Information Theory - Part 2: Maxwell's Demon
How can a theory about information and noise be considered as profound as relativity and quantum theory? Sounds ridiculous, right? So let’s check out the first big science-y problem that information theory solved. The second law of thermodynamics forbids the existence of a perpetual motion engine (That’s a machine that can run forever without any intervention that involves more work than the work you get from the machine itself). Why not, asked James Clark Maxwell, with his famous thought experiment known as Maxwell’s demon, devised in 1871. But first, a recap of some basics. Heat flows from a hotter to a colder place. As that heat flows, you can use (part of) that heat flow to do work. By definition, this means that once the two sides are at the same temperature (same heat), heat stops flowing (neither end is hotter anymore). And without heat flow, no work can be done. We also know that heat is just a measure of the average speed of molecules. And since those molecules...