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National Museum of Nuclear Science & History

Veterans Remember the Trinity Test

Trinity test shot 20 seconds

On July 16, 1945, at 5:29 AM MT, Manhattan Project scientists conducted the world’s first atomic bomb test at the Trinity site near Alamogordo, New Mexico. The Atomic Heritage Foundation is pleased to feature dozens of audio/visual interviews with Trinity test eyewitnesses on the “Voices of the Manhattan Project” website. From Manhattan Project director General Leslie R. Groves to scientists and soldiers, they recall the overwhelming force and terrifying beauty of the first nuclear explosion.                              


Leading Up to Trinity

Scientists feared the “Gadget,” the plutonium implosion device, would not work. As chemist George Kistiakowsky explained. “The physicists were very skeptical as to whether the lenses would work properly. I bet [J. Robert] Oppenheimer quite a bit of my money, about six or seven hundred dollars against ten dollars, that the explosive part would work and there would be some nuclear reaction.” He was right, and Oppenheimer paid him his due after the successful test.

Emilio Sègre, who would win the Nobel Prize in Physics in 1959, was one of the skeptical physicists. “I asked whether they were absolutely sure that the atmosphere wouldn’t catch fire. They tried to reassure me but that thing was pretty fearful. I can’t say that I started to calm down!”

Elsie McMillan described her husband Edwin McMillan’s uncertainty about what would occur on the evening of the Trinity Test. He told Elsie: “We know that there are three possibilities. One, that we will all be blown to bits, if it is more powerful than we expect. If this happens, you and the world will be immediately told. Two, it may be a complete dud. If this happens, you will also be told. Third, it may as we hope be a success. We pray without loss of any lives. In this case, there will be a broadcast to the world with a plausible explanation for the noise and the tremendous flash of light which will appear in the sky.”

The military wanted to keep the Trinity test a secret, no matter what happened. Thomas O. Jones was a counterintelligence officer at Los Alamos. “My role in that situation was to see whether this bomb went “pfump” or whether it took half of the state of New Mexico into the air and perhaps into flights around the world. My role was to see that whatever happened, nobody noticed.”

Despite the enormous tension before the Trinity test, General Groves proudly remembered that he remained calm and confident. “At Alamogordo, we had about three hours or four hours to wait for the bomb. The tents were flapping in the high wind. [James B.] Conant and [Vannevar] Bush were in the same tent with me. Afterwards they asked, “How on earth did you sleep? You went right to sleep while we stayed awake. With those tents flapping, how could you sleep?”

Physicist Raemer Schreiber explained why the Trinity Test was planned for 4:00 am. “They wanted to do it in dark, you see, in order to do a lot of the diagnostic work, high-speed camera photographs of it and so on. It had to go in the dark and it was also supposed to be clear enough so that the diagnostic aircraft who were sensing the instruments could sense blast gauges and so on and could orbit on the tower, which had a bright light on it.”


Witnessing the Test

A passing storm forced the test to be delayed for an hour. Finally, physicist Marvin Wilkening recalled the last few seconds: “There was a countdown by Sam Allison, the first time in my life I ever heard anyone count backwards. We used welder’s glass in front of our eyes, and covered all our skin. When the countdown ended, it was like being close to an old-fashioned photo flashbulb.”

Stanley Hall, a laboratory technician at Los Alamos, remembered hearing “The Star Spangled Banner” playing on the radio at the same time that the bomb went off. He likened the heat from the explosion to being “in the kitchen, and somebody opens the oven door, and a little warm air comes out. That’s about the way it felt ten miles away, like a warm breeze coming from an oven door.”

The sight of the explosion led to mixed feelings on the part of the eyewitnesses. William Spindel recalled: “It was the most shocking, enormous explosion that I had ever seen. I was about twenty miles away from the site. We were supposed to keep our eyes closed for the first ten seconds because of ultraviolet radiations.

“I estimated that at twenty miles away, the explosion traveling at the speed of sound would take about a minute to reach me. It was the most intimidating minute I have ever spent. Seeing the terrible ball, growing and growing, enormous colors. What kind of blast could it be when it finally got to me? Fortunately, it wasn’t that great because I’m still here.”

Hans Courant, who was a German refugee and physicist at Los Alamos, described his immediate reaction to the test. “My hands got warm from the heat from the bomb, which just grew and grew, and then eventually started up into the sky. But, I had been sitting there and I thought, “Oh, my God.”

Val Fitch, a member of the Special Engineer Detachment who would go on to the win the Nobel Prize in Physics in 1980, was amazed by the size of the explosion. “It’s hard to overstate the impact on the senses of something like that. First the flash of light, that enormous fireball, the mushroom cloud rising thousands of feet in the sky, and then, a long time afterwards, the sound. The rumble, thunder in the mountains. Words haven’t been invented to describe it in any accurate way.”

Roger Rasmussen, another member of the Special Engineer Detachment, remembered, “the brightest light came that I had ever observed with my eyes closed. That was the detonation, but there was no noise and no sound and nothing to see until our troop master said we could look up. We stood up and looked into this black abyss ahead of us. There was this beautiful color of the bomb, gorgeous. The colors were roving in and out of our visual range of course. The neutrons and gamma rays and all that went by with the first flash while we were down. There we stood, gawking at this.”


Reflections and Implications 

Felix DePaula, a soldier at Los Alamos, was less impressed. “The [Trinity test] didn’t make a big impression on me because the only thing I had ever seen in the way of explosives was firecrackers. But an older man, Pop Borden, had worked with dynamite before he got into the service. Four days after the detonation, Borden still couldn’t eat because he was so upset about the detonation: ‘That’s the most terrible thing I’ve ever seen in my life.’ Borden could see the devastation that it could bring on because he had something to compare it to. I had nothing to compare it to.”

Berlyn Brixner, the head of photography at the Trinity Test, was essentially dumbfounded by the explosion. “We had had previously what was called a dry run and they piled up a hundred tons of TNT and exploded that to give us a kind of a test with all of our equipment and cameras. That was just nothing compared to this explosion. I knew immediately that the explosion had exceeded the greatest expectations and that essentially we had won the war because that bomb would soon be used on Japan.”

Following the test, physicist Geoffrey Chew discussed the implications of such powerful technology with his group members. “We were very much aware that it was an important development in the history of the world.”

Officially, the cause of the explosion was reported as the accidental detonation of a bunker containing a number of high explosives and pyrotechnics. Chemist Lilli Hornig, who witnessed the test from the Sandia Mountains, recalled, “We stopped at a diner somewhere near Albuquerque for breakfast. And the guy behind the counter said, ‘You guys know anything about that explosion they had down at the proving grounds?’ We said, ‘What? No, we didn’t know about that.’”

For these interviews and more reflections on the test, visit “Voices of the Manhattan Project.”