Rankine temperature scale, temperature scale having an absolute zero, below which temperatures do not exist, and using a degree of the same size as that used by the Fahrenheit temperature scale. Absolute zero, or 0°R, is the temperature at which molecular energy is a minimum, and it corresponds to a temperature of - 459.67°F. Because the Rankine degree is the same size as the Fahrenheit degree, the freezing point of water (32°F) and the boiling point of water (212°F) correspond to 491.67°R and 671.67°R, respectively. The temperature scale is named after the Scottish engineer and physicist William John Macquorn Rankine, who proposed it in 1859. Another absolute temperature scale, the Kelvin temperature scale, is more commonly used for scientific measurements. See also Celsius temperature scale.