Microwave oven, as many great inventions, was invented by accident. Its inventor was Percy Spencer and he became interested in side effects of microwaves in 1945.
Percy Lebaron Spencer was born 19 July 1894 in a small town of Howland, Maine. He was parentless from an early age. His father died when he was only 18 months old, and his mother left him after that to his aunt and uncle. When he was only seven years old his uncle died and after that he was compelled to leave grammar school to earn money to support him and his aunt. When he was 12, he worked from morning until evening at a spool mill, a place where he stayed until he was 16 years old when he heard of a local paper mill that was going to begin using electricity. Intrigued by that that he began learning all he could about electricity and was one of three people who were hired to install electricity in the plant. When he was 18 he became interested in wireless communications and he joined the U.S. Navy where he became expert on radio technology by reading “a lot of textbooks” and he basically taught himself everything he knew about that theme. He also taught himself trigonometry, calculus, chemistry, physics, metallurgy, and other subjects.
In time he became one of the world’s leading experts in radar tube design. By 1939 he was working as the chief of the power tube division at Raytheon, which was a contractor for the United States Department of Defense and had a government contract to develop and produce combat radar equipment for M.I.T.’s Radiation Laboratory. One day while building magnetrons, important parts that generate microwaves for radars, he was standing in front of powered radar set. He noticed that the candy bar that he had in his pocket had melted. Although he was not the first to notice this effect, he was the first to express curiosity for it. He repeated the experiment with popcorns, which became the first food cooked with microwaves - on purpose. He also tried to microwave an egg, which exploded in the face of one of the experimenters. After that Spencer created the predecessor of a microwave oven by attaching a high density electromagnetic field generator to an enclosed metal box. It blocked escape of microwaves, which allowed for controlled and safe experimentation which Spencer continued with various food items. All experiments led to conclusion that when a food is placed in the box with the microwave energy, the temperature of the food rises rapidly.
Raytheon filed a United States patent application for Spencer's microwave oven on October 8, 1945. One such oven was soon placed in a Boston restaurant to be tested in working conditions. In time Percy Spencer became Senior Vice President and a Senior Member of the Board of Directors at Raytheon where he received 300 patents, a building is named after him and many other awards. It is interesting that he received no royalties his invention but he was paid a one-time $2 gratuity from Raytheon, which was a standard token payment of that time that the company made to all inventors on its payroll.