of this, Simpson became a founding member and first chairman of the Atomic Scientists of Chicago in August 1945, a day after the United States dropped the atomic bomb on Hiroshima and two years after the start of his career. He was also a co-founder that same year of the Bulletin of the Atomic Scientists. The bulletin's aim was to spell out the implications of the atomic bomb and provide rational courses of action in response to the implications. In the October 29, 1945 issue of Life, Simpson, along with Eugene Rabinowitch, spoke about their involvement with nuclear energy, and said that scientists for the first time had recognized a moral responsibility to warn of the danger of any further use of nuclear weapons. Simpson felt that scientists and engineers could no longer remain aloof from the consequences of their work. This same year Simpson began his tenure as a faculty member at the University of Chicago as a physics instructor, and remained there throughout his career, partaking in research until shortly before his death in August 2000. In 1945, he also worked as an unofficial adviser to Connecticut Senator Brien McMahon after taking a leave of absence from the university. As part of the university faculty, Simpson invented and patented a "gas flow α-particle proportional counter for measuring plutonium yields in the presence of high intensity fission products" by piping the plutonium-bearing gas through the counter itself. Simpson has 15 patents under his name, which include the multiwire proportional counter, a device that improves accuracy and reading speed of radiation, and the neutron monitor. Nancy Farley Wood worked with Simpson and is credited with the development and production of the radiation detectors for the laboratory. Simpson was a pioneer in the study of cosmic rays. Beginning in 1946 with investigations into cosmic ray neutrons in the lower atmosphere (developed from pre-World War II work by Serge Korff), he contributed significantly throughout the years to the field's development with his scientific investigations. Simpson's contributions were unique in that he accomplished his work in a way that boosted the accomplishments and careers of others around him. In 1955, he gave Eugene N. Parker a job as a research associate in the Enrico Fermi Institute of the University of Chicago, and his progress was largely a consequence of Simpson's continued support. In 1949, Simpson contributed to the discovery that the latitude effect