Robert Fox Bacher (August 31, 1905 – November 18, 2004) was an American nuclear physicist and one of the leaders of the Manhattan Project.

In December 1940, Bacher joined the Radiation Laboratory at MIT, although he did not immediately cease his research at Cornell into the neutron cross section of cadmium.

He also served on the U.S. Atomic Energy Commission, the civilian agency that replaced the wartime Manhattan Project, and in 1947 he became one of its inaugural commissioners.

His fees were paid by his family, but his father had a heart attack and could no longer afford them, so in 1927 Bacher moved back to Ann Arbor, where he lived at home,[4][5] and attended the University of Michigan.

[6] To build up the theoretical physics department at the University of Michigan, Randall recruited four distinguished young physicists to work at Ann Arbor in 1927: Otto Laporte, George Uhlenbeck, Samuel Goudsmit, and David M. Dennison.

His mother gave them a Ford Model A and the use of the family's lakeside holiday house, where they entertained guests including Paul Ehrenfest and Enrico Fermi.

In 1931, with a National Research Council Fellowship, he spent a year at the California Institute of Technology (Caltech) because Ira Bowen taught there.

He was researching the neutron cross section of cadmium, a topic of interest to Enrico Fermi, who was attempting to build a nuclear reactor, but whose figures did not agree with Bacher's.

[13] He later recalled: We quickly concluded that the ultimate discrimination between signals reflected from a target, as opposed to noise from the transmitter, should be done finally on the cathode-ray tube.

In addition, I want to express in writing my own confidence in your stability and judgement, qualities on which this stormy enterprise puts a very high premium.

[17] In July 1944, Oppenheimer reorganized the laboratory to focus on the problem of building an implosion-type nuclear weapon, which was necessary because the gun-type design would not work with plutonium.

This much larger division contained eleven groups headed by leaders who included William Higinbotham, Seth Neddermeyer, Edwin McMillan, Luis Alvarez and Otto Frisch.

It included Bacher, along with Samuel Allison, George Kistiakowsky, Deak Parsons, Charles Lauritsen and Hartley Rowe.

[20] Three days before the day the bomb was to be test detonated in the New Mexico desert, Bacher was part of the pit assembly team, which assembled the nuclear capsule (a cylindrical section of the uranium tamper, containing the plutonium core and initiator) in an old farmhouse near the Alamogordo testing site.

"[22] Bacher was packaging the third core for shipment to Tinian on August 12 at the Ice House at Los Alamos when he received word that the Japanese had initiated surrender negotiations.

[23] He had already set G Division the task of designing and building new types of cores and assemblies, and he co-authored a report with Robert Wilson urging the development of Edward Teller's Super bomb.

[25] In October 1946 David Lilienthal asked Bacher to become one of the inaugural commissioners of the United States Atomic Energy Commission, the civilian agency that was being formed to replace the wartime Manhattan Project.

As a Republican, Bacher was easily confirmed by the Senate members of the United States Congress Joint Committee on Atomic Energy by an 8–0 vote.

As he was the only one of the five commissioners who was a scientist—an important factor in his decision to accept the post—he played a leading role in the selection of the Atomic Energy Commission's influential General Advisory Committee[26] to which nine scientists were appointed: James Conant, Lee DuBridge, Enrico Fermi, Robert Oppenheimer, Isidor Isaac Rabi, Hartley Rowe, Glenn Seaborg, Cyril Stanley Smith and Hood Worthington.

These problems were on their way to resolution when Bacher observed the Operation Sandstone nuclear tests at Enewetak Atoll in 1948 as the Atomic Energy Commission's representative.

Senator Bourke Hickenlooper charged the commission with mismanagement, specifically cost overruns at Hanford, awarding a scholarship to a communist, and the loss of 289 grams (10.2 oz) of uranium from the Argonne National Laboratory.

Bacher felt obligated to return to Washington to testify on Lilienthal's behalf before the Joint Committee on Atomic Energy.

Bacher joined Oppenheimer, Parsons, General Hoyt Vandenberg, the Atomic Energy Commissioners and a British delegation under William Penney to discuss what to do.

Lauritsen had already hired Robert Langmuir to begin designing a new 600 MeV synchrotron, and Bacher found a large building to house it that had originally been used for grinding and polishing the Palomar Observatory's 200-inch (5,100 mm) mirror, but which had been empty since 1948.

He arranged for Atomic Energy Commission and Office of Naval Research grants worth $1 million to build it and the other required facilities, and $300,000 a year to run it.

[36] The relatively new field of radio astronomy sparked Bacher's interest, and he hired John Bolton and Gordon Stanley from the Australian Commonwealth Scientific and Industrial Research Organisation in 1955.

A grant from the Office of Naval Research allowed Bolton to build the Owens Valley Radio Observatory, which became an important center for the study of quasars.

During his second, he worked with James Fisk and Ernest Lawrence to examine how a Partial Nuclear Test Ban Treaty could be monitored.

[37][38] Bacher remained chair of the division of physics, mathematics and astronomy at Caltech until 1962, when he was appointed as vice president and provost.