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

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Answer 1

Thermal energy is like kinetic energy, but on a microscopic level. You can measure that energy in different materials at different temperatures, and extrapolate when it will be zero. If you have enough measurements in different materials at near-0°K, you’ll eventually hit a pretty accurate estimate of how much colder you need to go for that energy to reach zero.