The Microwave Oven

Percy L. Spencer, the inventor of the microwave oven, was born on this day in 1894 in Howland, Maine.

An orphan who never finished grammar school, Spencer got his training in radio electronics from the U.S. Navy. After World War I, he joined Raytheon as its 5th employee. During World War II, in conjunction with MIT physicists, he pioneered the use of magnetron vacuum tubes to change the shape of electromagnetic waves into "microwaves" and created combat radar equipment modules which were practical for use in bombers and effective enough for U.S. pilots to spot periscopes of German U-boats. The U.S. Navy awarded him the Distinguished Service Award, its highest civilian honor, for his innovations.

In 1945, however, Spencer stumbled upon the idea which would be his most lasting achievement: while standing in front of a radar power tube at the Raytheon factory, he reached into his shirt pocket and found that a candy bar he had put there had melted into a gooey mess. Sending an assistant out for a bag of unpopped popcorn, Spencer placed the bag in front of the waves emanating from the magnetron and watched as the popcorn began to pop. In another test the next day, he put an egg in a kettle in front of the magnetron; when an innocent colleague peeked into the kettle to see what Spencer was up to, the egg exploded in his face -- but Spencer was able to determine that the yolk was cooking faster than the white, meaning that by using the magnetron, he was able to cook food from the inside out by vibrating molecules inside the food. It was this phenomenon that would make the microwave ideal for pasteurization and sterilization as well as for basic food preparation.

Raytheon developed Spencer's idea and unveiled the first microwave oven, the Radarange, in 1947; it stood 6-feet tall, weighed 250 lbs. and cost about $3,000. In 1965, Raytheon acquired Amana Refrigeration and began selling more practical models. By 1975, sales of microwave ovens outpaced gas ranges, and over 200 million microwave ovens were in use by the end of the 20th century. Spencer died on September 8, 1970.

Categories: Inventions, Technology