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Definition: Gamow, George from Philip's Encyclopedia

US nuclear physicist, b. Russia. He developed the Big Bang theory and explained (with Ralph Alpher and Hans Bethe) the abundance of chemical elements in the universe. In molecular biology, Gamow deduced the triplet code (codon) of bases in DNA. With Edward Teller, he established the Gamow-Teller theory of beta decay.

Summary Article: Gamow, George (1904-1968) from The Hutchinson Dictionary of Scientific Biography

Place: United States of America

Subject: biography, physics

Russian-born US physicist who provided the first evidence for the Big Bang theory of the origin of the universe. He predicted that it would have produced a background of microwave radiation, which was later found to exist. Gamow was also closely involved with the early theoretical development of nuclear physics, and he made an important contribution to the understanding of protein synthesis.

Gamow was born in Odessa on 4 March 1904. He attended local schools and first became interested in astronomy when he received a telescope from his father as a gift for his 13th birthday. In 1922 he entered Novorossiysk University, but he soon transferred to the University of Leningrad (now St Petersburg) where he studied optics and later cosmology, gaining his PhD in 1928. Gamow then went to the University of Göttingen, where his career as a nuclear physicist really began. His work impressed Niels Bohr who invited Gamow to the Institute of Theoretical Physics in Copenhagen. There he continued his work on nuclear physics and he also studied nuclear reactions in stars. In 1929 Gamow worked with Ernest Rutherford at the Cavendish Laboratory, Cambridge. His work there laid the theoretical foundations for the artificial transmutation of elements, which was achieved in 1932.

Gamow returned to Copenhagen in 1930. From 1931 to 1933 he served as master of research at the Academy of Science in Leningrad and then, after being denied permission by the Soviet government to attend a conference on nuclear physics in Rome in 1931, he used the Solvay Conference held in Brussels in 1933 as an opportunity to defect. He settled in the USA where he held the chair of physics at George Washington University in Washington 1934-56. He then held the post of professor of physics at the University of Colorado until his death. In 1948 Gamow was given top security clearance and worked on the hydrogen bomb project at Los Alamos, New Mexico.

Later in life, he gained considerable fame as an author of popular scientific books, being particularly well-known for the ‘Mr Tompkins’ series. He was awarded the Kalinga Prize by UNESCO in 1956 in recognition of the value of his popular scientific texts. Gamow died in Boulder, Colorado, on the 20 August 1968.

Gamow's work can be broadly divided into two main areas: his theoretical contributions to nuclear physics, and astronomy. Some of his studies fell outside both of these disciplines.

His first major scientific work was his theory of alpha decay, which he produced in 1928 while at the University of Göttingen. He was able to explain why it was that uranium nuclei could not be penetrated by alpha particles that have as much as double the energy of the alpha particles emitted by the nuclei. This, he proposed, was due to a ‘potential barrier’ that arose due to repulsive Coulomb and other forces. The model represented the first application of quantum mechanics to the study of nuclear structure, and was simultaneously and independently developed by Edward Condon (1902-1974) at Princeton University.

During his visits to Copenhagen in 1928 and 1930, Gamow continued his work on nuclear physics and in particular on the liquid drop model of nuclear structure. This theory held that the nucleus could be regarded as a collection of alpha particles that interacted via strong nuclear and Coulomb forces. His work under Rutherford in 1929 was concerned with the calculation of the energy that would be required to split a nucleus using artificially accelerated protons. This work led directly to the construction of a linear accelerator in 1932 by John Cockcroft (1897-1967) and Ernest Walton, in which protons were used to disintegrate boron and lithium, resulting in the production of helium. This was the first experimentally produced transmutation that did not employ radioactive materials.

In collaboration with Edward Teller , Gamow produced in 1936 the Gamow-Teller selection rule for beta decay. This has since been elaborated, but was one of the first formulations to describe beta decay.

During World War II, Gamow was intimately concerned with the Manhattan Project on the development of the atomic bomb, and later contributed significantly to research at Los Alamos that led to the production of the hydrogen bomb.

His astronomical studies were concerned mainly with the origin of the universe and the evolution of stars. He followed the model devised by Hans Bethe on the mechanism by which heat and radiation are generated in the cores of stars (thermonuclear reactions), and postulated that a star heats up - rather than cools down - as its ‘fuel’ is consumed. In 1938 he related this theory to the Hertzsprung-Russell diagram. The following year, in collaboration with M Schoenberg, he investigated the role of neutrino emission in novae and supernovae. He then turned to the problem of energy production in red giant stars and in 1942 produced his ‘shell’ model to describe such stars.

Gamow's most famous contribution to astronomy began with his support in 1946 for the Big Bang theory of the origin of the universe proposed by Georges Lemaître. With Ralph Alpher he investigated the possibility that heavy elements could have been produced by a sequence of neutron-capture thermonuclear reactions. They published a famous paper in 1948, which became known as the Alpher-Bethe-Gamow (or alpha-beta-gamma) hypothesis, describing the ‘hot Big Bang’. They suggested that the primordial state of matter - which they called ylem, the term Aristotle had given to the ultimate state of matter - consisted of neutrons and their decay products. This mixture of neutrons, protons, electrons, and radiation was almost unimaginably hot. As this matter expanded after the hot Big Bang, it cooled sufficiently for hydrogen nuclei to fuse to form helium nuclei (alpha particles) - which explained the abundance of helium in the universe (one atom in 12 is helium).

The model's inability to account for the presence - and evident creation - of elements heavier than helium was later vindicated by the work of Geoffrey and Margaret Burbidge and their collaborators, who found some evidence of what they called nucleosynthesis, or nucleogenesis.

The hot Big Bang model indicated that there ought to be a universal radiation field as a remnant of the intense temperatures of the primordial Big Bang. In 1964 Arno Penzias and Robert Wilson detected isotropic microwave radiation. Research at Princeton University confirmed that this was 3K (−270°C/−454°F) black-body radiation, as predicted by Gamow's model. Gamow had in fact postulated the temperature of this radiation as 25K (−248°C/−414°F), but errors were found in his method that explained why his estimate was too high. The detection of this microwave radiation led most cosmologists to support the Big Bang model, in preference to the steady-state hypothesis proposed originally by Fred Hoyle, Hermann Bondi, and Thomas Gold.

In the entirely different field of molecular biochemistry, Gamow contributed to the solution of the genetic code in which virtually all hereditable biological information is stored. The double-helix model for the structure of DNA had been published in 1953 by James Watson and Francis Crick. The double helix consists of a twisted double chain of four types of nucleotides, sugar residues, and phosphates. Gamow realized that if three nucleotides were used at a time, 64 different triplets could be constructed. These could easily code for the different amino acids of which all proteins are constructed. Gamow's theory was found to be correct, and in 1961 the genetic code was cracked and the meanings of the 64 triplets identified.

Gamow was a talented and wide-ranging scientist who, with his fundamental contribution to cosmology, was responsible for the first clear indication of the origin of the universe.

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