:: :: History Pre Cold War Manhattan Project Trinity Eyewitness Cyril S. Smith

Trinity Test, July 16 1945 Eyewitness Report by Cyril S. Smith


DATE: July 25, 1945

TO: Lieutenant Taylor
FROM: C. S. Smith
SUBJECT: Trinity Shot

You requested me to write a brief description of the Trinity shot. Since this took place over a week ago my impressions have undoubtedly been modified very considerably by subsequent discussion and many features have faded from memory.

I was located at the base camp, behind a five foot embankment near the water tanks at T=0. I was facing away from the shot, somewhat bent down below the top of the bank. In addition, my eyes were partly covered by a welder's glass. For a time estimated as two seconds (though it may have been less) I was watching the ground through the corner of my eye. Even though this was lighted by reflection from the clouds, it was intensely bright and apparently free from color. Since the shot there has been some discussion of the duration of this intense light, but it is definitely my recollection that I opened and closed my eyes several times and waited for the light to decrease in intensity before turning to face the reaction zone directly. Even after the estimated 2 seconds the light was still intense enough to be clearly seen through the welder's glass but there was no direct ball of fire or structure or any symmetry, this part of the phenomenon evidently having ceased.

The appearance of a turbulent gas apparently undergoing combustion was quite surprising. It looked not much different from the film of the 100 ton shot or any large fire, for instance an oil tank fire or the Graf Zeppelin. After another second or two I removed the welder's glass and looked directly. As the main light became less intense, the bluish ionization zone became visible, extending to a diameter almost twice that of the area where there was incandescence. I noticed a dust cloud travelling near the ground, and at some stage (I am not sure whether early or late in the proceedings, but it was definitely illuminated by the shot) I noticed a ring, supposedly of moisture condensed by the rarefaction wave, at a level slightly below the clouds. This ring did not spread, but once formed seemed to remain stationary.

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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. The elation of most observers seemed to increase for a period of 30 minutes afterwards, as they had a chance to absorb the significance of the achievement.

The rising of the cloud of reaction products to above the cloud level seems to have proceeded rapidly but in a normal fashion. It was noticeable that there were a number of rough projections, indicating high local turbulence. Shortly after the smoke column with its mushroom top was formed, wind currents distorted it into a jagged or corkscrew appearance. There was a dust cloud over the ground, extending for a considerable distance. A cloud, whether of dust or moisture particles, hung close to the ground and slowly drifted east into the hills, persisting for over an hour.

The obvious fact that all of the reaction products were not proceeding upward in a neat ball but were lagging behind and being blown by low altitude winds over the ground in the direction of inhabited areas produced very definite reflection that this is not a pleasant weapon we have produced. Later reflections were on the manner of defense against it and the realization that a city is henceforth not the place in which to live.

I repeat that no attention should be paid to any comment made in this report, since the described events occurred many days ago.

Cyril Stanley Smith

cc: Hawkins File

Source: U.S. National Archives, Record Group 227, OSRD-S1 Committee, Box 82 folder 6, "Trinity." Transcription: Thank you Gene Dannen for transcribing this document.