Empirical observations of temperature

I have divided the old notes on temperature into three parts:

• Principle of the conservation of energy
• Empirical observations of temperature (this part)
• Energy and fundamental postulate 

Our feeling of hotness comes from everyday experiences. These experiences indicate that many levels of hotness exist, and that all levels of hotness can be mapped to a real variable.

Most of our feelings, however, cannot be mapped to a real variable. Think of happiness, love, anxiety. It is therefore extremely remarkable that the levels of hotness can be mapped to a real variable. What makes hotness so different from happiness?

To appreciate the difference, we will reflect upon how we discover the levels of hotness by using a particular kind of everyday experience: thermal contact.

We make the word hotness—in the precise way used here—synonymous to temperature. An essential step to understand how thermodynamics works is to get to know temperature. How is temperature abstracted from everyday experiences?