And since the microwave oven is still going, electric current keeps bouncing back and forth between the sides of the grape, and across any steam or hot molecules carried up by the fire.
The size of a microwave oven, it led to larger and more capable successors, Spirit and Opportunity in 2003, Curiosity in 2012, and now Perseverance. Lori Glaze is director of NASA's Planetary Science Division.
But just as it changed the course of the war, the magnetron soon changed the course of cooking around the world, becoming the primary component of today's microwave oven.
The Willinghams, both retired, turned up at a store in the suburbs of Chicago on Friday with a long shopping list: stove, refrigerator, microwave oven and dishwasher.