A Critique of Constructal Theory
I previously wrote On Constructal Law and Theory, in which I highlight some really big ideas in constructal theory; ideas that I think are directly implied by the constructal law. But I also note that constructal theory remains outside the mainstream discourse in contemporary theoretical physics, astrophysics, and cosmology. This article is intended to explore why, if it is indeed a fundamental law of nature, the existence and implications of the constructal law remain absent from both popular awareness and the canon of theoretical physics. And that being the case, what might be done to reconcile one with the other.
Adrian Bejan, who discovered the constructal law, researches engineering science and applied physics in thermodynamics, heat transfer, convection, design, and evolution in nature. He is the author of 30 books and 685 peer-reviewed articles which are widely cited. He has 79,000 citations on Google Scholar, and he’s the recipient of 18 honorary doctorates from universities in 11 countries. In 2018 he was awarded the Benjamin Franklin Medal for his work in thermodynamics and “constructal theory, which predicts natural design and its evolution in engineering, scientific, and social systems.”
The constructal law, if it holds true, applies beyond ‘engineering, scientific, and social systems.’ Indeed, it must apply universally, or be rejected as a law of nature. To the extent it can be articulated mathematically and proven experimentally, constructal theory would fundamentally advance our understanding of nature and the universe, not only in the lab, or light years away, but also in ourselves and the world around us.
That said, it is twenty-five years since Bejan’s discovery and publication of the constructal law in 1996. In the 2020 NYTimes best seller, The End of Everything (Astrophysically Speaking), cosmologist and theoretical astrophysicist Katie Mack explains “Our universe is changing, and we’ve only just begun to develop the theories and observations to understand exactly how.” She goes on to exquisitely describe what we know about the universe, how we know it, and what she calls “the forces that govern its evolution.” Yet the constructal law, which governs the evolution of flow systems such as the universe and everything in it, is not referenced or acknowledged.
There are reasons and precedents that help understand this latency. It can be helpful to understand this context, and use it to help further develop and experimentally test a theory of constructal mechanics.
There is a very close relationship between the constructal law, and the laws of thermodynamics established in the 19th century. The second law of thermodynamics, like the constructal law, was discovered by an engineer and stated as an axiom, derived from experience, as fundamental as any other law of nature. As formulated by Carnot and Clausius, thermodynamics was seen as a distinct science from the Newtonian establishment, as it was not based on mechanics of particles and forces. It was based initially on steam power, for industrial use. Thermodynamics built on concepts like temperature and entropy; concepts with no counterparts in Newtonian mechanics. It was later in the 19th century that a new generation of physicists showed the principles of thermodynamics could be deduced mathematically based on probabilities in what became known as statistical mechanics.
Bejan’s work in applied physics and engineering is in a different field, using very different tools and theoretical frameworks than those used in the fields of modern theoretical physics and cosmology. The different fields are not only separated by the tools of their respective trades, but also by institutional inhibitors to cross-pollination of ideas between fields such as thermodynamics and contemporary physics based largely on quantum mechanics. Where the former was thought to be understood two centuries earlier, the latter is driven to explore the frontiers of knowledge largely focused on quantum gravity. For the past few decades, institutional research money has showered funding and prestige on quantum gravity and string theory, where something as old as thermodynamics is considered less fertile ground for fundamental new insights.
Ironically, perhaps, thermodynamics may become cool again, as efforts to unify quantum mechanics and gravity have scientists looking back to our primordial plasma and the evolution of the universe in the moments and millenia following the big bang.
Not only are the theories disconnected, they are oriented in opposing directions. Theoretical physics is focused on the most fundamental principles, in the search for a unified theory of nature. As the recently deceased Nobel laureate Steven Weinberg suggests, in Dreams of a Final Theory:
“Think of the space of scientific principles as being filled with arrows, pointing toward each principle and away from the others by which it is explained. These arrows of explanation have already revealed a remarkable pattern: they do not form separate disconnected clumps, representing independent sciences, and they do not wander aimlessly — rather they are all connected, and if followed backward they all seem to flow from a common starting point. This starting point, to which all explanations may be traced, is what I mean by a final theory.”
But Bejan’s focus on applied physics leads to published research on a multitude of descriptive examples. He writes of hundreds of familiar phenomena from academia and aircraft to water, wealth and wind. It can be fascinating to consider all these examples, but I think the focus on descriptive examples is both too much and not enough for the stewards of the standard model to pay attention to. This sentiment was shared by Weinberg, when he wrote: “The reductionist attitude provides a useful filter that saves scientists in all fields from wasting their time on ideas that are not worth pursuing.”
As my studies of physics and cosmology have thus been inspired by (and remain centered on) constructal theory, the absence of any reference to the constructal law in @AstroKatie‘s recent book about the evolution of the universe was disappointing, but not surprising. It is actually a recurring experience in my studies, in which I have yet to find an authoritative text in either subject that recognizes the constructal law or theory.
From what I can tell, this omission is neither a rejection of the theory, nor ignorance of what might seem an obscure theory from a different branch of science. It seems rather worse than that, in that it’s not even the theory, but the very natural phenomena explained by the theory is readily ignored as complexity, chaos, or the unpredictability of nature; all inadequate explanations for the predictable tendency throughout nature for all that moves to evolve not towards disorder but to order, increasing structure, and diversity.
Weinberg dismisses these beautiful and ubiquitous asymmetries in nature as ‘chaos,’ and “the intrusion of historical accidents.” Stephen Hawking dismissed the complexity of nature as “trivial and unimportant details,” attributing it entirely to the uncertainty principle. By trivial and unimportant details, Hawking was referring such natural phenomena as mountains, rivers, trees, species including ours, who won WWII, and why Madonna was pictured on the cover of Cosmopolitan.
Gravity and uncertainty alone cannot explain the rich and predictable hierarchical patterns we see throughout nature, at all scales. But the bias and blindspots in premiere physics institutions demonstrate a tendency to ignore such matters, casually writing it off as complexity, chaos, or trivial and unimportant. This poses a challenge to proponents of constructal theory, as illustrated by Weinberg’s willingness to both accept and dismiss chaos theory:
“The existence of chaos does not mean that the behavior of a system … is somehow not completely determined by the laws of motion and gravitation and its initial conditions but only that as a practical matter we can not calculate how some things evolve.”
Suggesting that reconciling the standard model with the rich asymmetries in Nature is merely a matter of historical accidents, and being able to compute the calculations, may seem misguided. As Katie Mack put it, “Physicists get a little blase about the vastness of the cosmos and forces too powerful to comprehend.”
Constructal theory effectively displaces chaos, complexity and unpredictability as explanations for the evolution and diversity of Nature. It does so based on a physical law of nature that is predictable and measurable. But for constructal theory to be accepted and reconciled with the canon of modern physics, it must turn its focus from the descriptive examples to the general principles. These principles, which I refer to as constructal mechanics, must be reconciled with quantum mechanics and the standard models for particle physics and cosmology. Bonus points for unifying quantum mechanics and gravity, a la general relativity.
It’s a tall order, but I think that’s what it will take for the constructal law to be established, as I believe it ultimately will be, alongside the other laws of thermodynamics. The reason I’ve taken up these studies is because I believe it may be possible to reconcile a theory of constructal mechanics with both quantum mechanics and general relativity.
This series of articles is intended to explore these ideas to see what can be learned. Going forward I will go deeper into my study of quantum mechanics, and what mathematician and physicist Peter Woit describes as the ‘tools of production’ for modern theoretical physics.
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