How often has this happened to you? You think you understand a topic well. Then you realise that you hadn't quite understood it as well as you thought.I've been listening to the Feynman lectures in physics recently. Some of you may be familiar with these lectures. Richard Feynman was a brilliant physicist and an exceptional communicator. In the early 1960s, he was asked to deliver a two-year undergraduate physics course. This would have been "beneath him" as one of the most renowned physicists o...