Yesterday the temperature outside was 0.5 °C. Today, the temperature is 30 °C. 30 is 5300% more than 0.5, but today is obviously not 5300% hotter than yesterday.
In Fahrenheit, the temperatures are 33 °F and 86 °F, respectively. 160% hotter sounds more reasonable, but this argument uses the same logic as Celsius, just on a different scale.
Converting these temperatures to Kelvin, we get 273.70 K and 303.15 K, respectively. Since Kelvin is an absolute scale of temperature, can we correctly say that today is 11% hotter than yesterday?
Since temperature is relative, can we also claim that there is 11% more heat today?
Best Answer
Yes, it's 11% hotter today than yesterday. Of the three temperature scales you discussed, only the Kelvin scale allows meaningful ratios to be calculated. Dividing two temperatures expressed in Celsius or Fahrenheit is simply a mistake. There are numerous physical examples where it makes sense to multiply or divide by a Kelvin temp, e.g., the ideal gas law and the Stefan-Boltzmann law.
A similar example of the incorrect use of a scale of measurement would be if we were to call chocolate 1, vanilla 2, and strawberry 3, and then say that chocolate minus strawberry was -2. It's not a scale that is defined so as to make subtraction meaningful.
BTW, with a scale like celsius, division could result in the statement that today is infinitely more hot than yesterday, if the temperature yesterday was 0 C.