Robert F. Christy

He had an older brother, John, who was born in 1913.

Robert Frederick Christy (May 14, 1916 – October 3, 2012) was a Canadian-American theoretical physicist and later astrophysicist who was one of the last surviving people to have worked on the Manhattan Project during World War II.

He briefly served as acting president of California Institute of Technology (Caltech).

Robert Frederick Cohen was born on May 14, 1916, in Vancouver, British Columbia, the son of Moise Jacques Cohen, an electrical engineer, and his wife Hattie Alberta née Mackay, a school teacher.

He was named Robert after his maternal great uncle Robert Wood, and Frederick after Frederick Alexander Christy, the second husband of his maternal grandmother.

Moise changed the family surname to Christy by deed poll on August 31, 1918.

On November 4, Moise was accidentally electrocuted at work.

Hattie died after goitre surgery in 1926.

Christy and his brother were then cared for by Robert Wood, their grandmother Alberta Mackay, and their great aunt Maud Mackay.

A graduate of the University of British Columbia (UBC) in the 1930s where he studied physics, he followed George Volkoff, who was a year ahead of him, to the University of California, Berkeley, where he was accepted as a graduate student by Robert Oppenheimer, the leading theoretical physicist in the United States at that time.

Christy was educated at Magee High School, and graduated in 1932 with the highest examination score in the province of British Columbia.

He was awarded the Governor General's Academic Medal, and, importantly in view of his family's limited ability to pay, free tuition to attend the University of British Columbia (UBC).

At the award dinner he met the second-place winner, Dagmar Elizabeth von Lieven, whom he dated while at UBC.

He received his Bachelor of Arts (BA) degree in mathematics and physics with first class honors in 1935, and his Master of Arts (MA) degree in 1937, writing a thesis on "Electron attachment and negative ion formation in oxygen".

George Volkoff, a friend of Christy who was a year ahead of him at UBC, was accepted as a graduate student at the University of California, Berkeley, by Robert Oppenheimer, who led the most active school of theoretical physics in the United States at that time.

This inspired Christy to apply to the University of California as well.

He was accepted, and was awarded a fellowship for his first year.

At Berkeley he shared an apartment with Volkoff, Robert Cornog, Ken McKenzie and McKenzie's wife Lynn McKenzie.

For his thesis, Oppenheimer had him look at mesotrons, subatomic particles called muons today, that had recently been found in cosmic rays.

They were so-called because they were more massive than electrons but less massive than protons.

With the help of Shuichi Kusaka he performed detailed calculations of the particle's spin.

Christy could have graduated in 1940, but could not then be a teaching assistant, and this would have left him jobless and without income.

Christy received his doctorate in 1941 and joined the physics department of Illinois Institute of Technology.

He published two papers on mesotrons with Kusaka in the Physical Review, which formed the basis of his 1941 Doctor of Philosophy (PhD) thesis

In 1941, Oppenheimer found him a post at the physics department at Illinois Institute of Technology (IIT).

In May 1941, he married Dagmar von Lieven.

In 1942 he joined the Manhattan Project at the University of Chicago, where he was recruited by Enrico Fermi to join the effort to build the first nuclear reactor, having been recommended as a theory resource by Oppenheimer.

This brought him to the attention of Eugene Wigner, who hired him for the same money that IIT was paying him as a full-time research assistant, commencing in January 1942.

Enrico Fermi and his team from Columbia University arrived at the University of Chicago in January 1942 as part of an effort to concentrate the Manhattan Project's reactor work at the new Metallurgical Laboratory.

When Oppenheimer formed the Manhattan Project's Los Alamos Laboratory in 1943, Christy was one of the early recruits to join the Theory Group.

Christy is generally credited with the insight that a solid sub-critical mass of plutonium could be explosively compressed into supercriticality, a great simplification of earlier concepts of implosion requiring hollow shells.

For this insight the solid-core plutonium model is often referred to as the "Christy pit".

They had two sons: Thomas Edward (Ted), born in 1944, and Peter Robert, born in 1946.

IIT paid Christy $200 per month to teach 27 hours per week for 11 months per annum.

To keep abreast of developments in physics, he attended seminars at the University of Chicago.

After the war, Christy briefly joined the University of Chicago Physics department before being recruited to join the Caltech faculty in 1946 when Oppenheimer decided it was not practical for him to resume his academic activities.

He stayed at Caltech for his academic career, serving as Department Chair, Provost and Acting President.

In 1960 Christy turned his attention to astrophysics, creating some of the first practical computation models of stellar oscillations.

For this work Christy was awarded the Eddington Medal of the Royal Astronomical Society in 1967.

In the 1980s and 1990s Christy participated in the National Research Council's Committee on Dosimetry, an extended effort to better understand the actual radiation exposure due to the bombs dropped on Japan, and on the basis of that learning, better understand the medical risks of radiation exposure.