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Einstein Ceremony 2005 - Presentation of the Laureate
On 9th July, 2005, Murray Gell-Mann, one of the most famous physicists of the twentieth century, received the Albert Einstein Medal. The Nobel laureate has made significant contributions to the comprehension of elementary particle physics.


Peter Fricker, Murray Gell-Mann


Murray Gell-Mann, Peter Minkowski, Bundespräsident Schmid

Murray Gell-Mann was born on 15th September, 1929 in New York City. In 1955, he married the English archaeologist J. Margaret Dow with whom he had two children: Elizabeth Sarah, born in 1956, and Nicholas Webster, who came into the world in 1963. Margaret died in 1981. Murray Gell-Mann married Marcia Southwick in 1992 and has been recently divorced. Today he lives in Santa Fe, New Mexico.
Gell-Mann's interests extend to many subjects, including ornithology. history, historical linguistics, archaeology, and creative thinking, all of which influence his studies on the theory of complex adaptive systems. Complex adaptive systems (such as tribes, the human immune system, economic systems) are characterised by adaptability and learning aptitude and pursue general principles, although they can differ in their concrete physical appearance. Gell-Mann leaves open the question of whether the development of complex systems is a process inherent in evolution or accidental. He is also concerned with how knowledge and understanding are to be extracted from the welter of information that is available today as a result of computers and the internet. In his book, "The Quark and the Jaguar," Gell-Mann's intention to accommodate particle physics and biological and cultural evolution, natural selection, biodiversity, the human immune system, the acquisition of a language or the world economy becomes apparent.

In 1944, at the age of only fifteen, Murray Gell-Mann began his studies in physics at Yale University. In 1948, he received his B.S. After working with Enrico Fermi at the University of Chicago, he changed to the Massachusetts Institute of Technology. There he earned a doctorate in physics in January 1951 already. In the mid-fifties, Gell-Mann postulated reasons for the "strangeness" quantum number. Later, as a professor at the California Institute of Technology, he turned to the theory of weak interactions on one hand to quantum chromodynamics, which describes the strong interaction between quarks and their gauge boson, on the other. Professor Gell-Mann retired from Caltech in 1993 and subsequently moved to Santa Fe, NM, where he helped found the Santa Fe Institute, a scientific research think tank with particular interest in studying complex adaptive systems.

In 1969, Murray Gell-Mann earned the Nobel Prize in physics "for his contributions and discoveries concerning the classification of elementary particles and their interactions". This is an accurate paraphrase of what he had achieved in particle physics. Namely in the fifties, new particles were continually discovered, a progression that continued up to the seventies and involved the term "particle zoo".
To describe the properties of these proton-like and neutron-like particles with mostly short chacteristic lifetimes, physicists introduced new "labels", strictly speaking quantum numbers, in an attempt to sort out the hundreds of particles. Murray Gell-Mann was a pioneer at this. He introduced the quantum number "strangeness" on which he made demands already in 1953, independent from Katsuhiko Nishijima, to describe the peculiarly long characteristic lifetime of kaons and hyperons. Further progress for elementary particle classification was the octet model (eightfold way, following Buddhism) which Gell-Mann and Yuval Ne'eman presented in 1961.
The model made it possible to divide all the hadrons into families with eight or ten members. Even the neutron and the proton could be classified in this mathematically symmetric arrangement. Murray Gell-Mann provided the explanation in 1964, independent from George Zweig: The octet model can be understood the best when one figures the hadrons based on three and the mesons based on two even more elementary particles. Gell-Mann called these "sub-sub-atom particles" quarks, referring to: "Three quarks for Muster Mark!" from the novel Finnegan's Wake by James Joyce.
Today the existence of quarks is not in doubt; the first experimental proof for the substructure of hadrons was produced in 1974. The up-, down-, strange-, charmed-, bottom - and top- quarks carry electrical charges of plus or minus one third or plus or minus two thirds of the elementary charge. Hadrons consisting of three quarks sum, therefore, to either one elementary charge (as the protons) or two or have no charge (as the neutron).
Every quark carries a so-called colour charge. It is responsible for the strong interaction, similar to the electrical interaction which is caused by electrical charges, but more complicated. The strong nuclear force is mediated by gluons in a similar fashion to how the electromagnetic force is mediated by photons: It acts between two quarks by exchanging particles called gluons. There are eight types of gluons, each carrying a colour charge. This variety increases the number of conceivable combinations that are limited by restrictions. Similar to chemistry (description which atoms form which molecules) and nuclear physics (description which nucleus is formed by what number of protons and neutrons), quantum chromodynamics describe the cohesion of the baryons and the mesons as well as the nuclear force between nucleons.
Murray Gell-Mann was involved strongly in the development of quantum chromodynamics and is therefore considered as one of 20th century's most important theoretical physicists.

Dr. Hansjörg Friedli

 

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