to show a preference for additive forms such as IIII and VIIII instead of subtractive forms such as IV and IX. Both methods appear in documents from the Roman era, even within the same document, double subtractives also occur, such as XIIX or even IIXX instead of XVIII. Sometimes V and L are not used, with such as IIIIII. Such variation and inconsistency continued through the period and into modern times. Clock faces that use Roman numerals normally show IIII for four o’clock but IX for nine o’clock, however, this is far from universal, for example, the clock on the Palace of Westminster in London uses IV. Similarly, at the beginning of the 20th century, different representations of 900 appeared in several inscribed dates. For instance,1910 is shown on Admiralty Arch, London, as MDCCCCX rather than MCMX, although Roman numerals came to be written with letters of the Roman alphabet, they were originally independent symbols. The Etruscans, for example, used
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