1930-

American physicist whose work in particle physics led to the discovery of quarks, for which he shared the 1990 Nobel Prize for Physics. Until Friedman's experiments in the 1960s, it was thought that the proton and neutron had no internal structure. Friedman's work, carried out at high energies, showed the existence of sub-nuclear particles that scattered incident electrons in unexpected directions. This discovery was analogous to Ernest Rutherford's discovery of the atomic nucleus at the beginning of the twentieth century.