The Benard instability is a spectac

The Benard instability is a spectacular example of spontaneous self-organization. The nonequilibrium that is maintained by the continual flow of heat through the system generates a complex spatial pattern in which millions of molecules move coherently to form the hexagonal convection cells. Benard cells, moreover, are not limited to laboratory experiments but also occur in nature in a wide variety of circumstances. For example, the flow of warm air from the surface of the earth toward outer space may generate hexagonal circulation vortices that leave their imprints on sand dunes in the desert and on arctic snow fields.2 4 Another amazing self-organization phenomenon studied exten­ sively by Prigogine and his colleagues in Brussels are the so-called chemical clocks. These are reactions far from chemical equilib­ rium, which produce very striking periodic oscillations.2 5 For ex­ ample, if there are two kinds of molecules in the reaction, one "red" and one "blue," the system will be all blue at a certain point; then change its color abruptly to red; then again to blue; and so on at regular intervals. Different experimental conditions may also produce waves of chemical activity (see figure 5-2).To change color all at once, the chemical system has to act as a whole, producing a high degree of order through the coherent activity of billions of molecules. Prigogine and his colleagues dis­ covered that, as in the Benard convection, this coherent behavior emerges spontaneously at critical points of instability far from equilibrium.During the 1960s Prigogine developed a new nonlinear thermo­ dynamics to describe the self-organization phenomenon in open systems far from equilibrium. "Classical thermodynamics," he ex­ plains, "leads to the concept of 'equilibrium structures' such as crystals. Benard cells are structures too, but of a quite different nature. That is why we have introduced the notion of 'dissipative structures,' to emphasize the close association, at first paradoxical, in such situations between structure and order on the one side, and dissipation . . . on the other."2 6 In classical thermodynamics the dissipation of energy in heat transfer, friction, and the like was always associated with waste. Prigogine's concept of a dissipative structure introduced a radical change in this view by showing that in open systems dissipation becomes a source of order.