Lisa: The hula hoop is indeed a thing of wonder and beauty, and the late Mr. Knerr a true benefactor of the human race. My daughter has a hula hoop, and works it while watching TV. It’s fascinating to watch her. The hoop is a heavy one, assembled from sections; yet she manages to keep it going with body movements of about a sixteenth of an inch side to side, and no obvious effort, while laughing at some sitcom. “It’s a trick,” she tells me. I guess it is. I tried it, but after five minutes sweating, grunting, and moving my stiff, doughy hips halfway round the room, I’d kept the thing airborne for a total of about five seconds. I gave everyone a good laugh, anyway. We must all contribute what we can.