8 - Where Did the Chemical Elements Arise?

Summary

Among the immediate beneficiaries of ‘Science – the Endless Frontier,’ the new postwar policy of closely meshing basic research with applied scientific efforts of national interest, were astrophysicists studying the origins of the chemical elements. Cosmology, in particular, underwent a profound resurgence; a field that had previously been restricted to exploring arcane mathematical models suddenly found itself anchored to real-world nuclear physics. Increasingly detailed studies of nuclear interactions also began to shed light on nuclear processes in evolved stars. A sense of renewed excitement swept through the field!

Chandrasekhar's Early Venture into Cosmology

In 1942, Chandrasekhar and his University of Chicago doctoral student, Louis R. Henrich, had postulated that the Universe at some epoch could have been extremely dense and at a temperature of a few billion degrees Kelvin. They calculated the expected thermodynamic equilibrium distribution of nuclear species at different temperatures, and sought a range in which the chemical abundances of heavy elements came close to those observed in Nature. The conditions for this to happen, they estimated, were a temperature of order 8 × 10⁹ K and a density ρ = 10⁷ g/cm³. Although their work constituted a valiant attempt, they concluded that their paper, “should be regarded as of a purely exploratory nature and that such ‘agreements’ as may have been obtained should not be overstressed.”