George Gamow

George Gamow

The Russian-American physicist George Gamow (1904-1968) made important contributions to nuclear physics. He also did significant work in the fields of astrophysics and biology and wrote books popularizing science.

George Gamow was born in Odessa, Russia, on March 4, 1904. He became interested in physics at an early age, and when he was 18 he enrolled in the physico-mathematical faculty at Novorossia University in Odessa. After a year he transferred to the University of Leningrad, from which he eventually received a Ph.D. in 1928. That summer he visited the university in Göttingen, Germany. His work impressed the Danish physicist Niels Bohr so much that he was invited to be a fellow of theoretical physics at the University of Copenhagen. He remained in Denmark for one year, then spent the next year studying with Ernest Rutherford at the Cavendish Laboratory in England. He subsequently returned to the University of Copenhagen for another year.

In 1931 Gamow accepted the position of professor of physics at the University of Leningrad. After denying him permission to leave the country for two years, the Soviet government allowed him and his wife, Lynbov Vokhminzeva, to attend the 1933 Solvay Congress in Belgium; he took this opportunity to leave the Soviet Union forever. He spent the rest of the year at various scientific institutions all over Europe and was appointed professor of physics at the George Washington University in Washington, D.C., in 1934. Gamow remained there until 1956, when he transferred to the University of Colorado and divorced his wife. He married Barbara Perkins in 1958, and they remained in Colorado until his death in 1968. His career was extremely diverse: he delved into nuclear physics, astrophysics, biology, and writing.

Gamow's first major contribution to nuclear physics took place in Göttingen. He was intrigued by an unusual phenomenon that Rutherford had reported as a result of an alpha particle scattering experiment. When a uranium sample is bombarded with alpha particles (positively charged particles composed, like helium nuclei, of two protons and two neutrons), the particles are repelled by the electrostatic force exerted on them by the uranium nuclei, which are also positively charged. However, a uranium nucleus already contains alpha particles, and these remain there for a long time because the repulsive force exerted by a nucleus on alpha particles is overcome by the attractive force of the strong nuclear interactions at very close distances. The classical theories of physics maintained that the particles could never leave the nucleus because of the barrier that is created at the distance where the repulsive force becomes an attractive one. What puzzled Rutherford was that some alpha particles do leak out of the nucleus, though very slowly.

Gamow applied the new wave mechanics theories to this problem. In wave mechanics, the motion of particles is determined by "pilot waves," which are waves that can penetrate through any barrier. He showed that the alpha particles were in a sense "riding" on the pilot waves, enabling them to "tunnel" out through the barrier. This theory explained not only Rutherford's puzzle but also the relationship between the alpha particles emitted by different radioactive substances and the half-lives of the substances.

Gamow's second major contribution to nuclear physics was in the form of the Gamow-Teller selection rule for beta decay, a process whereby the nucleus of a radioactive atom emits an electron, thereby transforming itself into a different atom. In his theory of beta decay, Enrico Fermi had said that the electron leaves the nucleus straight out along the radius vector. Working with Edward Teller, Gamow showed that the electron could escape just as easily by moving in a hyperbolic trajectory. This discovery brought considerable insight into the magnetic interaction between the electron and the nucleus.

After this work Gamow turned his attention towards the application of nuclear physics to astrophysics. There had been previous, unsuccessful attempts to explain the abundance of nuclei in the cosmos in terms of thermodynamic equilibrium conditions. One of the problems with this approach was that the conditions for the formation of heavier nuclei were not the same as those for the formation of lighter nuclei. Gamow advocated the theory of the big bang and the expanding universe as a means of resolving the problem. He theorized that before the bang there was a fundamental state of matter he called "ylem" that consisted of a mixture of neutrons, electrons, and protons held together in a ball of high energy radiation. This ball then exploded and began to expand, allowing the fundamental particles to combine and form nuclei, and, eventually, elements—this is a process known as nucleo synthesis. He suggested that because such a universe was continually expanding, and hence changing, there would be sufficiently diverse conditions for elements of all different atomic weights to form in a non-equilibrium process. This theory also led Gamow to predict that there should be a certain level of remnant radiation from the big bang. This radiation was discovered accidentally almost 20 years later by researchers at Bell labs.

In 1954 Gamow turned to the field of biology, building on the work done by Francis Crick and James Watson on the helical structure of DNA (deoxyribonucleic acid). Gamow's work was in genetic coding theory, which deals with the way information is transferred in the genes. He used combinatorial mathematics to show that it was possible to establish the validity of certain proposed coding schemes by studying known sequences of amino acids.

Gamow also wrote many books popularizing science in an entertaining, innovative manner. This achievement won him the UNESCO Kalinga Award in 1956. He was a member of numerous scientific societies, among them the American Physical Society, the Washington Philosophical Society, the International Astronomical Union, and the Royal Danish Academy of Sciences and Letters.

Further Reading

Among the many books Gamow wrote to explain science to the layman are the well-known Mr. Tompkins books. Mr. Tompkins in Wonderland (1940) explains the theory of relativity, and Mr. Tompkins Explores the Atom (1944) discusses modern theories of the atom. He wrote several books on cosmology, including The Moon (1953) and a trilogy published in 1955 composed of The Birth and Death of the Sun, Biography of the Earth, and The Creation of the Universe. He had also been working on an autobiography, My World Line, at the time of his death. Incomplete, the book was published post-humously in 1970. □