In 1945, Raytheon engineer Percy Spencer noticed a peanut cluster candy bar melting in his pocket while standing near an active radar set. Instead of leaving, he popped corn kernels and exploded an egg in the beam, and a patent for microwave cooking followed that October. This episode traces the microwave oven from the 1933 Chicago World's Fair shortwave sandwich demonstration, through the British invention of the cavity magnetron by John Randall and Harry Boot, the Tizard mission that brought it to America, and the 750-pound, water-cooled 1947 Radarange, to the countertop model of 1967 that eventually landed in over 90 percent of US homes.

The second half digs into the physics: dielectric heating at 2.45 gigahertz, why polar molecules like water, fats and sugars flip millions of times per second, and why the inside-out cooking story is a m ...