TCS Daily

The Bomb Maker

By Sallie Baliunas - September 23, 2003 12:00 AM

In the opening decades of the 20th century, Europe created the revolutionary quantum physics, the theory of the atom and its interaction with light, a theory that overturned the 19th century's mechanistic view of the cosmos. In Copenhagen one of the great early theoreticians, Niels Bohr, had as a student the young Edward Teller, who had been born in Budapest, Hungary in 1908. As the Nazis took power in the 1930s, Teller and other brilliant minds of science fled to America. Edward Teller's long and active life in physics and American defense politics drew to a close alongside the summer of 2003.


Physicists in the 19th century thought they had conquered the dark ignorance of the material world. Matter consisted of sub-microscopic, impenetrable and immutable atoms. As instrumentation advanced, experiments in the late 19th century conducted by J. J. Thompson and others indicated structure in the supposedly impenetrable atom. Thompson and Lord Kelvin imagined a "Christmas pudding" model of the atom, formed out of positively-charged material, in which negatively charged particles called electrons were imbedded. Although Thompson and Kelvin's atomic model failed to explain much that was known about how atoms acted, it encouraged Ernest Rutherford, the son of a New Zealand farmer and Thompson's brilliant student, to reach inside the atom.


Rutherford thought to shoot positively charged, energetic particles (called alpha rays) emitted by radioactive elements like uranium, into atoms in gold and other metal foils only a few thousand atoms thick. As a positive particle passes by the negatively charged electrons on its way through an atom, Rutherford reasoned, the alpha particle would be deflected, or scattered, from its otherwise straight path, but only by a small angle, if the Christmas pudding model of the atom were correct. The deflection would be smaller than about one degree out of 360 degrees. Rutherford and his students H. W. Geiger and E. Marsden began to bombard metal foils and register the deflections, nearly all of which were zero or very small angles. But not all were. Some particles shot out at right angles to the incoming beam, and a few scattered back toward the beam's source. The Christmas pudding model of the atom could not explain the large angles.


Rutherford was startled. He said, "It was quite the most incredible event that ever happened to me in my life. It was as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you."


Rutherford's experiments meant that the atom contains a very compact nucleus with the positively charged particles (called protons) packed into a region approximately one one-hundred-thousandth the diameter of the atom. If an atom were thought of as the size of the length of a football field, then the nucleus would be no larger across than one-tenth of an inch. An electron orbits the tiny nucleus with a relatively vast space between them.


With Bohr, other early theoreticians in Europe -- A. Einstein, E. Shrodinger, W. Heisenberg, W. Pauli, P.A.M. Dirac and M. Born -- molded nearly incredible ideas about the quantum world. And as Teller arrived in the United States in 1938, the atom split. Otto Hahn and Fritz Strassman in Germany (along with former colleague Lise Meitner, who had fled to Stockholm from Germany) had been shooting beams of electrically neutral particles discovered in the atomic nucleus, called neutrons, at the massive uranium atom. A neutron entering the uranium nucleus can fracture the nucleus into two nearly equal and less massive nuclei, of krypton and barium. As expected, the process releases a tremendous amount of energy, some fifty times greater than the most energetic chemical reactions.


The release of so much energy by bombarding uranium nuclei with neutrons can be increased in a chain reaction as the bombarded uranium nuclei release neutrons that cause surrounding nuclei to fission, which releases still more neutrons, etc. On the eve of the United States' entry into World War II, physicists in Germany and the U.S. realized that a powerful bomb might be created from uranium fission. Teller and others worked on the war effort's Manhattan Project to build a nuclear bomb before Germany did.


During the Manhattan Project, Teller and colleagues thought that if lighter atoms, such as hydrogen, could be squeezed together under very high temperature and pressure to undergo fusion a bomb even more powerful than the fission bomb might be built. By the end of the war, the U.S., largely because of Teller's persuasiveness, embarked on a program to build the hydrogen bomb as a strategic asset in post-World-War II politics between the U.S. and the Soviet Union.


Solving the problem of generating the extreme temperature and pressure needed to force hydrogen nuclei to fuse together was the heart of "The Super," as Teller had called the hydrogen bomb. The conceptual barrier was breeched in part by Teller and Stanislaw Ulam, a mathematician with the ability that some people have to see patterns and predict trends, for example, in card games. The Teller-Ulam idea was to carefully focus the radiation from a fission bomb to compress the hydrogen nuclei so fusion occurs. America exploded its first hydrogen bomb, called the Mike Shot, in November, 1952 on Eniwetok. Mike Shot's explosive yield was just over ten megatons, compared to the smaller yield of 15 kilotons from the fission bomb Little Boy dropped on Hiroshima.


Teller's legacy includes the development of the U.S. hydrogen bomb program as a strategy in the Cold War, as the Soviet Union proceeded to develop its hydrogen bomb. The feasibility of such an enormous weapon cannot be separated from trepidation about its use, and that emotion also shapes Teller's legacy. Beyond the nuclear bombs that Teller helped create is Teller's enormous complexity. For example, physicist Robert Oppenheimer led the Manhattan Project, but Teller's statements about Oppenheimer as a security risk meant that Teller, not Oppenheimer, would oversee the hydrogen bomb program. And shortly after his work with Ulam, Teller derided Ulam's contribution to the successful design of the hydrogen bomb.


Our culture's fear of the hydrogen bomb is appropriate; some argue that the hydrogen bomb should never have been built. But policymakers, informed of Soviet intentions to build the hydrogen bomb, had little choice but to proceed with The Super, whose legacy includes Edward Teller.


For more reading: Thirty Years that Shook Physics, by George Gamow; Introducing Quantum Theory, by J. P. McEvoy and O. Zarate; and Dark Sun: The Making of the Hydrogen Bomb, by Richard Rhodes.


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