The impossible barber and other bizarre thought experiments

If you imagined that thought experiments were mere mental gymnastics meant to bamboozle the uninitiated, think again. Take Schrödinger's cat, perhaps the most famous example, which involves a cat that is simultaneously alive and dead. It seems bizarre – and that's the point. It was designed as a slap on the wrist for quantum theorists, to show that a theory that predicts such nonsense must be missing something. Current thinking is that perhaps nothing is missing, and quantum theory really is as weird as it seems.