Geiger and Marsden
Stories from Physics for 11-14 14-16 16-19
Experimental evidence for the nucleus was first collected by Ernest Marsden and Hans Geiger in 1909. Their experiment famously required an observer to notice tiny points of light, called scintillations, produced by the impact of an alpha particle. The delicate observation needed for this work required sharp eyesight – Marsden recalls being instructed by Geiger not to put his head out of the window when travelling by train, not due to safety concerns, but in case a smoke particle damaged his vision and reduced his ability to act as a human alpha particle detector.
Geiger and Marsden served on opposite sides of the Western Front during the First World War, Geiger as an artillery officer and Marsden in the sound-ranging section of the Signal’s Corps. During the fighting, Geiger managed to communicate with Marsden by sending a letter using Niels Bohr in Copenhagen as an intermediary.