Constructal Theory: The Science
Scientific thought is too often dominated by the reductionist point of view - I suppose it is the nature of the beast. In order to become established, modern scientists must spend a good portion of their lives studying some increasingly small sub-section of the natural world. Indeed, picking apart every little detail can lead to important, world changing, discoveries. But, increasingly we need to start putting the pieces back together. There have been tentative steps towards understanding these connections, and often the little steps have had tremendous impact. From Einstein's theories of general relativity and electromagnetism that enabled us to tap the energy of the atom, to Darwin's theory of evolution, the cornerstone of modern biology, we have reaped the rewards from putting pieces together. These scientists did not focus their studies on increasingly myopic topics, but instead expanded their ideas and fields in order to see the patterns in nature. Instead of being reductionists, they accepted a more holistic view while maintaining their scientific integrity, and may very well be called 'constructionists'. The theories they espoused challenged our world view, and changed our lives. Constructal Theory or CT (rather aptly named) is one theory of the same ilk.We have looked at CT in contrast to biomimicry, and drawn connections with sustainability. But what of the science? Where are the facts? Like gravity, CT is a theory. And like gravity, we can observe that the theory appears to be correct. When we have enough observations that support a theory, we can begin to say with confidence that this is indeed a scientific fact (until there is enough conflicting evidence- then we search for a new theory).
For the past ten years scientists around the world have used their expertise to observe the predictions of CT, and found ever increasing mountains of supporting evidence that it is a law of nature. Books and journal articles are emerging that cover the CT of specific fields and topics. The website dedicated to sharing this mountain of information is constructal.org. The website contains links to major publications and discussions on the issue of CT. Please feel free to delve deep into the science, a good primer would be this article (PDF) that details much of the research done recently. But for our purposes today, the following are some of the exciting ways constructal theory is expanding throughout science.
1. Climate Systems and Empirical Models
One of the hallmarks of CT's power is looking to see where it can displace an 'empirical model'. An empirical model is based only on data and is used to describe, not predict a system. An empirical model consists of a mathematical function (or equation) that captures the trend of the data. One of the problems with an empirical model is that they are notoriously poor at predicting events that have never happened before. Often the whole model must be thrown out if one element in the system has dramatically changed. Constructal threory's power on the other hand is that it explains why a system looks the way it does. This allows anyone with that understanding to predict with better accuracy, and predict the results of unprecedented events.
To get around to the point here- our climate is notoriously hard to predict. We currently use very complex empirical models consisting of multiple inputs to help us create weather and climate predictions- and as anyone who depends on the weather can tell you- we are not very good at it.
A study that looked at how CT might apply to climate systems was completed by creating a constructal model with 4 inputs-the temperature of the sun, the solar constant, cloud cover and the Earth's greenhouse factor. Out of these simple inputs the CT climate model achieved a first in all of climate science- it predicted the latitudinal boundaries of the Earth's three circulation zones - the Hadley, Ferrel and Polar cells - which comprise the main global circulation on Earth.
But that's not all...the simple model went on to achieve a good approximate speed of atmospheric and oceanic flow and the average temperature on Earth. The ability of constructal theory to displace empirical models gives us a key to understanding the results when we make unprecedented changes- something we are doing a lot of these days.
2. Biological Locomotion and Allometric laws
Another area of interest is when CT can identify or align with allometric laws. Allometric laws reflect proportionality between two elements of a biological system. For example, Kleiber's law, named after Max Kleiber, is the observation that for the vast majority of animals their metabolic rate scales to 3/4 power of the animal's mass. For example a cat, having a mass 100 times that of a mouse, will have a metabolism roughly 31 times greater than that of a mouse.
Constructal theory points out why this is the case, arguing that it is a law of all nature that there will be an inherent geometry that best distributes the imperfection, and is optimized for the many trade offs considered within the system. This inherent natural geometry applies to any organism wishing to be optimal. Most biological organism are fairly optimal most of the time, especially when you are dealing with something as serious as food, or locomotion. It is no surprise then to find CT predicts the allometric laws of biological locomotion we have observed for years in all modes of transportation (running, swimming, flying).
3. Social Dynamics and the Broad Range of Sciences
One of the newer fields constructal theory is assisting is the study of social dynamics. Adrian summarizes the seed of the idea behind this nicely.
No flow system is an island. No river exists without its wet plain. No city thrives without its farmland and open spaces. Everything that flowed and lived to this day to "survive" is in an optimal balance with the flows that surround it and sustain it. This balancing act—the optimal distribution of imperfection—generates the very design of the process, power plant, city, geography, and economics.
A new book is due out on the subject this spring. Given the broad range of scientific application it isn't surprising that there are articles from fields as diverse social science to materials science, from biology to physics- constructal theory impacts all areas of nature and all of our lives- we just didn't know it until now.