Murray Gell-Mann obituary
Murray Gell-Mann, who has died aged 89, was the leading figure in the study of elementary particle physics in the middle years of the 20th century. His work transformed the way that physicists conceive matter at the smallest length scales.
In 1950 the world of atomic and nuclear physics was relatively straightforward: atoms consisted of positively charged nuclei formed of protons and neutrons, with negatively charged electrons orbiting around them like planets round the sun, held together by photons, the quanta of quantum electrodynamics (QED). By 1975 the subject had changed beyond recognition, largely due to Murray's work. Protons and neutrons were no longer elementary particles: instead they themselves were composite structures formed of three quarks held together by gluons, the quanta of quantum chromodynamics (QCD).
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