English: In 1913, Hans Geiger and Ernest Marsden performed a scientific experiment by which they proved the existence of the atomic nucleus by measuring how a metal foil scatters a beam of alpha particles. This is a mock-up of a device they used to measure how alpha particles are scattered by a metal foil in relation to the foil's thickness. The brass ring and front glass plate have been cut to better display the inner workings. This computer-generated image is based on the description provided in Geiger and Marsden's original paper, The Laws of Deflexion of a Particles through Large Angles, published in 1913.