Came to the United States, 1915, naturalized, 1918. Bachelor of Arts, Johns Hopkins, 1918, Master of Arts, 1920, Doctor of Philosophy, 1921, honorary Doctor of Laws, 1976. Honorary Doctor of Science, University of Wisconsin, 1954.
In 1921, he was Paul Ehrenfest"s assistant in Leiden. 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. Together with Eugene Wigner, Breit gave a description of particle resonant states with the relativistic Breit–Wigner distribution in 1929, and with Edward Condon, he first described proton-proton dispersion.
He is also credited with deriving the Breit equation.
In 1934, together with John A. Wheeler, Breit described the Breit–Wheeler process. In 1939 he was elected to the National Academy of Sciences.
In April 1940, he proposed to the National Research Council that American scientists observe a policy of self-censorship due to the possibility of their work being used for military purposes by enemy powers in World World War World War II 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 the entire project
Breit was Associate Editor of the Physical Review four times (1927-1929, 1939-1941, 1954-1956, and 1961-1963). He was awarded the Franklin Medal in 1964. In 1967, he was awarded the National Medal of Science.
Fellow American Physical Society (T.I. Bonner prize 1969), Institute of Electrical and Electronics Engineers, Physical Society (London), American Association for the Advancement of Science, American Academy Arts and Sciences, Washington Academy Science, Geophysical Union. Member National Academy Science, Phi Beta Kappa, Sigma Xi.
Married Marjorie MacDill, December 30, 1927.