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Celsius, historically known as centigrade, is a scale and unit of measurement for temperature. As an SI derived unit, it is used by most countries in the world. It is named after the Swedish astronomer Anders Celsius (1701–1744), who developed a similar temperature scale. The degree Celsius (°C) can refer to a specific temperature on the Celsius scale as well as a unit to indicate a temperature interval, a difference between two temperatures or an uncertainty. Before being renamed to honour Anders Celsius in 1948, the unit was called ''centigrade'', from the Latin ''centum'', which means 100, and ''gradus'', which means steps. From 1744 until 1954, 0 °C was defined as the freezing point of water and 100 °C was defined as the boiling point of water, both at a pressure of one standard atmosphere with mercury being the working material. Although these defining correlations are commonly taught in schools today, by international agreement the unit "degree Celsius" and the Celsius scale are currently defined by two different temperatures: absolute zero, and the triple point of VSMOW (specially purified water). This definition also precisely relates the Celsius scale to the Kelvin scale, which defines the SI base unit of thermodynamic temperature with symbol K. Absolute zero, the lowest temperature possible, is defined as being precisely 0 K and −273.15 °C. The temperature of the triple point of water is defined as precisely 273.16 K and 0.01 °C.〔(【引用サイトリンク】title=SI brochure, section 2.1.1.5 )〕 This definition fixes the magnitude of both the degree Celsius and the Kelvin as precisely 1 part in 273.16 (approximately 0.00366) of the difference between absolute zero and the triple point of water. Thus, it sets the magnitude of one degree Celsius and that of one Kelvin as exactly the same. Additionally, it establishes the difference between the two scales' null points as being precisely 273.15 degrees Celsius ( and ).〔(【引用サイトリンク】title=Essentials of the SI: Base & derived units )〕 ==History== In 1742, Swedish astronomer Anders Celsius (1701–1744) created a temperature scale which was ''the reverse'' of the scale now known by the name "Celsius": ''0'' represented the boiling point of water, while ''100'' represented the freezing point of water. In his paper ''Observations of two persistent degrees on a thermometer'', he recounted his experiments showing that the melting point of ice is essentially unaffected by pressure. He also determined with remarkable precision how the boiling point of water varied as a function of atmospheric pressure. He proposed that the zero point of his temperature scale, being the boiling point, would be calibrated at the mean barometric pressure at mean sea level. This pressure is known as one standard atmosphere. The BIPM's 10th General Conference on Weights and Measures (CGPM) later defined one standard atmosphere to equal precisely per square centimetre (101.325 kPa).〔(【引用サイトリンク】title=Resolution 4 of the 10th meeting of the CGPM (1954) )〕 In 1743, the Lyonnais physicist Jean-Pierre Christin, permanent secretary of the ''Académie des sciences, belles-lettres et arts de Lyon''FR, working independently of Celsius, developed a scale where zero represented the freezing point of water and 100 represented the boiling point of water.〔Don Rittner; Ronald A. Bailey (2005): (''Encyclopedia of Chemistry.'' ) Facts On File, Manhattan, New York City. pp. 43.〕 On 19 May 1743 he published the design of a mercury thermometer, the "Thermometer of Lyon" built by the craftsman Pierre Casati that used this scale.〔''Mercure de France'' (1743): (''MEMOIRE sur la dilatation du Mercure dans le Thermométre.'' ) Chaubert; Jean de Nully, Pissot, Duchesne, Paris. pp. 1609–1610.〕〔''Journal helvétique'' (1743): (''LION.'' ) Imprimerie des Journalistes, Neuchâtel. pp. 308-310.〕〔''Memoires pour L'Histoire des Sciences et des Beaux Arts'' (1743): (''DE LYON.'' ) Chaubert, París. pp. 2125-2128.〕 In 1744, coincident with the death of Anders Celsius, the Swedish botanist Carolus Linnaeus (1707–1778) reversed Celsius's scale.〔Citation: Uppsala University (Sweden), ( ''Linnaeus' thermometer'' )〕 His custom-made "linnaeus-thermometer", for use in his greenhouses, was made by Daniel Ekström, Sweden's leading maker of scientific instruments at the time and whose workshop was located in the basement of the Stockholm observatory. As often happened in this age before modern communications, numerous physicists, scientists, and instrument makers are credited with having independently developed this same scale;〔Citation for Daniel Ekström, Mårten Strömer, Christin of Lyons: The Physics Hypertextbook, (''Temperature'' ); citation for Christin of Lyons: Le Moyne College, (''Glossary, (Celsius scale)'' ); citation for Linnaeus' connection with Pehr Elvius and Daniel Ekström: Uppsala University (Sweden), (''Linnaeus' thermometer'' ); general citation: The Uppsala Astronomical Observatory, (''History of the Celsius temperature scale'' )〕 among them were Pehr Elvius, the secretary of the Royal Swedish Academy of Sciences (which had an instrument workshop) and with whom Linnaeus had been corresponding; Daniel Ekström(), the instrument maker; and Mårten Strömer (1707–1770) who had studied astronomy under Anders Celsius. The first known Swedish document〔Citations: University of Wisconsin–Madison, (''Linnæus & his Garden'' ) and; Uppsala University, (''Linnaeus' thermometer'' )〕 reporting temperatures in this modern "forward" Celsius scale is the paper ''Hortus Upsaliensis'' dated 16 December 1745 that Linnaeus wrote to a student of his, Samuel Nauclér. In it, Linnaeus recounted the temperatures inside the orangery at the Botanical Garden of Uppsala University: 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「Celsius」の詳細全文を読む スポンサード リンク
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