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Day to mark the centenary of Ludwig Boltzmann's death, organized by Jacques Bouveresse, 22 November 2006

Ludwig Boltzmann

Born in Vienna in 1844, Ludwig Boltzmann committed suicide in Duino a century ago, on September 5 1906.

" At a time when the word "atom" falls daily before the eyes of the newspaper reader, the layman can scarcely form a correct representation of the difficulty that the pioneers of atomic physics had to overcome [...] to make the atomistic conception of the structure of matter obtain a validity recognized by the whole world " (E. Broda). Ironically, and tragically, it was in the years immediately following his death that the ideas Boltzmann had fought for and failed to impose himself won the day.

Boltzmann was both one of the last greats of classical physics and one of the pioneers of modern physics. " The God by whom kings reign is the fundamental law of mechanics ", he declared in 1900, at a time when novelty and the future were supposed to be represented by energeticism, and when he felt he was just about the last person who still dared to openly defend the point of view of the Ancients. But his work also had a considerable influence on modern physics, notably through Planck's work on light quanta and Einstein's on Brownian motion.

His role was absolutely decisive in the evolution and ultimate triumph of the kinetic-molecular theory of heat and matter. His name is attached, in particular, to two decisive contributions : the definition of entropy as a mathematically well-defined measure of what can be called the " disorder " of atoms, and the Boltzmann equation, which, from a historical point of view, is the first equation to describe the evolution of a probability over time. It is used today in a multitude of fields, at first sight quite different and far removed from that of the kinetic theory of gases (technology, meteorology, finance, etc.)

In physics, Boltzmann was almost as gifted as an experimenter as he was as a theorist ; and he also had a significant advantage over his opponents in the energy school, thanks to his far superior mastery of mathematics. (He himself held a chair in pure mathematics at the University of Vienna from 1873 to 1876, and subsequently maintained close relations with Felix Klein). His work is, moreover, a privileged meeting point between pure mathematics and physics ; and the future also proved him right when he wondered whether some of his most remarkable creations, whose physical significance was disputed at the time, might not be of special interest to mathematicians.

Finally, we must mention his major contribution to the philosophy of science, which is only just beginning to be truly recognized. It is generally accepted that he anticipated both some of the basic ideas of Popper's epistemology - in particular the evolutionary conception of the theory of knowledge and epistemology based on Darwin's theory, of which he was a passionate follower - and certain aspects of the Kuhnian theory of scientific revolutions. And we know from recently published manuscripts and letters that he even tried, in the last years of his life, to write a work of philosophy proper. There are serious reasons for seeing him as a representative of the Austrian philosophical tradition, whose ideas may have influenced Wittgenstein and the members of the Vienna Circle, and at times present a rather remarkable analogy with some of the theses of the philosophy " analytic " or " linguistic ".

On this day of commemoration, which brings together representatives from mathematics, physics, the history and philosophy of science, and philosophy itself, we shall try to do justice to some of the most important aspects of Boltzmann's work and the considerable legacy he has left us.