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The kilogram or kilogramme (SI unit symbol: kg), is the base unit of mass in the International System of Units (SI) (the Metric system) and is defined as being equal to the mass of the ''International Prototype of the Kilogram'' (IPK).〔(【引用サイトリンク】 url = http://www.bipm.org/en/scientific/mass/prototype.html )〕 The gram, 1/1000th of a kilogram, was originally defined in 1795 as the mass of one cubic centimeter of water at the melting point of water.〔''Gramme, le poids absolu d'un volume d'eau pure égal au cube de la centième partie du mètre, et à la température de la glace fondante.''; The term ''poids absolu'' was at the time used alongside ''masse'' for the concept of "mass" (which latter term had first been introduced in its strict physical sense in English in 1704). See e.g. Mathurin Jacques Brisson, ''Dictionnaire raisonné de toutes les parties de la Physique'', Volland, 1787, ( p. 401 ).〕 The original prototype kilogram, manufactured in 1799 and from which the IPK is derived, had a mass equal to the mass of 1.000028 dm3 of water at its maximum density at approximately 4 °C. The kilogram is the only SI base unit with an SI prefix ("kilo", symbol "k") as part of its name. It is also the only SI unit that is still directly defined by an artifact rather than a fundamental physical property that can be reproduced in different laboratories. Three other base units (Cd, A, mol) and 17 derived units (N, Pa, J, W, C, V, F, Ω, S, Wb, T, H, kat, Gy, Sv, lm, lx) in the SI system are defined relative to the kilogram, so its stability is important. Only 8 other units do not require the kilogram in their definition: temperature (K, °C), time and frequency (s, Hz, Bq), length (m), and angle (rad, sr).〔 The International Prototype Kilogram was commissioned by the General Conference on Weights and Measures (CGPM) under the authority of the Metre Convention (1875), and is in the custody of the International Bureau of Weights and Measures (BIPM) who hold it on behalf of the CGPM. After the International Prototype Kilogram had been found to vary in mass over time relative to its reproductions, the International Committee for Weights and Measures (CIPM) recommended in 2005 that the kilogram be redefined in terms of a fundamental constant of nature. At its 2011 meeting, the CGPM agreed in principle that the kilogram should be redefined in terms of the Planck constant. The decision was originally deferred until 2014; in 2014 it was deferred again until the next meeting.〔http://www.bipm.org/utils/common/pdf/CGPM-2014/25th-CGPM-Resolutions.pdf〕 The International Prototype Kilogram (IPK) is rarely used or handled. Copies of the IPK kept by national metrology laboratories around the world were compared with the IPK in 1889, 1948, and 1989 to provide traceability of measurements of mass anywhere in the world back to the IPK. The avoirdupois (or ''international'') pound, used in both the Imperial system and U.S. customary units, is defined as exactly , making one kilogram approximately equal to 2.2046 avoirdupois pounds. Other traditional units of weight and mass around the world are also defined in terms of the kilogram, making the IPK the primary standard for virtually all units of mass on Earth. ==Name and terminology== The word ''kilogramme'' or ''kilogram'' is derived from the French ''kilogramme'',〔 which itself was a learned coinage, prefixing the Greek stem of "a thousand" to ''gramma'', a Late Latin term for "a small weight", itself from Greek .〔 Greek (as it were , Doric ) means "something written, a letter", but it came to be used as a unit of weight, apparently equal to 1/24th of an ounce (1/288th of a ''libra'', which would correspond to about 1.14 grams in modern units), at some time during Late Antiquity. French ''gramme'' was adopted from Latin ''gramma'', itself quite obscure, but found in the ''carmen de ponderibus et mensuris'' (8.25) attributed by Remmius Palaemon (fl. 1st century), where it is the weight of two oboli (Charlton T. Lewis, Charles Short, ''A Latin Dictionary'' (s.v. "gramma" ), 1879). Henry George Liddell. Robert Scott. ''A Greek-English Lexicon'' (revised and augmented edition, Oxford, 1940) (s.v. γράμμα ), citing the 10th-century work ''Geoponica'' and a 4th-century papyrus edited in L. Mitteis, ''Griechische Urkunden der Papyrussammlung zu Leipzig'', vol. i (1906), 62 ii 27.〕 The word ''kilogramme'' was written into French law in 1795, in the ''Decree of 18 Germinal'',〔 〕 which revised the older system of units introduced by the French National Convention in 1793, where the ''gravet'' had been defined as weight (''poids'') of a cubic centimetre of water, equal to 1/1000th of a ''grave''.〔Convention nationale, décret du 1er août 1793, ed. Duvergier, ''Collection complète des lois, décrets, ordonnances, règlemens avis du Conseil d'état, publiée sur les éditions officielles du Louvre'', vol. 6 (2nd ed. 1834), (p. 70 ). The ''metre'' (''mètre'') on which this definition depends was itself defined as the ten-millionth part of a quarter of Earth's meridian, given in traditional units as 3 ''pieds'', 11.44 ''lignes'' (a ''ligne'' being the 12th part of an ''pouce'' (inch), or the 144th part of a ''pied''.〕 In the decree of 1795, the term ''gramme'' thus replaced ''gravet'', and ''kilogramme'' replaced ''grave''. The French spelling was adopted in the United Kingdom when the word was used for the first time in English in 1797, with the spelling ''kilogram'' being adopted in the United States. In the United Kingdom both spellings are used, with "kilogram" having become by far the more common.〔(【引用サイトリンク】Kilogram )〕〔 The spelling ''kilogram'' is the modern spelling used by the International Bureau of Weights and Measures (BIPM), the U.S. National Institute of Standards and Technology (NIST), the UK's National Measurement Office, National Research Council of Canada, and the National Measurement Institute, Australia.〕 UK law regulating the units to be used when trading by weight or measure does not prevent the use of either spelling. In the 19th century the French word ''kilo'', a shortening of ''kilogramme'', was imported into the English language where it has been used to mean both kilogram and kilometer. While ''kilo'' is acceptable in many generalist texts, for example ''The Economist'', its use is typically considered inappropriate in certain applications including scientific, technical and legal writing, where authors should adhere strictly to SI nomenclature.〔(【引用サイトリンク】title=kilo )〕 When the United States Congress gave the metric system legal status in 1866, it permitted the use of the word ''kilo'' as an alternative to the word ''kilogram'',〔(【引用サイトリンク】title=H.R. 596, An Act to authorize the use of the metric system of weights and measures )〕 but in 1990 revoked the status of the word ''kilo''. During the 19th century, the standard system of metric units was the centimetre–gram–second system of units, treating the gram as the fundamental unit of mass and the ''kilogram'' simply as a derived unit. In 1901, however, following the discoveries by James Clerk Maxwell to the effect that electric measurements could not be explained in terms of the three fundamental units of length, mass and time, Giovanni Giorgi proposed a new standard system which would include a fourth fundamental unit to measure quantities in electromagnetism.〔 (Original manuscript with handwritten notes by Oliver Heaviside )〕 In 1935 this was adopted by the IEC as the ''Giorgi system'', now also known as MKS system, and in 1946 the CIPM approved a proposal to adopt the ampere as the electromagnetic unit of the "MKSA system". In 1948 the CGPM commissioned the CIPM "to make recommendations for a single practical system of units of measurement, suitable for adoption by all countries adhering to the Metre Convention". This led to the launch of SI in 1960 and the subsequent publication of the "SI Brochure", which stated that "It is not permissible to use abbreviations for unit symbols or unit names ...".〔The French text (which is the authoritative text) states "''Il n'est pas autorisé d'utiliser des abréviations pour les symboles et noms d'unités ...''"〕 The CGS and MKS systems co-existed during much of the early-to-mid 20th century, but as a result of the decision to adopt the "Giorgi system" as the international system of units in 1960, the kilogram is now the SI base unit for mass, while the definition of the gram is derived from that of the kilogram. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Kilogram」の詳細全文を読む スポンサード リンク
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