When Ernest Rutherford arrived in Manchester at the end of May 1907, he was not greeted by his predecessor, Arthur Schuster, who was on the move, but by the latter's assistant: a 23-year-old German researcher named Hans Geiger.

The young man is on the way out: he has only come to England for a one-year internship and is preparing to return, at the start of the following school year, to Erlangen, Bavaria, where he was trained. He plans to continue his work there on the behavior of gases subjected to electric shocks.

But Rutherford's personality impresses him; and Rutherford himself is enthusiastic about the seriousness of the young German.

Eventually, Geiger will stay five more years with the New Zealand physicist. And he would participate in some of Rutherford's greatest discoveries of that time, including the structure of the atom (which would become the Bohr & Rutherford model of the atom).

It is also in Manchester that he will develop an idea of his boss with which his name will remain associated: a particle counter, the ancestor of the Geiger-Müller counter still used today to determine the amount of ionizing radiation.