“Mister Geoffrey, my experiment shows that the dynamo and the bulb are both working properly," I said. "So why won't the radio play?""I don't know," he said. "Try connecting them here."He was pointing toward a socket on the radio labeled "AC," and when I shoved the wires inside, the radio came to life. We shouted with excitement. As I pedaled the bicycle, I could hear the great Billy Kaunda playing his happy music on Radio Two, and that made Geoffrey start to dance."Keep pedaling," he said. "That's it, just keep pedaling.""Hey, I want to dance, too.""You'll have to wait your turn."Without realizing it, I'd just discovered the difference between alternating and direct current. Of course, I wouldn't know what this meant until much later.After a few minutes of pedaling this upside-down bike by hand, my arm grew tired and the radio slowly died. So I began thinking, "What can do the pedaling for us so Geoffrey and I can dance?”