Go forth and procure yourself a toothpaste tube. Full is better. Hold it in one hand, name side up, cap pointing away from you. Flip it end over end so it makes one revolution, and catch it. The tube will have rotated, so that the name side is down. This works nine out of ten times. If I try really hard, I can get it to flip without rotating, but the natural tendency is to rotate.
I don't understand it. Anyone?