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Fahrenheit (symbol °F) is a temperature scale based on one proposed in 1724 by the German physicist Daniel Gabriel Fahrenheit (1686–1736), after whom the scale is named. There exist several accounts of how he originally defined his scale. The lower defining point, 0 degrees, was established as the temperature of a solution of brine made from equal parts of ice and salt. Further limits were established as the melting point of water (32 degrees) and his best estimate of the average human body temperature (96 degrees, about 2-1/2 degrees less than modern measurements).〔(Fahrenheit temperature scale ), Encyclopedia Britannica Online. 25 September 2015〕 The scale is now usually defined by two fixed points: the temperature at which water freezes into ice is defined as 32 degrees, and the boiling point of water is defined to be 212 degrees, a 180-degree separation, as defined at sea level and standard atmospheric pressure. By the end of the 20th century, Fahrenheit was only used as the official temperature scale in the United States, the Bahamas, Belize, the Cayman Islands, and Palau as well as being the most common unofficial scale in many of the current and former US unincorporated territories. All other countries in the world now use the Celsius scale, defined since 1954 by absolute zero being -273.15° and the triple point of "specially prepared water" being at 0.01°.〔(Celsius vs. Fahrenheit )〕 ==Definition and conversions== On the Fahrenheit scale, the freezing point of water is 32 degrees Fahrenheit (°F) and the boiling point is 212 °F (at standard atmospheric pressure). This puts the boiling and freezing points of water exactly 180 degrees apart.〔 Therefore, a degree on the Fahrenheit scale is of the interval between the freezing point and the boiling point. On the Celsius scale, the freezing and boiling points of water are 100 degrees apart. A temperature interval of 1 °F is equal to an interval of degrees Celsius. The Fahrenheit and Celsius scales intersect at −40° (−40 °F and −40 °C represent the same temperature). Absolute zero is −273.15 °C or −459.67 °F. The ''Rankine'' temperature scale uses degree intervals of the same size as those of the Fahrenheit scale, except that absolute zero is 0 R—the same way that the ''Kelvin'' temperature scale matches the Celsius scale, except that absolute zero is 0 K. The Fahrenheit scale uses the symbol ° to denote a point on the temperature scale (as does Celsius) and the letter F to indicate the use of the Fahrenheit scale (''e.g.'' "Gallium melts at 85.5763 °F"), as well as to denote a difference between temperatures or an uncertainty in temperature (''e.g.'' "The output of the heat exchanger experiences an increase of 72 °F" and "Our standard uncertainty is ±5 °F"). For an exact conversion, the following formulas can be applied: •Fahrenheit to Celsius : (°F − 32) ÷ 1.8 =°C •Celsius to Fahrenheit : (°C × 1.8) + 32 =°F An approximate conversion between degrees Celsius and degrees Fahrenheit is as follows: •Fahrenheit to Celsius: Subtract 30 and halve the resulting number. •Celsius to Fahrenheit: Double the number and add 30. This formula gives an answer correct to within ±2.8 °C from 1 °F to 100 °F and is exact at 50 °F (calculations below). ((1 - 30) ÷ 2) - ((1 - 32) ÷ 1.8) = 2.72 ((50 - 30) ÷ 2) - ((50 - 32) ÷ 1.8) = 0 ((100 - 30) ÷ 2) - ((100 - 32) ÷ 1.8) = 2.77 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「fahrenheit」の詳細全文を読む スポンサード リンク
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