The Upside-Down Classroom

The class has a problem. The principal wants a photograph of the classroom window — the big one, the one the mango tree grows past — for the school anniversary display. But cameras are banned during school hours. Phones are banned during school hours. The art teacher is absent and has taken the one permitted camera with her. One student remembers something from last year's science fair: a photograph made in a dark room, with no glass lens, no chip, no battery. A dark box. A small hole. A paper screen. The light from the window comes through the hole and lands on the screen — and lands upside down. If you know why it goes upside down, you know exactly how every camera in the world works. If you don't, the image still appears. This is what a camera was, for three hundred years, before anyone put glass in one. Today, your team is going to build one.