The First War of Physics (47 page)

Even if the bomb worked, there was still considerable uncertainty about its potential yield. The scientists were running a pool. Teller had bet on an optimistic 45,000 tons of TNT equivalent. Serber 12,000 tons. Bethe 8,000 tons. Kistiakowsky 1,400 tons. Oppenheimer had bet on a pessimistic 300 tons. When Rabi arrived at Los Alamos he found that the only bet left open was for 18,000 tons, so he bought it.

As the morning of the test approached, the bad weather became the overriding worry. Storms had flared up on 14 July and were forecast to last for at least two days. At 2:00am on 16 July, thunderstorms were still raging, heavy rain and high winds lashing the Base Camp and command centre. The wooden structure at the top of the tower at Point Zero looked fragile in the midst of this elemental display. Some physicists worried that Fat Man might be detonated prematurely.

VIPs and scientists not directly involved in the final preparations or monitoring arrived to view the test on a cold and damp Compañia Hill, twenty miles north-west, at around 2:00am. Among them were Bethe, Chadwick, Fermi, Feynman, Frisch, Fuchs, Lawrence, Serber and Teller. They each held a plate of welder’s glass to protect their eyes. Teller had brought sunscreen. There were about twenty in the crowded command centre, preparing for the test with barely suppressed excitement. Groves
tried to keep Oppenheimer calm, taking him for quiet walks in the rain when he seemed about to explode.

The 4:00am deadline passed, but the weather gradually cleared and the time of the test was fixed for 5:30am. Bainbridge armed the bomb and returned to the command centre with Kistiakowsky and others who had spent the night playing nursemaid to Fat Man. At 5:10am on Monday, 16 July, the countdown began. Groves left the control bunker for Base Camp. Warning rockets were fired with five, two and then one minute to go.

The countdown reached zero. The firing circuit closed. Electronic detonators positioned symmetrically over Fat Man’s surface simultaneously triggered 32 separate explosions. The explosions burned through the bomb towards the centre, the expanding Shockwaves forced to turn, focusing their energy towards the core. The uranium tamper was collapsed in on itself, followed by the solid plutonium core. As the polonium and beryllium components of the initiator were crushed together, alpha particles released by the polonium chipped neutrons from the beryllium nuclei. The neutrons spilled into the small volume of high-density, super-critical plutonium. Fission upon fission of Pu-239 nuclei produced wave upon wave of neutrons, as matter converted into primordial energy.

Frisch described what happened next:

And then without a sound, the sun was shining; or so it looked. The sand hills at the edge of the desert were shimmering in a very bright light, almost colourless and shapeless. I turned round, but that object on the horizon which looked like a small sun was still too bright to look at. I kept blinking and trying to take looks, and after another ten seconds or so it had grown and dimmed into something more like a huge oil fire … It was an awesome spectacle; anybody who has ever seen an atomic explosion will never forget it. And all in complete silence; the bang came minutes later, quite loud though I had plugged my ears, and followed by a long rumble like heavy traffic very far away. I can still hear it.

The abstract scientific problem that Frisch and Meitner had wrestled with, that Christmas Eve in Kungalv, had become a horrifying reality.

Some laughed. Some cried. Most stayed silent. Fermi used a simple experiment, measuring how far some small pieces of paper were carried by the shockwave, to estimate that the bomb had produced a blast equivalent to 10,000 tons of TNT.
⁶

Kistiakowsky, blown over by the shockwave from the blast, got back to his feet and demanded his ten dollars from Oppenheimer. But Oppenheimer’s wallet was empty. ‘There floated through my mind a line from the Bhagavad-Gita,’ Oppenheimer later recalled, ‘in which Krishna is trying to persuade the Prince that he should do his duty: “I am become death, the shatterer of worlds.”’ Bainbridge was more forthright: ‘Oppie,’ he said, ‘now we’re all sons of bitches.’ At Base Camp, Groves, Conant and Bush acknowledged success with silent hand-shakes.

The atmosphere did not catch fire.

Raising the price

News of the successful test was passed to Truman and Byrnes in Potsdam. Secure in the knowledge that the Soviet Union was no longer needed to help end the war against Japan, Truman decided to let the Soviets in on the secret. A few days later he mentioned to Stalin that America had developed ‘a new weapon of unusual destructive force’.

Stalin didn’t seem very surprised. He told Molotov about the conversation. ‘They’re raising the price’, said Molotov. Stalin laughed. ‘Let them’, he said. ‘We’ll have to have a talk with Kurchatov today about speeding up their work.’

¹
By this time, army intelligence had built up a thick dossier on Rotblat, filled largely with fabrications. It was nevertheless agreed that he would leave without revealing his real reasons: he was to say that he was worried about his wife in Poland. See Brown, p. 284.

²
The 509th was termed a ‘Composite’ Group as it included both transport aircraft and bombers.

³
The military doctrine of rapid dominance, also known as ‘shock and awe’, is based on the use of overwhelming force and spectacular displays of power to undermine an enemy’s will to fight. The doctrine was developed at the US National Defense University in 1996, its authors citing the atomic bombing of Japan as an early example.

⁴
Yatskov suffered from a partial colour-blindness, unable to tell the difference between red and green. Consequently, when driving to an important meeting he could either concentrate on traffic signals or on his FBI tail, but not both. Feklisov would sometimes accompany him to make sure he wasn’t being followed.

⁵
Feynman borrowed Fuchs’ car to drive to Albuquerque two weeks later, on 16 June. He had received word that his wife, Arline, was very ill. After suffering delays resulting from three flat tyres, he arrived at the hospital just a few hours before she died.

⁶
The actual yield was 18,600 tons. Rabi won the bet.

Chapter 16

HYPOCENTRE

July–August 1945

A
s Frisch watched the false dawn of a small, man-made sun over the New Mexico desert, preparations were under way at Hunters Point naval shipyard in San Francisco to send the physicists’ first weapon to war. Furman, his artillery insignia incongruously stitched upside-down to his uniform, watched as the two components of the Little Boy uranium bomb were loaded on the USS
Indianapolis.
Inevitably, it was the large wooden crate that attracted all the attention. Some speculated that it contained Rita Hayworth’s underwear.

The small but rather heavy bucket carried on board by two sailors was much less conspicuous. It was a lead bucket and it contained the U-235 shy that would be fired into the hollow cylinder formed from the uranium target rings at the other end of the bomb. The bucket was bolted to the floor in the flag lieutenant’s cabin and placed under 24-hour armed guard.

The captain of the
Indianapolis
had not been advised of his mission, or his destination. Deke Parsons now told him that they were to head, unescorted, for Tinian Island in the Pacific. The captain eyed the lead bucket with some suspicion. ‘I didn’t think we were going to use bacteriological weapons in this war’, he said. He did not get an answer. Just four
hours after the successful Trinity test, the Little Boy uranium bomb left San Francisco bound for the Marianas.

Four days later, on Friday 20 July, a small team of physicists left Los Alamos for the same destination. Headed by Norman Ramsey, the team included Serber, Alvarez and Penney. Their job was to assemble the Little Boy and Fat Man bombs on Tinian Island and prepare them for delivery to their targets in Japan. From Albuquerque airport they flew first to Wendover airbase in Utah, headquarters of the 509th Composite Group on the edge of the Salt Lake desert. At Wendover the physicists were inducted into the US Army. Serber’s assimilated rank was that of Colonel. Alvarez was rather disappointed to find he was to be a Lieutenant Colonel. They were issued with passports, uniforms, dog tags, and service kit. Serber looked the most at home in uniform, attracting occasional salutes from passing GIs.

The team crossed the Pacific on a C-54 transport plane, hopped islands and arrived at North Field on Tinian Island on 27 July. The
Indianapolis
had delivered its cargo the previous day.
¹

Tinian is a small island, measuring twelve miles by five miles at its widest. Yet, by this stage in the war, North Field had become the world’s largest airport, consisting of six 8,500-foot runways that ended at the top of a sheer cliff perched 50 feet above the sea. The physicists would watch as, day after day, hundreds of B-29s took to the skies, following the ‘Hirohito Highway’ to rain death and destruction on Japanese cities in what Major General Curtis LeMay, commander of strategic air operations against Japan, called ‘fire jobs’. The heavily loaded bombers would dip alarmingly after clearing the runways, before climbing slowly to their cruising altitude. Sometimes the planes didn’t make it. They would ‘go skimming horribly into the sea, or into the beach to burn like a huge torch’. They were so loaded with bombs that fully 1 per cent of the planes risked this fate. LeMay had figured this was an acceptable loss compared to flying more sorties with lighter bomb loads.

On Tinian the physicists settled into a routine, as Serber explained to his wife Charlotte, waiting back in Los Alamos:

The form of life out here is quickly taking shape. We get up about 6:00am, and have breakfast at 7:00. Then everybody goes to work until 11:00. Lunch then, and lie around in the sun (if it’s out) till 1:00. Work till about 4:30, dinner about 5:00, kill time until 7:15 when there’s a movie or a show. The movies are preceded by 15 minutes of news and combat reports. After the movies to the officer’s club, for a drink or a beer or a coke, and to bed by about 10:00.

The physicists would go swimming from Yellow Beach in the afternoons. Serber was struck by the number of .50-calibre machine gun shells that littered the sea floor, testimony to the firepower of the American 2nd and 4th Marine Divisions that had invaded and captured Tinian in July–August 1944. Napalm had been used for the first time to firebomb Japanese strongholds hidden beneath the island’s foliage.

Tibbets and the crews of his fifteen specially modified B-29s had spent their time since arriving on Tinian practising flying to Iwo Jima and back. They practised dropping standard bombs and ‘pumpkins’, crude imitation bombs the size of Fat Man, made of concrete, each filled with 6,300 pounds of high explosive and painted bright orange. Only Tibbets knew what they were training for, and because of this he was himself forbidden from flying practice missions over enemy territory.

As nobody had ever dropped an atomic bomb before, Tibbets was understandably concerned for the safety of his crew, and himself. He had worked out an elaborate manoeuvre to avoid the likely effects of the blast, turning at 30,000 feet through about 150 degrees in 30 seconds, at 200 to 250 miles per hour, ending 1,500 feet lower than at the start of the turn. He asked Serber what he thought. Serber did some quick calculations and assured him that he would be perfectly safe.

No surrender, no concessions

As Little Boy and the team of physicists made their various ways to Tinian, political and military debates were raging in Potsdam and Tokyo. Decisions were being taken which would seal Japan’s fate and determine the role that atomic bombs would play in this fate.

Eisenhower learned about the success of the Trinity test from Stimson over dinner at Allied headquarters in Germany. He expressed the opinion that the bomb should not be used. The Japanese were ready to surrender, he claimed. ‘I was one of those who felt that there were a number of cogent reasons to question the wisdom of such an act.’ He did not want his country to be the first to use such a weapon. Stimson was furious. He was the one who had agreed to a $2 billion expenditure to build the atomic bomb, and he now felt burdened with the moral accountability for its use. Other American military leaders echoed Eisenhower’s sentiments, though some, like LeMay, more from practicality than from moral concerns. LeMay was systematically wiping out Japanese cities with his incendiary bombs. The war could be ended without atomic weapons. It was surely only a matter of time.