Bacher, Robert Fox

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Loudonville, Ohio, 31 August 1905; d. Montecito, California, 18 November 2004)

atomic spectra, nuclear physics, scientific administration.

Bacher will be remembered for his significant contributions to physics, education, and, as a public servant, to his country. In the 1930s he coauthored a standard work on atomic spectra, and went on to help Hans Bethe redefine the field of nuclear physics. During World War II, Bacher served as a leader in the effort to develop radar at the Massachusetts Institute of Technology (MIT) Radiation Laboratory, and went on to play a critical role in building the atomic bombs at Los Alamos, New Mexico.

In the decades following the war, Bacher held a number of federal posts before turning his attention to the California Institute of Technology (Caltech), an institution he helped restructure and modernize. Though history has often overlooked Bacher, he clearly remains one of the most talented, versatile, and influential physicists of his generation.

Early Life and Career. Bacher was born to Harry and Byrl Fox Bacher in Loudonville, Ohio, on 31 August 1905.

The family moved to Ann Arbor, Michigan, during Bacher’s early childhood. He first became acquainted with physics in high school, but initially had little enthusiasm for the field, as he recalled in a 1980 oral history interview: “Actually, I was more interested in chemistry than physics because the physics course I took, while very thorough, was really very dull.” In his senior year, Bacher’s vague interest in the sciences found a catalyst. During the 1980 interview, he shared an anecdote regarding his first trip to the University of Michigan chemistry library: “I went and was absolutely floored. I saw the first things I’d ever seen about the atom.” Bacher instantly developed a passion for science, and upon graduating in 1922 he enrolled at the University of Michigan to pursue his new dream of becoming a physicist.

Bacher obtained his bachelor of science degree in physics from Michigan in 1926. Having distinguished himself as an outstanding student during his years at Michigan, he gained acceptance into Harvard’s prestigious physics program. Bacher spent his first year of graduate school at Harvard before returning home to Ann Arbor to study at his alma mater. The high cost of tuition at Harvard, coupled with his father’s rapidly deteriorating physical condition, necessitated his return to Michigan. In 1928 the university awarded Bacher the Charles Coffin Fellowship, which helped ease his financial burden. It was the first of several such awards.

The same year Bacher returned to Michigan, Samuel Goudsmit joined the physics department’s staff.

Goudsmit, a Dutch theorist, soon became Bacher’s mentor. In fact, Bacher later stated in a 1981 oral history interview: “He had more influence on my education than anyone else.” Only a few years later, the pair would publish Atomic Energy States, as Derived from the Analyses of Optical Spectra (1932), a seminal work that is still referenced in the early twenty-first century.

The year 1930 proved to be a momentous one for Bacher. He completed work for his doctorate, joined the research society Sigma Xi and the American Physical Society, and won his second fellowship, this time from Caltech. He also married Jean Dow, whose family had been longtime neighbors of the Bachers. When his fellowship at Caltech ran out, Bacher was named a National Resident Fellow at MIT. Eager to return home, he accepted the Lloyd Fellowship from Michigan in 1932.

When his fellowship expired in 1933, Bacher found himself unemployed in Depression-battered Michigan. During the year that followed, Bacher had time to ponder the mysteries of the atom in depth. In doing so, he began to develop a new interest, as he related in his 1980 interview: “It turned me more toward doing research and turned my interests toward nuclear physics—I had worked in atomic spectra up until then—and this was a sort of fateful time for me.”

Bacher’s sojourn came to an end in 1934, when he accepted a position with Columbia University as an instructor. He stayed there for a year before moving on to Cornell University in 1935. While at Cornell, Bacher worked closely with the future Nobel laureate Bethe, who had undertaken the task of standardizing the field of nuclear physics. In a series of articles Bethe, along with Bacher and M. Stanley Livingston, reevaluated the existing literature, filled research gaps, and attempted to resolve standing research problems. These articles, which soon became collectively known as “Bethe’s Bible,” served as the standard text for generations of nuclear physicists to come.

World War II. Bacher remained on Cornell’s faculty through the end of World War II, enjoying a series of promotions: to assistant professor in 1937, to associate professor in 1940, and finally to professor in 1945. He became adept at performing cross-section measurements, and worked with Cornell colleagues Charles P. Baker and Boyce McDaniel to correct the boron absorption method that the Nobel laureate Enrico Fermi had popularized. In a 1984 interview, Bacher explained that upon learning of the team’s results, his friend Fermi said: “You’re right. You publish it. It’s good physics.” Bacher’s work with Goudsmit a decade earlier had established his credentials as a theorist. His ongoing collaborative relationship with Fermi would solidify his standing as an experimentalist. This near-unique combination would soon draw the attention of two critical wartime projects.

With the Japanese attack on Pearl Harbor just months away, Lee DuBridge recruited Bacher to serve as a leader at the MIT Radiation Laboratory (Rad Lab). Rad Lab scientists performed research on the new technology of radar, and Bacher led the division responsible for the development of equipment that could translate incoming signals. The Rad Lab employed Bacher until early 1943, when an acquaintance, J. Robert Oppenheimer, recruited him to work on the secret atomic bomb project at Los Alamos. Bacher, who had been working on problems in nuclear physics for the previous decade, hesitantly accepted.

Bacher and Manhattan Project consultant Isidor I. Rabi, who had been associate director of the Rad Lab since 1940, shared a serious concern: would the lab at Los Alamos fall under military control? The Manhattan Project’s director, General Leslie R. Groves, originally planned for all the scientists to become commissioned army officers. Bacher and Rabi flatly refused to accept their commissions. At first, this created somewhat of a crisis. General Kenneth D. Nichols, Groves’s deputy, relates in his memoir, The Road to Trinity:


In February 1943, [James] Conant, [Vannevar] Bush, Groves, [Col. J. C.] Marshall, and I met with Rabi and Bacher … and spent the better part of the day trying to convince them that a military laboratory was essential. However, they were adamant and made it clear that even if the initial research activities were conducted as a civilian organization, they would tender their resignations if it were later militarized, war or no war. (1987, p. 152)

Because Oppenheimer regarded the two MIT physicists as essential, their protests carried considerable weight. Thus, Los Alamos and other Manhattan Project installations remained under civilian control, although the threat of a military conversion loomed during the war.

While at Los Alamos, Bacher remained at the very core of the project. His first assignment was to head the Experimental Physics (P) Division, one of the laboratory’s four original technical divisions. Bacher’s division carried out a variety of experiments to demonstrate the viability of a nuclear bomb. During this period, Oppenheimer entrusted Bacher with additional responsibilities as well: Bacher was asked to serve on the governing board, and he chaired the coordinating council. These advisory committees created policy and coordinated research activities across the new laboratory. Over time Bacher, by then a close friend of Oppenheimer's, came to serve as the laboratory’s de facto deputy director.

By spring 1944, P Division scientists discovered that plutonium, unlike its fissionable counterpart uranium, would fizzle in a simple, gun assembly–type bomb. In order to use plutonium, the physicists would have to pursue a second method of ignition: implosion. Implosion was much more complicated than the gun method, but if it worked it would salvage the plutonium production program and probably yield a much more efficient weapon. Oppenheimer reorganized the laboratory in August 1944 in order to achieve maximum efficiency for the implosion effort. The P Division was disbanded and Bacher was made head of the new Weapons Physics, or “Gadget” (G) Division. The primary function of Bacher’s division was to propose and build an implosion bomb. To do this, Bacher assembled one of the most talented scientific teams in history. His group leaders included two future Nobel laureates, Luis Alvarez and Edwin McMillan, as well as Bruno Rossi, Otto Frisch, and several other internationally recognized physicists.

As 1945 began, Bacher’s division grew in confidence. Implosion appeared to be feasible, and a test date was scheduled for July. For the final push, Oppenheimer established the Cowpuncher Committee to drive implosion development through to completion. Bacher, along with five others, “rode herd” on the committee, their efforts eventually culminating in the 16 July Trinity test. An implosion bomb was successfully detonated early that morning, achieving a yield equivalent to twenty-one thousand tons of TNT. Bacher related his first thoughts after Trinity in his 1980 interview: “It was indeed an enormous relief. Everybody’s first reaction was a mixture of many things but everybody was terribly tired by the time that bomb went off.” The next implosion bomb would fall on Nagasaki, Japan, less than a month later, helping bring World War II to a close.

Bacher’s taxing work at Los Alamos left him exhausted. In January 1946, he returned to a full professorship at Cornell. Though he was happy to return to Ithaca, he could not avoid continued federal service. The previous November, he had already joined Dr. Richard Tolman’s Declassification Committee, which cleared thousands of Manhattan Project documents for release to the general public. Bacher also served on the Manhattan Project’s Advisory Committee on Research and Development as well as the Technical Committee on Inspection and Control. Additionally, he was a technical advisor to the United Nations (UN). As a member of Bernard Baruch’s UN mission, he helped develop policy to control atomic energy. Perhaps Bacher’s most enjoyable assignment came in conjunction with his work at the UN. He was selected to chair the planning committee for the new Brookhaven National Laboratory, a UN Atomic Energy Commission project.

AEC Commissioner. Bacher enjoyed much of his postwar work, welcoming the challenges of organizing the new Brookhaven Laboratory and the physics lab at Cornell. But unfortunately, duty called once again. In 1946, in order to address the unprecedented issues surrounding atomic energy, Congress established the U.S. Atomic Energy Commission (AEC). David E. Lilienthal, the Tennessee Valley Authority’s first chairman, was selected to chair the commission and recommended Bacher as a charter member. Bacher, who had already settled into his post-war life, was not excited about the prospect. Yet, Lilienthal was determined to acquire Bacher’s services, penning in his journal, “He has just what we need—a feeling for the subject, an understanding of how important the Atomic Energy Commission’s work is and can be, and a clear recognition of the central importance of an adjustment of the international impasse” (1964, p. 100). Working

behind the scenes, Lilienthal also secured the aid of Bacher’s good friend Oppenheimer. With Oppenheimer, Lilienthal, and his sense of duty urging him, Bacher decided to take the position. His knowledge, experience, and status as the only scientist on the commission prompted Lilienthal to exclaim, “He will make all the difference in the world” (p. 102).

Bacher’s selection was welcomed with almost universal acclaim. In fact, the most negative critique came from Edward Teller, who wrote in a letter to Maria Goeppert-Mayer, “Scientifically, we may have done worse by getting someone else,” conceding, “Bacher is a great administrator” (2001, pp. 263–264). Bacher began his term on 1 November 1946, and quickly developed friendships with the other commissioners. These friendships made his work bearable, but he never found the work appealing, despite its importance.

As the end of his first term approached, fatigue began to set in. Bacher desperately wanted to return to academia. However, it was becoming apparent, especially to Lilienthal, that Bacher would be extremely difficult to replace. Therefore, a compromise was reached: when the commissioners came up for reconfirmation, Bacher would accept only a one-year term. During his second term, Bacher continued to serve effectively. He educated his fellow commissioners on atomic energy and played a critical role in formulating early nuclear-weapons policy. On 10 May 1949, Bacher’s term came to a close.

Caltech and Scientific Advising. After leaving the AEC, Bacher immediately accepted the position of leader for the reeling Physics, Mathematics, and Astronomy Division at Caltech, where he had studied as a Fellow almost two decades before. Caltech’s president, Lee DuBridge, knew Bacher was the perfect man for the job. As Bacher’s former supervisor at the Rad Lab, DuBridge fully appreciated Bacher’s skills as a scientist and administrator. Now, DuBridge would count on his friend to help him restructure and modernize the small institution. Together, the team would gradually bring Caltech into a new era of prominence, returning it to the fore of the nation’s leading universities.

Though Bacher had left Washington, he did not refrain from engaging in nuclear-policy discussions. In 1950 he publicly questioned the usefulness of the hydrogen bomb in a Scientific American article, arguing that it would be of limited strategic value: “While it is a terrible weapon, its military importance seems to have been grossly overrated in the mind of the laymen.… The most tragic part is that the hydrogen bomb will not save us and is not even a very good addition to our military potential” (p. 14). In the same article, Bacher also called for openness on the part of the government. He remained true to this stance decades later, stating in an oral history interview: “I think it’s very important for people to be given as many facts as possible and to try and get them information which is both correct and non-inflammatory, whether this is pro or anti on the nuclear end of things.”

Throughout the 1950s Bacher worked on several projects and served on many committees. In 1951 he joined the Vista Project, which was led by DuBridge. The project identified specific military problems that the North Atlantic Treaty Organization would encounter in the event of a Soviet attack on Western Europe. Two years later, in 1953, he joined the Science Advisory Committee (SAC) for the Office of Defense Mobilization.

Bacher left the SAC in 1955, but in 1957 was asked to serve on the President’s Science Advisory Committee (PSAC), a higher level, expanded version of the SAC, which reported directly to the president. He accepted the new challenge at the urging of its chair, James R. Killian. As a member of the committee, Bacher actively engaged in the 1958 test-ban negotiations with the Soviets. The talks led to a temporary test moratorium but more importantly paved the way for the formal Limited Test Ban Treaty of 1963. Killian relates in his memoir, Sputnik, Scientists, and Eisenhower, Bacher “made important contributions to helping the policy makers to understand the complexities of the problem.” Killian continues, “In all of his work, he was deliberate, thorough, and judicial” (1977, p. 162). Bacher continued to serve the Eisenhower administration under the president’s second chief science advisor, Manhattan Project veteran George Kistiakowsky, until 1959, when he left the PSAC to spend more time at Caltech.

With DuBridge’s blessing, Bacher transformed Caltech into a center for research in the new field of high-energy particle physics as head of the Mathematics, Physics, and Astronomy Division. He brought in leading theorists, including the Nobel laureates Richard Feynman and Murray Gell-Mann, and constructed state-of-the-art tools such as the electron synchrotron, a high-energy accelerator. Throughout the 1950s and into the 1960s, Bacher carefully groomed the division, elevating it to one of the nation’s finest. For his outstanding efforts, he was made the university’s first provost in January 1962. In that capacity, he worked very closely with DuBridge and inherited many functions from the president’s office.

Despite his new role at Caltech, Bacher made time to participate in prominent professional societies. He was president of the American Physical Society for 1964, and served as president of the International Union of Pure and Applied Physics from 1969 to 1972. During his final years at Caltech he helped hire DuBridge’s successor, Harold Brown, and facilitated a seamless transition. Bacher retired from his duties as provost on 31 August 1970, his sixty-fifth birthday. He retained a faculty position and was immediately elected to the academic policy committee by his colleagues. Six years later, Bacher retired from the Caltech faculty and was awarded the title professor emeritus.

Retirement and Death. Even in retirement, Bacher remained active in the scientific community. He spent much of his time working on energy-related matters at the National Aeronautics and Space Administration and at Caltech’s Jet Propulsion Laboratory and often visited his colleagues back at the Physics, Mathematics, and Astronomy Division. In 1983, the fortieth anniversary of Los Alamos National Laboratory’s founding, Bacher served as master of ceremonies for the celebration. Many old friends, including Rabi, Bethe, and Alvarez, attended the celebration as well.

Robert Fox Bacher died in Montecito, California, on 18 November 2004. He lived a long life, and accomplished much during it. His work as a scientist and administrator with the Manhattan Project will probably remain his defining achievement, although this marked only the beginning of a remarkable career in science and public service. As an AEC commissioner, he tackled the international problems presented by atomic energy, remaining an active proponent of its responsible use throughout his life. He advised several luminaries, including Oppenheimer, Baruch, and President Dwight Eisenhower. Bacher also played a major role in transforming Caltech into one of the world’s premier institutions of higher learning. Despite the complex nature of his work and his impressive list of accomplishments, Robert Bacher remained a kind, modest gentleman. Perhaps Killian described him best in his memoir: “Those who knew him as a leading physicist and science administrator at Cal Tech and those who have sailed with him off the Pacific Coast can only think of him as a shining, gifted figure, friendly, thoughtful, and deeply devoted to his country” (1977, p. 163).



With Samuel A. Goudsmit. Atomic Energy States, as Derived from the Analyses of Optical Spectra. New York: McGraw-Hill, 1932.

———. “Atomic Energy Relations. I.” Physical Review 46 (1934): 948–969.

With Charles P. Baker and Boyce D. McDaniel. “Experiments with a Slow Neutron Velocity Spectrometer II.” Physical Review 69 (1946): 443–451.

With David Lilienthal et al. “First Report of the U.S. Atomic Energy Commission.” Science 105 (1947): 199–204.

“The Physicist and the Future Development of Atomic Energy.” Bulletin of the Atomic Scientists 4 (1948): 99–102.

“Research and the Development of Atomic Energy.” Science 109 (1949): 2–7.

“The Hydrogen Bomb: III.” Scientific American182 (1950): 11–15.

Interview by Mario Balibrera. Transcript, 1980. Los Alamos National Laboratory Archives. The Los Alamos National Laboratory Archives include multiple oral histories of Bacher, as well as his classified and unclassified wartime papers.

Interview by Mary Terrall. Transcript, 19 June 1981. California Institute of Technology Archives. The Caltech Archives include multiple oral histories of Bacher, as well as an extensive collection of Bacher’s papers.

Interview by Lillian Hoddeson and Allison Kerr. Transcript, 30 July 1984. Los Alamos National Laboratory Archives.

With Hans A. Bethe and M. Stanley Livingston. Basic Bethe:Seminal Articles on Nuclear Physics, 1936–1937. Los Angeles: Tomash; New York: American Institute of Physics, 1986.

Robert Oppenheimer, 1904–1967. Los Alamos, NM: Los Alamos Historical Society Press, 1999.


Carr, Alan B. Robert Bacher: The Forgotten Physicist. Los Alamos, NM: Los Alamos Historical Society Press, 2007.

Goodstein, Judith R. Millikan’s School: A History of the California Institute of Technology. New York: Norton, 1991.

Hoddeson, Lillian, Paul W. Henriksen, Roger A. Meade, et al. Critical Assembly: A Technical History of Los Alamos during the Oppenheimer Years, 1943–1945. Cambridge, U.K.: Cambridge University Press, 1993. Recognized by Los Alamos National Laboratory as an official wartime history of Project Y.

Killian, James R. Sputnik, Scientists, and Eisenhower: A Memoir of the First Special Assistant to the President for Science and Technology. Cambridge, MA: MIT Press, 1977.

Lilienthal, David E. The Journals of David E. Lilienthal. Vol. 2, The Atomic Energy Years, 1945–1950. New York: Harper and Row, 1964.

Nichols, Kenneth D. The Road to Trinity. New York: William Morrow, 1987.

Teller, Edward, with Judith L. Shoolery. Memoirs: A Twentieth-Century Journey in Science and Politics. Cambridge, MA: Perseus, 2001.

Alan B. Carr