eli5: If absolute 0 is only theoretical, how do we know what it is in Celsius and fereignheit

Question

eli5: If absolute 0 is only theoretical, how do we know what it is in Celsius and fereignheit

In: 0

Answer 1

The rate of temperature change is measurable and consistent enough that we can extrapolate what would happen past our ability to measure. This lets us “solve for 0” on the temperature scale, and so we know 0 Kelvin would happen at -273.15 Celsius.