Gerolamo Cardano

Gerolamo Cardano was born in Italy in 1501 and trained as a physician, but his restless intellect wouldn't stay in one discipline. He gambled seriously enough to study chance itself, introducing binomial coefficients and laying groundwork for probability theory in the West. In 1545 he published Ars Magna, the first European work to systematically use negative numbers and to acknowledge imaginary numbers; it also included solutions to cubic and quartic equations he credited to other mathematicians. Between medical practice and mathematical breakthroughs he invented mechanical devices - the combination lock, the gimbal's three concentric rings for free rotation, and the Cardan shaft with universal joints that still transmits rotary motion in vehicles. He described hypocycloids in 1570; the generating circles later bore his name and drove the first high-speed printing presses. By his death in 1576, six days before his 75th birthday, he'd written more than 200 works and become one of the most influential mathematicians of the Renaissance.