Johannes Diderik van der Waals

Johannes Diderik van der Waals was a Dutch theoretical physicist born 23 November 1837, who started his career teaching school before becoming the first physics professor at the University of Amsterdam in 1877. In his 1873 thesis, he tackled the problem of real gases behaving differently than ideal theory predicted, introducing an equation of state that accounted for the finite volume of molecules and the forces between them - at a time when many physicists, led by Ernst Mach and Wilhelm Ostwald, denied molecules even existed. His equation revolutionized the field: it affirmed the reality of molecules, allowed scientists to estimate their size and attraction, and gave them the tools to predict the critical points at which gases liquify. That work enabled the liquefaction of nitrogen, oxygen, hydrogen, and helium - Heike Kamerlingh Onnes used van der Waals's insights to make liquid helium in 1908, which led directly to the 1911 discovery of superconductivity. Van der Waals received the Nobel Prize in Physics in 1910 and died 8 March 1923, his name now attached to the forces, molecules, and radius that define molecular science.