1946

Microwave Oven

Percy Spencer (1894–1970)

Every now and then discoveries happen by accident. Once they do, engineers get hold of the discovery and incrementally improve it to the point where just about everyone can afford it. This is the story of the microwave oven.

The cooking power of microwaves was discovered by Percy Spencer, an engineer working near radar equipment, in 1945. Radar uses microwave radio pulses at thousands of watts to detect aircraft. The engineer noticed the chocolate bar in his pocket melting from the microwaves. Of course if the chocolate bar was melting, he was also cooking himself to some degree, and perhaps this discovery also led to some basic safety precautions.

If you have radar equipment handy, creating a crude microwave oven is easy. You take the radio waves from the radar transmitter and send them into a metal box. The radio waves will reflect off the walls of the box. Any food placed in the box heats up as the radio waves induce molecular motion in water and fat molecules.

The first commercial microwave ovens were sold in 1946. Called Radaranges, they were made by Raytheon, which also made the candy-bar-melting radar set. The Radaranges were basically a radar transmitter and a metal box with a door, packaged in the size and weight of a refrigerator. In today’s dollars this oven cost perhaps $50,000.

Microwave ovens were too expensive for most people to afford until engineers simplified things and brought the cost down in the 1970s. Those new designs also solved a big problem—protection against the empty state. Prior to the 1970s, it was catastrophic to run a microwave oven with nothing inside it.

Today we take microwave ovens completely for granted and prices have fallen as low as fifty dollars for simple ovens. We see microwave ovens everywhere—in hotel rooms, break rooms, dorm rooms. They are far faster than normal ovens and far more energy efficient—almost every bit of energy the oven uses goes into heating the food. The microwave oven is a great example of the power of engineering to bring a technology to millions of people.

SEE ALSO Women’s Engineering Society (1919), Electric Refrigeration (1927), Radar (1940), Frozen Pizza (1957).

A chef using a Raytheon RadaRange III, an early commercial microwave oven, circa 1958.