Constructal theory of flows governs social phenomena like rankings. A Duke University researcher says that his physics theory, which has been applied to everything from global climate to traffic patterns, can also explain another trend: why university rankings tend not to change very much from year to year. Like branching river channels across the earth’s surface, universities are part of a relatively rigid network that is predictable based on “constructal theory,” which describes the shapes of flows in nature, argues one professor of mechanical engineering.