Ludwig Boltzmann spent his career arguing that atoms were real, physical entities — not just convenient mathematical fictions. The scientific establishment, led by Ernst Mach and Wilhelm Ostwald, attacked his work relentlessly, dismissing atomic theory as metaphysical speculation. In 1906, exhausted by decades of intellectual combat and suffering from depression, Boltzmann hanged himself. Within years, Einstein and Perrin proved he had been right all along.

This episode traces Boltzmann from his Austrian childhood through the statistical mechanics that linked atoms to thermodynamics, the brutal academic wars over their existence, and the suicide that preceded his vindication by only a few years.

• Boltzmann's contributions to statistical mechanics and the entropy equation carved on his tombstone
• The positivist attack — Mach ...