Simon Stevin

Simon Stevin was born in Bruges around 1548 and spent his early career as a bookkeeper and merchant's clerk before enrolling at Leiden University in his mid-thirties. He settled into a life of applied mathematics in service of the young Dutch Republic, eventually becoming quartermaster general of the States Army and tutor to Prince Maurice of Orange.

His 1586 De Beghinselen des Waterwichts (The Principles of Hydrostatics) is the first rigorous treatment of fluid pressure after Archimedes. Stevin showed, by a geometric argument involving the imaginary freezing of part of a fluid into a rigid shape, that pressure on a horizontal surface depends on the height of the fluid above it and nothing else — not on the shape of the container, not on the total mass of fluid. The result, known as the hydrostatic paradox, dissolves only once you see that the container's walls absorb the extra weight in a wider vessel. He also derived the resolution of forces on an inclined plane, eight decades before Newton, using a clever diagram of beads on a frictionless triangle.

Stevin's 1585 pamphlet De Thiende made the case for decimal fractions in commerce, engineering, and currency — a reform Europe took more than a century to adopt fully but which Stevin lived to see take root in the Low Countries. He also built sand yachts that outran horses along Dutch beaches, designed sluice systems that drained swamps into farmland, and coined much of modern Dutch scientific vocabulary.