I should've guessed that you had a physics background, since that turned out to be an unexpectedly interesting problem. (The view from one of the moving rods in

I should've guessed that you had a physics background, since that turned out to be an unexpectedly interesting problem. (The view from one of the moving rods in particular was more subtle than I anticipated. As usual, once I stopped trying to intuit the answer and finally set it up carefully with 4-vectors the answer came out pretty cleanly.) I wonder if there's a good place to use this in my classes. (It was a bit more subtle than I'd usually throw at my sophomores...) What's your field?