In autumn 1920, due to the cold weather and the absence of heating some lectures were only attended by one or two students. At that difficult time Nikolay Semyonov and Pyotr Kapitsa discovered a way to measure the magnetic field of an atomic nucleus. Later the experimental setup was improved by Otto Stern and Walther Gerlach and became known as Stern–Gerlach experiment. In another laboratory another student of the Institute, Léon Theremin worked on the development of electronic musical instruments. His first demonstration of the "theremin" was held in Polytechnic Institute on November 1920.