ILYA PRIGOGINE: The impact of the 1977 Nobel Prize-winning chemist and physicist, Ilya Prigogine, who has died aged 86, stretched far beyond the realm of the physical sciences; he came to be regarded as one of the most influential scientific thinkers of the 20th century.
He won the prize in chemistry for research in the field of non-equilibrium thermodynamics, but underpinning much of Prigogine's work was an attempt to build a better understanding of the role of time and irreversible processes.
His ideas helped shape approaches to a wide range of disciplines, from evolution studies to traffic management. He was hailed in some quarters as "the grandfather of chaos theory", and has even been credited with influencing the works of Salvador Dalí, who was inspired by the new approaches to physics that began to emerge in the 1970s - the two met shortly before the artist's death in 1989.
The son of a factory director, Prigogine was born in Moscow, in the year of the Russian revolution. When the Bolsheviks began to target industrialists, the family fled to western Europe - first to Germany in 1921, and then to Belgium, where Prigogine eventually took citizenship in 1949. He was educated at the Athene school, and took degrees in chemistry at the Université Libre, Brussels, where he was to work for much of his professional life.
Prigogine sought to challenge the rigidity of classical physics and chemistry, specifically the second law of thermodynamics, which states that in any isolated physical system order inevitably decays. Shortly after the second World War, he demonstrated that, in a system powered by a particular energy source, structures can evolve and become more complex - what he called "dissipative structures". His concept has become known as complexity theory.
In an interview after he received the Nobel Prize, Prigogine explained his theory in terms of the development of two cities, one closed off from the outside world, the other a busy commercial hub. The first, he said, represented the closed system of classical physics and chemistry, which, according to the second law of thermodynamics, must eventually decay. The second is able to grow and become more complex, thanks to its interaction with the surrounding environment.
In the 1960s, Prigogine began to divide his time between Belgium and the US. In 1967, he became professor of physics and chemical engineering at the University of Texas at Austin, where he founded what became the Ilya Prigogine centre for studies in statistical mechanics and complex systems. He went on to hold the university's regental and Ashbel Smith chairs in physics and chemical engineering.
At the time of his death, Prigogine was director of the international Solvay institute for physics and chemistry in Brussels - a post he had held since 1959. In the 1990s, he was appointed special scientific adviser to the European Community and was named as an honorary member of UNESCO's world commission on culture and development.
His prolific output was reflected in his 20 books and almost 1,000 academic articles. He was a member of 70 academic institutions and the recipient of honorary degrees from 53 universities in more than 20 countries. He also received numerous national awards and prizes. In 1989, King Baudouin I of Belgium made him a viscount.
After his Nobel achievement, Prigogine's popularity in his adopted homeland was such that he was constantly recognised in the street, and no restaurant in Brussels would allow him to pay for a meal. But he also retained a strong sense of his roots, and invited many Russian scholars to work at the Solvay institute. From the mid-1950s, after Stalin's death, he visited Moscow regularly, staying at the old family home that, remarkably, was still occupied by relatives.
He is survived by his wife Marina Prokopowicz and sons Yves and Pascal.
Ilya Prigogine: born January 25th, 1917; died May 28th, 2003