Hour

An hour (symbol: h;[1] also abbreviated hr.) is a unit of time conventionally reckoned as ​124 of a day and scientifically reckoned as 3,599–3,601 seconds, depending on conditions.

The hour was initially established in the ancient Near East as a variable measure of ​112 of the night or daytime. Such seasonal, temporal, or unequal hours varied by season and latitude. The hour was subsequently divided into 60 minutes, each of 60 seconds. Equal or equinoctial hours were taken as ​124 of the day as measured from noon to noon; the minor seasonal variations of this unit were eventually smoothed by making it ​124 of the mean solar day. Since this unit was not constant due to long term variations in the Earth's rotation, the hour was finally separated from the Earth's rotation and defined in terms of the atomic or physical second.

In the modern metric system, hours are an accepted unit of time defined as 3,600 atomic seconds. However, on rare occasions an hour may incorporate a positive or negative leap second,[a] making it last 3,599 or 3,601 seconds, in order to keep it within 0.9 seconds of UT1, which is based on measurements of the mean solar day.

DigitalClock 1hour
Midnight to 1 a.m. on a 24-hour clock with a digital face
AnalogClockAnimation1 2hands 1h in 6sec
Midnight (or noon) to 1 on a 12-hour clock with an analog face

Name

Equation of time
The equation of time—above the axis the sundial will appear fast, compared with a clock showing local mean time, and below the sundial will appear slow.

The modern English word hour is a development of the Anglo-Norman houre and Middle English ure, first attested in the 13th century.[2][b] It displaced the Old English "tide" (Old English: tīd, "time")[4] and "stound" (stund, "span of time").[5] The Anglo-Norman term was a borrowing of Old French ure, a variant of ore, which derived from Latin hōra and Greek hṓrā (ὥρα). Like Old English tīd and stund, hṓrā was originally a vaguer word for any span of time, including seasons and years. Its Proto-Indo-European root has been reconstructed as *yeh₁- ("year, summer"), 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 o'clock, from the older of clock.[6] (10 am and 10 pm are both read as "ten o'clock".) Hours on a 24-hour clock ("military time") are expressed as "hundred" or "hundred hours".[7] (1000 is read "ten hundred" or "ten hundred hours"; 10 pm would be "twenty-two hundred".) Fifteen and thirty minutes past the hour is expressed as "a quarter past" or "after"[8] and "half past", respectively, from their fraction of the hour. Fifteen minutes before the hour may be expressed as "a quarter to", "of", "till", or "before" the hour.[8] (9:45 may be read "nine forty-five" or "a quarter till ten".)

History

Egypt

The ancient Egyptians began dividing the night into wnwt at some time before the compilation of the Dynasty V Pyramid Texts[9] in the 24th century BC.[10] By 2150 BC (Dynasty IX), diagrams of stars inside Egyptian coffin lids—variously known as "diagonal calendars" or "star clocks"—attest that there were exactly 12 of these.[10] Clagett writes that it is "certain" this duodecimal division of the night followed the adoption of the Egyptian civil calendar,[9] usually placed c. 2800 BC on the basis of analyses of the Sothic cycle, but a lunar calendar presumably long predated this[11] and also would have had twelve months in each of its years. The coffin diagrams show that the Egyptians took note of the heliacal risings of 36 stars or constellations (now known as "decans"), one for each of the ten-day "weeks" of their civil calendar.[12] (12 sets of alternate "triangle decans" were used for the 5 epagomenal days between years.)[13] Each night, the rising of eleven of these decans were noted, separating the night into twelve divisions whose middle terms would have lasted about 40 minutes each. (Another seven stars were noted by the Egyptians during the twilight and predawn periods, although they were not important for the hour divisions.) 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 (c. 1350 BC), the priests at Karnak were using water clocks to determine the hours. 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.[14] During the New Kingdom, another system of decans was used, made up of 24 stars over the course of the year and 12 within any one night.

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 sundials 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 Ra's solar barge travelled.[15] Protective deities were assigned to each and were used as the names of the hours.[15] As the protectors and resurrectors of the sun, the goddesses of the night hours were considered to hold power over all lifespans[15] and thus became part of Egyptian funerary rituals. Two fire-spitting cobras were said to guard the gates of each hour of the underworld, and Wadjet and the rearing cobra (uraeus) were also sometimes referenced as wnwt from their role protecting the dead through these gates. The Egyptian for astronomer, used as a synonym for priest, was wnwty, "One of the Hours" or "Hour-Watcher".[c] The earliest forms of wnwt include one or three stars, with the later solar hours including the determinative hieroglyph for "sun".[9]

East Asia

Clock Tower from Su Song's Book
A Chinese diagram from Su Song's AD 1092 Xinyi Xiangfa Yao illustrating his clocktower at Kaifeng.
Beijing 2006 1-14
A reconstruction of another kind of Chinese clepsydra in Beijing's Drum Tower

Ancient China divided its day into 100 "marks"[24][25] (Chinese: , oc *kʰək,[26] p ) running from midnight to midnight.[27] The system is said to have been used since remote antiquity,[27] credited to the legendary Yellow Emperor,[28] but is first attested in Han-era water clocks[29] and in the 2nd-century history of that dynasty.[30] It was measured with sundials[31] and water clocks.[d] Into the Eastern Han, the Chinese measured their day schematically, adding the 20-ke difference between the solstices evenly throughout the year, one every nine days.[29] During the night, time was more commonly reckoned during the night by the "watches" (Chinese: , oc *kæŋ,[26] p gēng) of the guard, which were reckoned as a fifth of the time from sunset to sunrise.[24][32]

Imperial China continued to use ke and geng but also began to divide the day into 12 "double hours" (t , s , oc *,[26] p shí, lit. "time[s]") named after the earthly branches and sometimes also known by the name of the corresponding animal of the Chinese zodiac.[33] The first shi originally ran from 11 pm to 1 am but was reckoned as starting at midnight by the time of the History of Song, compiled during the early Yuan.[34] These apparently began to be used during the Eastern Han that preceded the Three Kingdoms era, but the sections that would have covered them are missing from their official histories; they first appear in official use in the Tang-era Book of Sui.[30] Variations of all these units were subsequently adopted by Japan[32] and the other countries of the Sinosphere.

The 12 shi supposedly began to be divided into 24 hours under the Tang,[32] although they are first attested in the Ming-era Book of Yuan.[27] In that work, the hours were known by the same earthly branches as the shi, with the first half noted as its "starting" and the second as "completed" or "proper" shi.[27] In modern China, these are instead simply numbered and described as "little shi". The modern ke is now used to count quarter-hours, rather than a separate unit.

As with the Egyptian night and daytime hours, the division of the day into twelve shi has been credited to the example set by the rough number of lunar cycles in a solar year,[35] although the 12-year Jovian orbital cycle was more important to traditional Chinese[36] and Babylonian reckoning of the zodiac.[37][e]

Southeast Asia

In Thailand, Laos, and Cambodia, the traditional system of noting hours is the six-hour clock. This reckons each of a day's 24 hours apart from noon as part of a fourth of the day. 7 am was the first hour of the first half of daytime; 1 pm the first hour of the latter half of daytime; 7 pm the first hour of the first half of nighttime; and 1 am the first hour of the latter half of nighttime. This system existed in the Ayutthaya Kingdom, deriving its current phrasing from the practice of publicly announcing the daytime hours with a gong and the nighttime hours with a drum.[39] It was abolished in Laos and Cambodia during their French occupation and is uncommon there now. The Thai system remains in informal use in the form codified in 1901 by King Chulalongkorn.[40]

Other ancient cultures

Drei Horen
Two of the deified Hours of the Greeks and Romans

The Vedas and Puranas employed units of time based on the sidereal day (nakṣatra ahorātram). This was variously divided into 30 muhūtras of 48 minutes each or 60 dandas or nadís of 24 minutes each.[41] The solar day was later similarly divided into 60 ghaṭikás of about the same duration, each divided in turn into 60 vinadis.[41] The Sinhalese followed a similar system but called their sixtieth of a day a peya.

The ancient Greeks and Romans originally divided the day into 12 hours and the night into 3 or 4 night watches. They were notionally deified as the Horae, although sometimes only as a triad. The Greek astronomer Andronicus of Cyrrhus oversaw the construction of a horologion called the Tower of the Winds in Athens during the first century BC. This structure tracked a 24-hour day using both sundials and mechanical hour indicators.[42] The night was eventually also divided into 12 hours.

Middle Ages

Bishopstone sundial
A 7th-century Saxon tide dial on the porch at Bishopstone in Sussex, with larger crosses marking the canonical hours.[43]

During Europe's Middle Ages, the Roman hours continued to be marked on sundials but the more important units of time were the canonical hours of the Orthodox and Catholic Church. During daylight, these followed the pattern set by the three-hour bells of the Roman markets, which were succeeded by the bells of local churches. They rang prime at about 6 am, terce at about 9 am, sext at noon, nones at about 3 pm, and vespers at either 6 pm or sunset. Matins and lauds precede these irregularly in the morning hours; compline follows them irregularly before sleep; and the midnight office follows that. Vatican II ordered their reformation for the Catholic Church in 1963,[44] though they continue to be observed in the Orthodox churches.

When mechanical clocks began to be used to show hours of daylight or nighttime, their period needed to be changed every morning and evening (for example, by changing the length of their pendula). The use of 24 hours for the entire day meant hours varied much less and the clocks needed to be adjusted only a few times a month.

Modernity

The minor irregularities of the apparent solar day were smoothed by measuring time using the mean solar day, using the Sun's movement along the celestial equator rather than along the ecliptic. The irregularities of this time system were so minor that most clocks reckoning such hours did not need adjustment. However, scientific measurements eventually became precise enough to note the effect of tidal deceleration of the Earth by the Moon, which gradually lengthens the Earth's days.

During the French Revolution, a general decimalization of measures was enacted, including decimal time between 1793 and 1795. Under its provisions, the French hour (French: heure) was ​110 of the day and divided formally into 100 decimal minutes (minute décimale) and informally into 10 tenths (décime). This hour was only briefly in official use, being repealed by the same 1795 legislation that first established the metric system.

The metric system bases its measurements of time upon the second, defined since 1952 in terms of the Earth's rotation in AD 1900. Its hours are a secondary unit computed as precisely 3,600 seconds.[45] However, an hour of Coordinated Universal Time (UTC), used as the basis of most civil time, has lasted 3,601 seconds 27 times since 1972 in order to keep it within 0.9 seconds of universal time, which is based on measurements of the mean solar day at 0° longitude. The addition of these seconds accommodates the very gradual slowing of the rotation of the Earth.

In modern life, the ubiquity of clocks and other timekeeping devices means that segmentation of days according to their hours is commonplace. Most forms of employment, whether wage or salaried labour, involves compensation based upon measured or expected hours worked. The fight for an eight-hour day was a part of labour movements around the world. Informal rush hours and happy hours cover the times of day when commuting slows down due to congestion or alcoholic drinks are available at discounted prices. The hour record for the greatest distance travelled by a cyclist within the span of an hour is one of cycling's greatest honours.

Counting hours

Equatorial sundial topview
Top view of an equatorial sundial. The hour lines are spaced equally about the circle, and the shadow of the gnomon (a thin cylindrical rod) rotates uniformly. The height of the gnomon is ​512 the outer radius of the dial. This animation depicts the motion of the shadow from 3 a.m. to 9 p.m. on mid-summer's day, when the Sun is at its highest declination (roughly 23.5°). Sunrise and sunset occur at 3 a.m. and 9 p.m. respectively on that day at geographical latitudes near 57.5°, roughly the latitude of Aberdeen or Sitka, Alaska.
Planispheric astrolabe
Planispheric astrolabe designed for the latitude of Varese (Italy)

Many different ways of counting the hours have been used. Because sunrise, sunset, and, to a lesser extent, noon, are the conspicuous points in the day, starting to count at these times was, for most people in most early societies, much easier than starting at midnight. However, with accurate clocks and modern astronomical equipment (and the telegraph or similar means to transfer a time signal in a split-second), this issue is much less relevant.

Astrolabes, sundials, and astronomical clocks sometimes show the hour length and count using some of these older definitions and counting methods.

Counting from dawn

In ancient and medieval cultures, the counting of hours generally started with sunrise. Before the widespread use of artificial light, societies were more concerned with the division between night and day, and daily routines often began when light was sufficient.[46]

"Babylonian hours", as used on modern sundials, divide the day and night into 24 equal hours, reckoned from the time of sunrise.[47] They are so named from the false belief of ancient authors that the Babylonians divided the day into 24 parts, beginning at sunrise. In fact, they divided the day into 12 parts (called kaspu or "double hours") or into 60 equal parts.[48]

Unequal hours

Sunrise marked the beginning of the first hour, the middle of the day was at the end of the sixth hour and sunset at the end of the twelfth hour. This meant that the duration of hours varied with the season. In the Northern hemisphere, particularly in the more northerly latitudes, summer daytime hours were longer than winter daytime hours, each being one twelfth of the time between sunrise and sunset. These variable-length hours were variously known as temporal, unequal, or seasonal hours and were in use until the appearance of the mechanical clock, which furthered the adoption of equal length hours.[46]

This is also the system used in Jewish law and frequently called "Talmudic hour" (Sha'a Zemanit) in a variety of texts. The Talmudic hour is one twelfth of time elapsed from sunrise to sunset, day hours therefore being longer than night hours in the summer; in winter they reverse.

The Indic day began at sunrise. The term hora was used to indicate an hour. The time was measured based on the length of the shadow at day time. A hora translated to 2.5 pe. There are 60 pe per day, 60 minutes per pe and 60 kshana (snap of a finger or instant) per minute. Pe was measured with a bowl with a hole placed in still water. Time taken for this graduated bowl was one pe. Kings usually had an officer in charge of this clock.

Counting from sunset

In so-called "Italian time", "Italian hours", or "old Czech time", the first hour started with the sunset Angelus bell (or at the end of dusk, i.e., half an hour after sunset, depending on local custom and geographical latitude). The hours were numbered from 1 to 24. For example, in Lugano, the sun rose in December during the 14th hour and noon was during the 19th hour; in June the Sun rose during the 7th hour and noon was in the 15th hour. Sunset was always at the end of the 24th hour. The clocks in church towers struck only from 1 to 12, thus only during night or early morning hours.

This manner of counting hours had the advantage that everyone could easily know how much time they had to finish their day's work without artificial light. It was already widely used in Italy by the 14th century and lasted until the mid-18th century; it was officially abolished in 1755, or in some regions customary until the mid-19th century.[f]

The system of Italian hours can be seen on a number of clocks in Europe, where the dial is numbered from 1 to 24 in either Roman or Arabic numerals. The St Mark's Clock in Venice, and the Orloj in Prague are famous examples. It was also used in Poland and Bohemia until the 17th century.

The Islamic day begins at sunset. The first prayer of the day (maghrib) is to be performed between just after sunset and the end of twilight. Until 1968 Saudi Arabia used the system of counting 24 equal hours with the first hour starting at sunset.[49]

Counting from noon

For many centuries, up to 1925, astronomers counted the hours and days from noon, because it was the easiest solar event to measure accurately. An advantage of this method (used in the Julian Date system, in which a new Julian Day begins at noon) is that the date doesn't change during a single night's observing.

Counting from midnight

In the modern 12-hour clock, counting the hours starts at midnight and restarts at noon. Hours are numbered 12, 1, 2, ..., 11. Solar noon is always close to 12 noon (ignoring artificial adjustments due to time zones and daylight saving time), differing according to the equation of time by as much as fifteen minutes either way. At the equinoxes sunrise is around 6 a.m. (Latin: ante meridiem, before noon), and sunset around 6 p.m. (Latin: post meridiem, after noon).

In the modern 24-hour clock, counting the hours starts at midnight, and hours are numbered from 0 to 23. Solar noon is always close to 12:00, again differing according to the equation of time. At the equinoxes sunrise is around 06:00, and sunset around 18:00.

Derived measures

See also

Notes

  1. ^ Since 1972, the 27 leap seconds added to UTC have all been additions.
  2. ^ From the c. 1250 sermon for Sexagesima Sunday: ...Þos laste on ure habbeþ i-travailed...[3]
  3. ^ Wnwty is written variously as
    E34
    N35
    G43X1
    Z4
    N14
    ,[16]
    E34
    N35
    W24 X1 D4
    ,
    E34
    N35
    W24 X1 N14
    ,[17]
    E34
    N35
    W24
    X1
    N14A24A1
    Z2
    ,
    E34
    N35
    W24
    X1
    N14N5
    D4
    ,[18]
    E34
    N35
    W24
    X1
    Z4A1
    ,
    E34
    N35
    W24
    X1
    Z4N11
    N14
    D6
    ,
    E34
    N35
    W24
    X1
    Z4N14
    ,
    E34
    N35
    W24
    X1
    Z4N14A1
    ,
    E34
    N35
    W24
    X1
    Z4N2A24
    ,[19]
    E34
    N35
    X1
    Z4
    N14
    N5
    ,[20]
    N14
    ,[21]
    N14
    W24
    X1
    Z4
    ,[22] and
    N14
    X1 Z4
    .[23]
  4. ^ According to the 2nd-century Shuowen Jiezi, "A water clock holds the water in a copper pot and notes the marks [] by a rule. There are 100 marks which represent the day".
  5. ^ The late classical Indians also began to reckon years based on the Jovian cycle, but this was much later than their lunar calendar and initially named after it.[38]
  6. ^ There is a trace of that system, for instance, in Verdi's operas where in Rigoletto or in Un ballo in maschera midnight is announced by the bell striking 6 times, not 12. But in his last opera, Falstaff, strangely, he abandoned that style, perhaps under influence of contemporary trends at end of 19th century when he composed it, and the midnight bell strikes 12 times.

References

Citations

  1. ^ "Resolution 7", Resolutions of the CGPM: 9th Meeting, Paris: International Bureau of Weights and Measures, October 1948
  2. ^ OED, hour, n.
  3. ^ Morris, Richard, ed. (1872), "Old Kentish Sermons (Laud MS 471)", An Old English Miscellany, London: N. Trübner & Co. for the Early English Text Society, p. 34
  4. ^ OED, tide, n.
  5. ^ OED, stound, n.¹.
  6. ^ OED, clock, n.¹, & o'clock, adv. (and n.).
  7. ^ OED, hundred, n. and adj..
  8. ^ a b OED, quarter, n.
  9. ^ a b c Clagett (1995), p. 49
  10. ^ a b Clagett (1995), p. 50
  11. ^ Parker (1950), pp. 30-2.
  12. ^ Clagett (1995), p. 50–1
  13. ^ Clagett (1995), p. 218
  14. ^ Parker (1950), p. 40.
  15. ^ a b c Wilkinson (2003), p. 83.
  16. ^ Vygus (2015), p. 400.
  17. ^ Vygus (2015), p. 408.
  18. ^ Vygus (2015), p. 409.
  19. ^ Vygus (2015), p. 410.
  20. ^ Vygus (2015), p. 412.
  21. ^ Vygus (2015), p. 1235.
  22. ^ Vygus (2015), p. 1239.
  23. ^ Vygus (2015), p. 1240.
  24. ^ a b Stephenson (1997).
  25. ^ Steele (2000).
  26. ^ a b c Baxter & al. (2014).
  27. ^ a b c d Sōma & al. (2004), p. 887.
  28. ^ Petersen (1992), p. 129.
  29. ^ a b Petersen (1992), p. 125.
  30. ^ a b Sōma & al. (2004), p. 889.
  31. ^ Stephenson & al. (2002), pp. 15–16.
  32. ^ a b c Sōma & al. (2004), p. 888.
  33. ^ Sōma & al. (2004), p. 904.
  34. ^ Sōma & al. (2004), p. 896.
  35. ^ Canhão, Telo Ferreira (2013). "A Timeless Legacy: the Calendars of Ancient Egypt". Alexandrea ad Aegyptvm: The legacy of multiculturalismo in antiquity. Porto: Edições Afrontamento. pp. 283–301. doi:10.14195/978-989-26-0966-9_20. ISBN 9789892609669.
  36. ^ Zai, J. (2015), Taoism and Science, Ultravisum
  37. ^ Rogers (1998), pp. 9–28.
  38. ^ Sewell (1924), p. xii.
  39. ^ Thongprasert (1985), pp. 229–237.
  40. ^ "ประกาศใช้ทุ่มโมงยาม", Royal Gazette, No. 17 (PDF), 29 July 1901, p. 206. (in Thai)
  41. ^ a b Dershowitz & al. (2008), p. 207
  42. ^ "A Walk Through Time". National Institute of Standards and Technology. Retrieved 2 April 2014.
  43. ^ Wall (1912), p. 67.
  44. ^ Paul VI (4 December 1963), Constitution on the Sacred Liturgy, Vatican City, §89(d)
  45. ^ "Non-SI Units Accepted for Use with the SI, and Units Based on Fundamental Constants (contd.)", The International System of Units (SI), 8th ed., Paris: International Bureau of Weights and Measures, 2014
  46. ^ a b Landes (1983), p. 76.
  47. ^ "Different Classification of Hours". Math.nus.edu.sg. Retrieved 2018-09-20.
  48. ^ Holford-Strevens (2005).
  49. ^ "Saudi Aramco World : Dinner At When?". archive.aramcoworld.com.

Bibliography

Further reading

External links

12-hour clock

The 12-hour clock is a time convention in which the 24 hours of the day are divided into two periods: a.m. (from Latin ante meridiem, translates to, before midday) and p.m. (from Latin post meridiem translates to, past midday). Each period consists of 12 hours numbered: 12 (acting as zero), 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11. The 24 hour/day cycle starts at 12 midnight (may be indicated as 12 a.m.), runs through 12 noon (may be indicated as 12 p.m.), and continues to the midnight at the end of the day. The 12-hour clock has been developed from the middle of the second millennium BC to the 16th century AD.

The 12-hour time convention is common in several English-speaking nations and former British colonies, as well as a few other countries.

24-hour clock

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, and is used by international standard ISO 8601.A limited number of countries, particularly English-speaking, use the 12-hour clock, or a mixture of the 24- and 12-hour time systems. In countries where the 12-hour clock is still dominant, some professions prefer to use the 24-hour clock. For example, 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 patient's medical history. In the United States and a handful of other countries, it is popularly referred to as military time.

24 (TV series)

24 is an American action drama television series produced for the Fox network, created by Joel Surnow and Robert Cochran, and starring Kiefer Sutherland as counter-terrorist agent Jack Bauer. Each season, comprising 24 episodes, covers 24 hours in Bauer's life using the real time method of narration. Premiering on November 6, 2001, the show spanned 192 episodes over eight seasons; the series finale broadcast on May 24, 2010. In addition, a television film, 24: Redemption, was broadcast between seasons six and seven, on November 23, 2008. 24 returned with a ninth season titled 24: Live Another Day, which aired from May 5 to July 14, 2014. 24: Legacy, a spin-off series featuring new characters, premiered on February 5, 2017. After the cancellation of Legacy in June 2017, Fox announced its plan to develop a new incarnation of the franchise.The series begins with Bauer working for the Los Angeles–based Counter Terrorist Unit, in which he is a highly proficient agent with an "ends justify the means" approach, regardless of the perceived morality of some of his actions. Throughout the series most of the main plot elements unfold like a political thriller. A typical plot has Bauer racing against the clock as he attempts to thwart multiple terrorist plots, including presidential assassination attempts, weapons of mass destruction detonations, bioterrorism, cyber attacks, as well as conspiracies that deal with government and corporate corruption.

24 won numerous awards over its eight seasons, including Best Drama Series at the 2004 Golden Globe Awards and Outstanding Drama Series at the 2006 Primetime Emmy Awards. At the conclusion of its eighth season, 24 became the longest-running U.S. espionage/counterterrorism-themed television drama ever, surpassing both Mission: Impossible and The Avengers.

24 Hours of Le Mans

The 24 Hours of Le Mans (French: 24 Heures du Mans) is the world's oldest active sports car race in endurance racing, held annually since 1923 near the town of Le Mans, France. It is considered one of the most prestigious automobile races in the world and has been called the "Grand Prix of Endurance and Efficiency". The event represents one leg of the Triple Crown of Motorsport; other events being the Indianapolis 500 and the Monaco Grand Prix.

The race is organized by the Automobile Club de l'Ouest (ACO) and is held on the Circuit de la Sarthe, which contains a mix of closed public roads and dedicated sections of racing track, in which racing teams must balance the demands of speed with the cars' ability to run for 24 hours without mechanical failure. Of the 60 cars which qualified for the 2018 race, 41 cars ran the full duration.Since 2012, the 24 Hours of Le Mans has been a part of the FIA World Endurance Championship. Because of the decision to run a World Endurance Championship super-season in the period May 2018 to June 2019, the 24 Hours of Le Mans will be run twice in the same season: it will be both the second and the last round of the season. In 2011 it was a part of the Intercontinental Le Mans Cup, and it frequently formed a part of the World Sportscar Championship from 1953 until that series' final season in 1992.

Over time, Le Mans has influenced events that have sprung up all around the globe, popularizing the 24-hour format at locations such as Daytona, Nürburgring, Spa-Francorchamps, and Bathurst. The American Le Mans Series and Europe's Le Mans Series of multi-event sports car championships were spun off from 24 Hours of Le Mans regulations. Other races include the Le Mans Classic, a race for historic Le Mans race cars from years' past held on the Circuit de la Sarthe, a motorcycle version of the race which is held on the shortened Bugatti version of the same circuit, a kart race (24 Heures Karting), a truck race (24 Heures Camions), and a parody race 24 Hours of LeMons.

The 2019 24 Hours of Le Mans (French: 87e 24 Heures du Mans) will be held on June 15–16 at the Circuit de la Sarthe, Le Mans, France.

90th Academy Awards

The 90th Academy Awards ceremony, presented by the Academy of Motion Picture Arts and Sciences (AMPAS), honored the best films of 2017, and took place at the Dolby Theatre in Hollywood, Los Angeles, California. The ceremony was held on March 4, 2018, rather than its usual late-February date to avoid conflicting with the 2018 Winter Olympics. During the ceremony, AMPAS presented Academy Awards (commonly referred to as Oscars) in 24 categories. The ceremony was televised in the United States by American Broadcasting Company (ABC), produced by Michael De Luca and Jennifer Todd and directed by Glenn Weiss. Comedian Jimmy Kimmel hosted for the second consecutive year.In related events, the Academy held its 9th Annual Governors Awards ceremony at the Grand Ballroom of the Hollywood and Highland Center on November 11, 2017. On February 10, 2018, in a ceremony at the Beverly Wilshire Hotel in Beverly Hills, California, the Academy Scientific and Technical Awards were presented by host actor Sir Patrick Stewart.The Shape of Water won a leading four awards, including Best Picture and Best Director for Guillermo del Toro. Dunkirk won three awards; Blade Runner 2049, Coco, Darkest Hour, and Three Billboards Outside Ebbing, Missouri won two awards each. Frances McDormand and Sam Rockwell won Best Actress and Best Supporting Actor awards for Three Billboards Outside Ebbing, Missouri while Gary Oldman won Best Actor for Darkest Hour. Allison Janney won Best Supporting Actress honor for I, Tonya. With a U.S. viewership of 26.5 million, it was the least-watched show in Oscar history.

Ampere hour

An ampere hour or amp hour (symbol Ah; also denoted A⋅h or A h) is a unit of electric charge, having dimensions of electric current multiplied by time, equal to the charge transferred by a steady current of one ampere flowing for one hour, or 3600 coulombs. The commonly seen milliampere hour (mAh or mA⋅h) is one-thousandth of an ampere hour (3.6 coulombs).

Big Ben

Big Ben is the nickname for the Great Bell of the clock at the north end of the Palace of Westminster in London and is usually extended to refer to both the clock and the clock tower. The official name of the tower in which Big Ben is located was originally the Clock Tower, but it was renamed Elizabeth Tower in 2012 to mark the Diamond Jubilee of Elizabeth II.

The tower was designed by Augustus Pugin in a neo-Gothic style. When completed in 1859, its clock was the largest and most accurate four-faced striking and chiming clock in the world. The tower stands 315 feet (96 m) tall, and the climb from ground level to the belfry is 334 steps. Its base is square, measuring 39 feet (12 m) on each side. Dials of the clock are 23 feet (7.0 m) in diameter. On 31 May 2009, celebrations were held to mark the tower's 150th anniversary.Big Ben is the largest of the tower's five bells and weighs 13.5 long tons (13.7 tonnes; 15.1 short tons). It was the largest bell in the United Kingdom for 23 years. The origin of the bell's nickname is open to question; it may be named after Sir Benjamin Hall, who oversaw its installation, or heavyweight boxing champion Benjamin Caunt. Four quarter bells chime at 15, 30 and 45 minutes past the hour and just before Big Ben tolls on the hour. The clock uses its original Victorian mechanism, but an electric motor can be used as a backup.

The tower is a British cultural icon recognised all over the world. It is one of the most prominent symbols of the United Kingdom and parliamentary democracy, and it is often used in the establishing shot of films set in London. The clock tower has been part of a Grade I listed building since 1970 and a UNESCO World Heritage Site since 1987.

On 21 August 2017, a four-year schedule of renovation works began on the tower, which are to include the addition of a lift. There are also plans to re-glaze and repaint the clock dials. With a few exceptions, such as New Year's Eve and Remembrance Sunday, the bells are to be silent until the work has been completed in the 2020s.

Chris Tucker

Christopher Tucker (born August 31, 1971) is an American actor and stand-up comedian. He is known for playing the role of Smokey in F. Gary Gray's Friday and as Detective James Carter in Brett Ratner's Rush Hour film series. He became a frequent stand up performer on Def Comedy Jam in the 1990s. He appeared in Luc Besson's The Fifth Element, Quentin Tarantino's Jackie Brown, David O. Russell's Silver Linings Playbook, and Brett Ratner's Money Talks.

Daylight saving time

Daylight saving time (DST), also daylight savings time or daylight time (United States) and summer time (United Kingdom, European Union, and others), is the practice of advancing clocks during summer months so that evening daylight lasts longer, while sacrificing normal sunrise times. Typically, regions that use daylight saving time adjust clocks forward one hour close to the start of spring and adjust them backward in the autumn to standard time. In effect, DST causes a lost hour of sleep in the spring and an extra hour of sleep in the fall.George Hudson proposed the idea of daylight saving in 1895. The German Empire and Austria-Hungary organized the first nationwide implementation starting on April 30, 1916. Many countries have used at various times since then, particularly since the 1970s energy crisis. DST is generally not observed near the equator, where sunrise times do not vary enough to justify it. Some countries observe it only in some regions; for example, southern Brazil observes it, while equatorial Brazil does not. Only a minority of the world's population uses DST, because Asia and Africa generally do not observe it.

DST clock shifts sometimes complicate timekeeping and can disrupt travel, billing, record keeping, medical devices, heavy equipment, and sleep patterns. Computer software often adjusts clocks automatically, but policy changes by various jurisdictions of DST dates and timings may be confusing.

Eight-hour day

The eight-hour day movement or 40-hour week movement, also known as the short-time movement, was a social movement to regulate the length of a working day, preventing excesses and abuses. It had its origins in the Industrial Revolution in Britain, where industrial production in large factories transformed working life. The use of child labour was common. The working day could range from 10 to 16 hours, and the work week was typically six days a week. Robert Owen had raised the demand for a ten-hour day in 1810, and instituted it in his socialist enterprise at New Lanark. By 1817 he had formulated the goal of the eight-hour day and coined the slogan: "Eight hours' labour, Eight hours' recreation, Eight hours' rest". Women and children in England were granted the ten-hour day in 1847. French workers won the 12-hour day after the February Revolution of 1848. A shorter working day and improved working conditions were part of the general protests and agitation for Chartist reforms and the early organisation of trade unions.

The International Workingmen's Association took up the demand for an eight-hour day at its Congress in Geneva in 1866, declaring "The legal limitation of the working day is a preliminary condition without which all further attempts at improvements and emancipation of the working class must prove abortive", and "The Congress proposes eight hours as the legal limit of the working day."

Karl Marx saw it as of vital importance to the workers' health, writing in Das Kapital (1867): "By extending the working day, therefore, capitalist production...not only produces a deterioration of human labour power by robbing it of its normal moral and physical conditions of development and activity, but also produces the premature exhaustion and death of this labour power itself."Although there were initial successes in achieving an eight-hour day in New Zealand and by the Australian labour movement for skilled workers in the 1840s and 1850s, most employed people had to wait to the early and mid twentieth century for the condition to be widely achieved through the industrialised world through legislative action. The first country to adopt eight-hour working day nationwide was Uruguay. The eight-hour day was introduced on November 17, 1915, in the government of José Batlle y Ordóñez.

The first international treaty to mention it was the Treaty of Versailles in the annex of its thirteen part establishing the International Labour Office, now the International Labour Organization.The eight-hour day was the first topic discussed by the International Labour Organization which resulted in the Hours of Work (Industry) Convention, 1919 ratified by 52 countries as of 2016.

The eight-hour day movement forms part of the early history for the celebration of Labour Day, and May Day in many nations and cultures.

Kacey Musgraves

Kacey Lee Musgraves (born August 21, 1988) is an American singer and songwriter. She has won six Grammy Awards, four Country Music Association Awards and three Academy of Country Music Awards. Musgraves self-released three albums before appearing on the fifth season of the USA Network's singing competition Nashville Star in 2007, where she placed seventh. In 2008, Kacey recorded two singles for Triple Pop in Austin, Texas.She later signed to Mercury Nashville in 2012 and released her critically acclaimed debut album Same Trailer Different Park in 2013, winning the Grammy Award for Best Country Album. The album's lead single "Merry Go 'Round" won her the Grammy Award for Best Country Song. It also featured the platinum certified single "Follow Your Arrow" which won her the Country Music Association Award for Song of the Year. In 2015, she released her second studio album Pageant Material (2015) which also received critical acclaim and a Best Country Album Grammy nomination. Musgraves also released a Christmas-themed album, A Very Kacey Christmas in 2016.Her fourth studio album Golden Hour (2018) was released to widespread critical acclaim and won all four of its nominated Grammy Awards categories, including Album of the Year and Best Country Album. The album's first two singles, "Butterflies" and "Space Cowboy", won Best Country Solo Performance and Best Country Song, respectively. Golden Hour also won the Academy of Country Music and the Country Music Association Award for Album of the Year, making Musgraves only the 6th artist to win all three major Album of the Year (Grammy, CMA and ACM) awards for the same album as well as the 2nd artist to win the Grammy, CMA, ACM and all-genre Grammy Album of the Year.

Kilometres per hour

The kilometre per hour (American English: kilometer per hour) is a unit of speed, expressing the number of kilometres travelled in one hour.

Internationally, km/h is the most commonly used unit of speed on traffic signs and speedometers.

Kilowatt hour

The kilowatt hour (symbol kWh, kW⋅h or kW h) is a unit of energy equal to 3.6 megajoules. If energy is transmitted or used at a constant rate (power) over a period of time, the total energy in kilowatt hours is equal to the power in kilowatts multiplied by the time in hours. The kilowatt hour is commonly used as a billing unit for energy delivered to consumers by electric utilities.

Knot (unit)

The knot () is a unit of speed equal to one nautical mile per hour, exactly 1.852 km/h (approximately 1.15078 mph). The ISO standard symbol for the knot is kn. The same symbol is preferred by the Institute of Electrical and Electronics Engineers (IEEE); kt is also common, especially in aviation where it is the form recommended by the International Civil Aviation Organization (ICAO). The knot is a non-SI unit. Worldwide, the knot is used in meteorology, and in maritime and air navigation—for example, a vessel travelling at 1 knot along a meridian travels approximately one minute of geographic latitude in one hour.

Etymologically, the term derives from counting the number of knots in the line that unspooled from the reel of a chip log in a specific time.

Lok Sabha

The Lok Sabha (House of the People) is the lower house of India's bicameral Parliament, with the upper house being the Rajya Sabha. Members of the Lok Sabha are elected by adult universal suffrage and a first-past-the-post system to represent their respective constituencies, and they hold their seats for five years or until the body is dissolved by the President on the advice of the council of ministers. The house meets in the Lok Sabha Chambers of the Sansad Bhavan in New Delhi.

The maximum strength of the House allotted by the Constitution of India is 552. Currently, the house has 545 seats which is made up by the election of up to 543 elected members and at a maximum, 2 nominated members of the Anglo-Indian Community by the President of India. A total of 131 seats (24.03%) are reserved for representatives of Scheduled Castes (84) and Scheduled Tribes (47). The quorum for the House is 10% of the total membership. The Lok Sabha, unless sooner dissolved, continues to operate for five years from the date appointed for its first meeting. However, while a proclamation of emergency is in operation, this period may be extended by Parliament by law.An exercise to redraw Lok Sabha constituencies' boundaries is carried out by the Boundary Delimitation Commission of India every decade based on the Indian census, last of which was conducted in 2011. This exercise earlier also included redistribution of seats among states based on demographic changes but that provision of the mandate of the commission was suspended in 1976 following a constitutional amendment to incentivise the family planning programme which was being implemented. The 16th Lok Sabha was elected in May 2014 and is the latest to date. The schedule for the 2019 Lok Sabha Election has been announced by the Election Commission of India. Broken into seven phases the General Elections will be held from 11th April 2019 till 19th May 2019.

The Lok Sabha has its own television channel, Lok Sabha TV, headquartered within the premises of Parliament.

Sunshine duration

Sunshine duration or sunshine hours is a climatological indicator, measuring duration of sunshine in given period (usually, a day or a year) for a given location on Earth, typically expressed as an averaged value over several years. It is a general indicator of cloudiness of a location, and thus differs from insolation, which measures the total energy delivered by sunlight over a given period.

Sunshine duration is usually expressed in hours per year, or in (average) hours per day. The first measure indicates the general sunniness of a location compared with other places, while the latter allows for comparison of sunshine in various seasons in the same location. Another often-used measure is percentage ratio of recorded bright sunshine duration and daylight duration in the observed period.

An important use of sunshine duration data is to characterize the climate of sites, especially of health resorts. This also takes into account the psychological effect of strong solar light on human well-being. It is often used to promote tourist destinations.

Today (U.S. TV program)

Today, also called The Today Show, is an American news and talk morning television show that airs on NBC. The program debuted on January 14, 1952. It was the first of its genre on American television and in the world, and after 67 years of broadcasting it is the fifth-longest-running American television series.

Originally a weekday two-hour program from 7:00 a.m. - 9:00 a.m., it expanded to Sundays in 1987 and Saturdays in 1992. The weekday broadcast expanded to three hours in 2000, and to four hours in 2007 (though over time, the third and fourth hours became distinct entities). Today's dominance was virtually unchallenged by the other networks until the late 1980s, when it was overtaken by ABC's Good Morning America. Today retook the Nielsen ratings lead the week of December 11, 1995, and held onto that position for 852 consecutive weeks until the week of April 9, 2012, when Good Morning America topped it again. Today maintained its No. 2 status behind GMA from the summer of 2012 until it regained the lead in the aftermath of anchor Matt Lauer's departure in November 2017. In 2002, Today was ranked No. 17 on TV Guide's 50 Greatest TV Shows of All Time.The entertainment magazine Variety reported the 2016 advertising revenue during the first two hours of the show was $508.8 million.

Vevo

Vevo ( VEE-voh, an abbreviation for 'video evolution') is an American multinational video hosting service founded on December 8, 2009, as a joint venture among three major record companies: Universal Music Group (UMG), Sony Music Entertainment (SME) and EMI. In August 2016, Warner Music Group (WMG), the third-largest record company, agreed to license premium videos from its artists onto Vevo.Vevo only hosts music videos from both Universal Music Group and Sony Music Entertainment syndicated on YouTube and its website, with Google and Vevo sharing advertising and similar benefits. EMI also licensed its library of videos for Vevo shortly before its launch and its acquisition by UMG in 2012. Originally, Warner Music Group was reported to be considering hosting its content on the service after it launched, but formed an alliance with rival MTV Networks (now Viacom Media Networks). In August 2015, Vevo expressed renewed interest in licensing music from WMG, and its deal with WMG was completed on August 2, 2016, making the entirety of the "big three" record companies' music eligible for licensing to Vevo.

On May 24, 2018, Vevo announced that it was shutting down its consumer website and mobile app. Vevo currently only distributes via YouTube and as an app on select Smart TVs.

Watt

The watt (symbol: W) is a unit of power. In the International System of Units (SI) it is defined as a derived unit of 1 joule per second, and is used to quantify the rate of energy transfer. In dimensional analysis, power is described by .

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Measurement and
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Time in physics
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