Absolute Temperature

ABSOLUTE TEMPERATURE, is measured in degrees of the Celsius scale, but is counted from a point lying 273° below the freezing point of water. Such a system of counting is especially convenient for expressing the state of a gas by the Boyle-Gay-Lussac formula: according to Gay-Lussac's law, the volume of a gas (at constant pressure) is proportional to the expression: 1 + P/273, where P is the temperature in Celsius; rewriting this expression in the form T/273, we find that the volume will be proportional simply to the absolute temperature of the gas: T° = 273 + P. Often instead of the designation T°(abs.) the designation T°_K is used—in honor of the physicist Lord Kelvin, who substantiated the concept of absolute temperature. At present, in the evaporation of liquid helium, temperatures close to "absolute zero" have been reached: down to 0.9°_K (see Aggregate State).