  Solar energy remained an enigma for nearly a century. For a while astronomers
and physicists believed that the source of the Sun's energy was gravitational
contraction, but the theory turned out to be untenable. Inspired by the new
science of radioactivity, by the early twentieth century they increasingly
focused on subatomic processes. The paper outlines the attempts to solve the
solar energy problem in the period from about 1905 to 1938, which in the later
phase involved nuclear astrophysics, a new and exciting interdisciplinary
science. Although the problem was only satisfactorily solved with Hans Bethe's
theory of the late 1930s, the earlier attempts involving scientists such as
Arthur Eddington, Robert Atkinson and George Gamow can be considered a slow
preparation for Bethe's breakthrough.
