In 1945 an American engineer named Percy Spencer was testing a magnetron - a vacuum tube used in military radar systems. He noticed that a chocolate bar in his pocket had melted into a sticky mess. Curious, he held a bag of popcorn kernels up to the tube. They popped. Then he tried an egg. It exploded all over the lab.
Spencer realised the microwaves were jiggling water molecules in the outer layers of the food so fast that heat spread inward from there. (Microwaves don’t actually cook “from the inside out” - that’s a common myth.) In 1947 his company Raytheon sold the first microwave oven. It was nearly 6 feet tall, weighed 750 pounds and cost about $5,000 - roughly the price of a small car.
It took decades for microwaves to shrink down to kitchen size. By the 1980s they were in most American homes. Now you can warm leftovers in 30 seconds, all thanks to a melted chocolate bar in one engineer’s pocket.
