In the modern world, the microwave has become an indispensable appliance in households across the globe. According to a 2023 survey, around 90% of households in the United States own a microwave. Yet despite its widespread use, the origin of this popular and extremely useful appliance is likely to be unfamiliar to most people who own microwave ovens.
Percy Spencer was a self-taught physicist whose ingenious idea led to the creation of the microwave. Born in Howland, Maine, in 1894, Spencer received a cursory education and, by the fifth grade, had left school to work in a factory. He later applied to work at a local paper mill and was hired to install electricity in the plant, despite lacking formal training. Through sheer dedication and a strong desire to expand his learning, Spencer became an accomplished electrician and later joined the U.S. Navy as a radio operator. He independently pursued physics, trigonometry, chemistry, and calculus in his spare time, reading from textbooks while on night watch. After his naval service, Spencer joined the American Appliance Company, later known as Raytheon.
During World War II, Raytheon grew rapidly. The company was contracted by the U.S. Department of Defense to produce combat radar equipment to help the war effort. Raytheon was responsible for creating cavity magnetrons, high-powered vacuum tubes with cavities that produce microwave beams, enabling radar systems to detect enemy aircraft and ships. Spencer discovered a way of producing these magnetrons on a wider scale and was awarded the Distinguished Public Service Award by the U.S. Navy for his contribution.
But how did vacuum tubes and radar systems lead to the invention of a household appliance for cooking food? As the story goes, one day in 1945, while working with magnetrons, Spencer was standing in front of an active radar set when the chocolate bar in his pocket melted. Hypothesizing that electromagnetic radiation could be used to cook food, he tested his theory by popping popcorn kernels and cooking an egg near the active radar set. Spencer continued experimenting and came up with a design for the microwave involving a rectangular metal box. Raytheon spotted an opportunity to revolutionize food preparation and filed a patent for the microwave later that year. In 1946, the first iteration of the microwave oven, the Radarange, hit the U.S. market.
However, the microwave was not an instant success. Many people feared the effects of microwave radiation, while the cost and size of early microwaves made them impractical and unaffordable for the average American household. The first microwave ovens were almost 6 feet (1.8 m) long, weighed more than 750 pounds (340.2 kg), and cost a whopping $5,000. However, as microwave technology advanced, designs were modified to make microwaves much more affordable and practical, and households began to see the appeal of purchasing one to free up time in the kitchen.
Unfortunately, Spencer received little compensation for his role in the creation of the microwave and never received royalties from his invention. He was merely paid a one-time $2 bonus that Raytheon gave employees for patented inventions. Spencer reportedly received 300 patents during his time working for Raytheon. However, his invention wasn’t wholly overlooked. Despite his lack of formal education, Spencer was granted an honorary doctorate from the University of Massachusetts. Raytheon named a building at the Raytheon Missile Defense Center in Massachusetts in his honor.
Miraculous microwaves:
- In January 1947, the first public microwave was placed in New York City's Grand Central Terminal. It sold freshly made hot dogs.
- Microwaving spinach preserves an impressive amount of folate, a nutrient essential for cell growth and function. In contrast, stove cooking leads to a loss of around 77% of folate content in spinach.
- When heated in a microwave, eggs in their shells can explode dramatically due to an increase in pressure from the steam that builds up inside them.