Raytheon's radar melted a chocolate bar — the microwave oven was born

In 1945, Percy Spencer, a self-taught engineer at Raytheon, was standing in front of an active magnetron — the high-power vacuum tube that generates microwaves for radar — when he noticed the chocolate bar in his pocket had melted into a puddle. He was not trying to cook anything. He was testing radar equipment. But instead of ignoring the accident, Spencer wondered whether the microwaves could cook food deliberately.

He tested the idea by holding a bag of popcorn kernels near the magnetron; they popped across the room. He then tried a raw egg, which exploded in a colleague's face. Spencer confirmed the heating effect by feeding microwave power into a closed metal box, creating the first microwave oven prototype. Raytheon filed a patent for his microwave cooking process on 8 October 1945, awarded on 24 January 1950.

Raytheon demonstrated the first 'Radarange' in 1946 at the Waldorf-Astoria in New York. The first commercial units, built in 1947, were 1.8 metres tall, weighed 340 kilograms, consumed 3 kilowatts, were water-cooled, and cost about $3,000. Raytheon leased them to hotels and restaurants. The first home microwave arrived in 1956 from Tappan Stove (licensed by Raytheon), still priced at $1,250. Amana Corporation, owned by Raytheon, introduced the first countertop Radarange in 1967 at $495, sparking mass adoption.

Prices fell rapidly in the 1970s. By 1986, 25% of US households owned a microwave. By 1997, 90% did. Spencer, who had dropped out of grammar school at 12 and taught himself engineering, went on to hold over 100 patents. He was inducted into the National Inventors Hall of Fame in 1999. A radar component that melted a chocolate bar had become a kitchen essential — the microwave oven industry is now worth tens of billions of dollars annually.