hot "big bang" theory of the expanding universe. He was the earliest to employ Alexander Friedmann's and Georges Lemaître's non-static solutions of Einstein's gravitational equations describing a universe of uniform matter density and constant spatial curvature. Gamow's crucial advance would provide a physical reification of Lemaître's idea of a unique primordial quantum. Gamow did this by assuming that the early universe was dominated by radiation rather than by matter. Most of the later work in cosmology is founded in Gamow's theory. He applied his model to the question of the creation of the chemical elements and to the subsequent condensation of matter into galaxies, whose mass and diameter he was able to calculate in terms of the fundamental physical parameters, such as the speed of light c, Newton's gravitational constant G, Sommerfeld's fine-structure constant α, and Planck's constant h. Gamow's interest in cosmology arose from his earlier interest in energy generation and element production and transformation in stars. This work, in turn, evolved from his fundamental discovery of quantum tunneling as the mechanism of nuclear alpha decay, and his application of this theory to the inverse process to calculate rates of thermonuclear reaction. At first, Gamow believed that all the elements might be produced in the very high temperature and density early stage of the universe. Later, he revised this opinion on the strength of compelling evidence advanced by Fred Hoyle and others, that elements heavier than lithium are largely produced in thermonuclear reactions in stars and in supernovae. Gamow formulated a set of coupled differential equations describing his proposed process and assigned, as a PhD dissertation topic, his graduate student Ralph Alpher the task of solving the equations numerically. These results of Gamow and Alpher appeared in 1948 as the Alpher–Bethe–Gamow paper. Before his interest turned to the question of the genetic code, Gamow published about twenty papers on cosmology. The earliest was in 1939 with Edward Teller on galaxy formation, followed in 1946 by the first description of cosmic nucleosynthesis. He also wrote many popular articles as well as academic textbooks on this and other subjects. In 1948, he published a paper dealing with an attenuated version of the coupled set of equations describing the production of the proton and the deuteron from thermal neutrons. By means of a simplification and using the observed ratio of hydrogen to heavier elements, he was able to obtain the density of