- Kenneth Bainbridge: “No one who saw it could forget it, a foul and awesome display.”
- Enrico Fermi: “About 40 seconds after the explosion, the air blast reached me. I tried to estimate its strength by dropping from about six feet small pieces of paper before, during, and after the passage of the blast wave. Since, at the time, there was no wind I could observe very distinctly and actually measure the displacement of the pieces of paper that were in the process of falling while the blast was passing. The shift was about 2½ meters, which, at the time, I estimated to correspond to the blast that would be produced by ten thousand tons of T.N.T.”
- Kenneth Greisen: “A group of us were lying on the ground just outside of base camp (10 miles from the charge), and received time signals over the radio, warning us when the shot would occur. I was personally nervous, for my group had prepared and installed the detonators, and if the shot turned out a dud, it might possibly be our fault. We were pretty sure we had done our job well, but there is always some chance of a slip.”
- General Leslie R. Groves: “Drs. Conant and Bush and myself were struck by an even stronger feeling that the faith of those who had been responsible for the initiation and the carrying on of this Herculean project had been justified. I personally thought of Blondin crossing Niagara Falls on his tight rope, only to me this tight rope had lasted for almost three years and of my repeated confident-appearing assurances that such a thing was possible and that we would do it.”
- Joan Hinton: “It was like being at the bottom of an ocean of light. We were bathed in it from all directions. The light withdrew into the bomb as if the bomb sucked it up. Then it turned purple and blue and went up and up and up. We were still talking in whispers when the cloud reached the level where it was struck by the rising sunlight so it cleared out the natural clouds. We saw a cloud that was dark and red at the bottom and daylight at the top. Then suddenly the sound reached us. It was very sharp and rumbled and all the mountains were rumbling with it.”
- Joseph Kanon in his novel Los Alamos: “This was the real secret. Annihilation. Nothing else. A chemical pulse that dissolved finally in violet light. No stories. Now we would always be frightened.”
- Edwin McMillan: “The whole spectacle was so tremendous and one might almost say fantastic that the immediate reaction of the watchers was one of awe rather than excitement. After some minutes of silence, a few people made remarks like, “Well, it worked,” and then conversation and discussion became general. I am sure that all who witnessed this test went away with a profound feeling that they had seen one of the great events of history.”
- Frank Oppenheimer: “And so there was this sense of this ominous cloud hanging over us. It was so brilliant purple, with all the radioactive glowing. And it just seemed to hang there forever. Of course it didn’t. It must have been just a very short time until it went up. It was very terrifying. And the thunder from the blast. It bounced on the rocks, and then it went—I don’t know where else it bounced. But it never seemed to stop.”
- J. Robert Oppenheimer (in 1965): “We knew the world would not be the same. A few people laughed, a few people cried, most people were silent. I remembered the line from the Hindu scripture, the Bhagavad-Gita. Vishnu is trying to persuade the Prince that he should do his duty and to impress him takes on his multi-armed form and says, ‘Now, I am become Death, the destroyer of worlds.’ I suppose we all felt that one way or another.”
- Isidor I. Rabi: “It was seen to last forever. You would wish it would stop; altogether it lasted about two seconds. Finally it was over, diminishing, and we looked toward the place where the bomb had been; there was an enormous ball of fire which grew and grew and it rolled as it grew; it went up into the air, in yellow flashes and into scarlet and green. It looked menacing… A new thing had just been born; a new control; a new understanding of man, which man had acquired over nature.”
- Robert Serber: “The grandeur and magnitude of the phenomena were completely breath-taking.”
- Maurice Shapiro: “The shock wave from the explosion arrived about one and a half minutes after the flash of light, and I heard it as a sharp report. Although I had expected it, the intensity of the blast startled me. My impression at the time was that an enemy observer stationed about 20 miles from the scene of delivery would be deeply impressed, to say the least.”
- Cyril S. Smith: “At the instant after the shot, my reactions were compounded of relief that ‘it worked’; consciousness of extreme silence, and a momentary question as to whether we had done more than we intended. Practically none of the watchers made any vocal comment until after the shock wave had passed and even then the cheers were not intense or prolonged.”