Teaching the History of the Manhattan Project

By B. Cameron Reed, Alma College, reed@alma.edu

Students at the Trinity Test Site monument
Photo courtesy of Ed Neuenschwander and the Society of Physics Students.

Students at the Trinity Test Site monument.

The development of nuclear weapons during the Man­hattan Project in World War II is one of the most significant events of the twentieth century. The strategic, scientific, national policy, and security issues asso­ciated with nuclear weapons are never far from the headlines and will remain with us for gen­erations to come. If asked "What was the Manhattan Project and who was involved with it?", many individuals would prob­ably answer that it had some­thing to do with the making of atomic bombs and perhaps offer a name such as Oppenheimer or Fermi or (erroneously) Einstein. Beyond that, knowledge would likely become fuzzier, with some aware that the Trinity bomb was tested in New Mexico before Little Boy and Fat Man were dropped on Hiroshima and Nagasaki. While some respondents would know that those devices used uranium and plutonium as their "active ingre­dients," how many could explain how those materials were obtained and why their properties demanded radically different designs for the Hiroshima and Trinity/Nagasaki weapons? How many could give a cogent explanation of the term "critical mass?" Indeed, many of our physics majors probably graduate with little better understanding of the science underlying nuclear weapons than that with which they emerged from high school.

For several years I have taught a general-education course on the history of the Manhattan Project to students at Alma College in an effort to address, in a small way, the general lack of knowledge in this area. In this article I describe my experience in developing and teaching this class. I would be interested in knowing about the experi­ences of anyone else doing something similar.

Alma College is a strictly undergraduate liberal-arts school of about 1,300 students located in central Michigan. In addition to choosing a major, every student must com­plete a requisite number of credits in the humanities, social sciences, and natural sciences. These general-education requirements comprise about one- third of a student’s overall credit requirements for graduation. Within the natural sciences area we have a physical-science requirement, with courses such as astronomy, environ­mental studies, general physics, and chemistry being popular choices.

Alma operates on a "4-4-1" schedule: two traditional four-month terms (Fall and Winter), followed by a one-month Spring term. The latter begins in late April and runs for about 3.5 weeks until just before Memorial Day. During Spring term, students take one course intensively, often meeting every day for 3-4 hours (or even more if a lab is involved); they are required to complete two Spring terms to graduate. This provides a venue for courses that would not otherwise conveniently fit into a regular term: many offerings involve field work or a travel component. But since many students prefer not to travel for their Spring terms, a demand for on-campus classes always exists, particularly ones that carry general-education credit and have minimal prerequisites.

For many years I have person­ally been interested in the history and physics of the Manhattan Project. By the year 2002 I felt that I had acquired enough understanding of the physics of the topic that I was ready to offer a Spring-term course with a prerequisite of basic algebra. I have now taught the course a total of five times since then, as well as a spin-off  "First-Year Seminar" course that was offered for the first time in Fall 2009.

The text for the course is Richard Rhodes masterful book The Making of the Atomic Bomb, from which the course draws its title. Our Spring terms run about 19 instructional days, which corresponds to about one chap­ter per day. Students are expected to read each chapter the night before class. Class time then consists of me explaining the material with the aid of numerous PowerPoint slides, occa­sional videos, simple blackboard cal­culations, and demonstrations with equipment such as a Geiger counter and simple radioactive sources, an e/m tube to illustrate the idea of using magnetic fields to separate isotopes, and spectrum tubes. Students are often astonished to find that household smoke detectors and Fiestaware dishes are nuclear.

In the first incarnation of the class I stuck closely to the one-chapter-per-day prescription, but this proved not fully satisfying. Rhodes devotes space to topics such as weapons develop­ment in World War I and the persecu­tion of Jews, which, while relevant to his setting the historical stage, are not directly germane to the science of nuclear weapons. There is a lot to cover in 3.5 weeks; deleting these sec­tions from the "required reading" has freed up time to go into more detail on the science.

Like the chapters in Rhodes’ book, the course material goes largely in chronological order. We begin with the discovery of X-rays and radioac­tivity as the opening acts of modern physics, then move on to the work of Rutherford and Bohr, the discovery of the neutron, the work of Enrico Fermi, the discovery of fission and its interpretation by Meitner, Frisch, Bohr and Wheeler, the evolution of the understanding of the role of dif­ferent uranium isotopes in the fission process, the Szilard/Einstein letter, and the opening of World War II. After dis­cussing the establishment of the Man­hattan District, we look at what was done at Oak Ridge, Hanford, and Los Alamos, devote a class to the Trinity test, and then discuss the Hiroshima and Nagasaki missions. In the last couple days of class we look at some of the effects of nuclear weapons, the numbers of postwar tests and weap­ons in the world today (these always surprise students), and what relevant treaties are in effect. I also take some time to give students some direction on where to look for credible sources of material on the Project. (A Google search on "Manhattan Project" yields over 3 million hits.)

My goal for the class is that stu­dents emerge with a correct under­standing of the history and science of nuclear weapons. They should appreciate that the development of nuclear weapons was in no sense "pre-ordained," and that even many of the leading figures of the nuclear research community at the time were skeptical that such weapons could ever be realized. Students should be able to explain how these weapons were developed, how they work, what problems were overcome in making them, how a reactor differs from a weapon, why implosion is necessary for an efficient weapon, and why a lump of natural uranium or even a subcritical mass of U-235 sitting on a lab bench would be perfectly safe. Equally important, I always make sure to tell them something of the lives of the people involved: of Lise Meitner fleeing Germany just months before the discovery of fission, of Enrico Fermi and Hans Bethe and others making their way to America, of Oppenheimer’s brilliant, eclectic, and ultimately tragic life. For many students this may be the only physi­cal science class that they take during their college career, and I want them to know not only of the importance of the law of conservation of energy but also that science and engineering are done by real people who possess all the typical human strengths, fears, motivations, and fallibilities.

Grades are established in the usual ways: I always have tests which are multiple choice, short-answer, and fill-in-the-blank questions as well as brief homework assignments where students might have to balance reac­tions or compute an energy release or the like. On various occasions I have had them write a 1000-word end-of-course reflective summary paper or participate in a last-day session where they get a random question: "What were you most surprised to learn?" "What aspect of the Project would you want to learn more about, and why?" "Who associated with the Proj­ect would you like to have lunch with and what would you ask him or her?" When I did the course for a group of First-Year students in Fall 2009, the more extended time of a regular term allowed me to add an extra reading/writing component: each student was randomly assigned a different book to read and prepare a report on, with one cycle of submit-revise-resubmit. In most cases these were biographical works; one obviously cannot get into technical depth with such a class. The regular-term incarnation of the class also permitted more time at the end to examine weapons effects, postwar developments, and topics such as the CTBT and START talks.

Alma is a small school; I can reach only a tiny number of students with this material. Since 2002 just over 100 students have taken the course. Many tell me that they find it fascinating and informative; history students in particular seem to enjoy it, but students come from all disciplines. Beginning in 2007 I began taking an end-of-course survey, asking students to imagine themselves as President Truman in the summer of 1945 but with the benefit of some understand­ing of the functioning and effects of nuclear weapons, and asking them to choose (anonymously, if they desire) one of six statements that most closely matches their own thoughts. These range from (paraphrased) "The use of nuclear weapons against Japan with­out prior warning was entirely justi­fied ... " to "Nuclear weapons are a moral abomination...." Responses from 45 students have been collected so far. About half of these chose the first option (use entirely justified, would have acted in same way as President Truman), which is followed by about 10 students each for options along the lines of the first bomb being justified but allowing more time and warnings before subsequent ones; and a sort of middle-ground default option stating that the ferocity of the war, the loom­ing post-war geopolitical situation with Russia, and the tremendous resources that had been devoted to the project made the use of the bombs essentially a foregone conclusion, beyond any real control of any one person. One student opted for the "moral abomination in any circumstance" option.

There are plenty of books, papers, websites and videos out there on this topic. I humbly suggest that a good place to start is a Resource Letter of over 100 sources that I published in the September 2005 issue of American Journal of Physics. Later this year or early next I will be publishing a text under the Springer imprint titled The Physics of the Manhattan Project, which will treat the physics of the project at about a junior level. A tentative table of contents can be found at www.man­hattanphysics.com.

The Manhattan Project is a virtu­ally open-ended vehicle for teaching our students some physics, history, political science and sociology, and I encourage readers to think about offer­ing something along the lines I have described. If you are already doing so I would love to hear from you: What has been your experience? In what sort of venue to what student population? What has worked and what hasn’t?

Note Added: This article represents the views of the author, which are not necessarily those of the FHP or APS.