  Modern atomic and nuclear physics took its start in the early part of the
twentieth century, to a large extent based upon experimental investigations of
radioactive phenomena. Foremost among the pioneers of the new kind of physics
was Ernest Rutherford, who made fundamental contributions to the structure of
matter for more than three decades and, in addition, founded important research
schools in Manchester and Cambridge. This paper reviews the most important
aspects of Rutherford's scientific work in the period from about 1900 to 1920,
and it also refers to some of his last experiments of the 1930s. The emphasis
is on his theory of radioactive disintegration (1902), the discovery of the
atomic nucleus (1911), and the first artificially produced element
transformation (1919). Following the transmutation experiments, Rutherford
developed elaborate models of the atomic nucleus, but these turned out to be
unsuccessful. Other subjects could be included, but the three mentioned are
undoubtedly those of the greatest importance, the nuclear atom perhaps the
greatest and the one with the most far-reaching consequences.
