Two people. One has learned to ride a bike, rides it all the time and never falls off, but has never stopped to wonder how exactly it is that she is able to keep the bike upright when moving, or why this is impossible when the bike is still. The other has never ridden a bike, but she is fascinated by the (surprisingly complex) question as to how a bike stays upright when moving, and has studied the physics and physiology of bicycle riding in great detail. Which of the two understands more about riding bikes?