In the 1940s, geologist Hans Suess speculated that the regularity that was observed in the abundances of elements may be related to structural properties of the atomic nucleus. These considerations were seeded by the discovery of radioactivity by Becquerel in 1896 as an aside of advances in chemistry which aimed at production of gold. This remarkable possibility for transformation of matter created much excitement among physicists for the next decades, culminating in discovery of the atomic nucleus, with milestones in Ernest Rutherford 's scattering experiments in 1911, and the discovery of the neutron by James Chadwick (1932). After Aston demonstrated that the mass of helium is less than four times that of the proton, Eddington proposed that, through an unknown process in the Sun's core, hydrogen is transmuted into helium, liberating energy. Twenty years later, Bethe and von Weizsäcker independently derived the CN cycle, the first known nuclear reaction that accomplishes this transmutation. The interval between Eddington's proposal and derivation of the CN cycle can mainly be attributed to an incomplete understanding of nuclear structure. The basic principles for explaining the origin of elements and energy generation in stars appear in the concepts describing nucleosynthesis, which arose in the 1940s, led by George Gamow and presented in a 2-page paper in 1948 as the Alpher–Bethe–Gamow paper. A complete concept of processes that make up cosmic nucleosynthesis was presented in the late 1950s by Burbidge, Burbidge, Fowler, and Hoyle, and by Cameron. Fowler is largely credited with initiating collaboration between astronomers, astrophysicists, and theoretical and experimental nuclear physicists, in a field that we now know as nuclear astrophysics (for which he won the 1983 Nobel Prize). During these same decades, Arthur Eddington and others were able to link the liberation of nuclear binding energy through such nuclear reactions to the structural equations of stars.