Now that's heat

Put one hand in cold water, and one in hot, then place both hands in the same container of warm water. The temperature of the warm water’s the same, but the sensation will feel differently to both hands. Take a fully inflated bike tire, and deflate it with your fingernail or a thumbtack – your fingers will get cold – in fact you may even get frostbite. Why did the tire knob get cold – where did all the heat go? With our sensation of  hot and cold so subjective, it raises the fundamental question: just what IS heat? And, an even more fundamental question: if we don’t know what heat is, why do we have so many references to it in our culture? (heat score, a dog in heat, take the heat, in dead heat)

An early way people attempted to come to grips with the concept of heat was by devising a system to measure it.  In 1714, G.D. Fahrenheit proposed a scale to measure the “hotness” of an object that placed a salt water-ice mixture at 0 degrees, and the usual temperature of the human body at 96 degrees. By this definition, even that shaggy beer-bellied uncle of yours is hot. 96 degrees hot, to be exact. A newer and improved Celsius scale by Anders Celsius (with 0 C referring to water freezing and 100 C referring to water boiling) was developed 10 years after.

After a while, we developed a more dynamic idea of heat with caloric theory. Joseph Black first defined the concept of heat capacity in 1760: the amount of calorie required for raising or lowering the temperature of a body by 1 degree Celsius. And what is 1 calorie? A reference "amount" of heat; that is, the amount required to raise 1g of water by 1 Celsius from 15.35 C to 16.35 C.

It was a century later with the theories of Maxwell and Boltzmann that heat could be understood from a quantum mechanical perspective. From this perspective, heat is how fast and how vigorously atoms are vibrating. Remember kinetic energy from my previous post? Well, when bunch of atoms that are vibrating very quickly (something hot) are brought close to slowly vibrating atoms, there are interactions that slow the faster atoms and speed up the slower atoms (whether it be directly, through radiation, or through other means).

Now that we’ve been able to measure heat, and define heat, then next thing us humans devised was ways of harnessing that heat to make our lives easier (well, less physically burdensome).