What happens when the world's most brilliant scientists make a basic arithmetic error about a seemingly harmless element? On March 1, 1954, at Bikini Atoll, a thermonuclear device expected to yield five megatons exploded with fifteen, a thousand times more powerful than Hiroshima.

This episode untangles how a single blind spot in a room full of geniuses triggered a global crisis and helped birth modern environmental anxiety. We explore the elegant engineering of the Castle Bravo device, the fatal miscalculation about lithium-7, and the devastating human consequences when human engineering outpaced human foresight. It is a sobering reminder that what you don't know can hurt everyone.

• How the "dry" lithium deuteride design made a deliverable bomb possible
• The fatal assumption that 60 percent of the fuel, lithium-7, was iner ...