Celsius Celsius The Celsius scale, also known as the centigrade scale, is a temperature scale used by the International System of Units (SI). As an SI derived unit, it is used by all countries except the United States, the Bahamas, Belize, the Cayman Islands and Liberia. 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 or a unit to indicate a difference between two temperatures or an uncertainty. Before being renamed to honor Anders Celsius in 1948, the unit was
Scale of temperature is the function of the temperatures only: In addition, a reversible heat engine operating between temperatures "T" and "T" must have the same efficiency as one consisting of two cycles, one between "T" and another (intermediate) temperature "T", and the second between "T" and "T". This can only be the case if Specializing to the case that formula_5 is a fixed reference temperature: the temperature of the triple point of water. Then for any "T" and "T", Therefore, if thermodynamic temperature is defined by then the function "f", viewed as a function of thermodynamic temperature, is and the reference temperature