See also: Mef= [[degree]] or [[Centigrade]]

The degree Celsius (symbol °C or ℃ ) is the unit of the scale of Température Celsius, which is a unit derived from the international Système of units, introduced in 1948. Its name is a reference to the Astronome and Physicien Swedish Anders Celsius, inventor in 1742 of one of the first scales centigrades of temperature.

Definitions: the Centigrade temperature and its unit, the degree Celsius

The temperature Celsius T is defined by the difference T = T - T ₀ between two thermodynamic temperatures (in K) T and T ₀ with T ₀ = 273,15 K.

The unit of Celsius temperature is the degree Celsius (symbol °C), equal in magnitude to the unit Kelvin by definition: to express a difference in temperature , the units Kelvin and degree Celsius are equivalent and a interval of temperature in degree Celsius or Kelvin to the same numerical value: difference 37 (°C) - 25 (°C) = 12 °C = 12 K. But the two scales in temperature is not equivalent, in the absolute: 0 °C = 273,15 K.

The degree Celsius is a unit of the International scales of Temperature.

Consequence of the definition on the point of boiling of water and difference with the scale centigrade

The degree Celsius is defined by only one fixed point of 0°C in 273,15 K (which is the melting point of water) and a step identical to that of the thermodynamic temperature in Kelvin.

In other words, the Celsius scale is not strictly defined by the boiling point of water in 100 degrees under a Pression of a atmosphere in the sea level. This definition is that of the Degree centigrade. The difference is however very weak, of 1/4000ème, the boiling point of the water being of 99,975°C.

History

For the history of the scales centigrades which preceded the degree Celsius, to see Degree centigrade.

It is at the time of the 9th General conference of the weights and measures (CGPM), in 1948, that the international Système sliced between the three terms “centigrade degree”, “centesimal degree”, and “degree Celsius” in favor of the latter. The centesimal degree indicates also a Angle plan equal to the 1/400e of a Cercle ( Dictionnaire of the French Academy , 8th edition, 1932 - 1935); it is a synonym of Grade or Gon (its symbol is gon ).

The degree Celsius is the only metric unit whose name comprises a capital letter. The prefixes are applied to him normally; one thus can, for example, speech of “millidegré Celsius (symbol m℃)”.

Other scales

Note