In fact, there is an entire food industry based on this one appliance. Today, over 90% of American households own a microwave oven.
In 1942, a man named Dr. Percy Spencer was testing the magnetron and discovered that the candy bar in his pocket had melted. He conducted a series of tests and concluded that microwave energy caused food to cook much faster than the heat from a conventional oven.
Percy Lebaron Spencer (July 19, 1894 – September 8, 1969) was an American physicist and inventor. He became known as the inventor of the microwave oven.
By 1939, Spencer became one of the world’s leading experts in radar tube design. Spencer was now working at Raytheon, a contractor for the United States Department of Defense, as the chief of the power tube division. Largely due to his reputation and expertise, Spencer managed to help Raytheon win a government contract to develop and produce combat radar equipment for M.I.T.’s Radiation Laboratory. This was of huge importance to the Allies and became the military’s second highest priority project during WWII, behind the Manhattan Project. At that time, magnetrons were used to generate the microwave radio signals that are the core mechanism of radar, and they were being made at the rate of 17 per day at Raytheon. While working there, Spencer developed a more efficient way to manufacture them, by punching out and soldering together magnetron parts, rather than using machined parts. It also saw Spencer’s staff rise from 15 employees to 5,000 over the course of the next few years. His improvements were among those that increased magnetron production to 2,600 per day. For his work he was awarded the Distinguished Public Service Award by the U.S. Navy.
One day while building magnetrons, Spencer was standing in front of an active radar set when he noticed the candy bar he had in his pocket had melted. Spencer was not the first to notice this phenomenon, but he was the first to investigate it. He decided to experiment using food, including popcorn kernels, which became the world’s first microwaved popcorn. In another experiment, an egg was placed in a tea kettle, and the magnetron was placed directly above it. The result was the egg exploding in the face of one of his co-workers, who was looking in the kettle to observe. Spencer then created the first true microwave oven by attaching a high density electromagnetic field generator to an enclosed metal box. The magnetron emitted microwaves into the metal box blocking any escape, allowing for controlled and safe experimentation. He then placed various food items in the box, while observing effects and monitoring temperatures.
Raytheon filed a patent on October 8, 1945 for a microwave cooking oven, eventually named the Radarange. December 6 is Microwave Oven Day. In 1947 the first commercially produced microwave oven was about 6 feet tall, weighed about 750 lbs, and cost between $2,000 and $3,000. In 1967 the first relatively affordable ($495) and reasonably sized (counter-top) microwave oven was available for sale.