On 7 March 1911, Ernest Rutherford attended a meeting of the Manchester Literary and Philosophical Society, the society before which a century earlier John Dalton had reported the measurement of atomic weights. At the 1911 meeting Rutherford announced the discovery of the atomic nucleus. The American Physical Society has decided to mark the date as the beginning of a century of elementary-particle physics.
I think it’s a wise choice. For one thing, the experiment on which Rutherford based his conclusion about the nucleus, carried out under Rutherford’s direction by Hans Geiger and Ernest Marsden, was a paradigm for the scattering experiments that have been an occupation of particle physicists ever since. Only instead of a beam of protons or electrons from an accelerator, Geiger and Marsden used alpha particles from the radioactive decay of radium, incident on a gold foil target. And instead of wire chambers or spark chambers or...
