I just had a thought and a question - a few years ago my husband bought a radio and a very large flashlight for his Emergency Preparedness Kit - both of them operate on human power. On the radio I think you crank a handle, and on the flashlight I believe you have to squeeze something repeatedly, but on both of them roughly 5-15 minutes of fairly easy effort provide an hour or several hours of battery life. How does this equate with the herculean effort of lighting up a 60 watt lightbulb on a bicycle? Bear in mind that I never studied electricity in school, or after - if possible, use simple words and type slowly :)