By 1948, many scientists accept the notion of an expanding universe, which must have been hot and dense when it was young. This Letter summarizes the results from Ralph Alpher's (pictured) PhD Thesis and examines how the expansion would affect nuclear reactions, thus creating the chemical elements from a primordial dense neutron gas. For a visionary model that will be modified in some aspects over time, their comparison with available abundance data shows remarkable agreement, particularly for what becomes known as Big Bang nucleosynthesis. Incidentally, Gamow added the name of Hans Bethe—who had no role in the article—to form a pun on "alpha beta gamma." (See also Phys. Rev. Focus 15, story 16.)