The Rankine scale is an absolute scale whose degree size matches Fahrenheit. Zero °R is absolute zero (−459.67 °F). It is used in some US engineering thermodynamics — mainly aerospace, power plants and propulsion — where Fahrenheit-based calculations need an absolute reference.
Real-world: Room temperature ≈ 527 °R. Water boils at 671.67 °R. US rocket-engine thermodynamics textbooks use Rankine.
Read full rankine reference →The Celsius scale defines 0 °C as the freezing point of water and 100 °C as the boiling point at standard atmospheric pressure. Proposed by Anders Celsius in 1742, it is the everyday temperature unit in all countries except the US, Belize, the Bahamas, the Cayman Islands and Liberia.
Real-world: Room temperature is about 20 °C. Normal body temperature is 37 °C. Typical fridge setting is 4 °C. European winter can reach −20 °C; desert summer 45+ °C.
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