On July 16, 1945 the first nuclear bomb exploded near Alamogordo, New Mexico. The Trinity test marked the culmination of nearly four years of secret research led by an unprecedented collaboration of the world’s top scientists and the US military. It also guaranteed that the uranium gun-type weapon dropped on Hiroshima could be followed by another that used the plutonium implosion design tested at the Trinity Site. In essence, Trinity was a test-of-concept for the bomb that leveled Nagasaki.
The history of the Manhattan Project and the birth of the bomb have been examined and reexamined countless times over the past seven decades—as have the threats they posed to humanity.Though nearly all now are dead, many scientists, soldiers, and family members who attended the birth of the bomb documented their first-hand experiences in the pages of the Bulletin in a way that lives on, providing an exceptional and vivid glimpse of their struggles to achieve victory in war and science.
Read together, the eyewitness excerpts below offer a new retelling of the Trinity test, woven entirely from words that more than a dozen of the project’s protagonists first published in the Bulletin.
SUITABLE GROUND: ALAMOGORDO
Lt. Gen. Leslie R. Groves
Groves was the Army administrative officer in charge of the entire wartime Manhattan Project. Scientists at Los Alamos loathed his policy of “compartmentalization,” which aimed to isolate scientists to preserve secrecy.
In the early days, we believed that a gun-type bomb would be entirely satisfactory for both uranium-235 and for plutonium, and we did not feel that any full-scale test would be necessary. Later, when we learned that the gun-type would not be suitable for plutonium, we began to realize that we might find it advisable to test the implosion-type bomb. … As soon as a full-scale test—and it had to be full-scale—became likely, we began the search for a suitable testing ground.
Kenneth T. Bainbridge
Bainbridge, a Harvard University physicist who worked on the development of radar before joining the Manhattan Project, was in charge of the Trinity test shot.
The basic requirements for the Trinity test site were a flat area to facilitate measurements, a remote but accessible region which for security reasons could not easily be associated with Los Alamos, and an area which could be cleared of all inhabitants months before the test date. The area had to be remote from populated areas so that people could be evacuated in the event of a low-order detonation, which would distribute poisonous plutonium, or a high-level explosion, which would be accompanied by dangerous radioactive fall-out.
George B. Kistiakowsky
Kistiakowsky, a physical chemist from Harvard, led the X (explosives) division at Los Alamos, which developed the implosion lenses required to uniformly compress the bomb’s plutonium core. He later served as a science adviser to presidents Eisenhower and Kennedy.
The Alamogordo site chosen for the Trinity test is in the White Sands military reservation, about 200 miles south of Los Alamos, in the middle of an arid, sandy desert appropriately called Jornada del Muerto by the seventeenth-century Spaniards. Kenneth Bainbridge was in charge of selecting, and then developing, the test site. His organization grew large because, while confidence in the implosion process was growing slowly, ever more experiments were being invented and designed to observe the progress and consequences of the nuclear reaction or its absence, and the causes thereof.
Bainbridge had his field headquarters at an abandoned ranch, really just a group of crude shacks, about ten miles from the Trinity ground zero. To these he added more buildings, almost equally uncomfortable, since General Groves would not allow any “luxuries,” as he defined them. Life at the Trinity site was primitive and there was grumbling by those who had to spend weeks on end there and who, because of the strictures of secrecy, could not visit nearby towns for relaxation. Nonetheless, by a near miracle of hard work, an elaborate field-test installation was created in just a few months’ time.
Emilio Segrè
Italian physicist and winner of the 1959 Nobel Prize in Physics. Segrè headed the radioactivity research group at Los Alamos, and was responsible for measuring the gamma radiation from the Trinity blast.
In July many of the physicists moved to the desert site to prepare for the final tests. The tests consisted in the explosion of an atomic bomb containing Pu239, located at the top of a steel tower, and in the measurement of the energy released under various forms: light, gamma rays, shock wave, and so on.
We established ourselves in barracks, under paramilitary discipline, and Fermi participated in most of the work. He and [Herbert L.] Anderson also had a special post-explosion project, which was to collect some of the sand and rocks immediately under the tower that supported the bomb and measure the fission products found in the ground. The desert was extremely hot during the day but relatively cool at night, and occasionally there were heavy thunderstorms. In the strange surroundings—scorpions, and gila monsters abounded, and the plants, desert adapted, looked unfamiliar—the physicists and their helpers ran miles of cables, calibrated innumerable pieces of apparatus, developed routine procedures, and then tested and retested them, always with the thought that there could be no repetition in case of failure, a most unusual condition for an experimental physicist. We worked very hard—best in the early morning and with less vigor as the temperature rose and the light became blinding. In the evening, very tired, we returned to our cots in the barracks. I had brought a French novel to read, a practice I had formed years before as a soldier, and I found refreshment in diverting my thoughts from the present situation to an imaginary world.
“I doubt if anyone outside of New Mexico would ever have heard of Alamogordo if Los Alamos had not been selected as the site of our bomb laboratory.”
— Leslie R. Groves