Loomis received his Doctor of Philosophy from Harvard University in 1917 studying the field of thermodynamics.
Loomis was a Guggenheim Fellow in 1928 studying abroad at Zürich and Göttingen, and in 1929, Loomis came to the University of Illinois at Urbana Champaign to become the head of the Department of Physics, a position he would retain until 1957. Loomis was challenged in bringing top-notch physics talent to a university in the rural Midwest. The interruption of the war also required Loomis to restart his building of the physics department as two-thirds of the faculty he added in the 1930s moved elsewhere due to the many defense projects related to the war.
At the University of Illinois at Urbana Champaign the main physics building was renamed the Loomis Laboratory of Physics posthumously in his honor.
Fellow American Physical Society, (president 1949), American Optical Society, American Association for the Advancement of Science (vice president Section(s), B., 1948). Member American Association Physics Teachers, American Association University Professors, National Academy Science, American Institute Physics, Illinois Academy Science, Phi Beta Kappa, Sigma Xi. Clubs: Chaos (Chicago).
Married Edith Livingston Smith, July 24, 1922. Children: Margaret, Ann Livingston, Miriam Nye.