I remember friends who took Math 55 pulling ridiculously long hours. It either makes you or breaks you as a potential mathematician. One friend took up smoking

I remember friends who took Math 55 pulling ridiculously long hours. It either makes you or breaks you as a potential mathematician. One friend took up smoking, just so he would have an excuse to break. Two friends ended up becoming philosophers, which is the mathematics of the humanities. At the end of the class, they printed a t-shirt with a tiny little diagram on the breast, and "Math 55" on the back. The tiny little diagram? A Dynkin Diagram (http://mathworld.wolfram.com/DynkinDiagram.html http://mathworld.wolfram.com/DynkinDiagram.html). As the story goes, Prof. Pavel Etingof, before introducing Dynkin Diagrams, said: "If aliens ever came to earth, and told us that we were primitive, I would say 'No, we are not primitive', and I would show them Dynkin Diagrams to prove it."