He stayed in the US after being drafted and returned to Johns Hopkins University after the war, completing his BA in 1920.
He earned his PhD in 1924; his dissertation was A Study of Pfund's Pressure Gauge.
[1] He taught at New York University (NYU) from 1924 to 1943, before returning to Johns Hopkins to teach.
He studied probability theory, the scattering of electrons, and the discharges of electric eels.
According to T. D. Lee and C. N. Yang, parity violation implies that electrons produced by β decay should be longitudinally polarized.