Samuel King Allison was an American physicist.
Allison was born in Chicago, in 1900. He studied at the University of Chicago, receiving a Ph.D. in 1923.
With the outbreak of World War II, Allison served as a consultant to the National Defense Research Council in 1940. He was also a member of the Chicago Met Lab, and was among the team of scientists who achieved the world’s first self-sustaining nuclear chain reaction, Chicago Pile-1, in 1942. Allison would go on to be named director of the Met Lab. Fellow scientist Alvin Weinberg recalled:
"The laboratory had its giants—Enrico Fermi and Arthur Compton, and Leo Szilard, and Eugene Wigner; it had its pessimists and bureaucrats; and it had a lot of somewhat bewildered young people undertaking their first scientific jobs. It was Sam Allison who, with his extraordinary patience and insight, kept this disparate crew focused on the main job, which was to achieve success ahead of the Nazi competitors."
In 1944, Allison went to Los Alamos to become chairman of the Los Alamos Technical and Scheduling Committee. It was Allison who would count down the final seconds before the Trinity Test on July 16, 1945. He later joked about his fame, “I think I'm the first person to count backward.”
After the war, Allison was awarded the Medal of Merit in 1946 by General Leslie Groves for his work on the Manhattan Project. He returned to the University of Chicago to become the first director of the Enrico Fermi Institute for Nuclear Studies. He also worked with the National Academy of Sciences and was chairman of the NAS Committee on Nuclear Science.
Allison died on September 15, 1965 in Culham, England.