Eyewitness Report by Robert Serber

“I viewed the test, with the Coordinating Committee expedition, from a point about twenty miles away. At the instant of the explosion, I looked directly at it without eye protection. I saw first a yellow glow, which grew almost instantly into an overwhelming white flash, so intense that I was completely blinded. There was a definite sensation of heat. The brilliant illumination seemed to last for about three to five seconds, changing to yellow and then to red; at this stage, it appeared to have a radius of about twenty degrees. The first thing I succeeded in seeing after being blinded by the flash looked like a dark violet column several thousand feet high. This column must have been quite bright, or I would not have been able to distinguish it. I was regaining normal vision by twenty or thirty seconds after the explosion. At perhaps twenty thousand feet in height, two or three thin horizontal layers of shimmering white cloud were formed, perhaps due to condensation in the negative phase of the shock wave. Sometime later, the noise of the explosion reached us. It had the quality of distant thunder but was louder. Due to reflections from nearby hills, the sound returned and repeated and reverberated for several seconds, much like thunder. A column of white smoke appeared over the point of the explosion, rising very rapidly and spreading slightly as it grew. In a few seconds, it reached cloud level, and the clouds in the immediate neighborhood seemed to evaporate and disappear. The column continued to rise and spread to about twice the cloud level. There was no appearance of mushrooming at any size. A smoke cloud also was spreading near ground level. The grandeur and magnitude of the phenomenon were utterly breathtaking.”

Robert Serber

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.