DATE: 23 July 1945
TO: Captain T. O. Jones
FROM: Maurice M. Shapiro
SUBJECT: Observations of the Trinity Test
During the Trinity test, I was stationed about 20 miles away, with the members of the Coordinating Council.
At the time of the initial flash of light my eyes were not protected, and I was momentarily blinded, much as one would be in emerging suddenly from a dark room into bright sunlight. After a couple of seconds I regained sufficient sight to see the entire sky (in the direction of Trinity) aglow with an orange hue. This glow disappeared after a second or two, and then I saw a column of dark gases rising toward the overhanging clouds. Several people near me commented on the violet color of the cloud of gas, but I observed no such color, presumably because of the initial effect on my eyes. I estimated the width (or diameter) of the column of gas as roughly 1/5 mile. After a few minutes this column rose to a height which I judged to be 8 or 10 miles high, and then it spread laterally. There were a few small puffs of white vapor, which I interpreted as arising from a "cloud-chamber effect" (supersaturation followed by condensation of moisture).
The shock wave from the explosion arrived at 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.
Maurice M. Shapiro
Trinity Test - Eyewitness Accounts
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