27 November 2008

Operatic Atom Bombs

Dr Atomic
I'd wager the average person rarely (if ever), spends a Friday evening indulging in Die Meistersinger von Nurnberg, but operas aren't always long-winded scenes of voluptuous, ornately dressed characters bellowing incomprehensibly.

Producer John Adam's Doctor Atomic is a two-act opera about the making of the Atom Bomb, the nuclear weapon that was eventually dropped on Hiroshima and Nagasaki near the end of World War II.

The setting is the summer of 1945, in the desert of Los Alamos, New Mexico, where J. Robert Oppenheimer and a team of scientists gathered to build and test the bomb for the first time.

The opera focuses on renowned physicist Robert Oppenheimer and his scientific and moral dilemma surrounding the Los Alamos project-with lots of science thrown in. Created from various sources ( including declassified government documents), the text or libretto of the opera is littered with discussions on uranium and plutonium, the TNT equivalency of the bomb, and whether or not a test explosion might set the atmosphere on fire-an indisputably bad scenario.

In addition to being a brilliant theoretical physicist (he received his PhD at age 22), Oppenheimer loved the arts and culture; it is widely know that he decided to learn Sanskrit in order to read the Bhagavad Gita. He was appointed scientific director of the Manhattan Project after years of contributions to quantum mechanics, nuclear physics, spectroscopy, and astrophysics. He was first to publish a paper in the 1930s suggesting the existence of what now call black holes.

Atomic energy is created by the splitting (fission) or joining (fusion) of atoms- but only by using specific isotopes of uranium or plutonium can a massively destructive explosion be reached. The two atomic bombs detonated over Hiroshima and Nagasaki relied on fission.

Elements undergoing fission ( for example uranium) release neutrons. Some neutrons are scooped up by other uranium nuclei leading to more fission, while others escape the process altogether. If the expected number of neutrons which trigger new fissions is less than 1, a nuclear chain reaction may occur but the size will decrease exponentially.

Nuclear Fission Reaction
If the expected number of neutrons is greater than 1, the chain reaction will increase exponentially. The term 'critical mass' describes the point at which the expected number of neutrons causing fission is 1 or more, thus becoming a self-sustaining chain reaction.

The bomb released over Hiroshima used TNT to blow subcritical masses of uranium 235 together, resulting in a 10 kiloton explosion. "Fat man", the bomb used against Nagasaki was a subcritical mass of plutonium 239 squeezed to bit by TNT and causing a 20 kiloton explosion.

If you find yourself in the mood for an operatic pondering of nuclear fusion and fission, Dr. Atomic will finish a run at the Metropolitan Opera in New York Thursday November 12, ad then travel to London at the English National Opera.

www.physicscentral.com

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