Manhattan Project Scientists’ Reaction to the World’s First Atomic Bomb Test

By | July 16, 2023

Witnessing the Astonishing Transformation: Scientists’ Accounts

The night turned into day: an extraordinary moment that forever changed the course of human history. In the depths of the New Mexico desert, scientists involved in the Manhattan Project anxiously awaited the culmination of their groundbreaking work. On July 16, 1945, their efforts came to fruition as the world’s first atomic bomb was detonated at the Trinity site. The magnitude of the event, its blinding light and intense heat, left an indelible mark on the witnesses. Let us delve into the firsthand accounts of these remarkable scientists and gain insight into their profound experiences.

Richard Feynman: An Unforgettable Flash

Richard Feynman, positioned 20 miles from the Trinity site, received a pair of dark glasses for protection. However, he opted for an alternative view. He hopped into the cab of a truck, facing the direction of Alamogordo, using the windshield as his shield against harmful ultraviolet rays. With anticipation, Feynman awaited the spectacle about to unfold. As the detonation occurred, a tremendous flash illuminated the horizon. Reflexively, he instinctively ducked, shielding himself. When he glanced up once more, he witnessed a radiant transformation: the white light gradually morphed into hues of yellow and orange. “A big ball of orange, the center that was so bright, becomes a ball of orange that starts to rise and billow a little bit and get a little black around the edges, and then you see it’s a big ball of smoke with flashes on the inside of the fire going out, the heat.” After a minute and a half, the explosion’s thunderous sound finally reached Feynman, accompanied by the rumble of man-made thunder.

James Conant: Overwhelmed by an Illuminated Sky

James Conant had anticipated a swift flash of light. However, the luminosity was so intense that, for a fleeting moment, he believed “something had gone wrong.” It seemed as if the “whole world had gone up in flames.” The blinding radiance engulfed the sky, defying his expectations.

Bob Serber: Momentary Blindness and a Violet Column

Bob Serber, positioned 20 miles away, lay face down, gripping a piece of welder’s glass to shield his eyes. Just as his arm grew weary and he lowered the glass for a brief respite, the bomb detonated. In that moment, he experienced complete blindness from the brilliant flash. When his vision returned after half a minute, a striking violet column soared into the atmosphere, reaching heights of 20,000 to 30,000 feet. Even at such a distance, Serber could feel the heat on his face, a testament to the immense power unleashed.

Joe Hirschfelder: The Night Transformed into Day

Joe Hirschfelder, assigned the task of measuring the radioactive fallout from the explosion, vividly recounted the pivotal moment. As the detonation occurred, darkness was abruptly replaced by an overwhelming brightness. The chilling night transformed into a realm of warmth. The fireball expanded, evolving from white to yellow, and eventually to red, as it ascended into the sky. After approximately five seconds, darkness reclaimed its dominion, yet a purple glow bathed the surroundings akin to an aurora borealis. In awe, the scientists watched as the blast wave carried fragments of desert soil, whisking them away from their location.

Frank Oppenheimer: The Unearthly Cloud

Frank Oppenheimer, brother of J. Robert Oppenheimer, lay next to his sibling when the bomb detonated. Despite lying on the ground, he keenly felt the light of the initial flash permeate through his closed eyelids. When he gazed upward, he beheld the awe-inspiring fireball, swiftly followed by an otherworldly hovering cloud. Its brightness and purplish hue left him apprehensive, wondering if it would drift towards their position. The intensity of the flash’s heat surpassed his expectations. Within moments, the echoes of the explosion reverberated among the distant mountains. Frank recollected that the most terrifying sight was the luminous purple cloud, tainted with radioactive dust, ominously lingering in the atmosphere, its trajectory uncertain.

J. Robert Oppenheimer: A Moment of Relief and Triumph

J. Robert Oppenheimer himself lay facedown, just outside the control bunker, situated 10,000 yards south of ground zero. As the countdown approached its final moments, he muttered a heartfelt plea: “Lord, these affairs are hard on the heart.” An Army general observed Oppenheimer closely as the countdown concluded. The tension in Oppenheimer’s demeanor grew palpable with each passing second. He scarcely breathed, fixating his gaze straight ahead. Then, as the announcer shouted, “Now!” a blinding burst of light enveloped the area, promptly followed by the deep, rumbling roar of the explosion. In that instant, Oppenheimer’s face transformed, displaying an expression of immense relief. Although we cannot fully grasp the thoughts racing through Oppenheimer’s mind, his brother recalled that they shared the sentiment, “It worked.”

The Aftermath: A Testament to the Impact

In the aftermath of the detonation, physicist Isidor Rabi caught sight of Robert Oppenheimer from a distance. Oppenheimer’s stride exuded a sense of confidence and authority, leaving an indelible impression on Rabi. He vividly remembered the way Oppenheimer alighted from his car, walking with a certain swagger reminiscent of a scene from “High Noon.” It was a walk that embodied accomplishment and triumph.

When approached by William L. Laurence, the New York Times reporter selected to chronicle the event, Oppenheimer described his emotions with stark candor. He confessed that the blast had been “terrifying” and “not entirely undepressing.” After a momentary pause, he added a poignant reflection, “Lots of boys not grown up yet will owe their life to it.”


The detonation of the world’s first atomic bomb marked a pivotal moment in human history. Through the accounts of the Manhattan Project scientists, we gain glimpses into their awe, trepidation, and the lasting impact of that fateful day. The brilliant flash that transformed the night into day, the intense heat, and the unsettling aftermath were etched into their memories forever. The legacy of their work, fraught with triumph and tragedy, shaped the course of science and humanity’s relationship with unprecedented power.

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