A carpenter's son without Latin measured molecules many doubted existed
Johannes van der Waals couldn't enrol at university because he had never learned the classical languages. So the primary-school headmaster sat in on lectures as an outsider, until a change in Dutch law let the minister waive the requirement. His 1873 thesis estimated the size of molecules at a time when many physicists doubted they were real.
Born in Leiden in 1837, the eldest of a carpenter's ten children, he went to the kind of school working-class boys attended, finishing at fifteen and becoming a teacher's apprentice. He qualified as a primary teacher and head teacher, studied in his spare time to teach mathematics and physics at the new HBS secondary schools, and in 1866 took a post in The Hague, close enough to keep attending Leiden lectures. Leiden let outside students take up to four courses a year, which is how he got a foot in the door.
His thesis on the continuity of the gas and liquid states made a bold pair of assumptions: that molecules exist, and that they take up real space and pull on one another. From that he built an equation of state showing gas and liquid as two faces of one substance that shade continuously into each other. Fitting it to experiments yielded actual figures for molecular size and attraction. Maxwell praised the work in Nature. The weak pulls between molecules now carry van der Waals' name.
In 1880 he found the law of corresponding states, which recast his equation in terms of each substance's critical pressure, volume and temperature, making it universal. That guide helped James Dewar liquefy hydrogen in 1898 and Heike Kamerlingh Onnes produce liquid helium in 1908, the step that led Onnes to superconductivity in 1911.
In 1877 he became the first physics professor at the newly founded Municipal University of Amsterdam, staying until he retired at 70; his son, also a theoretical physicist, succeeded him. His wife Anna died of tuberculosis in 1881, aged 34, and he was so shaken that he published nothing for about a decade and never remarried. The Nobel Prize in Physics came in 1910, when he was 72. He died in Amsterdam in 1923.
Source: Johannes Diderik van der Waals
