Rutherford et al (1911) determine that a tiny, plus-charged nucleus is at the core of the atom with electrons orbiting in mostly empty space. Marsden (1913) introduces the concept of the isotope to explain elemental variations. First atomic transformations achieved by alpha particle bombardment (1919).
New types of radiation observed by Roentgen (x-rays, 1895) and Becquerel (beta rays, 1898) opened study of atomic transformation via radioactive decay. Key principles are established by M. Curie (process of beta decay, 1902) and Rutherford (principle of the half life, 1904).
Contradictory results clouded the theoretical picture in beta decay until an experimental refinement by Wu and Albert demonstrated agreement with the Fermi theory. Their breakthrough involved using a soap bubble process to create a monoatomic layer of radioactive copper.
Columbia University Technical Report 173 concluded that some corrections which the authors neglected in their calculations were substantial enough to render their conclusion questionable.
Rustad and Ruby acknowledged experimental errors in a post-deadline presentation at the 1958 winter meeting of the American Physical Society. No abstract was recorded but it was later described by Ruby as "mea culpa."
Attention to the problematic He6 recoil experiment came to a head in September 1957 at the Rehovoth Conference on Nuclear Structure, the first major nuclear conference convened in Israel. Wu, T.D. Lee, E. Konopinski, Harry Lipkin and Hans Frauenfelder were among those to weigh in.