In 1935 he used the Heisenberg uncertainty principle to show that the strong interactions between protons and neutrons could be mediated by a boson about 200 times the mass of an electron, with the short range of the strong nuclear force being associated with the mass of the boson. This particle, which Yukawa called the meson, was discovered in 1947. Yukawa was awarded the 1949 Nobel Prize for physics for predicting the existence of the meson.