The scientists who built it gave the bomber crew a 50 percent chance of survival, and they had run the math. The Tsar Bomba was the most powerful device ever detonated on Earth, a blast so violent its pressure wave circled the planet three times. And it could have been twice as powerful, if its creators hadn't deliberately sabotaged their own design.

This episode pulls apart the terrifying physics of the Soviet Union's Product 602, the Cold War fears that drove its creation, and the profound irony of how the ultimate weapon helped push the world away from atmospheric testing.

• How a 50-megaton yield equals roughly 1,570 times the combined Hiroshima and Nagasaki bombs, or all of World War II's explosives multiplied by ten
• The strategic imbalance of the late 1950s that drove Khrushchev to build a terrifying showpiece rather  ...