To revist this article, visit My Profile, then View saved stories. Happy Pi Day. Yes, it's March 14th. If you write that date like an American, it looks like this: 3/14, and that looks like 3.14. It's not the best representation of pi, but it will do. As is my tradition, I am going to do something with pi. (I have to keep the streak alive—my first Pi Day post was in 2010.) For today's pi post, let's talk about trains and things. In particular, how does a train stay on a track—especially when it's a track with a curve in it? It's easy right? You might think that these train wheels have a flange inside the track that prevents the wheel from coming off. If you look at a train wheel head-on, you might think it looks like this: