The Making of the Atomic Bomb: 25th Anniversary Edition

by Richard Rhodes

“Perhaps the greatest immediate danger which faces us is the probability that our ‘demonstration’ of atomic bombs will precipitate a race in the production of these devices between the United States and Russia.”

Szilard warning FDR/Truman

Oppenheimer was surprised and impressed. When Roosevelt died, he told an audience late in life, he had felt “a terrible bereavement . . . partly because we were not sure that anyone in Washington would be thinking of what needed to be done in the future.” Now he saw that “Colonel Stimson was thinking hard and seriously about the implications for mankind of the thing we had created and the wall into the future that we had breached.”

Conant mentioned the thermonuclear and asked Oppenheimer what gestation period that much more violent mechanism would require; Oppenheimer estimated a minimum of three years. The Los Alamos director took the floor then to review the explosive forces involved. First-stage bombs, he said, meaning crude bombs like Fat Man and Little Boy, might explode with blasts equivalent to 2,000 to 20,000 tons of TNT. That was an upward revision of the estimate Bethe had supplied the Target Committee at Los Alamos in mid-May. Second-stage weapons, Oppenheimer went on—meaning presumably advanced fission weapons with improved implosion systems—might be equal to 50,000 to 100,000 tons of TNT. Thermonuclear weapons might range from 10 million to 100 million tons TNT equivalent.

The surprise of the morning was perhaps Marshall’s idea for an opening to Moscow: “He raised the question whether it might be desirable to invite two prominent Russian scientists to witness the [Trinity] test.” Groves must have winced; after the years of secrecy, after the thousands of numb man-hours of security work, that would be a renunciation worthy of Bohr himself.

For the high-density form of Pu the critical mass within a heavy tamper is eleven pounds; even with a nutsized central hollow to encapsulate an initiator the Trinity core cannot have been larger than a small orange.

Very shortly before the test of the first atomic bomb, people at Los Alamos were naturally in a state of some tension. I remember one morning when almost the whole project was out of doors staring at a bright object in the sky through glasses, binoculars and whatever else they could find; and nearby Kirtland Field reported to us that they had no interceptors which had enabled them to come within range of the object. Our director of personnel was an astronomer and a man of some human wisdom; and he finally came to my office and asked whether we would stop trying to shoot down Venus.

“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.”

“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.”

Tinian is a miracle. Here, 6,000 miles from San Francisco, the United States armed forces have built the largest airport in the world. A great coral ridge was half-leveled to fill a rough plain, and to build six runways, each an excellent 10-lane highway, each almost two miles long. Beside these runways stood in long rows the great silvery airplanes. They were there not by the dozen but by the hundred. From the air this island, smaller than Manhattan, looked like a giant aircraft carrier, its deck loaded with bombers. . . .

In the light of the alternatives which, on a fair estimate, were open to us I believe that no man, in our position and subject to our responsibilities, holding in his hands a weapon of such possibilities for accomplishing this purpose and saving those lives, could have failed to use it and afterwards looked his countrymen in the face.

Stimson

Earlier in the war the city’s population had approached 400,000, but the threat of strategic bombing, so ominously delayed, had led the authorities to order a series of evacuations; on August 6 the resident population numbered some 280,000 to 290,000 civilians plus about 43,000 soldiers.

“Because the heat in [the] flash comes in such a short time,” adds a Manhattan Project study, “there is no time for any cooling to take place, and the temperature of a person’s skin can be raised [120° F] . . . in the first millisecond at a distance of [2.3 miles].”

The black-brushed calligraphy burned out of a rice-paper name card posted on a school building door; the dark flowers burned out of a schoolgirl’s light blouse. A human being left the memorial of his outline in unspalled granite on the steps of a bank. Another, pulling a handcart, protected a handcart- and human-shaped surface of asphalt from boiling.

Those who experienced the explosion within the city named it pika, flash, and those who experienced it farther away named it pika-don, flash-boom.

Of 76,000 buildings in Hiroshima 70,000 were damaged or destroyed, 48,000 totally. “It is no exaggeration to say,” reports the Japanese study, “that the whole city was ruined instantaneously.”

The text described the atomic bomb as “the equivalent in explosive power to what 2,000 of our giant B-29’s can carry on a single mission,” suggested skeptics “make inquiry as to what happened to Hiroshima” and asked the Japanese people to “petition the Emperor to end the war.”

Everyone felt that the sooner we could get off another mission, the more likely it was that the Japanese would feel that we had large quantities of the devices and would surrender sooner.

He decided to improvise. Although “nothing that could generate heat was ever allowed in an explosive assembly room,” he determined to “unsolder the connectors from the two ends of the cable, reverse them, and resolder them”:

The Emperor broadcast to a weeping nation on August 15; his 100 million subjects had never heard the high, antique Voice of the Crane before: Despite the best that has been done by everyone . . . the war situation has developed not necessarily to Japan’s advantage, while the general trends of the world have all turned against her interest.