|
|
| (One intermediate revision by one other user not shown) |
| Line 1: |
Line 1: |
| {{About|the unit of length|other uses of "metre" or "meter"|meter (disambiguation)}}
| | The writer's name is Christy. Office supervising is what she does for a living. Ohio is where his home is and his family members loves it. To play lacross is 1 of the issues she loves most.<br><br>my web-site; clairvoyants ([http://enterpal.com/index.php?do=/profile-39352/info/ going here]) |
| {{Use British English|date=September 2012}}
| |
| {{Infobox Unit
| |
| | |
| | name = Metre
| |
| | image = [[File:Platinum-Iridium meter bar.jpg|250px]]
| |
| | caption = Historical International Prototype Metre bar, made of an alloy of platinum and iridium, that was the standard from 1889 to 1960.
| |
| | standard = [[SI base unit]]
| |
| | quantity = [[Length]]
| |
| | symbol = m
| |
| | dimension = L
| |
| | namedafter =
| |
| | |
| | |
| | units1 = [[centimetre|cm]]
| |
| | inunits1 = {{gaps|100}}
| |
| | units2 = [[millimetre|mm]]
| |
| | inunits2 = {{gaps|1000}}
| |
| | units3 = [[kilometre|km]]
| |
| | inunits3 = {{gaps|0.001}}
| |
| | units4 = [[foot (unit)|ft]]
| |
| | inunits4 = {{gaps|3.28084}}
| |
| | units5 = [[inch|in]]
| |
| | inunits5 = {{gaps|39.3701}}
| |
| | |
| | |
| }}
| |
| {{Wiktionary|metre}}
| |
| The '''metre''' ([[American and British English spelling differences#-re, -er|International spelling]] as used by the [[International Bureau of Weights and Measures]]), or '''meter''' ([[American and British English spelling differences#-re, -er|American spelling]]), (SI [[Units of measurement|unit]] symbol: '''m'''), is the [[fundamental unit]] of length (SI [[Dimension of a physical quantity|dimension]] symbol: L) in the [[International System of Units]] (SI).<ref> | |
| {{cite web
| |
| |url=http://physics.nist.gov/cuu/Units/meter.html
| |
| |title=Base unit definitions: Meter
| |
| |publisher=[[National Institute of Standards and Technology]]
| |
| |accessdate=2010-09-28
| |
| }}</ref> Originally intended to be one ten-millionth of the distance from the Earth's [[equator]] to the North Pole (at sea level), its definition has been periodically refined to reflect growing knowledge of [[metrology]]. Since 1983, it has been defined as "the length of the path travelled by [[speed of light|light]] in [[vacuum]] during a time interval of {{sfrac|299,792,458}} of a [[second]]."<ref name="Res1">{{cite web |url=http://www.bipm.org/en/CGPM/db/17/1/ |title=17th General Conference on Weights and Measures (1983), Resolution 1. |accessdate=2012-09-19}}</ref>
| |
| | |
| == History ==
| |
| {{Main|History of the metre}}
| |
| | |
| A decimal-based unit of length, the ''universal measure'' or ''standard'' was proposed in an essay of 1668 by the English cleric and philosopher [[John Wilkins]].<ref name="Wilkins2007">[[#Wilkins2007|Wilkins c. 2007]]</ref> In 1675, the Italian scientist [[Tito Livio Burattini]], in his work ''Misura Universale,'' used the phrase ''{{lang|it|metro cattolico}}'' (lit. "[[wikt:catholic|catholic]] [i.e. universal] measure"), derived from the Greek {{lang|grc|[[wikt:μέτρον|μέτρον]] [[wikt:καθολικός|καθολικόν]]}} (''métron katholikón''), to denote the standard unit of length derived from a pendulum.<ref>{{cite journal | author = George Sarton | title = The First Explanation of Decimal Fractions and Measures (1585). Together with a History of the Decimal Idea and a Facsimile (No. XVII) of Stevin's Disme | journal = Isis | volume = 23 | number = 1 | year = 1935 | pages = 153–244 |url = http://www.jstor.org/stable/225223?&Search=yes&searchText=ISIS&searchText=Stevin&list=hide&searchUri=%2Faction%2FdoBasicSearch%3FQuery%3DStevin%2BISIS%26Search%3DSearch%26gw%3Djtx%26prq%3DStevin%26hp%3D25%26acc%3Doff%26aori%3Doff%26wc%3Don%26fc%3Doff&prevSearch=&item=7&ttl=326&returnArticleService=showFullText}}</ref> In the wake of the [[French Revolution]], a commission organised by the [[French Academy of Sciences]] and charged with determining a single scale for all measures, advised the adoption of a decimal system (27 October, 1790) and suggested a basic unit of length equal to one ten-millionth of the distance between the [[North Pole]] and the [[Equator]],<ref>('decimalization is not of the essence of the metric system; the real significance of this is that it was the first great attempt to define terrestrial units of measure in terms of an unvarying astronomical or geodetic constant.) The metre was in fact defined as one ten millionth of one quarter of the earth's circumference at sea-level.' [[Joseph Needham]], ''[[Science and Civilisation in China]],'' Cambridge University Press, 1962 vol.4, pt.1, p.42.</ref> to be called ''mètre'' ("measure") (19th March 1791).<ref>Paolo Agnoli,''Il senso della misura: la codifica della realtà tra filosofia, scienza ed esistenza umana,'' Armando Editore, 2004 pp.93-94,101.</ref><ref>{{cite web|url=http://gallica.bnf.fr/ark:/12148/bpt6k571270/f1.image |title=Rapport sur le choix d'une unité de mesure, lu à l'Académie des sciences, le 19 mars 1791 |language=French |publisher=Gallica.bnf.fr |date=2007-10-15 |accessdate=2013-03-25}}</ref><ref>Paolo Agnoli and Giulio D’Agostini,[http://arxiv.org/pdf/physics/0412078.pdf 'Why does the meter beat the second?,'] December, 2004 pp.1-29.</ref> The [[National Convention]] adopted the proposal in 1793. The first occurrence of ''metre'' in this sense in English dates to 1797.<ref>[[Oxford English Dictionary]], Clarendon Press 2nd ed.1989, vol.IX p.697 col.3.</ref>
| |
| [[Image:Dunkerque Belfort.JPG|thumb|[[Dunkirk#The prototype metre|Belfry, Dunkirk]]—the northern end of the meridian arc]]
| |
| [[Image:Monjuic's castle in Barcelona.jpg|thumb|[[Montjuïc#The prototype metre|Fortress of Montjuïc]]—the southerly end of the meridian arc]]
| |
| [[Image:Metre alloy.jpg|thumb|Creating the metre-alloy in 1874 at the Conservatoire des Arts et Métiers. Present Henri Tresca, George Matthey, Saint-Claire Deville and Debray]]
| |
| === Meridional definition ===
| |
| In 1668, Wilkins proposed using [[Christopher Wren]]'s suggestion of a [[pendulum]] with a half-[[Frequency|period]] of one [[second]] to measure a standard length that [[Christiaan Huygens]] had observed to be 38 [[Akker|Rijnland inches]] or {{frac|39|1|4}} [[Barleycorn (unit)|English inches]] (997{{nbsp}}mm) in length.<ref name="Wilkins2007">[[#Wilkins2007|Wilkins c. 2007]]</ref> In the 18th century, there were two favoured approaches to the definition of the standard unit of length. One approach followed Wilkins in defining the metre as the length of a pendulum with a half-period of one second, a '[[seconds pendulum]]'. The other approach suggested defining the metre as one ten-millionth of the length of the [[Earth]]'s [[meridian (geography)|meridian]] along a [[Circular sector|quadrant]]; that is, the distance from the [[Equator]] to the [[North Pole]]. In 1791, the [[French Academy of Sciences]] selected the meridional definition over the pendular definition because the force of [[Gravitation|gravity]] [[Geoid|varies slightly]] over the surface of the Earth, which affects the period of a pendulum.
| |
| | |
| To establish a universally accepted foundation for the definition of the metre, more accurate measurements of this meridian would have to be made. The French Academy of Sciences commissioned an expedition led by [[Jean Baptiste Joseph Delambre]] and [[Pierre Méchain]], lasting from 1792 to 1799, which measured the distance between a belfry in [[Dunkirk|Dunkerque]] and [[Montjuïc|Montjuïc castle]] in [[Barcelona]] to estimate the length of the [[meridian arc]] through Dunkerque. This portion of the meridian, assumed to be the same length as the [[Paris meridian]], was to serve as the basis for the length of the half meridian connecting the North Pole with the Equator.
| |
| | |
| The exact shape of the Earth is not a simple mathematical shape ([[sphere]] or [[oblate spheroid]]) at the level of precision required for defining a standard of length. The irregular and particular shape of the Earth (smoothed to [[sea level]]) is called a [[geoid]], which means "Earth-shaped". Despite this fact, and based on provisional results from the expedition, France adopted the metre as its official unit of length in 1793. Although it was later determined that the first [[International Prototype Metre|prototype metre bar]] was short by a fifth of a millimetre because of miscalculation of the [[flattening]] of the Earth, this length became the standard. The circumference of the Earth through the poles is therefore slightly more than forty million metres (40,007,863 m).<ref>[[#Humerfelt2010|Humerfelt 2010]]</ref>
| |
| | |
| === Prototype metre bar ===
| |
| | |
| In the 1870s and in light of modern precision, a series of international conferences was 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]] standards when constructed, distribute national metric prototypes, and maintain comparisons between them and non-metric measurement standards. The 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 Meter|International Prototype Metre]]'' as the distance between two lines on a standard bar composed of an alloy of ninety percent [[platinum]] and ten percent [[iridium]], measured at the melting point of ice.<ref>[[#nistmetre|National Institute of Standards and Technology 2003; Historical context of the SI: Unit of length (meter)]]
| |
| </ref>
| |
| | |
| The original international prototype of the metre is still kept at the BIPM under the conditions specified in 1889. A discussion of measurements of a standard metre bar and the errors encountered in making the measurements is found in a [[National Institute of Standards and Technology|NIST]] document.<ref name="Beers">[[#beers1992|Beers & Penzes 1992]]</ref>
| |
| | |
| === Standard wavelength of krypton-86 emission ===
| |
| In 1893, the standard metre was first measured with an [[interferometer]] by [[Albert Abraham Michelson|Albert A. Michelson]], the inventor of the device and an advocate of using some particular [[wavelength]] of [[light]] as a standard of length. 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 [[International System of Units]] (SI) as equal to 1,650,763.73 [[wavelength]]s of the [[orange (colour)|orange]]-[[red]] [[emission line]] in the [[electromagnetic spectrum]] of the [[krypton]]-86 [[atom]] in a [[vacuum]].<ref name="Marion">{{cite book |last=Marion |first=Jerry B. |title=Physics For Science and Engineering |year=1982 |publisher=CBS College Publishing |isbn=4-8337-0098-0 |page=3}}</ref>
| |
| | |
| === Speed of light ===
| |
| To further reduce uncertainty, the 17th CGPM in 1983 replaced the definition of the metre with its current definition, thus fixing the length of the metre in terms of the [[second]] and the [[speed of light]]:
| |
| | |
| ::The metre is the length of the path travelled by light in vacuum during a time interval of {{nowrap|{{sfrac|299,792,458}}}} of a second.<ref name="Res1" />
| |
| | |
| This definition fixed the speed of light in [[vacuum]] at exactly 299,792,458 metres per second. An intended by-product of the 17th CGPM's definition was that it enabled scientists to compare their lasers accurately using frequency, resulting in wavelengths with one-fifth the uncertainty involved in the direct comparison of wavelengths, because interferometer errors were eliminated. To further facilitate reproducibility from lab to lab, the 17th CGPM also made the iodine-stabilised [[helium–neon laser]] "a recommended radiation" for realising the metre.<ref name="recommendations" /> For the purpose of delineating the metre, the BIPM currently considers the HeNe laser wavelength, {{nowrap|λ{{sub|HeNe}}}}, to be 632.99121258 nm with an estimated relative standard uncertainty (''U'') of {{val|2.1|e=-11}}.<ref name="recommendations" /><ref name="uncertainty">The term "relative standard uncertainty" is explained by NIST on their web site: {{cite web |title=Standard Uncertainty and Relative Standard Uncertainty |work=The NIST Reference on constants, units, and uncertainties: Fundamental physical constants |url=http://physics.nist.gov/cgi-bin/cuu/Info/Constants/definitions.html |publisher=NIST |accessdate=19 December 2011}}</ref><ref>[[#NRC2010|National Research Council 2010]]</ref> This uncertainty is currently one limiting factor in laboratory realisations of the metre, and it is several orders of magnitude poorer than that of the second, based upon the caesium fountain [[atomic clock]] ({{nowrap|1=''U'' = {{val|5|e=-16}}}}).<ref>[[#NIST2011|National Institute of Standards and Technology 2011.]]</ref> Consequently, a realisation of the metre is usually delineated (not defined) today in labs as {{val|1579800.762042|(33)}} wavelengths of helium-neon laser light in a vacuum, the error stated being only that of frequency determination.<ref name="recommendations">{{cite web |title=Iodine ({{lambda}}≈633 nm) |publisher=BIPM |url=http://www.bipm.org/utils/common/pdf/mep/M-e-P_I2_633.pdf |work=MEP (''Mise en Pratique'') |year=2003 |format=PDF |accessdate=16 December 2011}}</ref> This bracket notation expressing the error is explained in the article on [[Standard uncertainty#Measurements|measurement uncertainty]].
| |
| | |
| Practical realisation of the metre is subject to uncertainties in characterising the medium, to various uncertainties of interferometry, and to uncertainties in measuring the frequency of the source.<ref name="Beers2" /> A commonly used medium is air, and the [[National Institute of Standards and Technology]] has set up an online calculator to convert wavelengths in vacuum to wavelengths in air.<ref name="NIST_calculator">The formulas used in the calculator and the documentation behind them are found at {{cite web |url=http://emtoolbox.nist.gov/Wavelength/Documentation.asp |title=Engineering metrology toolbox: Refractive index of air calculator |date=September 23, 2010 |publisher=NIST |accessdate=16 December 2011}} The choice is offered to use either the [http://emtoolbox.nist.gov/Wavelength/Edlen.asp modified Edlén equation] or the [http://emtoolbox.nist.gov/Wavelength/Ciddor.asp Ciddor equation]. The documentation provides [http://emtoolbox.nist.gov/Wavelength/Documentation.asp#EdlenorCiddor a discussion of how to choose] between the two possibilities.</ref> As described by NIST, in air, the uncertainties in characterising the medium are dominated by errors in measuring temperature and pressure. Errors in the theoretical formulas used are secondary.<ref name="errors">{{cite web |url=http://emtoolbox.nist.gov/Wavelength/Documentation.asp#UncertaintyandRangeofValidity |title=§VI: Uncertainty and range of validity |work=Engineering metrology toolbox: Refractive index of air calculator |date=September 23, 2010 |publisher=NIST |accessdate=16 December 2011}}</ref> By implementing a refractive index correction such as this, an approximate realisation of the metre can be implemented in air, for example, using the formulation of the metre as {{val|1579800.762042|(33)}} wavelengths of helium-neon laser light in vacuum, and converting the wavelengths in a vacuum to wavelengths in air. Of course, air is only one possible medium to use in a realisation of the metre, and any [[partial vacuum]] can be used, or some inert atmosphere like helium gas, provided the appropriate corrections for refractive index are implemented.<ref name="Dunning">{{cite book |title=Atomic, molecular, and optical physics: electromagnetic radiation, Volume 29, Part 3 |chapter=Physical limits on accuracy and resolution: setting the scale |url=http://books.google.com/books?id=FV4Y39AGYuYC&pg=PA316 |page=316 |first=F. B. |last=Dunning |first2=Randall G. |last2=Hulet |isbn=0-12-475977-7 |publisher=Academic Press |year=1997 |quote=The error [introduced by using air] can be reduced tenfold if the chamber is filled with an atmosphere of helium rather than air.}}</ref>
| |
| | |
| ====Length measurement in metres====
| |
| {{See also|Length measurement}}
| |
| Although the metre is now ''defined'' as the path length travelled by light in a given time, the practical laboratory length measurements in metres are determined by counting the number of wavelengths of laser light of one of the standard types that fit into the length,{{#tag:ref|The BIPM maintains a list of recommended radiations on their web site.<ref name="recommendations">{{cite web |title=Recommended values of standard frequencies |url=http://www.bipm.org/en/publications/mep.html |publisher=BIPM |date=9 September 2010 |accessdate=22 January 2012}}</ref><ref>[[#NPL2010|National Physical Laboratory 2010]]</ref>}} and converting the selected unit of wavelength to metres. Three major factors limit the accuracy attainable with laser [[Interferometry|interferometer]]s for a length measurement:<ref name="Beers2">
| |
| A more detailed listing of errors can be found in {{cite web |work=NIST length scale interferometer measurement assurance; NIST document NISTIR 4998 |title=§4 Re-evaluation of measurement errors |first=John S |last=Beers |first2=William B |last2=Penzes |url=http://www.nist.gov/calibrations/upload/4998.pdf |format=PDF |accessdate=17 December 2011 |date=December 1992 |pages=9 ''ff'' }}
| |
| </ref><ref name="Webster2">[[#Zagar1999|Zagar, 1999, pp. 6–65''ff'']]</ref>
| |
| * Uncertainty in vacuum wavelength of the source
| |
| * Uncertainty in the refractive index of the medium
| |
| * Least count resolution of the interferometer
| |
| Of these, the last is peculiar to the interferometer itself. The conversion of a length in wavelengths to a length in metres is based upon the relation:
| |
| | |
| : <math> \lambda = \frac{c}{n f} \ </math>
| |
| | |
| which converts the unit of wavelength {{lambda}} to metres using ''c'', the speed of light in a vacuum in m/s. Here ''n'' is the [[refractive index]] of the medium in which the measurement is made; and ''f'' is the measured frequency of the source. Although conversion from wavelengths to metres introduces an additional error in the overall length due to measurement error in determining the refractive index and the frequency, the measurement of frequency is one of the most accurate measurements available.<ref name="Webster2" />
| |
| | |
| === Timeline of definition ===
| |
| [[File:US National Length Meter.JPG|thumb|Closeup of National Prototype Metre Bar No. 27, made in 1889 by the [[International Bureau of Weights and Measures]] (BIPM) and given to the United States, which served as the standard for defining all units of length in the US from 1893 to 1960]]
| |
| | |
| * 1790 May 8{{spaced ndash}}The [[National Assembly (French Revolution)|French National Assembly]] decides that the length of the new metre would be equal to the length of a [[pendulum]] with a half-[[period (physics)|period]] of one [[second]].
| |
| * 1791 March 30{{spaced ndash}}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 (geography)|meridian]] along a quadrant through Paris, that is the distance from the equator to the north pole.
| |
| * 1795{{spaced ndash}}Provisional metre bar constructed of [[brass]]. Based on [[Friedrich Wilhelm Bessel|Bessel's]] ellipsoid and legally equal to 443.44 [[Line (unit)|lines]] on the ''toise du Pérou'' (a standard [[Units of measurement in France before the French Revolution#Length|French unit of length]] from 1747).
| |
| * 1799 December 10{{spaced ndash}}The French National Assembly specifies the platinum metre bar, constructed on 23 June 1799 and deposited in the [[National Archives of France|National Archives]], as the final standard. Legally equal to 443.296 lines on the ''toise du Pérou''.
| |
| * 1889 September 28{{spaced ndash}}The 1st [[General Conference on Weights and Measures]] (CGPM) defines the metre as the distance between two lines on a standard bar of an alloy of [[platinum]] with 10% [[iridium]], measured at the melting point of ice.
| |
| * 1927 October 6{{spaced ndash}}The 7th CGPM redefines the metre as the distance, at {{convert|0|C|F|abbr=on|lk=on}}, between the axes of the two central lines marked on the prototype bar of platinum-iridium, this bar being subject to one standard [[atmospheric pressure|atmosphere of pressure]] and supported on two cylinders of at least {{convert|1|cm|abbr=on}} diameter, symmetrically placed in the same horizontal plane at a distance of {{convert|571|mm}} from each other.
| |
| * 1960 October 14{{spaced ndash}}The 11th CGPM defines the metre as 1,650,763.73 [[wavelength]]s in a [[vacuum]] of the [[electromagnetic radiation|radiation]] corresponding to the transition between the 2p{{sup|10}} and 5d{{sup|5}} quantum levels of the [[krypton]]-86 [[atom]].<ref>[[#BarbrowJudson1976|Barbrow & Judson 1976, appendix 6.]]</ref>
| |
| * 1983 October 21{{spaced ndash}}The 17th [[CGPM]] defines the metre as the length of the path travelled by [[light]] in a [[vacuum]] during a time interval of {{sfrac|299,792,458}} of a [[second]].<ref>[[#taylor2008a|Taylor and Thompson (2008a), Appendix 1, p. 70.]]</ref>
| |
| * 2002{{spaced ndash}}The [[International Committee for Weights and Measures]] (CIPM) considers the metre to be a unit of [[proper length]] and thus recommends this definition be restricted to "lengths ℓ which are sufficiently short for the effects predicted by [[general relativity]] to be negligible with respect to the uncertainties of realisation".<ref name="taylor2008a77">[[#taylor2008a|Taylor and Thompson (2008a), Appendix 1, p. 77.]]</ref>
| |
| | |
| {| class="wikitable" style="margin:0 auto;"
| |
| |+Definitions of the metre since 1795<ref>[[#Cardarelli2003|Cardarelli 2003]]</ref>
| |
| ! Basis of definition
| |
| ! Date
| |
| ! Absolute<br>uncertainty
| |
| ! Relative<br>uncertainty
| |
| |-
| |
| | {{sfrac|10,000,000}} part of the quarter of a meridian, astronomical measure by Bessel (443.44 lines)
| |
| | 1792
| |
| | 0.5–0.1{{nbsp}}mm
| |
| | 10{{sup|−4}}
| |
| |-
| |
| | {{sfrac|10,000,000}} part of the quarter of a meridian, measurement by Delambre and Mechain (443.296 lines)
| |
| | 1795
| |
| | 0.5–0.1{{nbsp}}mm
| |
| | 10{{sup|−4}}
| |
| |-
| |
| | First prototype ''Metre des Archives'' platinum bar standard
| |
| | 1799
| |
| | 0.05–0.01{{nbsp}}mm
| |
| | 10{{sup|−5}}
| |
| |-
| |
| | Platinum-iridium bar at melting point of ice (1st [[CGPM]])
| |
| | 1889
| |
| | 0.2–0.1{{nbsp}}µm
| |
| | 10{{sup|−7}}
| |
| |-
| |
| | Platinum-iridium bar at melting point of ice, atmospheric pressure, supported by two rollers (7th CGPM)
| |
| | 1927
| |
| | n.a.
| |
| | n.a.
| |
| |-
| |
| | [[Hyperfine structure|Hyperfine]] atomic transition; 1,650,763.73 wavelengths of light from a specified transition in [[krypton]]-86 (11th CGPM)
| |
| | 1960
| |
| | 4 nm
| |
| | 4x10{{sup|−9}}<ref >[http://www.bipm.org/en/CGPM/db/17/1/ Definition of the metre] Resolution 1 of the 17th meeting of the CGPM (1983)</ref>
| |
| |-
| |
| | Length of the path travelled by light in a vacuum in {{sfrac|299,792,458}} of a second (17th CGPM)
| |
| | 1983
| |
| | 0.1{{nbsp}}nm
| |
| | 10{{sup|−10}}
| |
| |}
| |
| | |
| == SI prefixed forms of metre ==
| |
| [[SI prefix]]es are often employed to denote decimal multiples and submultiples of the metre, as shown in the table below. As indicated in the table, some are commonly used, while others are not. Long distances are usually expressed in km, [[astronomical unit]]s (149.6 Gm), [[light-year]]s (10 Pm), or [[parsec]]s (31 Pm), rather than in Mm, Gm, Tm, Pm, Em, Zm or Ym; "30 cm", "30 m", and "300 m" are more common than "3 dm", "3 dam", and "3 hm", respectively.
| |
| | |
| The term ''micron'' is often used instead of ''micrometre'', but this practice is officially discouraged.<ref>[[#taylor2008b|Taylor & Thompson 2003, p. 11.]]</ref>
| |
| | |
| {{SI multiples
| |
| | symbol=m
| |
| | unit=metre
| |
| | note=Common prefixed units are in '''bold''' face.
| |
| | n=|mc=|m=|c=|k=
| |
| | xd=[[decimetre]]
| |
| | xc=[[centimetre]]
| |
| | xmc=[[micrometre]]
| |
| | xf=[[femtometre]]
| |
| | xm=[[millimetre]]
| |
| | xn=[[nanometre]]
| |
| | xp=[[picometre]]
| |
| | xda=[[decametre]]
| |
| | xh=[[hectometre]]
| |
| | xk=[[kilometre]]
| |
| | xM=[[megametre]]
| |
| | xG=[[gigametre]]
| |
| | xT=[[1 terametre|terametre]]
| |
| | xP=[[1 petametre|petametre]]
| |
| }}
| |
| | |
| == Spelling ==
| |
| ''Metre'' is used as the standard spelling of the metric unit for length in all English-speaking nations except the USA, which uses ''meter''.<ref>[[#Naughtin2008|Naughtin 2008]]</ref>
| |
| | |
| The most recent official brochure, written in 2006, about the International System of Units (SI), ''Bureau international des poids et mesures'', was written in French by the [[International Bureau of Weights and Measures]]. An English translation (using the spelling: ''metre'') is included to make the SI standard "more widely accessible".<ref>[[#bipm2006|BIPM, 2006]], p. 130''ff''.</ref>
| |
| | |
| In 2008, the U.S. English translation published by the U.S. [[National Institute of Standards and Technology]] chose to use ''meter'' in accordance with the United States Government Printing Office Style Manual.<ref>The Metric Conversion Act of 1975 gives the Secretary of Commerce of the US the responsibility of interpreting or modifying the SI for use in the US. The Secretary of Commerce delegated this authority to the Director of the [[National Institute of Standards and Technology]] (NIST) ([[#turner|Turner]]). In 2008, NIST published the US version ([[#taylor2008a|Taylor and Thompson, 2008a]]) of the English text of the eighth edition of the BIPM publication ''Le Système international d'unités (SI)'' (BIPM, 2006). In the NIST publication, the spellings "meter", "liter" and "deka" are used rather than "metre", "litre" and "deca" as in the original BIPM English text ([[#taylor2008a|Taylor and Thompson (2008a), p. iii]]). The Director of the NIST officially recognised this publication, together with [[#taylor2008b|Taylor and Thompson (2008b)]], as the "legal interpretation" of the SI for the United States ([[#turner|Turner]]).</ref>
| |
| | |
| Measuring devices (such as [[ammeter]], [[speedometer]]) are spelt <!-- "Spelt" is UK English, "spelled" is both UK & US English. Guardian (UK) newspaper recommends "spelled" for simple past tense. --> "-meter" in all countries.<ref>
| |
| {{cite dictionary
| |
| |url=http://dictionary.cambridge.org/results.asp?searchword=ammeter
| |
| |title=Cambridge Advanced Learner's Dictionary
| |
| |year=2008
| |
| |publisher=[[Cambridge University Press]]
| |
| |accessdate=2012-09-19
| |
| }}, s.v. ammeter, meter, parking meter, speedometer.</ref> The word "meter", signifying any such device, has the same derivation as the word "metre", denoting the unit of length.<ref>
| |
| {{cite dictionary
| |
| |title=American Heritage Dictionary of the English Language
| |
| |edition=3rd
| |
| |year=1992
| |
| |location=Boston
| |
| |publisher=[[Houghton Mifflin]]
| |
| }}, s.v. meter.</ref>
| |
| | |
| == Equivalents in other units ==
| |
| {| class=wikitable style="margin:0 auto;"
| |
| |-
| |
| ! colspan="5" style="text-align:left;"|Metric unit<br>expressed in non-SI units
| |
| ! colspan="4" style="text-align:left;"|Non-SI unit<br>expressed in metric units
| |
| |-
| |
| | 1 metre ||≈ ||style="text-align:right;"|1.0936 ||[[yard]]s||
| |
| | 1 [[yard]]||≡ ||style="text-align:right;"|0.9144 ||metres
| |
| |-
| |
| | 1 metre ||≈ ||style="text-align:right;"|39.370 ||[[inch]]es||
| |
| | 1 [[inch]]||≡ ||style="text-align:right;"|0.0254 ||metres
| |
| |-
| |
| | 1 centimetre ||≈ ||style="text-align:right;"|0.39370 ||inch||
| |
| | 1 inch||≡ ||style="text-align:right;"|2.54 ||centimetres
| |
| |-
| |
| | 1 [[millimetre]] ||≈ ||style="text-align:right;"|0.039370 ||inch||
| |
| | 1 inch||≡ ||style="text-align:right;"|25.4 ||millimetres
| |
| |-
| |
| | 1 metre ||≡ ||style="text-align:right;"|[[Normalised notation|1×10{{sup|10}}]]||[[ångström]]||
| |
| | 1 ångström||≡ ||style="text-align:right;"|1×10{{sup|−10}} ||metre
| |
| |-
| |
| | 1 nanometre ||≡ ||style="text-align:right;"|10||ångström||
| |
| | 1 ångström||≡ ||style="text-align:right;"|100 ||picometres
| |
| |}
| |
| Within this table, "inch" and "yard" mean "international inch" and "international yard",<ref>[[#AstinKaro1959|Astin & Karo 1959]].</ref> respectively, though approximate conversions in the left-hand column hold for both international and survey units.
| |
| : "≈" means "is approximately equal to";
| |
| : "≡" means "equal by definition" or "is exactly equal to."
| |
| | |
| One metre is exactly equivalent to {{sfrac|10,000|254}}{{nbsp}}inches and to {{sfrac|10,000|9,144}}{{nbsp}}yards.
| |
| | |
| <!-- 1 metre ≈ 39.3700787401575 in / or 39.375 in = 1000.125 mm -->
| |
| A simple [[mnemonic]] aid exists to assist with conversion, as three "3":
| |
| : 1 metre is nearly equivalent to 3{{nbsp}}feet–{{frac|3|3|8}}{{nbsp}}inches.<ref>Well-known conversion, publicised at time of metrication.{{where|date=December 2010}}</ref> This gives an overestimate of 0.125{{nbsp}}mm.
| |
| | |
| The ancient Egyptian [[cubit]] was about {{frac|1|2}}{{nbsp}}m (surviving rods are 52.3–52.9{{nbsp}}cm.) Scottish and English definitions of [[ell]] (two cubits) were 0.941{{nbsp}}m and 1.143{{nbsp}}m, respectively. The ancient Paris ''toise'' (fathom) was slightly shorter than 2{{nbsp}}m, and was standardised at exactly 2{{nbsp}}m in the [[mesures usuelles]] system, such that 1{{nbsp}}m was exactly {{frac|1|2}}{{nbsp}}toise. The Russian [[versta]] was 1.0668{{nbsp}}km. The [[Scandinavian mile|Swedish mil]] was 10.688{{nbsp}}km, but was changed to 10{{nbsp}}km when Sweden converted to metric units.
| |
| | |
| == See also ==
| |
| * [[Conversion of units]] for comparisons with other units
| |
| * [[International System of Units]]
| |
| * [[Introduction to the metric system]]
| |
| * [[ISO 1]]{{spaced ndash}}standard reference temperature for length measurements
| |
| * [[Length measurement]]
| |
| * [[Metre Convention]]
| |
| * [[Metric system]]
| |
| * [[Metrication]]
| |
| * [[Orders of magnitude (length)]]
| |
| * [[SI prefix]]
| |
| * [[Speed of light]]
| |
| | |
| == Notes ==
| |
| {{Reflist|colwidth=30em}}
| |
| | |
| == References ==
| |
| * {{Anchor|cgpm1983}}17th [[General Conference on Weights and Measures]]. (1983). [http://www.bipm.org/en/CGPM/db/17/1/ Resolution 1.] [[International Bureau of Weights and Measures]].
| |
| * {{Anchor|AstinKaro1959}}Astin, A. V. & Karo, H. Arnold, (1959), [http://www.ngs.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf ''Refinement of values for the yard and the pound''], Washington DC: National Bureau of Standards, republished on National Geodetic Survey web site and the Federal Register (Doc. 59-5442, Filed, 30 June 1959, 8:45 a.m.)
| |
| * {{Anchor|BarbrowJudson1976}}Barbrow, Louis E. & Judson, Lewis V. (1976). ''[http://www.nist.gov/pml/pubs/sp447/index.cfm Weights and Measures Standards of the United States: A brief history] (Special Publication 447).''. National Institute of Standards and Technology.
| |
| * {{Anchor|beers1992}}Beers, J.S. & Penzes, W. B. (1992). [http://ts.nist.gov/MeasurementServices/Calibrations/upload/4998.pdf NIST Length Scale Interferometer Measurement Assurance.]{{failed verification |date=July 2012}} (NISTIR 4998). [[National Institute of Standards and Technology]].
| |
| * {{cite web |publisher=Bureau International des Poids et Mesures |year=2006 |url=http://www1.bipm.org/utils/common/pdf/si_brochure_8.pdf |format=PDF |title=The International System of Units (SI) |language=French |accessdate=18 August 2008 |ref=bipm2006}}
| |
| ** [http://www.bipm.org/en/si/si_brochure/ HTML version]. Retrieved 24 August 2008.
| |
| * {{Anchor|BIPMResolutions}}Bureau International des Poids et Mesures. (n.d.). [http://www.bipm.fr/en/convention/resolutions.html ''Resolutions of the CGPM''] (search facility). Retrieved 3 June 2006.
| |
| * {{Anchor|BIPMEvolution}}Bureau International des Poids et Mesures. (n.d.). [http://www1.bipm.org/en/si/history-si/evolution_metre.html ''The BIPM and the evolution of the definition of the metre'']. Retrieved 3 June 2006.
| |
| * {{Anchor|Cardarelli2003}}Cardarelli, Francois (2003). ''Encydopaedia of scientific units, weights, and measures: their SI equivalences and origins'', Springer-Verlag London Limited, ISBN 1-85233-682-X, page 5, table 2.1, data from Giacomo, P., ''Du platine a la lumiere'', Bull. Bur. Nat. Metrologie, 102 (1995) 5–14.
| |
| * {{Anchor|Humerfelt2010}}Humerfelt, Sigurd. (26 October 2010). ''[http://home.online.no/~sigurdhu/WGS84_Eng.html How WGS 84 defines Earth]''. Retrieved 29 April 2011.
| |
| * {{Anchor|Layer2008}}Layer, H.P. (2008). [http://www.mel.nist.gov/div821/museum/length.htm ''Length—Evolution from Measurement Standard to a Fundamental Constant'']. Gaithersburg, MD: National Institute of Standards and Technology. Retrieved 18 August 2008.{{failed verification |date=July 2012}} <!-- Information there not yet included in article -->
| |
| * {{Anchor|Mohr2007}}Mohr, P., Taylor, B.N., and David B. Newell, D. (28 December 2007). [http://physics.nist.gov/cuu/Constants/codata.pdf ''CODATA Recommended Values of the Fundamental Physical Constants: 2006'']. Gaithersburg, MD: National Institute of Standards and Technology. Retrieved 18 August 2008.{{dead link |date=July 2012}}
| |
| * {{Anchor|NIST2003}}National Institute of Standards and Technology. (December 2003). [http://physics.nist.gov/cuu/Units/index.html ''The NIST Reference on Constants, Units, and Uncertainty: International System of Units (SI)''] (web site):
| |
| ** {{Anchor|NISTbaseunits}}[http://physics.nist.gov/cuu/Units/units.html ''SI base units'']. Retrieved 18 August 2008.
| |
| ** {{Anchor|NISTbasedefinitions}}[http://physics.nist.gov/cuu/Units/current.html ''Definitions of the SI base units'']. Retrieved 18 August 2008.
| |
| ** {{anchor|nistmetre}}[http://physics.nist.gov/cuu/Units/meter.html ''Historical context of the SI: Metre'']. Retrieved 26 May 2010.
| |
| * {{Anchor|NIST2011}}National Institute of Standards and Technology. (27 June 2011). ''[http://www.nist.gov/pml/div688/grp50/primary-frequency-standards.cfm NIST-F1 Cesium Fountain Atomic Clock]''. Author.
| |
| * {{Anchor|NPL2010}}National Physical Laboratory. (25 March 2010). ''[http://www.npl.co.uk/science-technology/time-frequency/optical-frequency-standards-and-metrology/research/iodine-stabilised-lasers Iodine-Stabilised Lasers]''. Author.
| |
| * {{Anchor|NRC2010}}National Research Council Canada. (5 February 2010). [http://www.nrc-cnrc.gc.ca/eng/projects/inms/si-length.html Maintaining the SI unit of length]. Retrieved 4 December 2010.
| |
| * {{Anchor|Naughtin2008}}Naughtin, Pat. (2008). ''[http://www.metricationmatters.com/docs/Spelling_metre_or_meter.pdf Spelling metre or meter.]'' Author.
| |
| * {{anchor|penzes2005}}Penzes, W. (29 December 2005). [http://www.nist.gov/pml/div681/museum-timeline.cfm ''Time Line for the Definition of the Meter'']. Gaithersburg, MD: National Institute of Standards and Technology{{spaced ndash}}Precision Engineering Division. Retrieved 4 December 2010.{{dead link |date=July 2012}}
| |
| * {{Anchor|taylor2008a}}Taylor, B.N. and Thompson, A. (Eds.). (2008a). [http://physics.nist.gov/Pubs/SP330/sp330.pdf ''The International System of Units (SI)'']. United States version of the English text of the eighth edition (2006) of the International Bureau of Weights and Measures publication ''Le Système International d’ Unités (SI)'' (Special Publication 330). Gaithersburg, MD: National Institute of Standards and Technology. Retrieved 18 August 2008.
| |
| * {{Anchor|taylor2008b}}Taylor, B.N. and Thompson, A. (2008b). [http://physics.nist.gov/cuu/pdf/sp811.pdf ''Guide for the Use of the International System of Units''] (Special Publication 811). Gaithersburg, MD: National Institute of Standards and Technology. Retrieved 23 August 2008.
| |
| * {{Anchor|Tibo2005}}Tibo Qorl. (2005) [http://histoire.du.metre.free.fr/en/ The History of the Meter] (Translated by Sibille Rouzaud). Retrieved 18 August 2008.
| |
| * {{Anchor|turner}}Turner, J. (Deputy Director of the National Institute of Standards and Technology). (16 May 2008).[http://ts.nist.gov/WeightsAndMeasures/Metric/upload/FRN_Vol_73_No_96_16May2008_SI_Interpretation.pdf "Interpretation of the International System of Units (the Metric System of Measurement) for the United States"]. ''Federal Register'' Vol. 73, No. 96, p.{{nbsp}}28432-3.{{failed verification |date=July 2012}}
| |
| * {{Anchor|Wilkins2007}}Wilkins, J. (c. 2007). [http://www.metricationmatters.com/docs/WilkinsTranslationLong.pdf An essay towards a real character, and a philosophical language].[Also available [http://www.metricationmatters.com/docs/WilkinsTranslationShort.pdf without images of original].] Metrication Matters. (Reprinted from title page and pp. 190–194 of original, 1668, London: Royal Society)
| |
| * {{Anchor|Zagar1999}}Zagar, B.G. (1999). [http://books.google.com/books?id=VXQdq0B3tnUC&pg=PT164#PPT160,M1 Laser interferometer displacement sensors] in J.G. Webster (ed.). ''The Measurement, Instrumentation, and Sensors Handbook.'' CRC Press. isbn=0-8493-8347-1.
| |
| *
| |
| | |
| == Further reading ==
| |
| {{commonscat}}
| |
| * Alder, Ken. (2002). ''The Measure of All Things : The Seven-Year Odyssey and Hidden Error That Transformed the World.'' Free Press, New York ISBN 0-7432-1675-X
| |
| | |
| | |
| {{SI units}}
| |
| {{SI units of length}}
| |
| | |
| [[Category:Metrology]]
| |
| [[Category:SI base units]]
| |
| [[Category:Units of length]]
| |
| | |
| {{Link GA|ja}}
| |