Tuesday, April 15, 2008

John Archibald Wheeler (1911-2008)

I learnt of the passing of Johan Archibad Wheeler, undoubtedly one of the giants of theoretical physics. I am attaching below an obituary form the Telegraph.

Professor John Wheeler

Last Updated: 1:26am BST 15/04/2008

Professor John Wheeler, who died on Sunday aged 96, was, after Robert Oppenheimer and Edward Teller, the most famous non-Nobel prizewinner of the generation of scientists which developed quantum theory, though he was perhaps best known for coining the term "black hole".

Glenn Seaborg, Professor John Wheeler and President Lyndon B Johnson in 1968
John Wheeler [centre] won the US Atomic Energy Commission's Enrico Fermi Award presented by President Johnson [right]

Like Oppenheimer and Teller, Wheeler was a key figure in the Manhattan Project to develop the atomic bomb, and was active in the design and operation of the plutonium-producing reactors at Hanford, Washington. In some ways he had a greater claim than either of his colleagues to be the "father of the bomb" since he was the co-author of a ground-breaking theoretical work that underpinned it.

In the early 1930s Wheeler had studied in Copenhagen under the great Danish physicist Niels Bohr; and in 1939 he was one of the first to greet Bohr when he arrived in the United States. Bohr informed him that German scientists had succeeded in splitting uranium atoms, and within a few weeks they had jointly published a treatise entitled The Mechanism of Nuclear Fission, which described a theory of the process and served as a foundation for all future research. They proved that only uranium 235 was the fissionable element that could be used as the explosive in an atomic bomb or as fuel in a nuclear reactor. Their research also predicted the fissionable characteristics of plutonium before it had been synthesised.

Among the reticent ranks of theoretical physicists, Wheeler stood out for his flamboyance, his facility with words and his willingness to engage with popular science, a field in which he set a precedent followed by such figures as Stephen Hawking and Roger Penrose. He had a talent for inventing the catchy phrase that would lift theories from the dry scientific tomes into the popular consciousness.

The existence of "black holes" - collapsed stars which have a force of gravity so strong that nothing can escape, not even light - was predicted well before the 20th century, although their correct description had to await Einstein's theory of relativity. None the less, they had only a mathematical existence before Wheeler gave them their enigmatic moniker in 1967. The term captured the imagination of Hollywood scriptwriters and science fiction authors, and launched a huge wave of popular fascination with these gravity-defying voids.

John Archibald Wheeler was born on July 9 1911 at Jacksonville, Florida. His parents were librarians, and, as they moved from job to job, John grew up in California, Ohio and Vermont (where he recalled "going up to fetch the maple syrup every other day amid the snow"), and in Baltimore, Maryland.

Acquiring an interest in science from his parents, John read J Arthur Thompson's Outline of Science when he was 10. He was transfixed. After Rayen High School he spent a year at Baltimore City College before enrolling early as a scholarship student at Johns Hopkins University, where he not only won a prize for debating but also took a doctorate aged just 21 - on the dispersion and absorption of helium.

The early 1930s were exciting times in physics. The neutron and positron had been discovered, and the fields of nuclear physics and the quantum physics of subatomic particles were attracting the world's greatest minds. Wheeler went on to study at New York University with Gregory Breit, with whom he calculated the scattering of light with light, and at the University of Copenhagen with Niels Bohr, who had won the 1922 Nobel Prize in Physics for his investigations of the structure of the atom. "You can talk about people like Buddha, Jesus, Moses, Confucius," Wheeler said later, "but the thing that convinced me that such people existed were conversations with Bohr."

Returning to America in 1935, Wheeler was appointed assistant professor of Physics at the University of North Carolina, where he formulated and published mathematical equations to explain nuclear wave functions in electromagnetic radiation and developed the techniques and calculations for the scattering matrix hypothesis, which proved useful in later particle physics. In 1938 he joined the Physics faculty at Princeton as an assistant professor.

With the entry of the United States into the Second World War, Wheeler took leave of absence to work on the Manhattan Project, in which he conceived new techniques for the safe operation of nuclear reactors - including shielding and the elimination of noxious by-products - which have became standard procedures in nuclear engineering.

Unlike Oppenheimer and others, Wheeler never had any regrets about his participation, once observing that: "The largest hospital ever built in the history of the world was built on an island in the Pacific to take care of the casualties expected in the invasion of Japan, and I know that it was never used, and I've been thanked by at least half a dozen men who were slated to take part in the first invasion wave."

Indeed, he expressed regret that the bomb had not been ready in time to bring an early end to the war in Europe and possibly save his brother Joe, who died in combat in Italy in 1944. After the war he was a staunch defender of the German physicist Werner Heisenberg; and, despite the fact that Oppenheimer was a colleague at Princeton, he advised Edward Teller before he testified against Oppenheimer at a security hearing.

Wheeler continued to do government work after the war alongside his teaching commitments at Princeton. In 1949-50 he worked with Teller on the development of the hydrogen bomb, and between 1951 and 1953 he directed the operation of Project Matterhorn, a top-secret project to develop weaponry based on thermonuclear fuel. His passionate belief that the best research brains should be assisting in developing military weapons led to the formation of the Jason committee in 1960.

At the same time Wheeler continued to work in theoretical physics and quantum dynamics, working on Einstein's geometrical theory of gravitation for a better understanding of the problem of unifying electromagnetic and gravitational phenomena.

In 1954 he suggested a gravitational-electromagnetic entity known as a "geon", a ball of light radiation held together by its own gravity. The concept added to classical general relativity theory by explaining fields produced by bodies and the motions of bodies, and helped to rejuvenate general relativity by changing it from a preserve of mathematicians to a vital part of theoretical and observational physics. Under his leadership Princeton became the leading American centre of research into Einsteinian gravity.

In 1966 Wheeler was appointed Professor of Physics at Princeton and the following year became president of the American Physical Society. In the 1960s he published four important books: Geometrodynamics (1962), on the geometry of space; Gravitation Theory and Graviation Collapse (with BK Harrison, 1965); Spacetime Physics (with Edwin F Taylor, 1966); and Einstein's Vision (1968).

As well as his own original contributions, Wheeler left a huge mark on physics through the generations of students and academic colleagues who came under his influence and who developed his ideas. Among these were Richard Feynman, who shared the 1965 Nobel Prize in Physics for his work on quantum electrodynamics; and Hugh Everett, whose doctorate under Wheeler, which envisioned parallel universes endlessly branching out and splitting apart, inspired writers as well as cosmologists. In 1973, with two former students, Charles Misner and Kip Thorne, Wheeler published Gravitation, a book combining academic rigour with a breezy, gossipy style which helped to set a new direction in science writing and has never been out of print.

Wheeler's long-term interest in quantum theory and the measurement problem was expressed in a massive book, Quantum Theory and Measurement, written with Wojcieck Zurek (1983). His autobiography, Geons, Black Holes and Quantum Foam: A Life in Physics (co-written with Kenneth Ford) was published in 1999.

Though the Nobel, which many thought he deserved, eluded Wheeler, he won numerous awards for his work, including the US Atomic Energy Commission's Enrico Fermi Award in 1968.

In 1935 John Wheeler married Janette Hegner, who died last year. They had a son and two daughters.

1 comment:

A.P.Radhakrishna, Puttur said...

Beutifully written with full of information about great personality who was legend.