Editing George Gamow (section)

== Big Bang nucleosynthesis ==
Gamow's work led the development of the 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.<ref>Gamow, G. (1946, October 1 & 15), Physical Review.</ref> 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 <ref>for example, Gamow, G. (1942), Jour. Washington Academy of Sciences, Vol. 32</ref> and to the subsequent condensation of matter into galaxies,<ref>Gamow, G. (1968) 'On the Origin of Galaxies', Properties of Matter under Unusual Conditions (Edward Teller 60th Birthday Volume). New York; John Wiley & Sons, Inc. Interscience Publishers.</ref> whose mass and diameter he was able to calculate in terms of the fundamental physical parameters, such as the speed of light ''c'', the Newtonian constant of gravitation ''G'', the fine-structure constant ''α'', and the Planck constant ''h''.

Gamow's interest in cosmology arose from his earlier interest in energy generation and element production and transformation in stars.<ref>Gamow, G. (1935), Ohio Journal of Science, 35, 5.</ref><ref>Chandrasekhar, S., Gamow, G. and Tuve, M., (1938), Nature, May 28.</ref><ref>Gamow, G., Schoenberg, M., (1940), Physical Review, December 15.</ref> 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 [[stellar nucleosynthesis|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]].<ref>Alpher, R. A., Bethe, H., Gamow, G., (1948), Phys. Rev., April 1. The inclusion of Bethe's name is explained at [[αβγ paper]].</ref> 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,<ref>Gamow, G., Teller, E., (1939), Nature, January 21 and March 4.</ref> 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.<ref>Gamow and Critchfield (1949), "Theory of Atomic Nucleus and Energy Sources", Clarendon Press, Oxford</ref>

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 matter at the onset of nucleosynthesis and from this the mass and diameter of the early galaxies.<ref>Gamow, G., (1948), Nature, 162, October 30.</ref> In 1953 he produced similar results, but this time based on another determination of the density of matter and radiation, at the time at which they became equal.<ref>Gamow, G., (1953), Kongelige Danske Videnskabernes Selskab, 39</ref> In this paper, Gamow determined the density of the relict background radiation, from which a present temperature of 7 K was predicted – a value which was slightly more than twice the presently-accepted value.

In 1967, he published reminiscences and recapitulation of his own work as well as the work of Alpher and Robert Herman (both with Gamow and also independently of him).<ref>{{cite journal |last1=Alpher |first1=Ralph A. |last2=Gamow |first2=George |last3=Herman |first3=Robert |title=Thermal Cosmic Radiation and the Formation of Protogalaxies |journal=Proceedings of the National Academy of Sciences of the United States of America |date=1967 |publisher=NIH |volume=58|issue=6 |pages=2179–2186 |doi=10.1073/pnas.58.6.2179 |doi-access=free |pmid=16591578 |pmc=223817 |bibcode=1967PNAS...58.2179A }}</ref> This was prompted by the discovery of the [[cosmic microwave background radiation]] by Penzias and Wilson in 1965; Gamow, Alpher, and Herman felt that they did not receive the credit they deserved for their theoretical predictions of its existence and source.{{citation needed|date=July 2021}} Gamow was disconcerted by the fact that the authors of a communication<ref>Dicke, R. H., Peebles, P. J. E., Roll, P. G., and Wilkinson, T. D. (1965), ''Astrophysical Journal'', 142, 414</ref> explaining the significance of the Penzias/Wilson observations failed to recognize and cite the previous work of Gamow and his collaborators.{{citation needed|date=July 2021}}