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The Trinity Test was the first official detonation of a nuclear weapon. The test was conducted on July 16th, 1945 by the United States Army, as part of The Manhattan Project
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Explosion of the Trinity bomb.

History of the test


This test was intended to prove the radical new implosion weapon design that had been developed at Los Alamos during the previous year. This design, embodied in the test device called Gadget, involved a new technology that could not be adequately evaluated without a full scale test. The gun-type uranium bomb, in contrast, was certain to be effective and did not merit testing. In addition, since no nuclear explosion had ever occurred on Earth, it seemed advisible that at least one should be set off with careful monitoring to test whether all of the theoretical predictions held.

The origin of the name Trinity for this event is uncertain. It is commonly thought that Robert Oppenheimer provided the name, which would seem logical, but even this is not definitely known. A leading theory is that Oppenhimer did select it, and that he did so with reference to the divine Hindu trinity of Brahma (the Creator), Vishnu (the Preserver), and Shiva (the Destroyer). Oppenheimer had an avid interest in Sanskrit literature (which he had taught himself to read), and following the Trinity test is reported to have recited a passage from the Bhagavad-Gita.

If the radiance of a thousand suns Were to burst at once into the sky, That would be like the splendor of the Mighty One... I am become Death, The shatterer of Worlds.[1]

Before Trinity: The 100 Ton Test

To help in preparing the instrumentation for the Trinity shot, the "100 Ton Test" was fired on 7 May 1945. This test detonated 108 tons of TNT stacked on a wooden platform 800 yards from Trinity ground zero. The pile of high explosive was threaded with tubes containing 1000 curies of reactor fission products. This is the largest instrumented explosion conducted up to this date. The test allowed the calibration of instruments to measure the blast wave, and gave some indication of how fission products might be distributed by the explosion.[1]

The Gadget

On 12 July 1945, the Gadget components arrived at the test site. Assembly of the test device began at the McDonald Ranch farmhouse at Alamogordo at 1300 hours. Two days later, Robert Bacher drove the assembled core to Zero, where final assembly of the Gadget was conducted in a canvas tent at the basis of the tower. Later that same day, the assembled Gadget (without detonators) was hoisted to the top of the 100 foot test tower. On the night of July 15th, the detonators were installed in the Gadget, and assembly was completed. Dr. Norris Bradbury, supervising the assembly process noted in his log book: "Look for rabbit's feet and four leaf clovers. Should we have the chaplain down here"?[1]

The Trinity Test

At 5:29:45 A.M. (Mountain War Time), on 16 July 1945, The gadget was detonated at Trinity Site Zero, at the Alamogordo Test Range in the Jornada del Muerto desert, producing a yield of between 20 and 22 Kilotons.

In that brief instant in the remote New Mexico desert the tremendous effort of the brains and brawn of all these people came suddenly and startlingly to the fullest fruition. Dr. Oppenheimer, on whom has rested a very heavy burden, grew tenser as the last seconds ticked off. He scarcely breathed. He held on to a post to steady himself. For the last few seconds, he stared directly ahead and then when the announcer shouted "Now!" and there came a tremendous burst of light followed shortly thereafter by the deep growling roar of the explosion, his face relaxed into an expression of tremendous relief. Several of the observers standing back of the shelter to watch the lighting effects were knocked flat by the blast.
...All seemed to feel that they had been present at the birth of a new age -- The Age of Atomic Energy -- and felt their profound responsibility to help in guiding into the right channels the tremendous forces which had been unlocked for the first time in history."
~ 'Brigadier General Thomas F. Farrell', describing his impressions at S-10,000, a bunker 10,000 yards south of Trinity, quoted in The Day the Sun Rose Twice by Ferenc M. Szasz, pg. 88.[1]

The heat of the Trinity explosion melted the sandy soil around the tower to form a glassy crust known as "trinitite". Years later, with a view towards making the Trinity site a tourist-accessible national historic site (a plan that has never been carried out), the mildly radioactive crust was bulldozed into heaps and covered with soil.[1]


  1. 1.0 1.1 1.2 1.3 1.4 Trinity Test page of the Nuclear Weapon Archive website.

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