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Percy Spencer

PhysicistCambridge, MA

Military VeteranScientist
The Raytheon Company at its present day location in Marlborough, MA

Percy Spencer was an American physicist and inventor.

Spencer was born in 1894 in Howland, Maine. He dropped out of grammar school at age 12 to work as a spindle boy in a weaving mill, but in his early years he taught himself about electricity, even setting up a new electrical system at a local paper mill. When he was 18, Spencer joined the U.S. Navy as a radio operator. During this time he taught himself a number of scientific subjects, including calculus, chemistry, metallurgy, physics, and trigonometry. Spencer later remembered, “I just got hold of a lot of textbooks and taught myself while I was standing watch at night.”

After World War I, Spencer joined the American Appliance Company in Cambridge, MA, which would later become the Raytheon Company. During World War II, Raytheon was contracted by the British to mass produce their newest invention: combat radar equipment. In desparate need of radar to detect German planes and submarines, the British turned to the United States to produce the cavity magnetron, radar’s primary component. Spencer developed a system of mass production for the magnetron, increasing its production output to 2600 per day. With radar becoming increasingly commonplace, the head of Electronics at the U.S. Navy’s Bureau of Ships, Commodore Jennings Dow, asserted, “Raytheon radar had a marked effect on every major sea engagement of the war.” For his work during the war, Spencer received the Distinguished Public Service Award from the U.S. Navy, its highest civilian honor.

Spencer is best known as the inventor of the microwave oven. During his research into electromagnetic waves in the 1940s, Spencer noticed that a candy bar in his pocket melted when he was standing next to a magnetron. He realized that electromagnetic waves could be used to cook food, and Spencer subsequently filed a patent with Raytheon for the RadarRange in 1945. As Vannevar Bush once said, Spencer “earned the respect of every physicist in the country, not only for his ingenuity, but for what he has learned about physics by absorbing it through his skin.”

Spencer died on September 8, 1969 in Newton, MA.

Percy Spencer's Timeline
1894 Jul 19th Born in Howland, Maine.
1912 Joined the U.S. Navy as a radio operator.
19401945 Worked on the development of the cavity magnetron for the U.S. military.
1945 Filed a patent for the RadarRange, a precursor to the microwave.
1969 Sep 8th Died in Newton, MA.

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