Sturdy Hans Bethe found a way back from the precipice, Kistiakowsky remembers:
Sunday morning another phone call came with wonderful news. Hans Bethe spent the whole night of Saturday analyzing the electromagnetic theory of this experiment and discovered that the instrumental design was such that even a perfect implosion could not have produced oscilloscope records different from what was observed. So I became again acceptable to local high society.2398
When Groves called, Oppenheimer chatted happily about the Bethe results. The general interrupted: “What about the weather?” “The weather is whimsical,” the whimsical physicist said.2399 The Gulf air mass had stagnated over the test site. But change was coming. Jack Hubbard, the meteorologist, predicted light and variable winds the next day.
Stagnation exacerbated the July heat. Camera crews replacing battery packs damaged by a blown circuit burned their hands on metal camera housings. Frank Oppenheimer, thin enough not to suffer the heat unduly, hurried to construct a last-minute experiment less aloof than readings of light and radiation: he set out boxes filled with excelsior and posts nailed with corrugated iron strips to simulate the fragile Japanese houses where LeMay’s ubiquitous drill presses lurked. Groves had forbidden the construction of full-scale housing for the test, more scientific tomfoolery, a waste of money and time. Norris Bradbury’s instructions for bomb assembly as of Saturday listed “Gadget complete”; for “Sunday, 15 July, all day,” he advised his crews to “look for rabbits’ feet and four-leaved clovers.2400 Should we have the Chaplain down there?” Rabbits’ feet would turn up, but even chaplains would have had trouble finding a stem of clover on the Jornada.
Oppenheimer, Groves, Bainbridge, Farrell, Tolman and an Army meteorologist met with Hubbard at McDonald Ranch at four that afternoon to consider the weather. Hubbard reminded them that he had never liked the July 16 date. He thought the shot could go as scheduled, he noted in his journal, “in less than optimum conditions, which would require sacrifices.”2401 Groves and Oppenheimer repaired to another room to confer. They decided to wait and see. They had scheduled a last weather conference for the next morning at 0200 hours; they would make up their minds then. The shot was set for 0400 and they let that time stand.
Sometime early that evening Oppenheimer climbed the tower to perform a final ritual inspection.2402 There before him crouched his handiwork. Its bandages had been removed and it was hung now with insulated wires that looped from junction boxes to the detonator plugs that studded its dark bulk, an exterior ugly as Caliban’s. His duty was almost done.
At dusk the tired laboratory director was calm. He stood with Cyril Smith beside the reservoir at McDonald Ranch where cattle had watered and spoke of families and home, even of philosophy, and Smith found himself soothed. A storm was blowing up. Oppenheimer looked beneath it to anchorage, to the darkening Oscuras. “Funny how the mountains always inspire our work,” the metallurgist heard him say.2403
With the weather changing from stagnant to violent and with everyone short of sleep, moods swung at Base Camp. The occasion of Fermi’s satire that evening made Bainbridge furious. It merely irritated Groves:
I had become a bit annoyed with Fermi . . . when he suddenly offered to take wagers 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. He had also said that after all it wouldn’t make any difference whether the bomb went off or not because it would still have been a well worth-while scientific experiment. For if it did fail to go off, we would have proved that an atomic explosion was not possible.2404
On the realistic grounds, the Italian laureate explained with his usual candor, that the best physicists in the world would have tried and failed.
Bainbridge was furious because Fermi’s “thoughtless bravado” might scare the soldiers, who did not have the benefit of a knowledge of thermonuclear ignition temperatures and fireball cooling effects.2405 But a new force was about to be loosed on the world; no one could be absolutely certain—Fermi’s point—of the outcome of its debut. Oppenheimer had assigned Edward Teller the deliciously Tellerian task of trying to think of any imaginable trick or turn by which the explosion might escape its apparent bounds. Teller at Los Alamos that evening raised the same question Fermi had, but questioned Robert Serber, no mere uninformed GI:
Trying to find my way home in the darkness, I bumped into an acquaintance, Bob Serber. That day we had received a memo from our director . . . saying that we would have to be [at Trinity] well before dawn, and that we should be careful not to step on a rattlesnake. I asked Serber, “What will you do tomorrow about the rattlesnakes?” He said, “I’ll take a bottle of whiskey.”2406 I then went into my usual speech, telling him how one could imagine that things might get out of control in this, that, or a third manner. But we had discussed these things repeatedly, and we could not see how, in actual fact, we could get into trouble. Then I asked him, “And what do you think about it?” There in the dark Bob thought for a moment, then said, “I’ll take a second bottle of whiskey.”
Rabi, the real mystic among them, spent the evening playing poker.
Bainbridge managed a little sleep. He headed the Arming Party charged with arming the bomb. He was due at Zero by 11 P.M. to prepare the shot. An MP sergeant woke him at ten; he picked up Kistiakowsky and Joseph McKibben, the tall, lanky Missouri-born physicist responsible for running the countdown, and assembled with Hubbard and his crew and two security men. “On the way in,” Bainbridge remembers, “I stopped at S 10,000 and locked the main sequence timing switches. Pocketing the key I returned to the car and continued to Point Zero.”2407 A young Harvard physicist, Donald Hornig, was busy in the tower. He had designed the 500-pound X-unit of high-voltage capacitors that fired Fat Man’s multiple detonators with microsecond simultaneity, a crucial Luis Alvarez invention, and now was disconnecting the unit Bainbridge’s crews had used for practice runs and connecting the new unit reserved for the shot. In static test this Fat Man would be fired through cables from the S-10000 control bunker; the one to be shipped to Tinian, self-contained, would carry onboard batteries. Cables or batteries would charge the X-unit and on command it would discharge its capacitors to the detonators, vaporizing wires imbedded in the explosive blocks to start shock waves to set off the HE. “Soon after our arrival,” says Bainbridge, “Hornig completed his work and returned to S 10,000. Hornig was the last man to leave the top of the tower.”2408
Hubbard operated a portable weather station at the tower; to measure wind speed and direction the two sergeants who worked with him inflated and released helium balloons. At eleven o’clock he found the wind blowing across Zero toward N-10000. At midnight the Gulf air mass had thickened to 17,000 feet and arranged two inversions—cooler air above warmer—within its layered depths that might loop the radioactive Trinity column back down to the ground directly below.
To an observer traveling toward the desert from Los Alamos “the night was dark with black clouds, and not a star could be seen.”2409
Thunderstorms began lashing the Jornada at about 0200 hours on July 16, drenching Base Camp and S-10000. “It was raining cats and dogs, lightning and thunder,” Rabi remembers. “[We were] really scared [that] this object there in the tower might be set off accidentally. So you can imagine the strain on Oppenheimer.”2410 Winds gusted to thirty miles an hour. Hubbard hung on at Zero for last-minute readings—only misting drizzle had yet reached the tower area—and arrived eight minutes late for the 0200 weather conference at Base Camp, to find Oppenheimer waiting for him outside the weather center there.2411 Hubbard told him they would have to scrub 0400 but should be able to shoot between 0500 and 0600. Oppenheimer looked relieved.
Inside they found an agitated Groves waiting with his advisers. “What the hell is wrong with the weather?” the general greeted his forecaster.2412 Hubbard took the opportunity to repeat that he had never liked July 16. Groves demanded to know when the storm would pass.
Hubbard explained its dynamics: a tropical air mass, night rain. Afternoon thunderstorms took their energy from the heating of the earth and collapsed at sunset; this one, contrariwise, would collapse at dawn. Groves growled that he wanted a specific time, not an explanation. I’m giving you both, Hubbard rejoined.2413 He thought Groves was ready to cancel the shot, which seems unlikely given the pressure from Potsdam. He told Groves he could postpone if he wanted but the weather would relent at dawn.
Oppenheimer applied himself to soothe his bulky comrade. Hubbard was the best man around, he insisted, and they ought to trust his forecast. The others at the meeting—Tolman and two Army meteorologists, one more than before—agreed. Groves relented. “You’d better be right on this,” he threatened Hubbard, “or I will hang you.” He ordered the meteorologist to sign his forecast and set the shot for 0530. Then he went off to roust the governor of New Mexico out of bed to the telephone to warn him he might have to declare martial law.
Bainbridge at Zero was less concerned with local effects than with distant, even though he had personally locked open the circuits that communicated with the shelters. “Sporadic rain was a disturbing factor,” he recalls. “ . . . We had none of the lightning reported by those at the Base Camp about 16,000 yards away or at S 10,000, but it made interesting conversation as many of the wires from N, S, W 10,000 ended at the tower.”2414 About 0330 a gust of wind at Base Camp collapsed Vannevar Bush’s tent; he found his way to the mess hall, where from 0345 the cooks began serving a breakfast of powdered eggs, coffee and French toast.
The gods sent Emilio Segrè happier amusement. He had distracted himself through the evening with Andrè Gide’s The Counterfeiters and slept through the worst of the Base Camp storm. “But my attention was attracted by an unbelievable noise whose nature escaped me completely. As the noise persisted, Sam Allison and I went out with a flashlight and, much to our surprise, found hundreds of frogs in the act of making love in a big hole that had filled with water.”2415
Hubbard departed Base Camp at 0315 for S-10000. The rain had moved on. He telephoned Zero; one of his men there said the clouds were opening and a few stars shone. By 0400 the wind was shifting toward the southwest, away from the shelters. The meteorologist prepared his final forecast at S-10000. He called Bainbridge at 0440. “Hubbard gave me a complete weather report,” the Trinity director recalls, “and a prediction that at 5:30 a.m. the weather at Point Zero would be possible but not ideal. We would have preferred no inversion layer at 17,000 feet but not at the expense of waiting over half a day. I called Oppenheimer and General Farrell to get their agreement that 5:30 a.m. would be T = 0.”2416 Hubbard, Bainbridge, Oppenheimer and Farrell each had veto over the shot. They all agreed. Trinity would fire at 0530 hours July 16, 1945—just before dawn.
Bainbridge had arranged to report each step of the final arming process to S-10000 in case anything went wrong. “I drove McKibben to W 900 so that he could throw the timing and sequence switches there while I checked off his list.” Back at Zero Bainbridge called in the next step “and threw the special arming switch which was not on McKibben’s lines. Until this switch was closed the bomb could not be detonated from S 10,000.2417 The final task was to switch on a string of lights on the ground which were to serve as an ‘aiming point’ for a B-29 practice bombing run. The Air Force wanted to know what the blast effects would be like on a plane 30,000 feet up and some miles away. . . . After turning on the lights, I returned to my car and drove to S 10,000.” Kistiakowsky, McKibben and the security guards rode with him. They were the last to leave the site. Behind them searchlight beams converged on the tower.
The Arming Party arrived at S-10000, the earth-sheltered concrete control bunker, at about 0508. Hubbard gave Bainbridge his signed forecast. “I unlocked the master switches,” Bainbridge concludes, “and McKibben started the timing sequence at –20 minutes, 5:09:45 a.m.”2418 Oppenheimer would watch the shot from S-10000, as would Farrell, Donald Hornig and Samuel Allison. With the beginning of the final countdown Groves left by jeep for Base Camp. For protection against common disaster he wanted to be physically separated from Farrell and Oppenheimer.
Busloads of visitors from Los Alamos and beyond had begun arriving at Compañia Hill, the viewing site twenty miles northwest of Zero, at 0200. Ernest Lawrence was there, Hans Bethe, Teller, Serber, Edwin McMillan, James Chadwick come to see what his neutron was capable of and a crowd of other men, including Trinity staff no longer needed down on the plain. “With the darkness and the waiting in the chill of the desert the tension became almost unendurable,” one of them remembers.2419 The shortwave radio requisitioned to advise them of the schedule refused to work until after Allison began broadcasting the countdown. Richard Feynman, a future Nobel laureate who had entered physics as an adolescent via radio tinkering, tinkered the radio to life. Men began moving into position. “We were told to lie down on the sand,” Teller protests, “turn our faces away from the blast, and bury our heads in our arms. No one complied. We were determined to look the beast in the eye.”2420 The radio went dead again and they were left to watch for the warning rockets to be fired from S-10000. “I wouldn’t turn away . . . but having made all those calculations, I thought the blast might be rather bigger than expected. So I put on some suntan lotion.”2421 Teller passed the lotion around and the strange prophylaxis disturbed one observer: “It was an eerie sight to see a number of our highest-ranking scientists seriously rubbing sunburn lotion on their faces and hands in the pitch-blackness of the night, twenty miles from the expected flash.”2422
The countdown continued at S-10000. At 0525 a green Very rocket went up. That signaled a short wail of the siren at Base Camp. Shallow trenches had been bulldozed below the south rim of the Base Camp reservoir for protection and since these men watched ten miles closer to Zero than the crowd on Compañia Hill they planned to use them. Rabi lay down next to Kenneth Greisen, a Cornell physicist, facing south away from Zero. Greisen remembers that he was “personally nervous, for my group had prepared and installed the detonators, and if the shot turned out to be a dud, it might possibly be our fault.”2423 Groves found refuge between Bush and Conant, thinking “only of what I would do if, when the countdown got to zero, nothing happened.”2424 Victor Weisskopf remembers that “groups of observers had arranged small wooden sticks at a distance of 10 yds from our observation place in order to estimate the size of the explosion.” The sticks were posted on the rim of the reservoir. “They were arranged so that their [height] corresponded to 1000 ft. at zero point.”2425 Philip Morrison relayed the countdown to the Base Camp observers by loudspeaker.
The two-minute-warning rocket fizzled. A long wail of the Base Camp siren signaled the time. The one-minute warning rocket fired at 0529. Morrison also meant to look the beast in the eye and lay down on the slope of the reservoir facing Zero. He wore sunglasses and held a stopwatch in one hand and a piece of welder’s glass in the other. The welder’s glass was stockroom issue: Lincoln Super-visibility Lens, Shade #10.
At S-10000 someone heard Oppenheimer say, “Lord, these affairs are hard on the heart.”2426 McKibben had been marking off the minutes and Allison broadcasting them. At 45 seconds McKibben turned on a more precise automatic timer. “The control post was rather crowded,” Kistiakowsky notes, “and, having now nothing to do, I left as soon as the automatic timer was thrown in . . . and went to stand on the earth mound covering the concrete dugout. (My own guess was that the yield would be about 1 kt [i.e., 1,000 tons, 1 kiloton], and so five miles seemed very safe.)”2427
Teller prepared himself further at Compañia Hill: “I put on a pair of dark glasses. I pulled on a pair of heavy gloves. With both hands I pressed the welder’s glass to my face, making sure no stray light could penetrate around it. I then looked straight at the aim point.”2428
Donald Hornig at S-10000 monitored a switch that could cut the connection between his X-unit in the tower and the bomb, the last point of interruption if anything went wrong. At thirty secon
ds before T = 0 four red lights flashed on the console in front of him and a voltmeter needle flipped from left to right under its round glass cover to register the full charging of the X-unit. Farrell noticed that “Dr. Oppenheimer, on whom had rested a very heavy burden, grew tenser as the last seconds ticked off. He scarcely breathed. He held on to a post to steady himself. For the last few seconds, he stared directly ahead.”2429
At ten seconds a gong sounded in the control bunker. The men lying in their shallow trenches at Base Camp might have been laid out for death. Conant told Groves he never imagined seconds could be so long. Morrison studied his stopwatch. “I watched the second-hand until T =—5 seconds,” he wrote the day of the shot, “when I lowered my head onto the sand bank in such a way that a slight rise in the ground completely shielded me from Zero.2430 I placed the welding glass over the right lens of my sun glasses, the left lens of which was covered by an opaque cardboard shield. I counted seconds and at zero began to raise my head just over the protecting rise.” Ernest Lawrence on Compañia Hill had planned to watch the shot through the windshield of a car, allowing the glass to filter out damaging ultraviolet, “but at the last minute decided to get out . . . (evidence indeed I was excited!).”2431 Robert Serber, his bottles of whiskey to succor him, stared twenty miles toward distant Zero with unprotected eyes. The last decisive inaction was Hornig’s:
Now the sequence of events was all controlled by the automatic timer except that I had the knife switch which could stop the test at any moment up until the actual firing . . . I don’t think I have ever been keyed up as I was during those final seconds . . . I kept telling myself “the least flicker of that needle and you have to act.” It kept on coming down to zero.2432 I kept saying, “Your reaction time is about half a second and you can’t relax for even a fraction of a second.” . . . My eyes were glued on the dial and my hand was on the switch. I could hear the timer counting . . . three . . . two . . . one. The needle fell to zero. . . .
Making of the Atomic Bomb Page 92
