The effects could well be called unprecedented, magnificent, beautiful, stupendous, and terrifying. No manmade phenomenon of such tremendous power had ever occurred before.
—Gen. Thomas Farrell, eyewitness at the Trinity test, writing the day afterwards
The Road to Trinity
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Manhattan Project scientists and engineers were confident the gun-type uranium bomb would work. They were less sure of the more complicated implosion-type plutonium bomb. In 1944, Project leadership began planning for a full-scale test of the latter, with physicist Kenneth Bainbridge in charge.
Base Camp at Trinity Site. Some of these buildings have been built for the test, others are from a ranch which was taken over by the government. Los Alamos Historical Society Photo Archives.
Bainbridge selected a remote, sparsely populated desert near Alamogordo, 220 miles south of Los Alamos, as the site codenamed “Trinity.” The Alamogordo Bombing and Gunnery Range, in the Jornada del Muerto desert, was 35 miles southeast of Socorro. Historians are uncertain exactly how the codename Trinity was selected, but after the fact, Los Alamos Laboratory Director J. Robert Oppenheimer wrote that he may have been inspired by the poetry of John Donne.
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Batter my heart, three-person'd God, for you |
At Trinity Site
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The military began work at Trinity Site in December of 1944. The pace of preparations quickened in the spring of 1945, soon reaching a fever pitch. By the summer the Project raced to complete the test in time to strengthen President Truman’s hand in negotiations with Soviet leader Joseph Stalin over postwar Europe at the Potsdam Conference in July.
Hundreds of people, soldiers and civilians, worked in secret in the desert. Test explosions, not involving nuclear materials, began in May. Early in the morning on July 13, couriers drove a U.S. Army sedan from Los Alamos to the test site, carrying the explosives assembly for the Trinity Test in the back seat. Scientists and engineers assembled the test device on site at Trinity. |
Military police (MPs) at Trinity Site. Back row: Bisher, Jeffery, Barnett, Chambers, and Noble. Front row: Agnew, Snodgrass, and Wendelin. Los Alamos Historical Society Photo Archives, Marvin Davis Collection.
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The Test
The device exploded for the Trinity Test, called the Gadget, was an experimental prototype of an atomic bomb. The military planned on detonating atomic bombs in the air, to maximize the force of the shockwave, so the Gadget was lifted to the top of a 100-foot tower for the test. The test was scheduled for 4:00 a.m. on July 16. Summer thunderstorms rolled into the desert that night.
The Trinity Test tower under construction. In this photo people are working at the top and the base of the tower. Los Alamos Historical Society Photo Archives.
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The Gadget is suspended by tackle at the top of the tower. Norris Bradbury (left) and an unidentified Project employee stand behind the Gadget. Los Alamos Historical Society Photo Archives, LANL Collection, TR Series.
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In spite of the thunderstorms, the detonation took place at 5:29:45 a.m. on July 16, 1945. Tensions ran high. Observers held their breaths. Then, as eyewitness James Conant recalled the next day, “The whole sky [was] suddenly full of white light like the end of the world.” The explosion was roughly equivalent to an explosion of 21,000 tons of TNT. In his report on the test, Robert Serber said, “The grandeur and magnitude of the phenomenon was completely breathtaking.” For many, awe at the terrifying yet magnificent sight—history’s first atomic explosion—was accompanied by a simple sense of relief that it worked.
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Four platoons of soldiers stood ready to evacuate nearby residents if the winds threatened to carry fallout over their homes. No evacuations were deemed necessary, but a few days after the test local ranchers found white splotches on the hides of some of their cows, likely caused by radioactive dust.
Some families in Los Alamos were told to wake up early and look south on the morning of the test. From houses, or wrapped in blankets up on the mountainside, they saw what looked like the light of a sunrise. Most did not know that they were witnessing the light of the dawn of the atomic age.
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Visitors to the Los Alamos History Museum can look through the windows through which Elsie McMillan and Lois Bradbury saw the light from the Trinity Test.
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Eyewitnesses Interviewed for Voices of the Manhattan Project
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Voices of the Manhattan Project is a joint project by the Atomic Heritage Foundation and the Los Alamos Historical Society to collect oral histories from Manhattan Project veterans and their family members to create a public archive of first-hand accounts of the Manhattan Project.
Jack Aeby's 35mm Perfex Forty-Four camera on display in the Los Alamos History Museum. Aeby used this camera to take the only color published photo of the Trinity Test. On the orange block beside the camera is a bit of firing cable used for the test, and behind it is a piece of glass used in an observation bunker.
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In this photo of the Trinity Test taken by Jack Aeby, the mushroom cloud has developed, and the light of the explosion is reflected on the clouds above Ground Zero. Los Alamos Historical Society Photo Archives, Aeby Collection.
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Additional Photos
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The Los Alamos Historical Society was supported by a generous grant from the National Endowment for the Humanities and the New Mexico Humanities Council in the creation of this page.
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