Like every other year, in the beginning of October, there were speculations about who would be the Nobel Prize winners in Physiology or Medicine, Physics, Chemistry, Literature, Peace and Economics. On October 5, the Royal Swedish Academy of Sciences announced that the Nobel Prize in Physics for 2021 was awarded “for groundbreaking contributions to our understanding of complex physical systems”, with one half jointly to Syukuro Manabe (Princeton University, USA) and Klaus Hasselmann (Max Planck Institute for Meteorology, Hamburg, Germany) and the other half to Giorgio Parisi (Sapienza University of Rome, Italy). The topic came as much of a surprise to many science enthusiasts, as they asked — What is a complex system?
What is a complex system?
A safety pin, invented and patented by Walter Hunt in 1849, is an example of a “simple system”. Whereas, the first human spaceflight Vostok 3KA space capsule, launched with cosmonaut Yuri Gagarin aboard in 1961, was certainly not a simple technological invention and rather a “complicated system”. Interestingly, complex systems consist of multiple, interspersed, intertwined systems of units, where the collective behaviour of their constituent units entails “emergent properties” that cannot be inferred from properties of the parts, linking them to the famous quotation from Aristotle: “The whole is more than the sum of its parts”.
Normally, systems vary from each other not only in terms of their constituents but also in how these constituents interact with one another. Though diamond and graphene are composed of identical carbon atoms, they have very different properties due to how these atoms interact with each other. Contrarily, many gases can be described by the same set of laws despite their constituent molecules being different. So, if one knows the fundamental gas law, then one can predict the properties (such as the temperature or pressure) of such a gaseous system. But, it is practically impossible to gauge the complexity of the human brain and predict its behaviour, even though one understands fairly well how a single neuron behaves. The complexity of the brain arises due to the network of neurons and their interactions!
Science of complex systems and their applications
The primary focus of most scientific disciplines is the components themselves. Thus, in the natural sciences (physical and biological), the traditionally adopted perspective was that of the reductionist ̶̶ equating a system merely as an aggregate of its parts. However, from the last few decades of the twentieth century, the focus has gradually shifted to studying the collective behaviour of the components of the complex system and of the emergent properties that cannot be predicted or even understood as an aggregate behaviour of constituents. We can try to understand this by the example of social insects like ants. Each ant will go in search of forage, following a simple set of “local rules” that governs its own actions. Very interestingly, the interactions between ants lead to emergent hierarchical social structures like the formation of ant-colony. Similar behaviour is found in many other complex systems with multiple interconnected components.
Complex systems are ubiquitous ̶̶ from ant-colonies to flocks of migrating birds; from the way humans interact within societies to patterns of transportation and telecommunication networks across the globe. Similar mathematical processes seem to describe the emergent power-laws or fractal structures across widely varying physical systems like plants, snowflakes, earthquakes, and galactical objects, as well as in socio-economic systems like income, wealth and consumption distributions in countries, stock market prices, city sizes, urban growth and migration. These mathematical laws manifest in the forms of Pareto law, Zipf law, Gutenberg-Richter law, etc.
Over the entire course of the universe’s evolution, new entities and even new laws governing those entities have emerged. This emergence will continue. Therefore, it is heartening to see that ‘emergence’ has reappeared in science after making a brief introduction in the early 20th century. The whole philosophy of the complex systems approach is a paradigmatic shift in the way of doing science. It is a more holistic approach.
Pioneering Indian contributions and centres
Several groups of Indian researchers have made pioneering contributions to the field of complex systems specifically in the areas of income and wealth distributions, financial markets, social networks, etc. Also, many of the premier educational institutions like Jawaharlal Nehru University, IIT Madras, ICTS-TIFR, etc. have been conducting Masters and post-graduate programmes in complex systems or complexity science. Since large quantities of data and cheap computational power are now available, complexity scientists are discovering new understandings and making radical scientific breakthroughs. For a developing country like India, the advancement in complexity science will have far-reaching consequences in society and further influence the breakthroughs in health, welfare, environment and many other intricate problems.
Prof Anirban Chakraborti is the Dean of the School of Engineering and Technology, BML Munjal University, Gurugram (anirban.chakraborti@bmu.edu.in). Dr Kiran Sharma is an Assistant Professor at the School of Engineering and Technology, BML Munjal University, Gurugram (kiran.sharma@bmu.edu.in). Views expressed are their own
