In this eyewitness account of the Trinity test, carried out at Alamogordo, New Mexico, on July 16, 1945, physicist Luis W. Alvarez documented the explosion from his perch between the pilot and co-pilot in a B-29 flying near the blast.
Alvarez, who worked on the bomb’s detonators, was also a observer on a B-29 that flew in formation with the Enola Gay when it bombed Hiroshima in August, 1945. Physicist Lawrence Johnston, then Alvarez’s assistant, accompanied him on both missions. Johnston remembered that Alvarez got the observer job after telling J. Robert Oppenheimer
that he would like to get involved in the Pacific operations…Oppenheimer needed someone to measure the explosive energy of the bombs which were to be dropped on Japan, and Luie [Luis] took the job in April 1945.