Hans Geiger

Johannes Wilhelm Geiger was born 30 September 1882, a German experimental physicist who would give radiation a voice. He carried out the Rutherford scattering experiments - firing particles at gold foil, expecting them to pass through, watching them ricochet - and in that deflection found proof of the atomic nucleus. Later he invented the Geiger counter, the device that turns ionizing radiation into audible warning. He also performed the Bothe-Geiger coincidence experiment, confirming that energy holds its ground even when light meets particle. His brother Rudolf charted weather and climate; Hans charted the invisible. He died 24 September 1945, six days short of sixty-three.