Fanny Cook Gates (26 April 1872 – 24 February 1931) was an American physicist, an American Physical Society fellow and American Mathematical Society member. She made contributions to the research of radioactive materials, determining that radioactivity could not be destroyed by heat or ionization due to chemical reactions, and that radioactive materials differ from phosphorescent materials both qualitatively and quantitatively.More specifically, Gates showed that the emission of blue light from quinine was temperature dependent, providing evidence that the emitted light is produced from phosphorescence rather than radioactive decay. She also served as head of the Physics department at Goucher, Professor of Physics and Dean of Women at Grinnell College, and the Dean of Women at the University of Illinois. Education and career Gates received her B.S. from Northwestern University in 1894 and her M.A. in 1895, and finally her Ph.D. from the University of Pennsylvania in 1909. She wrote her PhD dissertation on "The Conductivity of Gases Caused by Certain Chemical Changes." She published two papers during graduate school on the subject of radioactivity. From 1895-1897, she was a scholar and fellow in mathematics at Bryn Mawr College, where she received a President's European Fellowship. In the fall of 1897 she attended the University of Göttingen to further her studies in mathematics and physics; and in the winter of 1898, furthered her studies at the Polytechnik Institute at Zurich. Gates returned to the U.S. in 1898 to accept a position at the Women's College of Baltimore (Goucher University), where she ordered in advance of her arrival, additional physics equipment to build her lab to study spectra and X-rays. She remained at Goucher for 13 years, leaving in 1911 to work for the University of Chicago. From 1902-1903 she took a leave of absence from Goucher and worked with Ernest Rutherford and Harriet Brooks at McGill University, Montreal, where her research on radioactivity continued, proving that radioactive phenomena were not simple chemical or physical processes. In 1905, Gates worked with J.J. Thomson, her research continued to support her reputation in the scientific community. In 1911, Gates left her position at Goucher in Baltimore to accept a research position at the University of Chicago. Two years after that she was offered a Professor of Physics and Dean of Women position at Grinnell College in Iowa. She continued in this role for three years before moving to the University of Illinois at Urbana-Champaign