Interview with Adrian Bejan

There’s a New Law in Physics and It Changes Everything: Constructal Law. It governs Evolution in Biology, Physics, Technology and Social Organization.

Adrian Bejan (J.A. Jones Distinguished Professor of Mechanical Engineering, Duke University) has identified a basic Law of Physics that describes and predicts how design patterns emerge over time, he contends that one can construct a “constructal theory” about any system, animate, inanimate or technological (see more about this at Constructal Theory Web Portal). This last one of course got my attention and I have been peppering my posts with little constructal tidbits ever since. Anybody who has participated in the phenomenon of viral social media understands, intuitively, what Bejan is describing mathematically. There are characteristic ways that flows change their configuration over time to flow more (and more!).

In many parts of science, and in life, we have “black boxed” the processes through which things change. We put energy into a box called entropy and note that it dissipates. We are born and then we die—but in between something happens, we live. The Constructal Law is important because it not only describes the patterns of change in the world within and around us, but it allows us to predict how the configuration of those patterns will evolve over time.

Q: In the simplest non-technical terms, what is the Constructal Law?

A: The Constructal Law is my statement that there is a universal tendency (a phenomenon) toward design in nature, in the physics of everything. This tendency occurs because all of nature is composed of flow systems that change and evolve their configurations over time so that they flow more easily, to create greater access to the currents they move.

Q: What makes this a law of physics instead of just a theory?

A: Fantastic question! Very few people know the difference. I was lucky to have this explained to me by Angele Kremer-Marietti, a French professor of philosophy of science, in Paris in 2004. Even though I correctly named it the Constructal Law in 1996, I incorrectly referred to it in some of my early articles as constructal “theory.”

A theory is a purely mental image of how something should be. In other words, the thought in the dark (with eyes closed) comes first, and the comparison with nature (eyes open) comes later. If the imagined agrees with the real, then the theory is correct.

A law is a concise statement that summarizes a distinct and universal tendency in nature (the phenomenon), previously not recognized as distinct. The key word is “universal.” A law is for everything, it is obeyed by every system imaginable (bodies, rivers, machines). A law underpins as many theories as the “things” that the mind wishes to explore, for example:

If that thought in the dark is about what the shape of snowflakes should be according to the Constructal Law (this has happened to me), then the outcome (the mental viewing, the idea) is the constructal “theory” of the snowflake’s tree-shaped architecture.

In practical terms, a law and and the many theories supported by it are predictive. The law is universal, while any given theory is specific. You can use both to imagine what will be.

The world managed without Galileo’s gravity phenomenon, as it did without the phenomenon of “design in nature,” but both laws are in fact primary principles that cannot be deduced from other laws of physics.

Snowflakes and river basins and cooling systems for computer chips are all discussed in the Design in Nature book, along with many more constructal theories of inanimate, animate and social design phenomena.

The bottom line is that the law is one, the theories are many, and the empirical observations are immense in number. This hierarchy is the essence of the evolutionary design of science itself, which is also a constructal theory.

Q: Wait a minute, does this have anything to do with the “theory” of intelligent design?

A: First, let’s be clear about what we mean by “design” when we discuss “design in nature”. The word “design” has two meanings, the noun and the verb.

The noun “design” means a drawing, figure, configuration, image, pattern, rhythm or motif. The Constructal Law is about this, the natural occurrence and evolution of flow configurations. It captures this natural phenomenon. Design in nature happens, and the Constructal Law states why and in what direction it should happen.

The verb “to design” is the human urge of contriving and extending the reach and power of each individual. Those who design are designers. The Constructal Law of design in nature is not about the designer. It has nothing to do with “intelligent design.”

Science is the search for the laws that govern natural phenomena. Science is not the search for the designer, one or many. The latter is a much older search called religion.

A new law of physics improves everyone’s thinking ability, across the board. This has been my experience with the Constructal Law, as I lecture in universities, industry, high schools, and retirement homes. Everybody gets it.

Along the way people realize that catchy words like “intelligent design,” “turbulence,” “chance” and “randomness” are not predictive, are not “theory”. These are puzzles that the Constructal Law solves with ease, one by one.

The book Design in Nature is the story of how the Constructal Law empowers the reader to predict what had been puzzling, so that we can all move on.

Q: It seems that Darwin’s theory of natural selection led people in all disciples during the 20th century to latch onto randomness as a way of denying the primacy of a “designer.” How does randomness fit into the Constructal Law?

A: With maturing systems we generally see the hand-in-glove of diversity and pattern. Both are needed to irrigate the landscape better and better with what flows. Like in any river basin, the diverse is the actual drawing (crooked channels, wet mud, fallen trees), and the pattern is the tree design based on the rule of 4 tributaries.

Both happen more and more as the life of the evolutionary design rolls by. We see it in old river basins, animal lungs, old technologies, and 100-year old Olympic sports.

You are correct about Darwin, that his descendants latched on to randomness and chance, except that his narrative is no “theory”. It is not predictive—how can it be? It is about throwing the dice. Darwin’s narrative is at best descriptive of what might have happened en route to today.

Darwin’s ideas are strictly about animate systems. The Constructal Law is about everything, animate, inanimate, and human and machine species (about us and our extensions, contrivances, vehicles and global tapestry of links).

The Constructal Law defines in physics terms what it means to be “fit”. It defines in physics terms what it means to be “alive”, and why the “adaptable” is more likely to survive. “Freedom is good for design”, is one of my favorite lines in the book and the class room.

The Constructal Law has countless applications because it puts biological design and evolution within the realm of physics, along with everything else that did not have a home in “hard science” until now : economics, social dynamics, business, and government.

Q: We don’t usually think of physics this way, but the Constructal Law is quite hopeful. It’s about how things get better. Are you an optimistic person?

A: When you grow up under communism you have to be an optimist, to survive.

Q: You say “Freedom is good for design,” can you elaborate on that idea more?

A: Freedom is the most fundamental property of nature. Freedom means the ability of a flow configuration to change, to morph, to spread and to retreat. It is the natural property that makes all design possible.

The natural tendency expressed by the Constructal Law (toward easier flow, and greater access to inputs over time) is visible everywhere because all natural flow systems possess freedom. Without freedom to change, design and evolution cannot happen.

With freedom, a natural flow system evolves with progressively greater flow performance. Freedom is the sine qua non condition for improvements over time. Freedom is good for design.

We are all familiar with how freedom empowers design, but we take this truth for granted. We do not think about it… until freedom vanishes. To make a drawing look better, we change it, we color it, and we replace it. None of this would be possible without the freedom to change the drawing.

More freedom means to be able to change more features of the flow design. Engineering and civilization are all about this. We can make a fluid flow more easily through a pipe if we have the freedom to enlarge the pipe diameter. We can facilitate the flow even more if—in addition—we have the freedom to shorten the pipe.

Freedom can be measured. The design features that can be changed are called degrees of freedom. The pipe diameter and length are 2 degrees of freedom. The width, length and surface type of a road are 3 degrees of freedom. Power plants, cities, businesses and governments have many more. In this direction toward “more” degrees of freedom, our imagination, creativity, ingenuity—and affluence—blossom.

Freedom is not appreciated precisely because it is everywhere. Just like gravity was before Galilei’s law made it a fundamental notion in physics. Today, the Constructal Law makes freedom and its fruits (design, evolution, performance) fundamental notions in physics.

Q: But what about “bad” design, where does that come from?

A: All design is imperfect. This is a good thing, because it leaves the road wide open for discovering better flowing designs tomorrow. Imagine a world in which nothing could change because it is already perfect: no change means no life—a flow system that is not alive.

“Bad” design is a thought that emerges in retrospect. This thought is trivial, because of the dynamic (evolutionary) nature of design: yesterday’s design appears to be weaker that today’s.

A human design extension such as the wheel with wooden spokes may strike us as “bad” today, because of the modern evolution of wheel technology. Yet, in the 1700s and 1800s, the wheel with wooden spokes was a great facilitator of human movement over the landscape in comparison with the solid wooden wheel of antiquity.

The river basin serves as inanimate metaphor for the bad-design-in-retrospect phenomenon. The river channel with a tree log fallen across it may strike us as “bad”. Yet, the river water will remove the obstacle and make the river basin even better. What appears as “bad” today serves as an opportunity for better design and evolution tomorrow. Even when the tree log fell in, the river design had been perfected relative to what it had been decades earlier.

The animate metaphor for bad-design-in-retrospect is animal movement. Running animals move animal mass on land more efficiently than swimming animals move in water. Fliers move animal mass more efficiently than runners and swimmers. These designs of animal mass vehicles occurred in the time sequence predicted by the Constructal Law—swimmers then runners and then fliers—not the other way around.

Swimming was a perfected design before the emergence of runners, and running was perfected before the emergence of fliers. The old design of locomotion looked “bad” in retrospect, from the vantage point of the new. Yet, the new did not displace the old. The new and the old together move a lot more animal mass than just the old alone alone. This is the time arrow of the Constructal Law.

Q: But when it comes to design by humans, don’t we have the ability to make “bad” designs and convince ourselves that they are good? Doesn’t our self-consciousness make us uniquely suited to talking ourselves into bad, unnatural solutions that would never, otherwise occur in nature?

A: Manmade designs are natural, because on the whole they happen in the direction of facilitating and enhancing our movement on the landscape. This is the bird’s eye view, broadly speaking, the “big history” that is captured by the Constructal Law.

Not every individual detail agrees at every moment with the broad view—think of the tree log that falls across the brook and slows it. The effect is local and short lived. The constructal urge is what happens immediately, which is that the river basin marshals all its waters to remove the tree log, or to carve a path around it.

Q: So, manmade designs behave like natural flow systems if you have a long enough timeframe, but the puzzling thing for us as humans is the persistence of bad designs, of intractable configurations that limit the freedom to improve flow. What explains, for instance, the persistence of the North Korean regime, when its neighbor to the south enjoys a standard of living ten times as high?

A: Your example with North versus South Korea is very appropriate. When we fly at night from Tokyo to Seoul, we see the lights below. Over Korea, an explosion of light (power) in the South is in sharp contrast with the total darkness over the North. Why? Because power means movement, and the rigid system (communism) strangles all its flows. We see the same night contrast between the lights of Florida and the darkness of Cuba.

Six decades of strangulation are far too long for the three generations sentenced to die at the bottom of the rain barrel. Yet, this is just one frame—a blip—in the movie of design evolution of civilization in big history. Like the tree log effect, the rigid designs of North Korea and Cuba are short lived. Dictators and their enablers better pay attention to this Constructal Law prediction—it is physics, not opinion!

Before 1989, the lights of Western Europe burned in sharp contrast with the dark of Eastern Europe. Today, the sea of lights has invaded the dark swamp and set it in motion—vascularizing it with freely morphing designs. This is the future of all the swamps, and the “tree logs” that stand in the way will be removed or bypassed.

Q: If any flow system can be improved over time (given freedom), do you have a standard series of steps or procedures you use to analyze the degrees of freedom that are available in a given design configuration and identify where improvements can be made?

A: Yes, and in fact I teach the philosophy of this very topic with Prof. Sylvie Lorente in the textbook Design with Constructal Theory (Wiley, 2008) and in the course with the same name at Duke University and other leading universities all over the world. The best introduction to the method is in Design in Nature, in particular, chapters 1-5.

Here is a brief sequence of steps toward Constructal Design:

  • Define Your System: Identify clearly and unambiguously what constitutes your “system”, i.e. the region in space, or the amount of mass that is the subject of your thinking, analysis and design.
  • Identify the Flows: Make sure your system has the freedom to change, and that you understand “what flows” within it, i.e. why your system is a “flow system.”
  • Start Simple: Allow only one feature of your system to change at first. This endows your system with one degree of freedom. Study if and how changes to this feature increase the flow access of the currents that inhabit your system. Incorporate the first feature with which you found that your system performs best into your design (be alert, this is not the end!).
  • Add a Degree of Freedom: Allow a second feature to change freely. As you investigate this second degree of freedom, you will find another best feature, and adopt it. With this second feature in place, go back to step 3 and refine that first feature to work with the second.
  • And Another…: Allow a third feature to vary freely, find the best variant of this feature, and then go back and repeat steps 3 and 4, i.e refine the preceding two features.
  • And so on: This is a construction process with no end, except the finite time of the investigator.

In the evolution of technology, this sequence happens naturally, but slowly, in haphazard bursts of individual creativity. Usually, one step (one degree of freedom) represents a single invention, such as Traian Vuia’s air-tube tires on the first airplanes, one century ago. With the method of Constructal Design, I think entire companies and industries can fast forward the design evolution of their technologies and reduce trial and error.

Nature behaves in the same way, imperceptibly, all the time, and on a much broader range of degrees of freedom. This is why with the Constructal Law we have been able to predict (with eyes closed) the designs of inanimate flow systems (e.g. river basins, turbulence, snow flakes) and animate flow systems (e.g. lungs, vegetation, animal locomotion). And we can use this method to investigate and innovate social, political and technological systems as well.


Source: Forbes