Sideswipe: May 20: Gendered ready meals 19 May, 2021 05:00 PM 3 minutes to read * Not the size of an actual man How the microwave was invented The microwave oven is of the all-time great "accidental" discoveries of science. In the 1940s, American engineer Percy Spencer was working at Raytheon Technologies testing an active radar while he had a chocolate bar in his pocket. At some point, he noticed that the chocolate had melted into his pocket. Rather than merely changing his trousers, he realised the potential to heat food using a high-density electromagnetic field (and presumably also changed his trousers). He first experimented by getting a bag of popcorn, and attempting to heat that. It worked. He pushed his luck and tried to heat an egg, which exploded spectacularly, thus also inventing the "don't put an egg in the microwave" rule. Spencer next worked on putting magnetrons (which create microwave radiation) inside a Faraday cage (which blocks electromagnetic fields). The result was a massive microwave oven – around the size of a fridge – which Raytheon began to sell commercially to restaurants in 1947, at $5000 (around $60,000 today). However, the microwave was not widespread until it was made smaller and cheaper, which wouldn't really happen until the late 1960s or early 1970s.