Charles-Augustin de Coulomb

Charles-Augustin de Coulomb was born in Angoulême in 1736 into a modest administrative family and trained at the École royale du génie de Mézières, the finest military engineering school in Europe. For nearly twenty years he served as an officer of the Corps du Génie, designing fortifications in Martinique and inspecting military works across France. The West Indian posting ruined his health but gave him his first research problem: how thick must a retaining wall be before the earth behind it would slip? That practical question produced his 1773 memoir on the mechanics of soils, the founding document of modern geotechnical engineering.

Back in France he turned to the subjects that would make his name. In 1781 he published three laws of friction — static versus kinetic, independence from contact area, proportionality to normal load — results so clean that engineers still teach them as Amontons–Coulomb friction. Four years later he built the torsion balance, an instrument sensitive enough to weigh the force between two electrified pith balls, and used it to prove what Joseph Priestley had guessed: electric force falls off as the inverse square of distance, exactly like gravity. A parallel set of experiments established the same law for magnetic poles. These two papers, delivered to the Académie des Sciences between 1785 and 1789, are the foundation on which every later equation of electrostatics rests.

Coulomb survived the Revolution by keeping his head down on a small estate near Blois. Napoleon recalled him to public service as an inspector-general of education, a position he held until his death in 1806. He was a cautious experimentalist, skeptical of grand theories, and most of his papers are organised around a single instrument and a single measurement pushed to the edge of what contemporary precision allowed. The unit of electric charge carries his name because the quantity he measured — how much force one charge exerts on another — is the quantity every later electromagnetic law takes for granted.