Evangelista Torricelli

Born 15 October 1608, Torricelli studied under Benedetto Castelli and made his name young in mathematics and physics. In 1643 he inverted a glass tube filled with mercury into a dish and watched it settle at a fixed height — the column held up by atmospheric pressure, the space above it a vacuum. The experiment answered why water pumps failed past a certain depth and introduced the barometer to the world. He also advanced optics and contributed to the method of indivisibles, a precursor to calculus. He died 25 October 1647, nine days past his thirty-ninth birthday; the unit of pressure, the to…