In the late 1950s the US government weighed a multi-billion-dollar anti-ballistic missile shield against a nine-minute cartoon about a turtle named Bert, and concluded the cartoon was the more practical defense. This episode revisits the 1952 civil defense film Duck and Cover, drawing on declassified memos, blast physics papers and Cold War strategy analyses to explain why hiding under a school desk was not naive, but a calculated bet on saving lives on the periphery of a nuclear blast.

The conversation sets the scene with the shock of the Soviet Joe-1 test in 1949, the Korean War, and the Desert Rock exercises that put troops in trenches near live detonations. It then walks through the physics of thermal flash versus delayed shockwave, showing how a drilled reflex could keep people from being blinded or shredded by flying glass miles from  ...