history. As Janov Pelorat, a character in the later novels of the Foundation series, explained:

Hari Seldon devised psychohistory by modeling it upon the kinetic theory of gases. Each atom or molecule in a gas moves randomly so that we can’t know the position or velocity of any one of them. Nevertheless, using statistics, we can work out the rules governing their overall behavior with great precision. In the same way, Seldon intended to work out the overall behavior of human societies even though the solutions would not apply to the behavior of individual human beings.7

In other words, put enough people together and the laws of human interaction will produce predictable patterns—just as the interactions and motion of molecules determine the temperature and pressure of a gas. And describing people as though they were molecules is just what many physicists are doing today—in effect, they’re taking the temperature of society.

One of the best ways to take that temperature, it turns out, is to view society in terms of networks. In much the same way that “temperature” captures an essential property of a jumble of gas molecules, network math quantifies how “connected” the members of a social group are. Today’s new network math applies statistical mechanics to all sorts of social phenomena, from fashion trends and voting behavior to the growth of terrorist cells. So just as Asimov envisioned, statistical physics has been enlisted to describe human society in a mathematically precise way.

For the most part, this merger of network math and statistical mechanics has been exploring human behavior without recourse to the modern views of game theory built on Nash’s math. After all, Nash’s original formulation had its limits; what works on paper does not always play out the way his math predicts in real-world games. But the latest research has begun to show ways that game theory can help make sense out of the intricate pattern of links in complicated networks. The game theory approach may be able to induce the world of complex networks to more readily surrender its secrets.

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