Prigogine, Ilya (1917–2003)

It is unusual that a winner of the Nobel Prize in chemistry succeeds in arousing a continuing interest of nonscientists in his research. Ilya Prigogine, who won that most prestigious award in 1977, is the exception that proves the rule. His study of the thermodynamics of irreversible processes not only is important in the history of science but also may have far-reaching implications for the philosophical understanding of time, which Prigogine discussed in a series of popular books read by a wide audience.

Ilya Romanovich Prigogine was born on January 25, 1917, in Moscow. Because his family had trouble with the Soviet regime that had been established after the October Revolution, the Prigogines emigrated in 1921 to Germany and in 1929 to Belgium. Prigogine studied chemistry at the Free University in Brussels, where he also became professor after the Second World War. In 1959, he was appointed director of the International Solvay Institutes in Brussels and professor at the University of Austin in Texas. There he also founded, in 1967, the Center for Statistical Mechanics and Thermodynamics. For his scientific work, Prigogine was honored not only by the Nobel Prize but also by more than 50 honorary degrees as well as by a Belgian title of nobility, viscount. On May 28, 2003, Prigogine died in Brussels.

Prigogine's principal field of research was thermodynamics, the science of energy and its transformations. Classical thermodynamics studies closed systems—systems that are thermically isolated from their environment and whose entropy can, according to the second law of thermodynamics, only be constant or increase. On a macroscopic level this means that closed systems become more and more disordered. Yet everyone can observe physical systems that, at least temporally, show an increase in order, for example, organisms. These are open systems; that is, systems that, by constantly exchanging energy with their surroundings, increase their internal order. To develop and maintain the complexity of their bodies, organisms must eat, breathe, and excrete. It is, however, not the case that every open system is able to increase its own complexity; only open systems that are far from thermodynamic equilibrium self-organize (equilibrium means a state in which the forces acting on the system are in balance). Prigogine called nonequilibrium systems dissipative structures, and he tried to apply their thermodynamic analysis not only to organisms but also to social systems.

A characteristic feature of dissipative structures is that they are historical systems: The processes by which they originate, develop, preserve themselves, and dissolve are irreversible. Prigogine's theory of nonequilibrium systems can thus be regarded as a physics of history. He considered his model of dissipative structures to be more realistic than the classical models of closed systems and near-equilibrium open systems. Consequently, regarding the basic ontological categories of natural science, Prigogine argued passionately for a revolution whose maxim is succinctly expressed by the title of one of his books on philosophy of nature, from Being to Becoming (1980). In this work, two concepts of time are distinguished. The concept of external and universal time refers to time as a parameter of motion; it is used when we want to communicate about processes and use clocks as instruments to quantify the succession of events by counting conventionally fixed units. The concept of internal and individual time refers to time as a property of the development of physical systems; it is used when we want to determine the intrinsic age of a system by counting the number of irreversible transformations of a certain type that have been generating the present state of the system.

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