Boltzmann's tombstone carries the entropy formula his rivals refused to accept
Ludwig Boltzmann explained heat and disorder by counting the countless ways atoms can arrange themselves. Many leading scientists of his day denied atoms existed at all, and he spent his last years defending them. Within a few years of his death in 1906, experiments proved him right.
Born on 20 February 1844 in Erdberg, on the edge of Vienna, Boltzmann was the son of a tax official and grandson of a clockmaker from Berlin. He was taught at home until ten and lost his father at fifteen. At the University of Vienna, the physicist Josef Stefan handed him James Clerk Maxwell's papers on gases, and at just 25 he became a full professor of mathematical physics at Graz.
Maxwell had used statistics to describe how fast gas molecules move. Boltzmann pushed much further, extending the distribution to liquids and solids and writing the first equation for how such a distribution changes over time. His central insight was that systems drift toward disorder simply because disordered arrangements vastly outnumber orderly ones. In 1877 he gave entropy its modern definition as a constant times the logarithm of the number of microscopic arrangements, and Max Planck later named that constant after him. He even toyed with discrete energy levels, treating them as a mathematical convenience, which makes him a forerunner of quantum theory.
Graz gave him 14 happy years. In 1872 he met Henriette von Aigentler, a would-be science teacher barred from auditing lectures, and backed her successful appeal; they married in 1876. His students included Svante Arrhenius, Walther Nernst, Paul Ehrenfest and Lise Meitner. When he took over Ernst Mach's philosophy course in Vienna in 1903, crowds spilled down the staircase and the emperor invited him to a reception.
Mach and Wilhelm Ostwald argued that energy, not matter, was fundamental, and a leading journal editor would let Boltzmann call atoms only convenient fictions. Struggling with what might now be recognised as bipolar disorder, he resigned in May 1906 and took his own life that September while on holiday near Trieste. Jean Perrin's colloid experiments of 1908 and 1909 soon confirmed the reality of atoms, and Boltzmann's formula is carved on his grave in Vienna.
Source: Ludwig Boltzmann
