Percy Spencer: The Man Who Changed Cooking

What do popcorn and TV dinners have to do with World War II?

More than one might think, thanks to Percy Spencer, an American inventor with only a grade school education. Despite humble beginnings, Spencer would invent one of the country’s most ubiquitous appliances.

And that was after he had already been hailed as a war hero.

Working for the Raytheon Company, an appliance maker and defense contractor , in the early 1940s, Spencer was making important improvements to radar when he inadvertently discovered the mechanics of the microwave oven.

The combined effort would prove crucial to both the Allies in World War II and, subsequently, millions of hungry families.

Contributing to the Allies

When self-taught engineer Percy Spencer started working for Raytheon in the 1920s, revolutionizing American dinner culture was likely far from his mind.

Spencer’s interest was in microwaves – a wavelength of electromagnetic radiation more powerful than radio waves, but not quite as strong as infrared light.

At the outset of the war, Raytheon was contracted by the British to produce magnetron tubes, the high-voltage, energy-generating heart of its all-important microwave radar systems.

Over one weekend in 1941, Spencer improved and simplified the technology. He made several changes that would improve magnetron tube production and radar systems, according to Raytheon’s website.

The result was staggering: Spencer’s adjustments increased daily production from 17 tubes to 2,600, according to the National Inventors Hall of Fame profile on the scientist, making Raytheon the single most important supplier of magnetron tubes for the Allied powers.  The Allies’ superior radar technology later in the war is credited by many historians as a key to their victory, according to the U.S. Army Research, Development and Engineering Command website.

But Spencer wasn’t done.

Pop goes the microwave

The story of the melted chocolate bar is now well known.

Spencer, working at his Raytheon laboratory in 1945, stands in front of one of his magnetron tubes and notices something unusual: The candy bar in his pocket has melted. Naturally curious, Spencer places a few kernels of popcorn in front of the tube and they, too, react, exploding into a puffy white snack, according to Raytheon’s account.

Spencer had discovered the microwave oven — the kind we know today, albeit in its crudest form.

The accidental experiment worked because when radar microwaves penetrate a food, they cause friction within its molecules, which generates heat .

Microwaves hit the countertop

With military business drying up after the war, the discovery couldn’t have come at a better time for Raytheon. Recognizing the implications of Spencer’s finding, the company moved quickly to produce prototypes of the microwave oven, the first of which stood 5 feet, 6 inches (167 centimeters) and weighed 750 pounds (340 kilograms), according to the Massachusetts Institute of Technology’s profile on Spencer.

Raytheon held a contest among its employees to give it a brand name, and the winning entry was the Radarange.

Due to the ovens' size and questions about safety, Raytheon had difficulty marketing them until 1967, when it introduced an affordable countertop version, according to the company.

In the years since, the microwave oven has sold better than most people could have predicted. Today over 90 percent of American homes have a microwave, according to the U.S. Bureau of Labor Statistics.

• 7 Gadgets That Changed the World
• Video: Future Kitchen Has Flashy Food, 'Smart' Pantry and the Counter's a Stove
• Electrical Bloodsuckers: How to Slay 'Energy Vampires' in Your Home