Hans Geiger was a German nuclear physicist best known for his invention of the Geiger counter, a device used for counting atomic particles, and for his pioneering work in nuclear physics with Ernest Rutherford.

Johannes Wilhelm Geiger was born in Neustadt an-der-Haardt (now Neustadt an-der-Weinstrasse), Rhineland-Palatinate, Germany, on September 30, 1882. His father, Wilhelm Ludwig Geiger, was a professor of philology at the University of Erlangen from 1891 to 1920. The eldest of five children, two boys and three girls, Geiger was educated initially at Erlangen Gymnasium, from which he graduated in 1901. After completing his compulsory military service, he studied physics at the University of Munich, and at the University of Erlangen where his tutor was Professor Eilhard Wiedemann. He received a doctorate from the latter institution in 1906 for his thesis on electrical discharges through gases.

That same year, Geiger moved to Manchester University in England to join its esteemed physics department...