James Van Allen (1914-2006)

Photo by Tom Jorgensen. Courtsey: University of Iowa Office of University Relations.

Physicist James A Van Allen, a pioneer in space exploration who discovered the radiation belts surrounding the Earth that now bear his name died Wednesday morning, Aug. 9, 2006, of heart failure at University of Iowa Hospitals and Clinics. He was 91.
He was Regent Distinguished Professor of Physics in the University of Iowa College of Liberal Arts and Sciences.

Van Allen gained global attention in the late 1950s when instruments he designed and placed aboard the first US satellite, Explorer I, discovered the bands of intense radiation that surround the earth. The bands, later named in his honor, spawned a new field of research known as magnetospheric physics, an area of study that now involves more than 1000 investigators in more than 20 countries.

The discovery propelled the United States in its space exploration race with the Soviet Union and prompted Time magazine to put Van Allen on the cover of its May 4, 1959, issue. Among the other accomplishments of which he was most proud was his 1973 first-ever survey of the radiation belts of Jupiter using the Pioneer 10 spacecraft and his 1979 discovery and survey of Saturn's radiation belts using data from the Pioneer 11 spacecraft.

Between 1949 and 1962 he was the leader of a number of scientific expeditions to study cosmic rays and the Earth’s magnetic field, using American ships, in the Central Pacific, the Gulf of Alaska, the Arctic, the Atlantic, Central Pacific, South Pacific and Antarctic areas. He pioneered the use of balloons, Aerobee rockets and the combination of the two, for the measurement of the intensity of cosmic rays at high altitudes. It was this work that led to his involvement in Explorer 1 and the discovery of the belts that bear his name.

Even though he retired from full-time teaching in 1985, Van Allen continued to monitor data gathered by other satellites and served as an interdisciplinary scientist for the Galileo spacecraft, which reached Jupiter in 1995.

Van Allen published more than 280 research papers in scientific journals and research monographs. He edited the book Scientific Uses of Earth Satellites (1958); co-authored Pioneer — First to Jupiter, Saturn and Beyond (1980); wrote Origins of Magnetospheric Physics (1983); wrote 924 Elementary Problems and Answers in Solar System (1993); and edited Cosmic Rays, The Sun and Geomagnetism: The Works of Scott E. Forbush (1993).

The Collected Papers of Albert Einstein, Vol. X

The 10th volume of The Collected Papers of Albert Einstein is being released this week by Princeton University Press under the editorship of the Einstein Papers Project at the California Institute of Technology. The Collected Papers of Albert Einstein is a collaborative project with participants from several countries. These volumes are edited by Diana Kormos-Buchwald, a professor of history at Caltech; Tilman Sauer, a senior research associate in history; Ze'ev Rosenkranz, Jozsef Illy, and Virginia Iris Holmes, members of the research staff in the Einstein Papers Project; and by associate editors Jeroen van Dongen, Daniel Kennefick, and A.J. Kox.

Volume 10 contains Einstein's correspondence from May to December 1920, as well as a substantial number of previously unavailable letters from 1909 to 1920, most of them written by Einstein. These originate from the bequest of family correspondence deposited at the Albert Einstein Archives at the Hebrew University in Jerusalem by his stepdaughter Margot Einstein, who stipulated that they remain closed for twenty years after her death.

In the latter half of 1920, Albert Einstein faced a series of increasingly acrimonious public attacks against his recently confirmed theory of general relativity. He considered leaving Berlin, which would have deprived Germany of its most famous scientist. Colleagues, friends, and unknown admirers offered support, while Einstein worried about the care of his two sons and ex-wife in Switzerland, and his new family in Berlin.

Scientific issues are discussed in the correspondence as well, shedding light on his associations with fellow physicists in Europe and the United States, and his lectures on the special and general theories of relativity within Germany and during his trips to Holland, Denmark, and Norway. The documents present the challenges Einstein faced as a result of his recently acquired celebrity status, his subsequent entrance into the public arena, and the contentious public attacks against relativity.

The intensity of this period, during which anti-Semitism and nationalistic sentiment seeped into scientific debate, is reflected in numerous letters. The successful completion of the intricate process of Einstein's appointment as Special Professor at the University of Leyden leads to his well-known inaugural lecture on "Ether and Relativity" in October 1920. The letters document in detail his sojourns in the Netherlands, the hospitality of many Dutch colleagues, his involvement with issues at the forefront of physics, and especially his significant intellectual and personal bonds with Paul Ehrenfest. He visits Oslo and Copenhagen, where he meets with Niels Bohr, and receives invitations to America.

The hardbound copy costs $110. The paperback copy costs $45.

[News Source: Caltech Media Relations, Pasadena, CA 91125]

Ray Davis (1914-2006)

photo courtsey: Brookhaven National Laboratory, Long Island

Ray Davis, the physics Nobel laureate of 2002, passed away on Wednesday due to complications from Alzheimer's disease at his home in New York. He was 91.

Raymond Davis Jr. was born on Oct. 14, 1914 in Washington, D.C. He received bachelor's and master's degrees in chemistry from the University of Maryland and a doctorate in physical chemistry from Yale University in 1942. Davis spent most of his career (since 1948) at the Brookhaven National Laboratory on Long Island and was a pioneer of neutrino astrophysics.

Neutrinos are small particles that travel at nearly the speed of light, have little or no mass and no charge and interact only extremely rarely with other matter. Neutrinos took centerstage in astrophysics in 1920s. The first hints that the sun was nuclear-powered appeared at that time when experiments showed that a helium atom, which contains two protons and two neutrons, has less mass than four hydrogen atoms -- essentially four protons.

British astrophysicists concluded that the fusion of four hydrogen atoms into a helium atom in the interior of the sun could release substantial amounts of energy, plus two neutrinos. Researchers calculated that only one in trillion solar neutrinos that reached Earth would strike an atomic nucleus, the rest simply passing through unnoticed.

At that time many researchers believed that detection of neutrinos which hardly ever interacts with matter would be impossible. Davis was virtually the only one who thought otherwise. In an audacious experiment, Davis set out to detect these theoretically predicted solar neutrinos. He filled a giant tank with 600,000 litres of "cleaning fluid" (chemists usually call them perchloroethylene) -- 2,300 feet underground in the Barberton Limestone Mine in Ohio in 1961. His team was looking for the occurence of very rare events when a solar neutrino would interact with a chlorine atom to produce radioactive argon. But when he added these signals up, the team found that the Sun was producing only about a third of the neutrinos it should have been based on the best solar models available.

The main problems were coming from cosmic rays and other sources of radiation which were leaking through even the depth of 2300 feet and was causing error in his estimate.

In his second attempt in late 60s Davis installed a 100,000-gallon tank of perchloroethylene 4,850 feet below the ground in the Homestake Gold Mine in Lead, S.D. This time his team synthesized 100 atoms of radioactive argon, added them to the perchloroethylene, then successfully re-extracted them. After much tedious refinements in their observational techniques the detector began observing neutrinos. Over the 30 years of experimentation, about 2,000 neutrino events were observed, demonstrating conclusively the occurrence of nuclear fusion in the sun.

The story didn't end there. In fact a new story began. The number of neutrinos detected by Davis group was only about 1/3rd of the total expected by scientists. This is what came to be known as the "solar neutrino problem." The theoretical models predicting the numbers were developed principally by the late John Bahcall of the Institute for Advanced Study in Princeton, who died in August last year. During those decades strong suspicions were raised at Davis' experiment by several scientists that it was at fault.

Ultimately, other researchers concluded that both Davis and Bahcall were right: the neutrinos produced by the Sun, which are all "electron-type" neutrinos, were oscillating into muon- and tau-like neutrinos on their journey to Earth. These could not interact with chlorine. Those two other types of neutrinos ultimately were observed, but no one would have looked for them had Davis not went forward (despite criticism and scoffing of other researchers who doubted his experiments), fighted with all kinds of challenges offered by the nature and conclusively demonstrated that neutrinos could be detected in the first place.

From time to time in order to advance science to a new level and to open new doors of the universe, we need true leaders who can come forward and accept the challenge and fight against all kinds of adversities offered by nature or man-kind and finally establish the truth and expand the horizon. Raymond Davis Jr was one such leader and he'll be remembered as the physicist who could solve the mystery of the sun.

Owen Chamberlain (1920-2006)

Owen Chamberlain, 1950s (photo courtesy: Lawrence Berkeley National Laboratory)

Nobel Laureate Physicist Owen Chamberlain died yesterday at the age of 85 in his Berkeley home. Owen was a Professor Emeritus of physics at University of California, Berkeley. Chamberlain died quietly in bed from complications of Parkinson's disease, which had plagued him for many years.

He and fellow UC Berkeley physicist Emilio Segrè, both researchers at the former Radiation Laboratory that is now Lawrence Berkeley National Laboratory won the Nobel Prize in Physics in 1959 for their discovery of the antiproton, the antimatter equivalent and negatively-charged mirror image of the proton. This previously postulated subatomic particle was the second antiparticle to be discovered and led directly to the discovery of many additional antiparticles.

Chamberlain worked on the U.S. atom bomb project from 1942 to 1946. He was present at the first atomic bomb test at Alamogordo, New Mexico, in 1945, losing a $5 bet that it would not explode.

Later, while completing his Ph.D. at the University of Chicago, he worked at Argonne National Laboratory, in Illinois. In 1948 he joined the faculty of the University of California at Berkeley, where he became a full professor in 1958. There he conducted research on alpha particle decay, neutron diffraction in liquids, and high-energy nuclear particle reactions.

His proton- and neutron-scattering experiments were conducted with the 184-inch cyclotron at the Radiation Laboratory on the hill above the campus, while his and Segrè's experiments with the antiproton were conducted with the UC Berkeley Bevatron, at the time the largest "atom smasher" in the world. Using it, Chamberlain achieved the first triple-scattering experiment with polarized protons. He and Segrè used the bevatron to produce antiprotons in 1955.

Although he retired in 1989, Chamberlain continued to attend weekly departmental colloquia at Berkeley, including one just last week.