Eyewitness Report by Philip Morrison

“I observed the Trinity shot looking toward Zero from a position on the south bank of the base camp reservoir directly beside the larger water tank. There were three distinct stages in the process I saw, which I describe consecutively as follows:”

1. Instantaneous glow and ball of fire

“At time T = -45 seconds, I lay prone facing Zero wearing ordinary sunglasses and holding in one hand a stopwatch and in the other the welding glass issued by the stockroom. I watched the second-hand until T = -5 seconds when I lowered my head onto the sand bank so that a slight rise in the ground completely shielded me from Zero. I placed the welding glass over the right lens of my sunglasses, the left lens of which was converted by an opaque cardboard shield. At zero, I counted seconds and began to raise my head just over the protecting rise. The gadget went off during this motion while I was looking at it, or possibly a tiny fraction of a second before. I first saw a brilliant violet glow entering my eyes by reflection from the ground and the surroundings generally. I had not raised my head enough to envision Zero. Immediately after this brilliant violet flash, which was somewhat blinding, I observed through the welding glass, centered in the tower’s direction, an enormous and bright disk of white light. The sensation lasted briefly, and the light was so great that I could not be sure of the observed shape. I remember it only as a well-marked, vaguely round pattern. This disk was a true white, even though the welding glass made the sun’s disk distinctly deep green. On subsequently looking at the noon sun through these glasses, I have been led to estimate this initial stage of the gadget as corresponding to a color much whiter or bluer and a brightness several times greater than that of the noon sun. I felt an intense sensation of heat on the exposed skin of my face and arms, lasting for several seconds and at least as fierce as the direct noon sun.

It should be noted that my eyes were adapted to twilight or perhaps even to somewhat brighter light because of the use of the radio dial light I had made just previous to the T -45 second signal.”

2. Growth of the mushroom

“The bright disk produced an after-effect in my eyes for less than two seconds, which spoiled the details of the following process. I quickly realized that my vision was improving, and the image was becoming much fainter and less white. I then took off the welding glass and, several seconds later, the sunglasses as well. Beginning at T = +2 to 3 seconds, I observed the somewhat yellowed disk beginning to be eaten from below by dark obscuring matter. Meanwhile, the whole surface of the plain was covered with cases being thrown into the air as the motion continued outward from Zero. In a matter of a few seconds more, the disk had nearly stopped growing horizontally and was beginning to extend in a vertical direction while its appearance had transformed into a brightly glowing, distinctly red column of flame mixed with swirling obscuring matter. The queue looked rather like smoke and flame rising from an oil fire. This turbulent red column rose several thousand feet in a few seconds, growing a mushroom-like head of the same kind. This mushroom was fully developed, and the glowing structure was complete at about 15,000 feet. I do not recall whether this stage was reached before or after the arrival of the shock. At T +30, I realized the surprise was due very soon, and I huddled closer to the ground in anticipation of a severe shock. The arrival of the air shock at T +45 on my stopwatch came as an anti-climax. I noticed two deep thuds, which sounded like a kettle drum rhythm being played some distance away. I remember the sound without important high-frequency components, such as cracks. There was no earth tremor perceptible to me at any time. The ground on which I was lying was a very loosely packed mud dike.”

3. Appearance of the smoke cloud

“After the passage of the shock, I stood up to watch the end of the mushroom. The red glow died out, and the mushroom appeared as a smoke or cloud hanging over Zero. In another minute or so, the smoke had arranged itself in three instead well-defined oblique clouds forming roughly a vertical Z. The lowest cloud was reasonably well-defined and stretched north at a slight angle. At a couple of thousand feet, it appeared to bend around almost double and to stretch about southeast for a somewhat greater distance. This second cloud again seemed broken off rather sharply, and a large cloud gradually spread with a less and less well-defined shape from the upper end of the second step. This process was nearly complete when the upper cap was applied over most of the bowl at about 30,000 feet. There was a strong impression of definite layers in the wind structure, and even some water vapor clouds seemed to mark the boundaries between winds of different directions. The completion of this stage took many minutes. Finally, the cloud was rather well dispersed toward north 10,000 at a relatively low level, had overspread at an intermediate level to the Oscuro mountains, and was drifting slowly south and southeast on a higher level.”

Other observations:

“After T = +50 seconds, I distinctly smelled a faint but marked odor of ozone or corona discharge ionization upon standing up. At T +15 minutes or more, I observed Zero through a battery commander’s periscope set of 8-power. Not much detail was visible in this region. A sort of dust haze seemed to cover the area. A remarkable heat shimmer was noticed on the horizon directly above the Zero area. It was shortly after this that I saw the Jumbo Tower was missing. The size and distance figures mentioned here are based on judgments of angular size and the assumption of 18,000 yards distance from Zero to base camp.”