Johannes Geiss: The Humble Beginnings of an Octogenarian

Abstract

Johannes Geiss studied physics at Gottingen University at a time when luminaries like Max Planck, Max v. Laue, Werner Heisenberg and Carl Friedrich v. Weizsacker were teaching there and luminaries-to-be like Hans Georg Dehmelt and Wolfgang Paul were just starting their careers, next door in the same institute. Johannes started out in the lofty spheres of theoretical physics working with Max v. Laue on problems in superconductivity (Geiss 1951a, 1951b). Somehow, the theoretical work did not quite appeal to him so he returned down to earth and measured the isotopic composition of so-called “common lead” (Geiss 1954), with Wolfgang Paul his thesis adviser and Friedrich Houtermans taking a lively and keen interest in the results and their interpretation. In those days, only little more than 50 years ago, mass spectrometric isotope abundance measurements were a tedious affair, not at all comparable with the operation of modern semi-automatic instruments. Strip chart recorders, although already available, were not affordable at Gottingen in those destitute post-war years, so the ion currents had to be measured by means of mirror galvanometers, preferably at night when there was nobody else in the laboratory to interfere with the measurements. The magnetic field had to be tuned by hand; readings of the position of the light spot from the galvanometer mirror, on a translucent scale, had to be taken and the numbers jotted down, all in a semi-darkened room. But