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Kilometre

Kilometre

A kilometre (American spelling: kilometer), symbol: km is a unit of length in the metric system equal to 1000 metres (from the Greek words χίλια (khilia) = thousand and μέτρο (metro) = count/measure). It is approximately equal to 0.621 miles, 1094 yards or 3281 feet. Slang terms for kilometre include "klick" (sometimes spelt "click" or "klik") and "kay" (or "k"). All these slang terms can also refer to kilometres per hour.

Metric system

:Main articles: Metric system and Metre Like the kilometre, all units of length in the metric system are based on the metre, by adding an SI prefix that stands for a power of ten, such as hecto for one hundred to form hectometre (= 0.1 kilometre) or mega for one million to form megametre (= 1,000 kilometre). The metre is not only the basis for all units of length in the metric system, but also of units of area (the square metre) and volume (the cubic metre). This extends to the kilometre, so one can have square and cubic kilometres. Unicode has symbols for "km" (㎞), for square kilometre (㎢) and for cubic kilometre (㎦); however, they are useful only in CJK texts, where they are equal in size to one Chinese character.

Pronunciation

In theory, the pronunciation of the word kilometre should have the stress placed on the first syllable, in line with other metric prefixes (as in kilogram, kilojoule and, analogous, kilobyte). However, pronunciation with the stress on the second syllable is usual in English.

American English

American English (AmE) is the dialect of the English language used mostly in the United States of America. Crystal (1997) estimates that approximately two thirds of native speakers of English live in the United States. American English is also sometimes called United States English or U.S. English.

History

English was inherited from British colonization. The first wave of English-speaking immigrants was settled in North America in the 17th century. In that century, there were also speakers in North America of the Dutch, French, German, myriad Native American, Spanish, Swedish, Scots, Welsh, Irish, Scottish Gaelic and Finnish languages.

Phonology

In many ways, compared to British English, American English is conservative in its phonology. The conservatism of American English is largely the result of the fact that it represents a mixture of various dialects from the British Isles. Dialect in North America is most distinctive on the East Coast of the continent; this is largely because these areas were in contact with England, and imitated prestigious varieties of British English at a time when those varieties were undergoing changes. The interior of the country was settled by people who were no longer closely connected to England, as they had no access to the ocean during a time when journeys to Britain were always by sea. As such the inland speech is much more homogeneous than the East Coast speech, and did not imitate the changes in speech from England. East Coast-influenced non-rhotic pronunciations may be found among blacks throughout the country.]]Most North American speech is rhotic, as English was in most places in the 17th century. Rhoticity was further supported by Hiberno-English, Scottish English, and West Country English. In most varieties of North American English, the sound corresponding to the letter "R" is a retroflex semivowel rather than a trill or a tap. The loss of syllable-final r in North America is confined mostly to the accents of eastern New England, New York City and surrounding areas, South Philadelphia, and the coastal portions of the South. Dropping of syllable-final r sometimes happens in natively rhotic dialects if r is located in unaccented syllables or words and the next syllable or word begins in a consonant. In England, lost 'r' was often changed into (schwa), giving rise to a new class of falling diphthongs. Furthermore, the 'er' sound of (stressed) fur or (unstressed) butter, which is represented in IPA as stressed or unstressed is realized in American English as a monophthongal r-colored vowel. This does not happen in the non-rhotic varieties of North American speech. Some other British English changes in which most North American dialects do not participate:
- The shift of to (the so-called "broad A") before alone or preceded by . This is the difference between the British Received Pronunciation and American pronunciation of bath and dance. In the United States, only linguistically conservative eastern-New-England speakers took up this innovation.
- The shift of intervocalic to glottal stop , as in for bottle. This change is not universal for British English (and in fact is not considered to be part of Received Pronunciation), but it does not occur in most North American dialects. Newfoundland English and the dialect of New Britain, Connecticut are notable exceptions. On the other hand, North American English has undergone some sound changes not found in Britain, at least not in standard varieties. Many of these are instances of phonemic differentiation and include
- The merger of and , making father and bother rhyme. This change is nearly universal in North American English, occurring almost everywhere except for parts of eastern New England, like the Boston accent.
- The replacement of the lot vowel with the strut vowel in what, was, of, from, everybody, nobody, somebody, anybody, because, and in some dialects want.
- The merger of and . This is the so-called cot-caught merger, where cot and caught are homophones. This change has occurred in eastern New England, in Pittsburgh and surrounding areas, and from the Great Plains westward.
- Vowel merger before intervocalic . Which (if any) vowels are affected varies between dialects.
- The merger of and after palatals in some words, so that cure, pure, mature and sure rhyme with fir in some speech registers for some speakers.
- Dropping of after alveolar consonants so that new, duke, Tuesday, suit, resume, lute are pronounced , , , , , .
- Æ-tensing in environments that vary widely from accent to accent. In some accents, particularly those from Philadelphia to New York City, and can even contrast sometimes, as in Yes, I can vs. tin can .
- Laxing of , and to , and before , causing pronunciations like , and for pair, peer and pure.
- The flapping of intervocalic and to alveolar tap before reduced vowels. The words ladder and latter are mostly or entirely homophonous, possibly distinguished only by the length of preceding vowel. For some speakers, the merger is incomplete and 't' before a reduced vowel is sometimes not tapped following or when it represents underlying 't'; thus greater and grader, and unbitten and unbidden are distinguished. Even among those words where and are flapped, words that would otherwise be homophonous are, for some speakers, distinguished if the flapping is immediately preceded by the diphthongs or ; these speakers tend to pronounce writer with and rider with . This is called Canadian raising; it is general in Canadian English, and occurs in some northerly versions of American English as well (often just applying to the diphthong , but not to ).
- Both intervocalic and may be realized as or , making winter and winner homophones. This does not occur when the second syllable is stressed, as in entail.
- The pin-pen merger, by which is raised to before nasal consonants, making pairs like pen/pin homophonous. This merger originated in Southern American English but is now widespread in the Midwest and West as well. Some mergers found in most varieties of both American and British English include:
- The horse-hoarse merger of the vowels and before 'r', making pairs like horse/hoarse, corps/core, for/four, morning/mourning etc. homophones.
- The wine-whine merger making pairs like wine/whine, wet/whet, Wales/whales, wear/where etc. homophones. Many older varieties of southern and western American English still keep these distinct, but the merger appears to be spreading.

Differences in British English and American English

Main article: American and British English differences American English has both spelling and grammatical differences from British English (or Commonwealth English), some of which were made as part of an attempt to rationalize the English spelling used by British English at the time. Unlike many 20th century language reforms (for example, Turkey's alphabet shift, Norway's spelling reform) the American spelling changes were not driven by government, but by textbook writers and dictionary makers. The first American dictionary was written by Noah Webster in 1828. At the time America was a relatively new country and Webster's particular contribution was to show that the region spoke a different dialect from Britain, and so he wrote a dictionary with many spellings differing from the standard. Many of these changes were initiated unilaterally by Webster. Webster also argued for many "simplifications" to the idiomatic spelling of the period. Somewhat ironically, many, although not all, of his simplifications fell into common usage alongside the original versions, resulting in a situation even more confused than before. Many words are shortened and differ from other versions of English. Spellings such as center are used instead of centre in other versions of English. Conversely, American English sometimes favors words that are morphologically more complex, whereas British English uses clipped forms, such as AmE transportation and BrE transport or where the British form is a back-formation, such as AmE burglarize and BrE burgle (from burglar).

English words that arose in the U.S.

A number of words that arose in the United States have become common, to varying degrees, in English as it is spoken internationally. Although its origin is disputed, the most famous word is probably OK, which is sometimes used in other languages as well. Other American introductions include "belittle," "gerrymander" (from Elbridge Gerry), "blizzard", "teenager", and many more.

English words obsolete outside the U.S.

A number of words that originated in the English of the British Isles are still in everyday use in North America, but are no longer used in most varieties of British English. The most conspicuous of these words are fall, the season; to quit, as in "to cease an activity" (as opposed to "to leave a location" as still used in most other Anglophone countries); and gotten as a past participle of get. Americans are more likely than Britons to name a stream whose breadth or volume is judged insufficient for it to be a river or a creek. The word diaper goes back at least to Shakespeare, and usage was maintained in the U.S. and Canada, but was replaced in the British Isles with nappy. Some of these words are still used in various dialects of the British Isles, but not in formal standard British English. Many of these older words have cognates in Lowland Scots. The subjunctive mood is livelier in North American English than it is in British English; it appears in some areas as a spoken usage, and is considered obligatory in more formal contexts in American English. British English has a strong tendency to replace subjunctives with auxiliary verb constructions.

Regional differences

Main article: American English regional differences Spoken American English is not homogeneous throughout the country, and various regional and ethnic variants exist. These differences affect both pronunciation and the lexicon, and can make one accent a little difficult for speakers of another accent to understand. General American is the name given to any American accent that is relatively free of noticeable regional influences. It enjoys high prestige among Americans, but is not a standard accent in the way that Received Pronunciation is in England.

References

External links

- [http://www.pbs.org/speak/ Do You Speak American]: PBS special
- [http://cfprod01.imt.uwm.edu/Dept/FLL/linguistics/dialect/ Dialect Survey] of the United States, by Bert Vaux et al., Harvard University. The answers to various questions about pronunciation, word use etc. can be seen in relationship to the regions where they are predominant.
- [http://www.ling.upenn.edu/phono_atlas/home.html Phonological Atlas of North America] at the University of Pennsylvania
- [http://students.csci.unt.edu/~kun Guide to Regional English Pronunciation] includes working versions of the Telsur Project maps from the Phonologial Atlas site
- [http://www.peak.org/~jeremy/dictionary/ The American•British British•American Dictionary]
- [http://classweb.gmu.edu/accent/ Speech Accent Archive]
- [http://www.world-english.org/ World English Organization]
- [http://www.esuus.org English Speaking Union of the United States]
- [http://canadianenglish1.narod.ru American Canadian British English Lexical Differences In One Table]
- [http://australianenglish1.narod.ru Australian American British English Lexical Differences In One Table And More]
- [http://www.englisch-hilfen.de/en/words_list/british_american.htm British, American, Australian English - Lists and Online Exercises]
- [http://www.globalenglishsalon.com/ Listen to spoken American English (midwest

Length

:This article is about the concept and measurement of distance. For usage in cricket, see line and length. In general English usage, length (symbols: l, L) is but one particular instance of distance – an object's length is how long the object is – but in the physical sciences and engineering, the word length is in some contexts used synonymously with "distance". Height is vertical distance; width (or breadth) is a lateral distance; an object's width is less than its length. No one speaks of "the length from here to Alpha Centauri", but rather of "the distance from here to Alpha Centauri," but when one speaks of distance more abstractly, one says "A kilometre or a mile, is a unit of length" or "...of distance", and the two statements are synonymous. Likewise, a mountain might be a mile in height. Length is the metric of one dimension of space. The metric of space itself is volume, or (length)³. Length is commonly considered to be one of the fundamental units, meaning that it cannot be defined in terms of other dimensions. However, a set of units can be constructed where units of length can be derived from fundamental physical constants - see Planck units and Planck length. Colloquially length sometimes refers to duration, especially when used in context of music.

Units of length(SI)

The SI unit of Length is the metre (U.S. spelling: meter), from which can be derived:from the regular basis of the foundation of the whole world
- centimetre
- kilometre

Other units of length

The Imperial and US customary units of length

- inch
- foot
- yard
- mile

Units are used in astronomy

- Astronomical unit
- Light year
- Parsec

External links

- [http://www.unitconversion.org/unit_converter/length.html Length Converter: convert between units of length, such as meter, yard, mile, and so on]
- [http://www.unitconversion.org/unit_converter/length-v.html Length Conversion table: convert selected unit to all other units of length]
- [http://calc.skyrocket.de/en/ Online Unit Converter - Conversion of many different units]
- Category:Norm ko:길이 ja:長さ

Metric system

The metric system is a system of units for measurement developed in late 18th century France to replace the disparate systems of measures then in use with a unified, natural and universal system. In the early metric system there were several fundamental or base units, the grad or grade for angles, the metre for length, the gram for weight and the litre for capacity. These were derived from each other via the properties of natural objects. Other units were derived from these fundamental units. Multiples and submultiples of metric units are related by powers of ten; the names for these are formed with prefixes. This relationship is compatible with the decimal system of numbers and it contributes greatly to the convenience of metric units. As the result of scientific progress, refinements, and different choices of base units, there have been a number of attempts at creating metric systems. The modern metric system (modern meaning post-1960) is now widely used throughout the world and is called the International System of Units (SI).

History

The proliferation of disparate measurement systems was one of the most frequent causes of disputes amongst merchants and between citizens and tax collectors. A unified country with a single currency and a countrywide market, as most European countries were becoming by the end of the 18th century, had a very strong economic incentive and was in a position to break with this situation and standardise on a measuring system. The inconsistency problem was not one of different units but one of differing sized units so instead of simply standardizing size of the existing units, the leaders of the French post-revolution government decided that a completely new system should be adopted. The first official adoption of such a system occurred in France in 1791 after the French Revolution of 1789. The creators of this metric system tried to choose units that were logical and practical. The revolution gave an opportunity for drastic change with an official ideology of "pure reason". It was proposed as a considerable improvement over the inconsistent collection of customary units that existed before. The adoption of the metric system in France was slow, but its desirability as an international system was recognised by geodesists and others. Since then a number of variations on the system evolved. Their use spread throughout the world, first to the non-English-speaking countries, and more recently to the English-speaking countries. The whole system was derived from the properties of natural objects, namely the size of the Earth and the weight of water, and simple relations in between one unit and the other. In order to determine as precisely as possible the size of the Earth, several teams were sent over several years to measure the length of as long a segment of a meridian as feasible. It was decided to measure the meridian spanning Barcelona and Dunkirk which was the longest segment almost fully over land within French territory. It should be noticed that even though, during the many years of the measurement, hostilities broke out between France and Spain, the development of such a standard was considered of such value that Spanish troops escorted the French team while in Spanish territory to ensure their safety. The whole process ended in the proclamation on June 22nd, 1799 of the metric system with the storage in the Archives of the Republic of the physical embodiments of the standard, the prototype metre and the prototype kilogram, both made in a platinum alloy, witnessed by representatives of the French and several foreign governments and most important natural philosophers of the time. Later improvements in the measurement of both the size of the Earth and the properties of water revealed discrepancies between the metric standards and their originally intended values. The Industrial Revolution was well under way and the standardisation of mechanical parts, mainly bolts and nuts, was of utmost importance and they relied on precise measurements. Though these discrepancies would be mostly hidden in the manufacturing tolerances of those days, changing the prototypes to conform to the new and more precise measurements would have been impractical particularly since new and improved instruments would continually change them. It was decided to break the linkage between the prototypes and the natural properties they were derived from. The prototypes then became the basis of the system. The use of prototypes, however, is problematic for a number of reasons. There is the potential for loss, damage or destruction. There is also the problem of variance of the standard with the changes that any artefact can be expected to go through, though they be slight. Also whilst there may be copies, there must be only one official prototype which cannot be universally accessable. The metre had been defined in terms of such a prototype and remained so until in 1960 the metre was defined as a certain number of wavelengths of a particular frequency of light emitted by a certain element. Since 1983 the metre has been defined as a fraction of the speed of light. Thus the definition of the metre ultimately regained a linkage with a natural property, this time a property immutable in our universe and truly universal. The kilogram is now the only base unit still defined in terms of a prototype. Since 1899, the kilogram has been formally anchored to a single platinum-iridium cylinder in Sèvres, France. On the 20th of May 1875 an international treaty known as the Convention du Mètre (Metre Convention) was signed by 17 states. This treaty established the following organisations to conduct international activities relating to a uniform system for measurements: #Conférence générale des poids et mesures (CGPM), an intergovernmental conference of official delegates of member nations and the supreme authority for all actions; #Comité international des poids et mesures (CIPM), consisting of selected scientists and metrologists, which prepares and executes the decisions of the CGPM and is responsible for the supervision of the International Bureau of Weights and Measures; #Bureau international des poids et mesures (BIPM), a permanent laboratory and world centre of scientific metrology, the activities of which include the establishment of the basic standards and scales of the principal physical quantities and maintenance of the international prototype standards. The SI system has been adopted by nearly all the world's nations through a process called metrication. Today 95% of the world's population live in metricated countries. However the use of some non-metric units persists even in these countries.

Goals

The metric system was designed with several goals in mind.

Neutral and universal

The designers of the metric system meant to make it as neutral as possible so that it could be adopted universally. When the metric system was being developed, France was using the French Republican Calendar which was falling in disuse and was finally abolished due in part to two design faults: dates were counted from the day the French First Republic was proclaimed and the names of the months were related to purely local events, such as Brumaire (Misty), Nivose (Snowy) which didn't hold true even within the French territory itself. Other units were derived from the length of the foot of some ruler and often changed along with succession. The new units should have no dependency to such national, local or temporal circumstances.

Any laboratory should be able to replicate them

The usual way to establish a standard was to make prototypes of the base units and distribute copies. This would make the new standard reliant on the original prototypes which would be in conflict with the previous goal since all countries would have to refer to the one holding the prototypes. The designers developed definitions of the base units such that any laboratory equipped with proper instruments should be able to make their own models of them. The original base units of the metric system could be derived from the length of a meridian of the Earth and the weight of a certain volume of pure water. They discarded the use of a pendulum since its period or, inversely, the length of the string holding the bob for the same period changes around the Earth. Likewise, they discarded using the circumference of the Earth over the Equator since not all countries have access to the Equator while all countries have access to a section of a meridian.

Decimal multiples

All multiples and submultiples of the base units should be in powers of ten. Neither fractions would be in halves as it is customary in fractions of inches, nor derived units would be related to the base units by multiples other than powers of ten, as is the case with twelve inches making a foot. The practical benefits of a decimal system can be seen in the relatively recent decimalisation of the British and Irish Pound (1971) or the stock prices in the stock exchanges in the United States (2000-2001). It is worth noticing that the metric system also contains a base unit for angles called gon or grad based on decimal fractions where a right angle is divided in 100 gons, each gon containing 100 minutes, each decimal minute containing 100 seconds. In fact, a kilometre is the length of an arc spanning a decimal minute of a gon of latitude. This is similar to the nautical mile which is the length of a minute of a degree of latitude. On the other hand, the metric system didn't define a decimal unit of time since that was already part of the French Republican Calendar and fell into disuse along with it. Use of decimal prefixes drove the adoptation of the metric system and have historically been seen as a self-evidently easier method of calculation. However, in the modern computer age, decimal is considered a reflection of biological accident: 10 fingers on two hands. It is no longer seen as the most natural or mathematically fundamental system of arithmetic, that mantle having passed to binary and other powers of 2 such as hexadecimal. This undermined a core rationale for the metric system's power of 10 based units.

Common prefixes

All derived units would use a common set of prefixes for each multiple. Thus the prefix kilo could be used both for weight (kilogram) or length (kilometre) both indicating a thousand times the base unit. This didn't prevent the popular use of names for some derived units such as the tonne which is a megagram while a quintal is accepted as 100 kilograms; both are derived from old customary units and were rounded to metric.

Practical

The base units had to be close to the size of customary units then in use. The metre, being close to a yard, was expected to be more popular than the failed decimal hour of the Republican Calendar which was 2.4 times the normal hour.

Metric systems other than the 'modern metric system' (SI)

The original French system

The original French system somewhat continued the tradition of having separate base units for geometrically related dimensions, i.e. metre for lengths, are (100 m²) for areas, stere (1 m³) for dry capacities and litre (1 dm³) for liquid capacities. The hectare which is a hundred ares or a square 100m on a side or 2.5 acres is still in use to measure fields. The base unit of mass was the gram but, being so small, the platinum prototype for mass was made of the kilogram and it is still the prototype in the SI. It included only few prefixes from milli, one thousandth to myria ten thousand. Several national variants existed thereof with aliases for some common subdivisions. In general this entailed in redefinition of other units in use, e.g. 500-gram pounds or 10-kilometre miles. An example of these is mesures usuelles (or metrified English unit though never officially adopted). However it is debatable whether such systems are true metric systems.

Centimetre-gram-second systems

Early on in the history of the metric system various centimetre gram second system of units (CGS) had been in use. These units were particularly convenient in science and technology.

Metre-kilogram-second systems

Later metric systems were based on the metre, kilogram and second (MKS) to improve the value of the units for practical applications. MKSC, metre-kilogram-second-coulomb systems and MKSA, metre-kilogram-second-ampere systems are extentions of these. The International System of Units (Système international d'unités or SI) is the current international standard metric system and the system most widely used around the world. It is based on the metre, kilogram, second, ampere, kelvin, candela and mole.

Metre-tonne-second systems

The metre-tonne-second system of units (MTS) was based on the metre, tonne and second. It was invented in France and mostly used in the Soviet Union from 1933 to 1955.

Gravitational systems

Gravitational systems use the kilogram-force as a base unit of force, with mass measured in a unit known as the hyl, TME, mug or metric slug.

Spelling variations

Several nations, notably the United States, typically use the spellings 'meter' and 'liter' instead of 'metre' and 'litre'. This is in keeping with standard American English spelling (for example, Americans also use 'center' rather than 'centre,' using the latter only rarely for its stylistic implications; see also American and British English differences). In addition, the official US spelling for the SI prefix 'deca' is 'deka'. The US government has approved these spellings for official use. In scientific contexts only the symbols are used; since these are universally the same, the differences do not arise in practice in scientific use. The unit 'gram' is also sometimes spelled 'gramme' in English-speaking countries other than the United States, though that is an older spelling and use is declining.

Metre

:This article is about the unit of length. For other uses of metre or meter, see meter (disambiguation). The metre (Commonwealth English) or meter (American English) (symbol: m) is the SI base unit of length. It is defined as the length of the path travelled by light in absolute vacuum during a time interval of 1/299,792,458 of a second. Adding SI prefixes to metre creates multiples and submultiples; for example kilometre (1000 metres; kilo- = 1000) and millimetre (one thousandth of a metre; milli- = 1 / 1 000).

Conversions

1 metre is equivalent to:
- exactly 1/0.9144 yards (approximately 1.0936 yards)
- exactly 1/0.3048 feet (approximately 3.2808 feet)
- exactly 10000/254 inches (approximately 39.370 inches)

History

The word metre is from the Greek metron (μετρον), "a measure" via the French mètre. Its first recorded usage in English is from 1797. In the 18th century, there were two favoured approaches to the definition of the standard unit of length. One suggested defining the metre as the length of a pendulum with a half-period of one second. The other suggested defining the metre as one ten-millionth of the length of the earth's meridian along a quadrant (one-fourth the polar circumference of the earth). In 1791, the French Academy of Sciences selected the meridional definition over the pendular definition because of the slight variation of the force of gravity over the surface of the earth, which affects the period of a pendulum. In 1793, France adopted the metre, with this definition, as its official unit of length. Although it was later determined that the first prototype metre bar was short by a fifth of a millimetre due to miscalculation of the flattening of the earth, this length became the standard. So, the circumference of the Earth through the poles is approximately forty million metres. Earth in a vacuum.]] In the 1870s and in light of modern precision, a series of international conferences were held to devise new metric standards. The Metre Convention (Convention du Mètre) of 1875 mandated the establishment of a permanent International Bureau of Weights and Measures (BIPM: Bureau International des Poids et Mesures) to be located in Sèvres, France. This new organisation would preserve the new prototype metre and kilogram when constructed, distribute national metric prototypes, and would maintain comparisons between them and non-metric measurement standards. This organisation created a new prototype bar in 1889 at the first General Conference on Weights and Measures (CGPM: Conférence Générale des Poids et Mesures), establishing the International Prototype Metre as the distance between two lines on a standard bar of an alloy of ninety percent platinum and ten percent iridium, measured at the melting point of ice. In 1893, the standard metre was first measured with an interferometer by Albert A. Michelson, the inventor of the device and an advocate of using some particular wavelength of light as a standard of distance. By 1925, interferometry was in regular use at the BIPM. However, the International Prototype Metre remained the standard until 1960, when the eleventh CGPM defined the metre in the new SI system as equal to 1,650,763.73 wavelengths of the orange-red emission line in the electromagnetic spectrum of the krypton-86 atom in a vacuum. The original international prototype of the metre is still kept at the BIPM under the conditions specified in 1889. To further reduce uncertainty, the seventeenth CGPM of 1983 replaced the definition of the metre with its current definition, thus fixing the length of the metre in terms of time and the speed of light: :The metre is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second. Note that this definition exactly fixes the speed of light in a vacuum at 299,792,458 metres per second. Definitions based on the physical properties of light are more precise and reproducible because the properties of light are considered to be universally constant.

Timeline of definition

- 1790 May 8 — The French National Assembly decides that the length of the new metre would be equal to the length of a pendulum with a half-period of one second.
- 1791 March 30 — The French National Assembly accepts the proposal by the French Academy of Sciences that the new definition for the metre be equal to one ten-millionth of the length of the earth's meridian along a quadrant (one-fourth the polar circumference of the earth).
- 1795 — Provisional metre bar constructed of brass.
- 1799 December 10 — The French National Assembly specifies that the platinum metre bar, constructed on 23 June 1799 and deposited in the National Archives, as the final standard.
- 1889 September 28 — The first CGPM defines the length as the distance between two lines on a standard bar of an alloy of platinum with ten percent iridium, measured at the melting point of ice.
- 1927 October 6 — The seventh CGPM adjusts the definition of the length to be the distance, at 0 °C, between the axes of the two central lines marked on the prototype bar of platinum-iridium, this bar being subject to one standard atmosphere of pressure and supported on two cylinders of at least one centimetre diameter, symmetrically placed in the same horizontal plane at a distance of 571 millimetres from each other.
- 1960 October 20 — The eleventh CGPM defines the length to be equal to 1,650,763.73 wavelengths in vacuum of the radiation corresponding to the transition between the 2p¹⁰ and 5d⁵ quantum levels of the krypton-86 atom.
- 1983 October 21 — The seventeenth CGPM defines the length to be distance travelled by light in vacuum during a time interval of 1/299 792 458 of a second.

External links

- [http://www.unitconversion.org/unit_converter/length.html?unit=meter&value=1 Length Converter: convert metre to other units, such as yard, mile, and so on]
- [http://physics.nist.gov/cuu/Units/meter.html History of the metre at the U.S. National Institute of Standards and Technology (NIST)]
- [http://www.mel.nist.gov/div821/museum/timeline.htm Timeline of history of the metre at the NIST]
- [http://www1.bipm.org/en/scientific/length/ Bureau International des Poids et Measures - Lengths] Category:SI base units Category:Units of length ko:미터 ms:Meter ja:メートル simple:Metre th:เมตร

Mile

A mile is a unit of distance (or, in physics terminology, length) currently defined as 5,280 feet, 1,760 yards, or 63,360 inches. Today, one mile (often called "statute mile") is equal to about 1,609 m on land and one nautical mile to exactly 1,852 m at sea and in the air. The term has also been used to describe other lengths--see below for the details. Abbreviations for mile are "mi." in the U.S., and "ml" and "m" in the UK. The mile was first used by the Romans and originally denoted a distance of 1,000 (double) steps ("mille passuum" in Latin), which amounted, at approximately 0.75 m per (single) step, to 1,500 metres per mile. In modern usage, there are various miles:
- The statute mile, or more specifically
- The international mile is the one typically meant when the word mile is used without qualification. It is defined to be precisely 1,760 international yards (by definition, 0.9144 m each); it is therefore exactly 1,609.344 m. (1.609344 km) It is used in the United States and the United Kingdom as part of the Imperial system of units. The international mile is equivalent to 8 furlongs, or 80 chains, or 5,280 international feet.
- The U.S. survey mile is precisely equal to 5,280 U.S. survey feet or 6,336/3,937 km or, approximately 1,609.347 m. One international mile is precisely equal to 0.999 998 survey mile. The survey mile is used by the United States Public Land Survey System.
- The statute mile simply means "a mile of 5,280 feet", without specifying which foot is used. The term is therefore ambiguous.
- The obsolete Scottish and Irish miles, longer than the English (nautical mile) by about a half.
- The international nautical mile is defined to be exactly 1,852 m. It is used universally for aviation, naval and maritime purposes and originated from the geographical mile.
- In Norway and Sweden, a distance of 10 km is most commonly referred to as a mile or metric mile, see mil.
- In sports such as athletics and speedskating, the term metric mile is used to denote a distance of 1.5 km.
- The German mile was reckoned to be the 15th part of a degree (and thus about four nautical miles in length).
- The Danes, Swedes, and Hungarians had long miles, which were about a German mile and a half.
- The Dutch mile, was nearly the 19th part of a degree. The Polish mile was nearly equal to the Dutch mile.
- The Italian mile was a thousand paces of 5 Roman feet each (the Roman foot being one fifth of an inch less than the London foot). One mile is precisely 80 chains long. See Edmund Gunter.

Reference

[http://listserv.dartmouth.edu/scripts/wa.exe?A2=ind0108&L=nisus&T=0&F=&S=&P=42289 'Of Divers Measures'], in Laurence Echard, 1741, The Gazetteer's or Newsman's Interpreter, London: Ballard et al. (first published 1703)

External links

- [http://ts.nist.gov/ts/htdocs/230/235/appxc/appxc.htm NIST General Tables of Units of Measurement] Category:Ancient Rome Category:Units of length Category:Imperial units Category:Customary units in the United States ja:マイル simple:Mile

Foot (unit of length)

:For other uses, see Foot (disambiguation). A foot (plural: feet) is a non-SI unit of distance or length, measuring around a third of a metre. There are twelve inches in one foot and three feet in one yard. The international standard symbol for feet is ft (see ISO 31-1, Annex A). The standardization of weights and measures has left several different standard foot measures. The most commonly used foot today is the English foot, used in the United Kingdom and the United States and elsewhere, which is defined to be exactly 0.3048 metre. This unit is sometimes denoted with a prime (e.g. 30′ means 30 feet), often approximated by an apostrophe. Similarly, inches can be denoted by a double prime (often approximated by a quotation mark), so 6′ 2″ means 6 feet 2 inches. In addition to the current standard international foot, there is also a slightly different U.S. survey foot, used only in connection with surveys by the U.S. Coast and Geodetic Survey, it is defined as exactly 1200/3937 m (610 nm greater than 0.3048 m).[http://www.ngs.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf] The foot as a measure was used in almost all cultures. The first known standard foot measure was from Sumeria, where a definition is given in a statue of Gudea of Lagash from around 2575 BC. The imperial foot was adapted from an Egyptian measure by the Greeks, with a subsequent larger foot being adopted by the Romans.

Etymology

The popular belief is that original standard was the length of a man's foot. The original measurement was from King Henry I, who had a foot 12 inches long; he wished to standardise the unit of measurement in England. The average foot length is about 9.4 inches (240 mm) for current Europeans. Approximately 996 out of 1000 British men have a foot that is less than 12 inches long. A plausible explanation for the missing inches is that the measure did not refer to a naked foot, but to the length of footwear. This is consistent with the measure being convenient for practical purposes such as on building sites etc. People almost always pace out lengths whilst wearing shoes or boots, rather than removing them and pacing barefoot.

External link

- http://www.onlineconversion.com/ from feet to international system
- http://www.knowledgedoor.com/1/Library_of_Units_and_Constants/Group_Index/foot_group.htm Foot Foot Foot Category:Human-based units of measure ja:フィート

Klick

Klick (sometimes spelled click, but that may also mean one second of arc) is a common military term meaning kilometre (or sometimes kilometres per hour). Its use became popular among soldiers in Vietnam during the 1960s, although veterans of the war recall its usage as early as the 1950s. Its origin is sometimes linked with the Australian army in Korea. The term is of unknown origin. It is most likely an example of condensed pronunciation or contraction of the term kilometre or possibly otomonopedic of the sound of a military compass's bezel ring, although other theories exist. The term is currently also used by civilians, particularly in Canada where road signs and car speedometers use kilometres.

External links

- [http://usmilitary.about.com/library/milinfo/faq/blklickdef.htm Alternative Theory]
- [http://www.randomhouse.com/wotd/index.pperl?date=19960719 Concise Definition] Category:Military slang

Metric system

History

Goals

The metric system was designed with several goals in mind.

Neutral and universal

Any laboratory should be able to replicate them

Decimal multiples

Common prefixes

Practical

Metric systems other than the 'modern metric system' (SI)

The original French system

Centimetre-gram-second systems

Early on in the history of the metric system various centimetre gram second system of units (CGS) had been in use. These units were particularly convenient in science and technology.

Metre-kilogram-second systems

Metre-tonne-second systems

The metre-tonne-second system of units (MTS) was based on the metre, tonne and second. It was invented in France and mostly used in the Soviet Union from 1933 to 1955.

Gravitational systems

Gravitational systems use the kilogram-force as a base unit of force, with mass measured in a unit known as the hyl, TME, mug or metric slug.

Spelling variations

Metre

Conversions

1 metre is equivalent to:
- exactly 1/0.9144 yards (approximately 1.0936 yards)
- exactly 1/0.3048 feet (approximately 3.2808 feet)
- exactly 10000/254 inches (approximately 39.370 inches)

History

Timeline of definition

External links

Hectometre

Conversions

1 metre is equivalent to:
- exactly 1/0.9144 yards (approximately 1.0936 yards)
- exactly 1/0.3048 feet (approximately 3.2808 feet)
- exactly 10000/254 inches (approximately 39.370 inches)

History

Timeline of definition

External links

Length

Units of length(SI)

The SI unit of Length is the metre (U.S. spelling: meter), from which can be derived:from the regular basis of the foundation of the whole world
- centimetre
- kilometre

Other units of length

The Imperial and US customary units of length

- inch
- foot
- yard
- mile

Units are used in astronomy

- Astronomical unit
- Light year
- Parsec

External links

Area

:This article explains the meaning of area as a physical quantity. The article area (geometry) is more mathematical. See also area (disambiguation). Area is a quantity expressing the size of a part of a surface. Surface area is the summation of the areas of the exposed sides of an object.

Units

Units for measuring surface area include: :square metre = SI derived unit :are = 100 square metres :hectare = 10,000 square metres :square kilometre = 1,000,000 square metres :square megametre = 10¹² square metres Imperial units, as currently defined from the metre: :square foot (plural square feet) = 0.09290304 square metres. :square yard = 9 square feet = 0.83612736 square metres :square perch = 30.25 square yards = 25.2928526 square metres :acre = 160 square perches or 43,560 square feet = 4046.8564224 square metres :square mile = 640 acres = 2.5899881103 square kilometres Old European area units, still in used in some private matters (e.g. land sale advertisements) :square fathom = 3.5967 square metres :cadastral moon(acre) = 1600� square fathoms = 5755 square metres The article Orders of magnitude links to lists of objects of comparable surface area.

Useful formulas

- Area of a rectangle (and, in particular, a square): length × width
- Area of a triangle: ½ × base × height
- Area of a

Kilometre

Metric system

Pronunciation

See also

American English

History

Phonology

Differences in British English and American English

English words that arose in the U.S.

English words obsolete outside the U.S.

Regional differences

See also

Further reading

References

External links

Length

Units of length(SI)

Other units of length

The Imperial and US customary units of length

Units are used in astronomy

See also

External links

Metric system

History

Goals

Neutral and universal

Any laboratory should be able to replicate them

Decimal multiples

Common prefixes

Practical

Metric systems other than the 'modern metric system' (SI)

The original French system

Centimetre-gram-second systems

Metre-kilogram-second systems

Metre-tonne-second systems

Gravitational systems

Spelling variations

See also

Metre

Conversions

History

Timeline of definition

See also

External links

Mile

See also

Reference

External links

Foot (unit of length)

Etymology

See also

External link

Klick

External links

Metric system

History

Goals

Neutral and universal

Any laboratory should be able to replicate them

Decimal multiples

Common prefixes

Practical

Metric systems other than the 'modern metric system' (SI)

The original French system

Centimetre-gram-second systems

Metre-kilogram-second systems

Metre-tonne-second systems

Gravitational systems

Spelling variations

See also

Metre

Conversions

History

Timeline of definition

See also

External links

Hectometre

Conversions

History

Timeline of definition