Degree Celsius

Article

May 25, 2022

The degree Celsius (in symbols ° C; Italian pronunciation: / ˈʧɛlsjus /; Swedish pronunciation: / ˈsɛlsjɵs /), also called centigrade in the past, is the unit of a measurement scale for temperature, so called from the name of the astronomer Swedish Anders Celsius (1701-1744), who first proposed it in 1742. The Celsius scale fixes the melting point of ice in an air-saturated water mixture at 0 ° C and the boiling point at 99.974 ° C under standard pressure conditions (1 bar, slightly less than one atmosphere, pressure at which water boils at 100 degrees Celsius). Originally the scale devised by Celsius had the boiling point of water at 0 ° C, and the melting point at 100 ° C; after his death, however, the scale was reversed in 1745 by Linnaeus or Daniel Ekström, the manufacturer of the thermometers used by Celsius, transforming it into the one in common use today. The current official definition of the Celsius scale places 0.01 ° C as the triple point of water, and one degree as 1 / 273.15 of the temperature difference between the triple point of water and absolute zero. This definition ensures that the temperature difference of one degree Celsius represents the same temperature difference of one kelvin.

Conversion

The thermometric scales of Celsius and Fahrenheit cross at the same value of −40 degrees, i.e. the value of −40 ° C corresponds to that of −40 ° F. One method of converting Celsius to Fahrenheit is to multiply by 1.8 and add 32. ° F ° C × 1.8 + 32 Conversely, to convert Fahrenheit to Celsius you need to subtract 32 and divide by 1.8. ° C (° F - 32) / 1.8 The Celsius scale is used in most of the world on a daily basis, although in the media it was still frequently referred to as centigrade until the 1990s, particularly in weather forecasts. In the United States (as well as in non-incorporated territories and freely associated states of the Pacific), in Belize, Liberia and some Caribbean islands, the Fahrenheit scale is used, but these countries also use the Celsius scale or the kelvin in the context of scientific or technological applications. Other temperature scales are: Newton (around 1700), Rømer (1701), Fahrenheit (1724), Réaumur (1731), Delisle o de Lisle (1738), Rankine (1859), kelvin (1862) and Leyden (around 1894) . Note that "kelvin" is lowercase because it is an SI unit, even though it derives from the noble title of scientist William Thomson. According to the ISO 31-0 standard, universally adopted for the expression of units of measurement, which today is integrated in the ISO 80000-1: 2009 standard, in the texts it is prescribed to insert a spacing between the numerical value and the symbol of degrees Celsius

Degree centigrade

Since there are one hundred divisions between the freezing point and the boiling point, the original term for this system was degree centigrade or centesimal degree. In 1948 the name was officially changed to Celsius by the ninth Conférence générale des poids et mesures (CR 64), to eliminate a number of ambiguities: the prefix centi- is used by the SI system for submultiples; a more correct name, at least since Linnaeus reversed the scale, would therefore have been "hectogrado"; also hectogrado is ambiguous and in oenology it indicates the alcohol content per hectolitre of wine; the term "degree centigrade" was also used to indicate the centesimal degree used for measuring angles; The decision of the Conférence générale des poids et mesures was aimed at eliminating ambiguities and unequivocally associating the creation of the scale with Celsius (despite the important contribution of Linnaeus); furthermore, the scale was aligned to those Kelvin, Fahrenheit, Réaumur and Rankine, all of which had the name of their inventor as their name. Despite this, in Italy degrees Celsius are still often referred to as "degrees centigrade".

Notes

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