| absolute temperature scale A temperature scale having absolute zero as the lowest temperature. Absolute temperature scales only have positive numbers. The Kelvin scale and the Rankine scale are absolute temperature scales. Compare relative temperature scale. |
any thermometric scale on which a reading of zero coincides with the theoretical absolute zero of temperature-i.e., the thermodynamic equilibrium state of minimum energy. The standard measure of temperature in the International System of Units is the Kelvin (K) scale, on which the only point established by arbitrary definition is the unique temperature at which the liquid, solid, and vapour forms of water can be maintained simultaneously. The interval between this temperature and absolute zero is defined as 273.16 kelvins, and the temperature of this "triple point" is designated 273.16 K (since 1967, no longer written K). In essence, the Kelvin scale is the Celsius (C) temperature scale shifted by 273.15 degrees (because the triple point of water is actually 0.01 C), with the same size unit of temperature.