KELVIN

An absolute temperature scale named after Lord Kelvin (William Thomson, 1824-1907), who devised it in 1848. It has the same degree size as the Celsius scale, but was extended down to absolute zero (0 K is -273.15° C), which refers to the temperature at which all molecular motion would theoretically cease (i.e., the zero pressure for a gas). It is a resetting of the Celsius scale to reflect thermodynamic principles and eliminate the need for negative numbers. In this scale the freezing point of water is 273 K and the boiling point is 373 K. Temperatures very close to absolute zero have been produced in the laboratory.