Scale of temperature the Swedish astronomer Anders Celsius (1701–1744), who developed a similar temperature scale two years before his death. 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). 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. Although these defining correlations are commonly taught in schools today, by international agreement the unit "degree Celsius" and
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