J. Willard Gibbs

Josiah Willard Gibbs was an American mathematical physicist whose quiet, modest lifestyle at Yale University masked an intellect that revolutionized physical chemistry and statistical mechanics. After earning the first American engineering doctorate in 1863, Gibbs studied in Paris, Berlin, and Heidelberg before becoming professor of mathematical physics at Yale—serving without salary for his first nine years.

Between 1875 and 1878, Gibbs published his monumentally influential monograph On the Equilibrium of Heterogeneous Substances. In it, he united thermodynamics and chemistry, introducing fundamental concepts including chemical potential, the Gibbs phase rule, and free energy (now called Gibbs free energy, G), which determines whether chemical reactions occur spontaneously. Furthermore, Gibbs independently invented modern 3D vector analysis (dot and cross products) and coined the term 'statistical mechanics'. Albert Einstein called him 'the greatest mind in American history.'