He was born in the city of Nikolayev in the family of the book publisher Alfred Schneider. After the death of his mother in 1911, his father left for the United States of America. Until 1915, Gregory studied at the Oleksandrivska gymnasium. In 1915, he followed his father to USA. He studied at Johns Hopkins University: in 1918 he obtained a Bachelor degree, in 1920 a Master degree, and in 1921 he earned a PhD in physics. In 1921-1922, he worked as a researcher at Leiden University.
In 1922-1923, he was a research fellow at Harvard University. From 1923 to 1924, he was an assistant professor at the University of Minnesota. In 1925, while at the Carnegie Institution of Washington, Breit joined with Merle Tuve in using a pulsed radio transmitter to determine the height of the ionosphere, a technique important later in radar development.[3]
During the early stages of the war, Breit was chosen by Arthur Compton to supervise the early design of the first atomic bomb during an early phase in what would later become the Manhattan Project. Breit resigned his position in 1942, feeling that the work was going too slowly and that there had been security breaches on the project; his job went to Robert Oppenheimer, who was later appointed to scientific director of what became Project Y, the design and testing of the weapon.
In 2014, experimentalists proposed a way to validate an idea by Breit and John A. Wheeler that matter formation could be achieved by interacting light particles ("Breit–Wheeler process").[9]
Breit was associate editor of the Physical Review four times (1927-1929, 1939-1941, 1954-1956, and 1961-1963).
^Bethe, H. A., and E. E. Salpeter; Quantum Mechanics of One- and Two-Electron Atoms, Plenum Press, 1977, p. 181
^Hughes, Vernon; Iachello, Francesco; Kusnezov, Dimitri (2001). The Gregory Breit Centennial Symposium: Yale University, USA. Singapore River Edge, N.J: World Scientific. p. 9. ISBN978-981-02-4553-5.
