The Demon Core: Plutonium Sphere That Killed Two Scientists and Destroyed a City

Added: 2026-05-15

[00:00:00]Did you know a 14-pound metal ball killed two scientists and later helped destroy a city? The demon core looked harmless, just a sphere of plutonium sitting in a Los Alamos lab. But this innocent-looking object became one of the deadliest things on Earth. In August 1945, physicist Harry Daghlian was working alone late at night. He accidentally dropped a brick onto the core. Instantly, the room filled with a brilliant blue flash. Daghlian knew immediately what it meant. He was dead.

[00:00:28]The plutonium had gone critical. A chain reaction flooded his body with lethal radiation. [music] Nine months later, Louis Slotin made his own fatal mistake.

[00:00:38]A screwdriver slipped during an experiment. Again, that terrifying blue glow filled the room. Slotin calmly told his colleagues to mark their positions.

[00:00:47]He knew they were all exposed. Both men died agonizing deaths from [music] radiation poisoning. Their bodies literally cooked from the inside. The demon core wasn't finished. Weeks later, it was loaded into a bomb and dropped on Nagasaki. One small sphere, three separate tragedies, hundreds of thousands dead.