Einstein's only experiment
On the occasion of the central annual meeting of the Deutsche Physikalische Gesellschaft (DPG – German Physical Society) an exhibition was opened in the context of the awarding of the DPG prizes on 6 March 2005 in the Hermann von Helmholtz building of the Berlin Institute, in which Einstein‘s only publicized experimental work, carried out 90 years earlier in the Berlin Physikalisch-Technische Reichsanstalt (PTR), was documented.
Immediately upon his arrival in Berlin in the year 1914, Einstein utilized the outstanding experimental opportunities in the PTR and observed, together with his Dutch colleague Johannes Wander de Haas the rotary oscillation of a small iron cylinder stimulated bymeans of an alternating magnetic field. The cause of the magnetism of the cylinder he conjectured to be the magnetic moments of the electrons in the cylinder material, the cause of which one assumed to be the ampere molecular currents. By aligning the momentsin the field of a coil, it was possible for Einstein and de Haas to enable the cylinder to rotate: the Einstein-de Haas effect was discovered and the so-called "gyromagnetic ratio" of the electrons was determined. The correct interpretation today identifies the effect as the impact of the then still unknown electronic spin.
The historical experiment can be viewed and set into operation as a trueto- the-original and functional replica. It is framed in the exhibition by other examples of historical and modern easuring techniques which utilize the properties of electrons.
Replica of the historical Einstein-de Haas experiment in the PTB