The Mathematics of Heat
Unlike length or weight, which have absolute zeros conceptually mapped to '0', temperature scales are offset and scale differently. This means you cannot just multiply to convert them; you must use linear algebraic formulas.
The Big Three
- Celsius (°C): The global standard, originally defined by the freezing (0°C) and boiling (100°C) points of water.
- Fahrenheit (°F): Used primarily in the USA. Water freezes at 32°F and boils at 212°F.
- Kelvin (K): An absolute scale used in science. 0 K is absolute zero, where all thermal motion stops.
Historical and Engineering Scales
- Rankine (°R): An absolute scale favored by some US engineers. It uses the Fahrenheit degree scale but starts at absolute zero.
- Delisle (°De): Developed by a French astronomer, this unusual scale runs backwards—boiling water is 0°De and freezing is 150°De.
- Réaumur (°Ré): Widely used in Europe in the 18th and 19th centuries, notably mentioned in classic Russian literature. Water freezes at 0°Ré and boils at 80°Ré.