If Papa Was A Rolling Stone, He'd Obey The Laws Of Physics

If Papa Was A Rolling Stone, He'd Obey The Laws Of Physics

2:00pm Aug 12, 2016
An ash plume and drainage pattern from Mt Cleveland, a stratovolcano in the Aleutian Islands, both show the dendritic, or tree-like pattern defined by the constructal law.
  • This image of Ireland from space displays the tree-shaped concept of the constructal law. The majority of energy is centered in the the large cities, where it radiates out to progressively smaller towns and villages.


  • The evolutionary tree of life conforms to the constructal law. Similar species progress up in distinct branches and radiate out progressively to subspecies, and individual species.

    Carl Zimmer. Evolution (William Heinemann, 2002)

  • The human circulatory system conforms to constructal law. The bulk of the blood is carried through larger arteries, and distributed out to progressively smaller veins and capillaries.


  • The Amazon river system follows the "tree-shaped" pattern, dictated by the constructal law.

Dr. Adrian Bejan, Duke University

If your papa was actually a rolling stone, your mama could have kept track of him. That’s because his travel distance and travel time would be predictable! In fact, you and mama could’ve used basic math skills to find him. He’d have been thrilled.

As it turns out, the same principle used to find rock-daddy also defines the plume of his cigarette smoke, as well as river systems, migrating bison, the veins in your body, and the branches on a tree, according to Dr. Adrian Bejan, Professor of Mechanical Engineering at Duke University.

With mathematics from early middle school, you can show that the larger stone should keep rolling longer than the smaller stone. It should roll farther.  

And then, as if that was not a wonderful surprise, it turns out that when you put the lifetime and the life travel together, and calculate the number of rolls that the stone should take, you discover that the number is a constant. The big rock rolls as many times as the small rock. That’s the way things should be.

In turbulence, small eddies come together into bigger billows. Look at the smoke from a smokestack. The whirls are small, and then they roll into bigger and bigger things. And then, in each big wheel there’s a happy coexistence of few large and many small. That population is naturally heretical.

Nature is unruly; she obeys very few laws, and those are the laws of physics.

A scientific law explains that a phenomenon will happen in a predictable way. Every time.

Bejan is credited with defining a law of physics called the constructal law, which, in a recent paper published in the journal Nature Scientific Reports, he refined to include the forces that shaped the surface of the earth, rolling stones, and turbulent eddies in water and air. (Read about it here)

"The constructal law is very simple statement. It says that for any finite size flow system to persist in time, it must evolve, meaning change in time, such that it provides easier and easier access to what flows."

The law governs flowing systems, and its signature is a tree-shaped pattern. Natural and manmade systems, like rivers, or a system of roads, all have a few large branches, carrying the bulk of traffic to progressively smaller and more numerous branches, where it is dispersed -- to wherever Papa lays his hat.

"It is a design that happens. This is where nature comes in. She gives birth to these things," says Bejan. "And, the undeniable observation, which is universal, is that flow leads to better flow. Not the other way around."

This progression is literally “evolution,” meaning a change that happens in a discernible direction in time. And according to Bejan, the theory of evolution by natural selection is predicted by, and corresponds directly to, the constructal law.

Life’s move from the ocean, to land and eventually to air is a progression that conserves energy. Now, the energy to move a small distance in the oceans can get you to great distances by air.  

And that’s evolution in a particular direction. According to contractual law, it should have happened in that direction. From sea, to sea plus land, to sea plus land plus air. Not the other way around. With this in mind I was able to predict what everybody knows. The larger should move faster, and should move farther, and should be more efficient as vehicles carrying weight.

I’m not describing new things. I am simply putting old things together into a much smaller pencil holder; you see? That’s the power of a law of physics.


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