Contructal law says that flow systems will shape themselves to flow more easily over time, eventually making a tree shape. One example Bejan gives is the representation of the Mississippi River basin.
"In reality, that is not a static drawing. That is a dynamic, a morphing animal, which is called a Mississippi flow, which is from an area, a huge area, to one point," Bejan said.
The design of tree branches, rivers, the air passages in the human lung and even man-made products, like highways, make a similar flow, according to Bejan's theory. But the theory doesn't just describe the flow of corporeal beings. The flow of an idea is also tree shaped.
"Anything that flows, the animate, the inanimate and our social dynamics is subject to this law and, for that matter, to any other law of physics," Bejan said.
But not everything grows and branches out. It is here that constructal law makes the distinction between what is "alive" and what is "dead."
"To be alive means to be a flow system that is free to change its configuration over time," Bejan said. "Dead are samples of, say, crystals or solid. Dead is anything that shows absolutely no movement."
However, a dead flow is not irreversible. Bejan said a glass of water is dead, but if the water is exposed to air and thus evaporated, it would re-enter a flow system.
Bejan's idea of constructal law came about in contention to a speech given by Ilya Prigogine, a Nobel Prize laureate for chemistry and proponent of chaos theory, at a 1995 science conference in France. According to Bejan, Prigogine said similar branching shapes in nature were coincidental.
Chaos theory holds that small changes in initial condition end in widely diverse results and makes them unpredictable, despite being deterministic in nature. Constructal law directly conflicts with this notion.
He is currently trying to change the way people think about the universe with his new book Design in Nature: How the Constructal Law Governs Evolution in Biology, Physics, Technology, and Social Organization.