The Weirdest Thing I Learned This Week · Popular Science

Killer Demon Core, Victorian Theater-Kid Ghosts, Louis Pasteur's Secrets

March 25, 2026·1 hr 18 min·7 clips

A dying scientist's last act was to turn his fatal accident into valuable research data.

This episode explores two distinct historical phenomena involving deception and danger. The main story focuses on the "demon core," a 14-pound plutonium sphere created during the Manhattan Project that was destined for a third atomic bomb on Japan. After Japan's surrender, the core remained at Los Alamos for testing purposes. In August 1945, physicist Harry Daglian was conducting criticality experiments using tungsten carbide bricks to reflect neutrons back into the core. When he accidentally dropped a brick directly onto the core, it went critical, exposing him to a fatal dose of radiation. He died 25 days later. The second incident occurred in May 1946 when physicist Louis Slotin was training his replacement, Alvin Graves. Slotin, known for his reckless bravado and casual approach to safety protocols, was using screwdrivers instead of proper shims to maintain a gap between two beryllium hemispheres surrounding the core. When the screwdriver slipped, the hemispheres closed completely, causing another criticality accident. Witnesses reported an intense heat wave and blue Cherenkov radiation. Slotin immediately recognized he was fatally exposed and instructed everyone to mark their positions with chalk to create a scientific record of radiation exposure at different distances. He died nine days later. The episode explains that neutron radiation is particularly dangerous because neutrons are electrically neutral and can penetrate most materials, passing directly through human tissue and damaging DNA. The inverse square law means radiation exposure decreases exponentially with distance from the source. After Slotin's death, manual criticality experiments were banned in favor of remote-controlled procedures. The demon core was eventually melted down and reused in other nuclear weapons. The second story shifts to Victorian-era Australia, where "ghost hoaxing" became a widespread phenomenon. With no professional police force and a newly colonized society, individuals took advantage of the lawless environment to terrorize communities while disguised as supernatural beings. Examples include the "Wizard Bombardier," who wore white robes and threw stones at people, and Herbert Patrick McLennan, who covered himself in phosphorescent paint and carried a cat-o'-nine-tails whip to attack women. When a five-pound bounty was placed on McLennan's capture, he declared war on the community and threatened to shoot anyone who pursued him. He was eventually captured and revealed to be a respected clerk and public speaker. These ghost hoaxers exploited people's superstitions and the lack of law enforcement to engage in elaborate pranks that often crossed into criminal behavior.

As heard by us

A lively, weird tour through science history where the strangest material lands with the cleanest impact.

Curiosity is handled like a relay race here, moving from a radioactive core with a horror-tinged nickname to a tragic stretch of nuclear history, all while the host pair keeps the pace light enough for the grim material to stay in motion.

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Why you'd press play

For when radioactive history and a very strange nuclear-era cautionary tale sound like your kind of weird.

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