A subcritical ball of plutonium sat on a lab bench at Los Alamos, harmless until someone got careless. Twice, less than a year apart, a single mistake sent it supercritical in a blue flash — and both men in the room knew instantly they were already dead. It became known as the demon core.
Kyle Hill's meticulous, unnerving reconstruction of both accidents — what actually happens to a body when a plutonium core flashes critical a foot from your hands.
The full dossier: a 6.2 kg plutonium-gallium sphere built as a third bomb for Japan, spared by the surrender, and then turned into a research object that killed the people studying it.
August 1945: working alone at night, the 24-year-old physicist fumbled a tungsten-carbide brick onto the core. He watched his own hands blister and died 25 days later.
The eerie symmetry nobody planned: both deaths on a Tuesday, both on the 21st of the month, both men dying in the same hospital room a year apart.
Plainly Difficult walks through the physics and the procedure — including the screwdriver Louis Slotin used to hold two beryllium hemispheres apart, against everyone's advice.
The Atomic Heritage Foundation on why these experiments were nicknamed 'tickling the dragon's tail' — and how the second death finally ended hands-on criticality work forever.
The core Oppenheimer left out of the movie: melted down in 1946, its plutonium recycled — and reborn decades later as one of the internet's strangest running memes.