Evangelista Torricelli

Evangelista Torricelli (1608-47), Italian mathematician and physicist, best known for the invention of the barometer. Torricelli was born in Faenza and educated at the Collegio di Sapienza in Rome. From 1641 to 1642 he was Galileo's secretary. On Galileo's death in 1642, Torricelli succeeded him as professor of philosophy and mathematics at the Florentine Academy. Torricelli gave a definition of atmospheric pressure and in 1643 invented the barometer. He was the author of a treatise on motion, Trattato del moto (circa 1640), and Opera geometrica (1644). A unit of measurement, the torr, which is used by physicists working in near-vacuum conditions to indicate atmospheric density and barometric pressure, is named after Torricelli. See also Barometer; Vacuum.