Ernest Rutherford, at the University of Manchester, interprets the results of the alpha-particle scattering experiment on gold foil carried out by Hans Geiger and Ernest Marsden: while most alpha particles passed through the foil undeviated, a small but significant fraction was deflected at large angles, even backward — something incompatible with the then-prevailing atomic model (Thomson's "plum pudding"). Rutherford concludes that the atom's positive charge and nearly all its mass must be concentrated in a tiny, dense nucleus, with electrons orbiting around it in a mostly empty space. The nuclear model replaces Thomson's model and is the basis on which, a year later, Niels Bohr would introduce quantized energy levels.