Folklores in Physics

When I did dimploma work in mathematics, on one occasion my supervisor said to me: "In mathematics and science there are things called folklores". What he referred to in his field was the existence of theorems that everyone went around believing that someone had proved but which in reality nobody had ever proved. We are  not talking about grand famous conjectures like the Riemann hypothesis but typically minor theorems in some new emerging field. In particular he remembered a conference where somebody, lets call him Y, went before the audience and announced that he was going to prove Theorem X and almost everyone in the audience started laughing. Theorem X was a folklore, but only Y knew about it.

During recent years I think I have discovered a folklore in Physics. I'm not talking about the Greenhouse Effect, physicists don't know anything about that, and besides, it is not really the kind of folklore we are discussing here. I'm talking about the folklore about the atmospheric temperature lapse rate. Almost every physicist, chemist, (and zoologist) think that it is simple and was solved long ago. Or put in other words: Nowadays every Tom, Dick and Harry thinks that somebody else knows how to derive it, but they are wrong. 

If you ask a physicist, if you get any answer at all he or she will probably say that it follows from fundamental gas laws. If pushed on the details about which of the infinite number of lapse rates you can derive from the fundamental gas laws he or she will probably say, look in the litterature, Gibbs must have solved it. But Gibbs never solved it, and neither did anyone else. The problem was discussed intensively long ago, but was forgotten and left unsolved by physicists. This void was then filled with the Greenhouse Effect, but they never told us about it...