The thorny thought experiment has been turned into a real experiment — one that physicists use to probe the physics of information ============================================================= It took physicists 115 years to tame Maxwell’s Demon. The universe bets on disorder. Imagine, for example, dropping a thimbleful of red dye into a swimming pool. All of those dye molecules are going to slowly spread throughout the water. Physicists quantify this tendency to spread by counting the number of possible ways the dye molecules can be arranged. There’s one possible state where the molecules are crowded into the thimble. There’s another where, say, the molecules...