The Physics of Society

Review of

Critical Mass:

How One Thing Leads to Another

By Philip Ball

New York: Farrar, Straus and Giroux, 2004, 469 pages.

Victor J. Stenger

In his richly illustrated earlier book, The Self-Made Tapestry, Philip Ball presented many beautiful examples of self-organization in nature that provided a strong antidote for those who still labor under the delusion that mindless natural processes are unable to account for the complex world we see around us. The fact that many patterns observed in biological systems are also present in non-living systems and can be understood in terms of elementary, reductionist physics also provides an antidote for those who still labor under the delusion that special, holistic, biological processes are needed to account for the complexity of life. Simplicity easily begets complexity in the world of locally interacting particles.

In his new book, Critical Mass, Ball carries this message forward to the science of society. He shows that much of social behavior can be modeled in terms of interacting parts obeying a few simple rules. The models exhibit many of the features of physical systems such as fluids and magnets.

For example, if you graph the proportion of adults who are married versus the economic incentive to stay married you get a flattened S-shaped curve that resembles a graph of density versus pressure for certain fluids (van der Waals fluids). This implies that two possible stable states of society exist, one with a high and one with a low marriage proportion, analogous to the gas and liquid states of a fluid. Adding a third dimension for the strength of social attitudes gives the "Gibbs surface" that appears when a third dimension of temperature is added to the fluid graph.

Ball reports extensively on work being done in many institutions around the world, mostly with the aid of computer simulations. Here his examples include pedestrian and auto traffic flow, business and economics, politics, and networks, among others. I particularly enjoyed his discussion of the Internet and how it grew spontaneously, without design, into a "scale free" network that is on the one hand extremely robust against failures and on the other hand highly susceptible to deliberate attack. In fact, some epidemics, such as AIDS, seem to exhibit the same properties as computer virus epidemics rather than the forms usually assumed by medical epidemiologists. That is, they, too, are scale free.

Of course, Ball does not claim that individual human behavior can be predicted, or even that the models of social behavior imply the kind of Newtonian determinism that Enlightenment philosophers such as Thomas Hobbes assumed. Noise—that is, random fluctuations--play an important role. Humans have free will, but their decisions are still constrained to lie within limits analogous to the way the motion of a particle is constrained by conservation of energy and momentum. The large numbers involved permit statistical techniques to be used to describe overall group behavior. The result is that modeling social systems using physical principles can provide some useful insights on how me might modify our designs of highways, economic systems, political alliances, and various networks. Indeed, the models suggest how cooperative behavior and even altruism can arise naturally in systems largely governed by self-interest, and how these lead to decreasing tensions and a better chance of human survival.

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Victor J. Stenger is Emeritus Professor of Physics and Astronomy at the University of Hawaii, Adjunct Professor of Philosophy at the University of Colorado, and president of the Colorado Citizens for Science. His latest book is Has Science Found God? His Website is at http://www.Colorado.edu/philosophy/vstenger/.