The microwave oven is so ordinary today that it's easy to forget it had to be invented. No one set out to build a faster way to reheat leftovers. Instead, the story starts with radar equipment, a curious engineer, and a candy bar that didn't survive his workday.
Here's the short answer. In 1945, Percy Spencer, an engineer at the company Raytheon, was working with an active radar set when he noticed the candy bar in his pocket had melted. He wasn't the first person to notice this heating effect, but he was the first to investigate it seriously. His experiments led to the first commercial microwave oven.
The Self-Taught Engineer
Spencer's own story is remarkable. Born in Howland, Maine, in 1894, he was orphaned at a young age and left grammar school to help support himself and his aunt. As a boy, he worked from sunrise to sunset at a spool mill.
He joined the U.S. Navy at 18, inspired by reading about the wireless operators aboard the Titanic. On night watches, he taught himself from textbooks, picking up trigonometry, calculus, chemistry, physics, and more. By 1939, he was one of the world's leading experts in designing radar tubes.
During World War II, Spencer ran Raytheon's power tube division, which grew from 15 workers to more than 1,000. He found a way to boost production of magnetrons, the tubes that generate microwaves for radar, from 100 to 2,600 a day.
Popcorn and an Exploding Egg
After the candy bar incident, Spencer started testing food. The first thing he deliberately cooked was popcorn, which became the world's first microwave popcorn. Next came an egg. Placed in a kettle under a magnetron, it exploded in the face of a curious co-worker who was peering inside.
To study the effect safely, Spencer fed microwave power into a metal box that kept the energy from escaping. Food placed inside heated up quickly. On October 8, 1945, Raytheon filed a patent application for his microwave cooking process.
Like many famous invention stories, the candy bar moment has taken on the feel of a legend, and some accounts describe it that way. But the experiments, the patent, and the machine that followed are all part of the documented history.
The Giant First Microwave
The first commercial microwave oven, the Raytheon Radarange, went on sale in 1947. It was nothing like today's countertop models. It stood almost 6 feet tall, weighed about 750 pounds, and was water-cooled. Its name came from an employee contest.
Early units went to restaurants, hotels, railroads, and ships, often leased rather than sold. By March 1948, about 100 were in commercial use in the United States. The ocean liner SS United States even had one aboard.
Into the Home Kitchen
It took a while for microwaves to reach ordinary homes. A home model licensed from Raytheon went on sale from Tappan in 1956, but it was still too large and expensive for most families. In 1967, Raytheon's Amana division introduced a popular countertop Radarange for $495, a hefty price at the time. Microwaves became affordable for most households in the late 1970s, and prices fell quickly in the 1980s.
So the next time you pop a bag of popcorn in the microwave, think of Percy Spencer and his sticky pocket. A melted snack, plus a lot of curiosity, ended up changing the way the world cooks.
