Early on Friday, the two parts of the bomb were delivered to the temporary “clean room” set up in the abandoned McDonald ranch house, which had been vacuumed and whose windows had been sealed with black electrical tape against the pervasive dust. That morning, the final assembly phase began, with eight scientists outfitted in white surgical coats bending over a makeshift laboratory table where the plutonium pieces had been arranged on sanitized brown paper. The initiator, Hans Bethe’s creation, was a spherical shell of beryllium containing polonium, which on implosion would mix and produce the triggering neutrons. Warm to the touch, it was very carefully placed inside the two halves of the plutonium core, the mating pieces of the globe fitting together like a particularly lethal puzzle. Oppenheimer hovered in the background next to Thomas Farrell, the boyish young brigadier general whom Groves had chosen to represent him at the assembly site because of his rule that both project leaders not be present in situations where there was “an element of danger.” Waiting on the dirt road outside stood four jeeps, their motors idling, just in case the core accidentally went critical.
By afternoon, the core was mounted in a cylindrical plug of uranium and ready to go. The scientists gingerly placed it on a small litter and carried it out to the backseat of the same sedan they had driven to the desert. They eased the car into gear and rolled toward the one-hundred-foot tower. At ground zero, at the base of the tower, was a tentlike enclosure covering Kistiakowsky’s partially assembled implosion device, a five-foot sphere complete save for the cylindrical plug containing the plutonium and the initiator. The plug was attached to a manually operated hoist and, while everyone held his breadth, gently lowered into the bowel of the high-explosive shell. The first attempt to insert the plug failed, inducing a horrifying moment of panic. A few people stepped out of the tent to steady their nerves, while Oppenheimer, Kistiakowsky, and Bacher tried to calmly assess what had gone wrong. Bacher quickly surmised that the sweltering heat inside the farmhouse, combined with the car ride, had raised the temperature of the plutonium core and caused it to expand, whereas deep down in the shell it was still very cold. With prolonged contact, however, the temperatures would equalize, and the minutely calibrated plug would probably fit. A few minutes later, the plug finally slid into place. With that crisis averted, the explosive blocks were packed in without further complication, and the test device was buttoned up for the night.
Early Saturday morning at Trinity brought a singularly peculiar sight. The tent was removed, and the physicists prepared to raise the bomb assembly to the top of the tower using a huge winch, which Groves had procured for the astronomical price of $20,000. But the scientists, novices when it came to large-scale construction, had been so worried by the possibility that the cable would snap and the five-ton device would fall that they arranged to take some highly unusual precautions. Standing by all around the base of the tower were large army trucks containing hundreds of mattresses, the great mountains of striped cotton ticking visible above the metal siding. After they had hesitantly wound the device about fifteen feet in the air, a contingent of GIs rushed in and stacked nearly twelve feet of bedding on the ground directly underneath it. Just in case Fat Man fell, it would have something soft to land on. The gadget was then safely hoisted onto the tower, brought to the corrugated-steel shack on the top of the platform, where the detonators were inserted, and hooked up to the firing console.
With the finished bomb assembly poised on the tower, it looked like everything was going according to plan but the weather. A hot, sultry air mass had moved in, and the atmosphere thickened palpably. It began to drizzle lightly, promising the usual late afternoon thunderstorm. Watching the wind and lightning playing around the one-hundred-foot steel structure, it was hard not to imagine the tower as a giant lightning rod sticking out above the flat desert plain. The mood at base camp was strained. They were all keyed up in the extreme, and the waiting was making everything worse. While the instrument crews worked desperately to complete the last-minute checks on their vast array of equipment, senior scientists like Rabi, who had completed their part of the preparations, tried to relax by playing poker. Just when it seemed like the only threat to the test going forward as scheduled was the darkening sky, Oppenheimer received crushing news from Los Alamos. A coded telephone message reported that the dummy rig that was to be a dry run for Trinity, using an almost identical explosive assembly but without the plutonium core, had been tested in an empty canyon and had not worked properly. The experiment’s failure virtually guaranteed the implosion method would not create a nuclear reaction. The bomb would be a dud.
It was a shocking setback. Oppenheimer called an emergency meeting, but it quickly deteriorated into a shouting match with Kistiakowsky identified as the chief villain. “After that a perfectly ghastly scene developed,” recalled Kistiakowsky. “Oppenheimer, of course, who was responsible for the whole thing, being top dog at Los Alamos, was at the point of complete nervous exhaustion. You can’t blame him. He was really emotional, essentially telling me I might be responsible for the total failure of the project and how terrible it was. And how could I have trusted all these young people who worked for me, and were probably incompetent, etc., etc.” The fault finding continued, with Groves and Conant, who had by now arrived in Albuquerque, hauling Kistiakowsky over the carpet for what seemed like hours. “All of which was very unpleasant,” added Kistiakowsky. “So I finally said, at one point, ‘Look, Oppie, I bet you a month’s salary of mine against ten dollars that my part of the bomb will work.’”
They spent a long, miserable night contemplating what the failure of the bomb at Trinity might mean. Bush recalled a gloomy dinner he shared with Oppenheimer in Albuquerque that night, after a meeting at the Hilton Hotel with a large number of VIPs and army generals that Groves had invited to observe the test. Oppenheimer had put on a brave face, but his growing despair was expressed in the stanza from the Bhagavad Gita that he quoted before turning in, though whether for inspiration or consolation, Bush could not be sure:
In battle, in forest, at the precipice in the mountains,
On the dark great sea, in the midst of javelins and arrows,
In sleep, in confusion, in the depths of shame,
The good deeds a man has done before defend him.
Early on Sunday, July 15, another phone call came, this one bringing a reprieve. Bethe had stayed up all night recalculating the results of the experiment and had discovered an error, rendering the dummy test results meaningless. Chances were good the gadget would work after all. Kistiakowsky was out of the doghouse and, as he drolly observed, “became again acceptable to local high society.” Oppenheimer cheered up immediately and went off to find Hubbard and his meteorologists. By Saturday evening, Groves had arrived at base camp with Conant and Bush, and they had dinner with Oppie in the mess, followed by a general meeting covering such topics as how to avoid eye damage and the recommended evacuation routes in case fallout came their way. Conant took an interest in the betting pool on the size of the explosion, and privately figured on 4,400 tons but declined to sign up. “The atmosphere was a bit tense as might be expected,” he noted, “but everyone felt confident the bomb would explode.”
Groves was considerably less sanguine about the state of affairs. “The weather was distinctly unfavorable,” he recalled in his memoir. “There was an air of excitement at the camp that I did not like, for this was a time when calm deliberation was most essential.” Oppenheimer was “getting advice from all sides on what should and should not be done,” and Groves did not like what he was hearing.
The test had originally been scheduled for 4:00 A.M. on July 16, when most of the surrounding population would be sound asleep and there would be the least number of witnesses. But the weather was interfering with their plans, and there was talk of a postponement. It had become increasingly misty and blustery, and it rained intermittently. Some of the scientists were afraid there might be “a reversal,” that the winds would change direction and
blow the radioactive debris over Trinity base camp and the outlying areas. Others expressed concern that the excessive moisture might have damaged the connections and increased the chances of short circuits, even a misfire. They were urging the test be postponed for at least twenty-four hours.
When he had heard enough from the doomsayers, Groves pulled Oppenheimer into an empty office where they could discuss the matter privately. As the night wore on, Groves had become increasingly anxious about security and was convinced they should carry out the test, even under less than ideal circumstances. He worried that “every hour of delay would increase the possibility of someone’s attempting to sabotage the tests.” While Oppenheimer and his top advisors had held up admirably, Groves also worried that someone might become unnerved. If they lost a key physicist, it could cripple the operation and affect the test. “The strain had been great on all our people, and it was impossible to predict just when someone might give under to it,” he reasoned.
Groves was still annoyed with Fermi, who had remained completely cool amid all the bedlam, but that evening had unaccountably announced his intention of taking bets from his fellow scientists “on whether or not the bomb would ignite the atmosphere, and if so, whether it would merely destroy New Mexico or destroy the world.” Bainbridge had also been furious when he heard talk of the atmosphere being detonated. That possibility had been raised by Teller back in Berkeley, rehashed at Los Alamos, and roundly shot down by Bethe. Bainbridge considered it “thoughtless bravado to bring up the subject as a table and barracks topic before soldiers unacquainted with nuclear physics and with the results of Bethes studies.”
At the end of their discussion, Groves and Oppenheimer were in agreement: there was no need to postpone the test for a day, but they might have to put it off for an hour or two. Groves had decided to put his faith in Hubbard’s forecast, which called for a clear early morning with light winds. They would meet again at 1:00 A.M. and review the situation.
Groves elected to go to bed and urged Oppenheimer to get some rest, but noted later that he “did not accept my advice and remained awake, I imagine constantly worrying.”
At 1:00 A.M. Groves got up and prepared to join Oppie in the forward barricade. Conant, who was quartered in the same tent as Groves, recalled that from 10:30 P.M. to 1:00 A.M. the wind blew very hard—the canvas tent flaps slapped loudly—and then it poured for an hour. The storm had kept him up, and he was amazed the general had managed to sleep right through it. Oppenheimer and Groves drove the three miles to the control station at South 10,000. To protect the scientists and their equipment, the control dugout was built of wood and reinforced concrete, and buried under huge mounds of earth, 10,000 yards, or 6.2 miles, from ground zero. General Farrell was waiting for them as well as Bainbridge, who supervised all the detailed arrangements for the test, and Kistiakowsky, who was among the scientists keeping watch over Fat Man during its last night cradled in the tower. Hubbard, the weather expert, was there, along with a handful of army officers and soldiers. The dugout was a beehive of activity, but there was far less confusion than before, and the atmosphere was now one of forced calm. The physicists had been rehearsing for this moment for months and were focused on checking and rechecking their instruments and radios. The main worry was still the rain, which had let up some but had not stopped. After a brief huddle, they decided to postpone the test—first for an hour, then later for another thirty minutes.
Every five or ten minutes, Groves and Oppenheimer left the dugout and went outside to see if the weather was showing any signs of improving. By 3:30 A.M., the sky was still heavily overcast, but a few stars were becoming visible. They decided they would be able to go forward. Farrell remembered the scene inside the control station as “dramatic beyond words”:
In and around the shelter were some twenty-odd people concerned with last-minute arrangements prior to firing the shot… . For some hectic two hours preceding the blast, General Groves stayed with the Director, walking with him and steadying his tense excitement. Every time the Director would be about to explode because of something untoward happening, General Groves would take him off and walk with him in the rain, counseling him and reassuring him that everything would be all right.
With daybreak only an hour away, the decision was made—the firing would occur at 5:30 A.M. Thirty minutes before zero hour, the five men guarding the bomb at the tower threw the last safety switches and high-tailed it back to the shelter in their jeeps. In case of car trouble, they should have time to make it back on foot, but Groves comforted himself with the idea that “since Kistiakowsky was one of the five … they would find a safe position even in the event of a complete breakdown.” With twenty minutes to go, Groves returned to base camp, the safest close observation point, leaving Farrell, Oppenheimer, and his men behind. Farrell, in his account for the War Department, reported that once the countdown began and the intervals shrank from minute to seconds, “the tension increased by leaps and bounds.”
Everyone in that room knew the awful potentialities of the thing that they thought was about to happen. The scientists felt that their figuring must be right and the bomb had to go off but there was in everyone’s mind a strong measure of doubt. The feeling of many could be expressed by “Lord, I believe; help Thou mine unbelief.” We were reaching into the unknown and we did not know what might come of it. It can be safely said that most of those present—Christian, Jew and atheist—were praying and praying harder than they had ever prayed before. If the shot were successful, it was a justification of the several years of intensive effort of tens of thousands of people—statesmen, scientists, engineers, manufacturers, soldiers, and many others in every walk of life.
Through the loudspeaker, they heard Allison counting the seconds—minus 45, minus 40, minus 30, minus 20, minus 10. As the last seconds ticked off, Oppenheimer’s thin body tensed. Farrell kept his eyes on Oppenheimer, who had carried this “very heavy burden” for the past twenty-eight months. “He scarcely breathed,” he remembered. “He held a post to steady himself. For the last few seconds, he stared directly ahead and then when the announcer shouted, ‘Now!’ and there came this tremendous burst of light followed shortly thereafter by the deep growling roar of the explosion, his face relaxed into an expression of tremendous relief.”
Kistiakowsky, who was standing outside the barricade, was knocked flat by the blast. When he reached Oppenheimer, he slapped him on the back and blurted out the first thing that came to mind: “Oppie, you owe me ten dollars!” It was “a silly thing to say,” he admitted later, but he was still smarting over the accusations that his explosives work might have been shoddy. Oppenheimer, still at a loss for words as he watched the huge orange ball of fire rise slowly above the plain, pulled out his wallet and stared numbly at it for a moment before shaking his head. It was empty.
Then Oppenheimer was surrounded by jubilant physicists, who were jumping up and down, pounding each other on the back, and shouting congratulations. Bainbridge went around personally thanking everyone on his team, and when he reached Oppie, he said, “Now we’re all sons of bitches.” Conscious that they were waiting for his reaction, and fully aware of the moment’s historic proportions, Oppenheimer walked out of the shelter and stood on the sand. Gazing out at the twisting column of smoke, he solemnly quoted a line from sacred Hindu writings that his assistant, Priscilla Greene, had no doubt he had prepared in advance for the occasion. As Oppenheimer later famously painted the scene:
A few people laughed, a few people cried. Most people were silent. I remembered the line from the Hindu scripture, the Bhagavad Gita: Vishnu is trying to persuade the Prince that he should do his duty and to impress him he takes on his multi-armored form and says, “I am become Death, the destroyer of worlds.” I suppose we all thought that, one way or another.
Back at base camp, Groves, Conant, and Bush had viewed the explosion from a shallow trench. “It was agreed,” Conant wrote in his diary of the day’s events, “that because of the expected
(or hoped!) bright flash and the ultra violet light (no ozone to absorb it) it would be advisable to lie flat and look away at the start, then look through the heavy dark glass.” They lay there belly down, facing 180 degrees away from the spot on the tarpaulin. The last ten seconds, he whispered to Groves, seemed terribly long. Conant kept his eyes open, looking at the horizon opposite the spot:
Then came a burst of white light that seemed to fill the sky and seemed to last for seconds. I had expected a relatively quick and bright flash. The enormity of the light and its length quite stunned me. My instantaneous reaction was that something had gone wrong and that the thermal nuclear transformation of the atmosphere, once discussed as a possibility and only jokingly referred to a few minutes earlier, had actually occurred.
Slightly blinded for a second, Conant turned on his back as quickly as possible, and watched the fireball through the welder’s glass. “At this stage it looked like an enormous pyrotechnic display with great boiling of luminous vapors, some spots being brighter than others,” he recalled. “Very shortly this began to fade and without thinking the glass was lowered and the scene viewed with the naked eye. The ball of gas was enlarging rapidly and turning into a mushroom. It was reddish purple, and against the early dawn very luminous.” Then someone shouted to look out for the detonation wave, which hit them like a sharp gust of wind some forty seconds after zero. While impressive, Conant recalled that both the blast and the sound were less startling than he had expected because the shock of the first sensory image was still so dominant in his mind: “My first impression remains the most vivid, a cosmic phenomenon like an eclipse. The whole sky suddenly full of white light like the end of the world. Perhaps my impression was only premature on a time scale of years!”
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