Percy LeBaron Spencer was born in 1894 in Howland, Maine, and orphaned at a young age. When he was 18 months old, his father died, and his mother was unable to care for him. Spencer was sent to live with his aunt and uncle. Then, when Spencer was seven, his uncle died. He left grammar school to earn money to support himself and his aunt.
When Spencer was 12, he began working sunrise to sunset at a spool mill. When he was 16, he was hired to install electricity at a local paper mill, despite never formally training in electrical engineering. Before being hired, Spencer had heard the paper mill would be installing electricity, and he quickly learned as much as possible about the subject. In 1910 in rural Maine, electricity was not well known or understood.
When he turned 18, Spencer joined the U.S. Navy to gain experience in wireless communications, which he had been interested in since learning of the wireless operators aboard the recently sunk Titanic. In the Navy, Spencer made himself an expert on radio technology by obtaining a lot of textbooks and teaching himself while standing watch at night. Subsequently, he taught himself trigonometry, calculus, chemistry, physics, and metallurgy.
When Spencer was appointed chief of the power tube division at Raytheon in 1939, he grew his division from 15 to more than 1000 staff. Spencer helped Raytheon win a government contract to develop and produce combat radar equipment for M.I.T.’s Radiation Laboratory. The contract was hugely important to the Allies in World War II, and the combat radar project became the military’s second-highest priority project behind the Manhattan Project. For Spencer’s work, he was awarded the Distinguished Public Service Award by the Navy.
Though it was a known phenomenon that a candy bar would melt near magnetrons, no one had investigated why. When Spencer noticed the phenomenon, he decided to experiment using food, such as popcorn kernels. Move over Orville Redenbacher – Spencer invented the first microwave popcorn. He also placed an egg in a tea kettle, with a magnetron directly above the kettle; the egg exploded inside the kettle.
Spencer created the first true microwave oven by attaching a high-density electromagnetic field generator to an enclosed metal box. The magnetron emitted microwaves into the metal box blocking any escape and allowing for controlled and safe experimentation. The first commercially producted microwave oven was about 6 feet tall, weighed about 750 pounds, and cost about $5000. In 1967, the first affordable, reasonably sized, counter-top Radarange brand microwave oven was made available for sale, for $495, by Amana, a division of Raytheon.
For his invention of the microwave, Spencer received no royalties, but he was paid a one-time $2.00 gratuity from Raytheon – the same token payment the company made to all inventors on its payroll for company patents at that time.
Spencer became Senior Vice President and a Senior Member of the Board of Directors at Raytheon. He received 300 patents during his career. Several Raytheon facilities were named after him: first, a facility in Burlington, Massachusetts involved in vacuum tube development and manufacturing was named Spencer Labs; a new building at the Raytheon Missile Defense Center in Woburn, Massachusetts, was later named in his honor, and an early Radarange model sits in the lobby of the building, across from the dining center.
Spencer became a member of the Institute of Radio Engineers, a Fellow in the American Academy of Arts and Sciences, and an Honorary Doctor of Science of the University of Massachusetts.
Spencer and his wife, Louise, had three children: John, James, and George. He died in Newton Massachusetts in late 1970, at the age of 76. Spencer’s friends included Omar Bradley (First Chairman of the Joint Chiefs), William Redington Hewlett, David Packard (co-founders of Hewlett-Packard), and Vannevar Bush (inventor, engineer, and WWII head of the U.S. Office of Scientific Research and Development). Bush said that “every physicist in the country” respected Spencer for not only his ingenuity but “what he has learned about physics by absorbing it through his skin.”
Thanks to Spencer, different wavelengths of microwaves are used to keep an eye on weather conditions and rain structures via satellites, and are able to penetrate clouds, rain, and snow; other technology uses microwaves to monitor sea levels to within a few centimeters.
In perhaps the least popular evolution of Spencer’s discovery, police are known to use radar guns to monitor a vehicle’s speed by continually transmitting microwaves to measure the waves’ reflections.