By Abdul-Aziz Mohammed
The title of this article no doubt strikes you as very odd. You probably never thought you would see the words “Social” and “Physics” juxtaposed, and are probably wondering “What on earth could bring them together?”
Well, plenty as it turns out. Not only that, the association actually goes back centuries. Around 16th-17th centuries, a notion began to take hold off some of Europe’s brightest thinkers. The notion was that there were natural laws that governed the evolution of society and that rational thinking and the appropriate scientific methods could uncover these laws. In other words, they believed in a “science of society” and also believed that this science could be deduced with the right methods. In this, they were inspired by the major breakthroughs men like Johannes Kepler, Galileo and Isaac Newton in understanding the mechanics behind the evolution of the physical universe.
One of the first of these social thinkers was the great English political philosopher, Thomas Hobbes (1588-1679). Taking a big cue from the work Galileo had done to try to understand the laws of motion, Hobbes tried by reasoning from first principles, to develop a science of human interactions, politics and society. The result of this ambitious effort is captured in his master work, Leviathan published in 1651. In adopting the methods of a scientist to come up with a political theory, Hobbes distinguished himself from most other political theorists that came before him.
When the Leviathan was published, it displeased most people because of the conclusions it drew, but it did have its admirers, if only for its method. One of them was William Petty (1623-1687), who had been a professor of anatomy at Oxford University. In fact, he felt Hobbes had not gone far enough (With the benefit of hindsight, it is however clear that Hobbes had a deeper appreciation of what a science of society should be about). This was because, though the Leviathan had been inspired by physics, it was completely qualitative in nature. William Petty felt that a science of society needed to be quantitative. Petty believed that society could only be understood to the degree that it could be measured and quantified. To this end, he wrote a book titled Political Arithmetick, in which he purported to develop, a “political arithmetic”, which he claimed could free a nation’s leaders from man’s irrationality, and be used to fashion sound and verifiable principles of governance.
Hobbes and Petty were by no means alone in this quest to develop a science of society. In the 1660s, a London-based businessman with scientific inclinations by the name of John Graunt (1620-1674), who happened to be a friend of Petty’s introduced what he referred to as the study of “social numbers” as a means to guide political policy. These social numbers captured different aspects of societal phenomena. The social numbers Graunt was most interested in were death rates. These he published in a book titled Observations Upon the Bills of Mortality. In it, he drew up tables of mortality figures, including causes of death and ages at death. The book was a hit. For all its flaws, it was yet considered a bountiful resource for those who would want to understand the ebb and flow of society. For this he was elected a Fellow of the Royal Society, the premier scientific organization of its time. Petty would continue to revise the Observations after Graunt’s death. By the year 1749, a German by the name of Gottfried Achenwall came up with the name Statistiks for the study of social numbers. This was subsequently translated to the English Statistics. At the time though, the subject merely consisted of the tabulation of numbers. It hardly contained the sophisticated mathematical techniques that have been added to the subject.
We will look at one more social thinker (there were many others), who perhaps more than any other person contributed to the development of the science of society That is the person of Adolphe Quetelet (1796-1874), a Belgian astronomer. He took the ideas of the aforementioned people and others, and weaved them all into a coherent whole. He put forth his ideas in a scientific paper titled mecanique sociale (“social mechanics”), in which he drew direct analogies between the organizing forces of the solar system and those of an orderly social system, with the aim of showing that society was as rule-based as astronomy.
Now at some point in the 19th century, all this work done by all these people striving for a science of society came to the notice of two physicists; the Briton James Clerk Maxwell (1831-1879) and the Austrian Ludwig Boltzmann (1844-1906). These two were tackling problems in the branch of physics known as Thermodynamics among other problems (Maxwell would also do groundbreaking work in the field of electromagnetism). Thermodynamics is the study of the applications of the motion of heat. Most of the fundamental breakthroughs in the field of thermodynamics took place in the 19th century and were made largely by these two men. At the time, Maxwell was studying the motion of gas particles. Maxwell was aware that the motion of individual gas particles was hopelessly random making it impossible to deduce anything intelligent about it. However, on reading a book on the progress the science of society had made up to that point, he noticed a powerful similarity to his own work in physics that suggested a way forward. From reading the book, he noticed that while it was impossible to predict when any one individual will die for example, when you study death in aggregate like in the case of the number deaths occurring in a nation, inevitably a certain kind of order and statistical regularities emerge that are amenable to intelligent analysis and can be used for the basis of forecasting. He suspected that the same would prove true for gas particles and in this he was correct. Boltzmann would put Maxwell’s work on a more secure footing. The work of the two men would lead to the emergence of a new branch of physics known as Statistical Physics. The new field would then continue to develop independently from the science of society, right up to the very present.
What has now happened in the millennium is that statistical physics is now returning the favour to the science of society. Statistical Physics has of recent started infiltrating the social sciences. Physicists are using the tools of statistical physics that they have developed over a century, to tackle contemporary social problems. I will be doing a 4- or 5-part series on how statistical physics is being used to solve modern societal problems, starting with traffic or as we call it in Nigeria, “go-slow”.
Statistical physics can now help us understand how traffic moves and how it clogs. Researchers worldwide have been devising models derived from the physics of liquids and gases which can predict when and where congestion occurs and what form it will take. Traffic has been found to have its own peculiar laws of motion.
“Traffic Physics” actually got its start in the 1950s when a fluid dynamicist by the name of James Lighthill proposed that traffic flow was rather like fluid flowing through a pipe. With the help of an academic colleague, he fashioned this insight into a theory of traffic flow known as the Lighthill-Whitham model. In this model, the individuality of drivers is submerged beneath average driving behavior, just as the theory of fluid motion ignores the vagaries of individual molecules.
Soon after, a group at General Motors developed one of the first of wat are known as car-following models. This model treated cars as discrete objects, as opposed to a flowing fluid. It also assumed that each driver modified his or her speed in response to what the car ahead did. The driver would accelerate or brake depending on two factors: the distance to the car ahead and the relative speed of the two cars.
In the early 1990s, a physicist by the name of Michael Schreckenberg of the University of Duisburg, Germany built in collaboration with a colleague, a traffic model based on the idea of a cellular automaton. A cellular automaton consists of a regular grid of cells, with each cell able to take one of a finite number of states. In the model, the road is divided into a series of cells, each of which can either be empty or occupied by a vehicle. The vehicles move from cell to cell in each time step. Each car wants to reach a preferred speed, and also wants to avoid collisions. Some randomness is added to the model is added to simulate the fact that no one accelerates or brakes perfectly.
It is fair to ask at this point whether these models truly predict real life traffic behavior or whether they are just fancy computer games. In1996, two researchers at Daimler-Benz research laboratories observed traffic patterns on the popular highway known as the autobahn that were precisely forecast by the Schreckenberg model. Another model built in 1998 by physicist Dirk Helbing and a collaborator in Stuttgart, Germany can predict with uncanny accuracy, how traffic would develop as the hours passed, when fed with real life data.
One very important insight that has come out of all this traffic physics research is that fluctuations play a crucial role in causing traffic jams. What this implies is that in many a traffic jam, there is really no “cause” as such. Jams could result simple because drivers (sometimes just a single driver) get too close to the car in front and then slow abruptly, causing the phenomenon to cascade. In other cases, the research confirms what we would consider commonsensical causes of traffic like bottlenecks, on-ramps and hills.
In the final analysis it does seem that traffic physics is proving its worth as regards traffic management. I can only hope that organizations like our Federal Road Safety Commission (FRSC) or Lagos State Traffic Management Agency (LASTMA) can hop onto this exciting bandwagon.
Bibliography
- Ball, Philip. 2005 Critical Mass: How One Thing Leads to Another. London: Arrow Books
