Thermodynamics Smackdown Explained

So, yesterday featured a silly poll about underappreciated old-timey physicists. Who are these people, and why should you know about them?

Taking them in reverse order of the voting:

Rudolf Clausius is the originator of the infamous Second Law of Thermodynamics, which states that the entropy of any closed system will tend to increase. He was one of the most important figures in terms of systematizing the study of thermodynamics, pulling a lot of other people's work together, and showing how it all fit.

James Joule was a brewer as well as a physicist, making him a really good guy to know. He's famous for demonstrating the equivalence of heat and mechanical energy with an experiment that used a falling weight to turn a paddle-wheel in a sealed tank of water, and demonstrated that the temperature of the water increased by an amount that corresponded to the work done by the falling weight. This experiment is a royal pain in the ass to do well, and the unit of energy is rightly named in his honor.

William Thomson was the given name of Lord Kelvin, for whom the absolute temperature scale is named. He is noted for his famous machine, his work on the first transatlantic telegraph cable, and, of course, his work on thermodynamics.

Robert Boyle was more properly a "natural philosopher" than a physicist, and played an important role in the early development of both chemistry and physics. His most famous work involved using early vacuum pumps to study the behavior of gases, and led to Boyle's Law, stating the inverse relationship between the pressure and volume of a gas at constant temperature.

Sadi Carnot was a French military engineer and physicist who worked out pretty much everything there is to know about engines in 1824. Of course, his book quickly went out of print, and wasn't truly appreciated until it was rediscovered by Clausius ten years later, by which time Carnot had died of cholera. C'est la vie. He laid out the basic principles by which heat energy is converted to useful work, and anybody who has ever taken a class on how an engine works has listened to talk of the Carnot cycle.

Ludwig Boltzmann was an Austrian physicist who really marks the point where thermodynamics becomes statistical mechanics. He pioneered the idea of the entropy of a system as a function of the number of microscopic states available to that system, which is the essential core of statistical physics. Once you have that idea, you can reformulate all the thermodynamic principles derived by the other guys on this list in terms of the distribution of energy states in a system, an idea which completely transformed the study of heat and entropy.

Left off the list because I was putting names down very hastily was Josiah Gibbs, whose name adorns a very ugly building at Yale that I used to cut through when the weather was bad. Gibbs is best known for the Gibbs free energy, which is tremendously important in chemistry, but not something I've ever used much.

In terms of overall importance to modern science, Boltzmann is the clear winner, I think. I voted for Carnot, though, because I think it's particularly impressive how he got so much right without any sort of idea of what was going on at a microscopic scale. Boltzmann transformed thermodynamics into statistical mechanics, but Carnot took a bunch of noodling around with hot things and turned it into the science of thermodynamics.

So that's the big thermodynamics smackdown. Stay tuned for more polls, and more historical physicists.