Laertes scratches the back of his neck. "I may misspeak regarding the application of the principle to flight, for I have only read of such things in books here, and never observed them directly," he says. "But the principle is that fluids--like air--exert less pressure when they move at great speeds, and more pressure when they move at slower speeds. Thus, airplanes fly because they are contrived to push air over their wings at greater speeds than the air moving beneath them. The wings, answering the greater pressure from beneath, raise the airplane into the sky."