Of eggs and nuclear physics


The latest XKCD cartoon made me smile, but also reminded me of the darker side of the history of nuclear physics.

The mouseover text on the cartoon’s Web page reads:  “The foil on the toothpick represents the blue flash”.  The “blue flash” refers to what became known as the “demon core”, used in two lethal experiments in the Los Alamos nuclear research laboratories shortly after World War II.  Wikipedia summarizes:

The Demon Core was a spherical 6.2-kilogram (14 lb) subcritical mass of plutonium 89 millimetres (3.5 in) in diameter, manufactured during World War II by the United States nuclear weapon development effort, the Manhattan Project, as a fissile core for an early atomic bomb. It was involved in two criticality accidents, on August 21, 1945, and May 21, 1946, each of which killed a person.

The core was intended for use in a possible third nuclear weapon to be dropped on Japan, but when Japan’s surrender made this unnecessary, it was repurposed for testing. It was designed with a small safety margin to ensure a successful explosion of the bomb. The device briefly went supercritical when it was accidentally placed in supercritical configurations during two separate experiments intended to guarantee the core was close to the critical point. The incidents happened at the Los Alamos Laboratory, resulting in the acute radiation poisoning and subsequent deaths of scientists Harry Daghlian and Louis Slotin. After these incidents the spherical plutonium core was referred to as the “Demon Core”.

There’s more at the link.

I highly recommend reading the Wikipedia article, and/or the article “The Third Core’s Revenge“, to get some idea of how hazardous early nuclear experiments were, before our knowledge of the science had improved.  We can smile at the cartoon’s depiction of the “Demon Egg”, but two men lost their lives to the real thing.



  1. The movie "Fat man and little boy" shows this with great accuracy. As a Navy Nuke, the calculations they used for radiation exposure were spot on.

  2. "Fat Man And Little Boy" is a fair to middlin' movie. However, although the calculations and actions are fairly accurate the timing is wrong. The accident happened August 21 1945, nearly 2 weeks after the Hiroshima and Nagasaki weapons were dropped and almost a month after the Trinity test which in the movie the accident was shown to proceed/be roughly coincident with. I'm fine with folks tweaking things in fiction, but if you're going to make something even vaguely documentary keep the time order intact don't tweak things for drama, that's lazy script writing.

  3. Your mistake is thinking it's any such vague documentary.

    It's a drama, and your criticism is therefore misguided.

    There's a movie industry word for documentary: it's "documentary".

    The unfortunate death of one poor schlub after the Trinity explosion would have been cinematically stupid and anti-climactic, regardless of the historical timeline.

    While the scenes of that death were well-done, it was ultimately pointless, and added to the plot simply to underscore the editorial message that nukes=evil.

    They would have done better to use the stime to have the scientists watching newsreels of the fighting in okinawa, to underscore the necessity of the bombs rather than an all-out invasion of the Japanese mainland.

    But Hollywierd Leftism is dug in like a tick, and baked into every cake.

  4. Actually, read a book about the demon core experiments, years ago, with accounts by scientists who were there. It was a really fascinating book; just wish I could remember the title.

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