Harold Agnew carrying the plutonium core of the Nagasaki Fat Man bomb

Harold Agnew carrying the plutonium core of the Nagasaki Fat Man bomb, 1945

This was taken on Tinian Island in 1945. Agnew was a physicist with the Manhattan Project and an observer on the Hiroshima mission. He flew in a plane behind the Enola Gay. His smile sort of disconnects the viewer from the reality of the situation. That box is the direct cause of the deaths of approximately 70,000 people. That little box will change the course of history, and he’s holding it like it’s his lunch. The oddest thing here is that a whole group of the scientists had photos of themselves posing with the plutonium. They were proud of their invention, and the fact that they were making history. For a whole host of reasons they had no second thoughts about what they were planning to do.

The plutonium core in Fat Man weighed 6.2 kg or about 14 lb, The pit is 9 cm (4 inches) across. And only about one fifth of it, a bit over 1 kg (2 pounds) undergoes a fission reaction. And only a gram (1/30th of an ounce) of that gets converted into explosive energy equal to 21,000 tons of TNT.

But what would happen if he were to drop it by accident? To explode the core has to reach critical mass. In a Uranium bomb the pieces are kept separate so they remain “subcritical”. The pieces are individually not of the size to independently start the chain reaction. The explosion is triggered by one piece being fired at the other like a bullet down a gun barrel. The same style of box was used for the first three cores: the Trinity core, the Fat Man core, and the Demon Core. It was made of magnesium, to dissipate heat and not reflect neutrons. It could also carry several neutron initiators inside of it as well. It was safe to drop; the box would just bounce (yes, they tested it). The rubber “feet” are just laboratory stoppers with screws drilled through them. The whole thing was made by hand, of course. The box was designed by the physicist Philip Morrison, later famous for the “Powers of Ten” series.

He kept this photo as a souvenir, but the FBI had a problem with it. As Agnew told the story later:

I was in Chicago after the war in 1946. The FBI came and said they believed I had some secret pictures. They went through my pictures and found nothing. Then like a fool I said, “Maybe this one is secret.” They wanted to know what that thing was. I told them and they said that it must be secret and wanted the picture. I wanted the picture so they agreed if I scratched out the “thing” I could keep the slide.

 

Interesting stuff

If Japan hadn’t surrendered unconditionally, their war with Russia might have gotten a lot bloodier than it was. The presence of the US in Japan at the end of the war might have been the only thing that saved them from being invaded by the Soviet Union. The US had three choices:

1. Drop the bomb and wait for unconditional surrender.
2. Accept a conditional surrender and let Japan go on and fight the Soviet Union (a certain defeat which could have resulted in yet more power for the Soviet Union).
3. Invade mainland Japan and force unconditional surrender at the expense of 1,000,000+ casualties per side.

There are a lot of theories, many of which are advanced by US detractors concerning why the US dropped the bomb besides “quick end of the war” or that the Japanese surrendered for any reason but the bombs being dropped. The truth is complex, as the Soviets, by treaty, declared war on Japan and began invading the occupied territories on August 9, which was after Hiroshima and before Nagasaki. In July of 1945, less than a month before the atom bombs were dropped, the US intercepted internal Japanese communications (from Foreign Minister Togo) saying that Japan would never accept unconditional surrender and would instead fight until the bitter end. Making matters more confusing, Japanese published two justifications for surrender, one saying the bombs, the other claiming Soviet declarations. If anything, this is an indicator that both were reasons. The truth is, the US most likely dropped the bombs primarily as a desire to end the War with Japan. Any message to the Soviets would have been most likely viewed as a bonus. Japan’s surrender was probably a result of realizing it had no way out as a result of both the Bombs and Soviet declaration of war.

In the words of Dwight Eisenhower:

Secretary of War Stimson, visiting my headquarters in Germany, informed me that our government was preparing to drop an atomic bomb on Japan. I was one of those who felt that there were a number of cogent reasons to question the wisdom of such an act… During his recitation of the relevant facts, I had been conscious of a feeling of depression and so I voiced to him my grave misgivings, first on the basis of my belief that Japan was already defeated and that dropping the bomb was completely unnecessary, and secondly because I thought that our country should avoid shocking world opinion by the use of a weapon whose employment was, I thought, no longer mandatory as a measure to save American lives. It was my belief that Japan was, at that very moment, seeking some way to surrender with a minimum loss of ‘face’. The Secretary was deeply perturbed by my attitude…” In a Newsweek interview, Ike would add: “…the Japanese were ready to surrender and it wasn’t necessary to hit them with that awful thing.”

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