Ernest Walton was an Irish experimental physicist who gained renown for achieving, with physicist John D. Cockcroft, the first artificial disintegration of an atomic nucleus, without the use of radioactive elements. Their breakthrough was accomplished by artificially accelerating a beam of protons (basic particles of the nuclei of atoms that carry a positive charge of electricity) and aiming it at a target of lithium, one of the lightest known metals. The resultant emission of alpha particles, that is, positively charged particles given off by certain radioactive substances, indicated not only that some protons had succeeded in penetrating the nuclei of the lithium atoms but also that they had somehow combined with the lithium atoms and had been transformed into something new. Although the process was not an efficient energy producer, the work of Walton and Cockcroft stimulated many theoretical and practical developments and influenced the whole course of...