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The word "radar" was invented by scientists of the United States Navy during World War II. The word comes from the first letters in the term "radio detection and ranging.""Detection," as used here, means finding an object or target by sending out a radio signal t ....

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.... in which direction the target is moving. This information can be used to direct the firing of guns and missiles to protect a country against attack. In peacetime, radar can help navigate ships, land planes in a fog, and guide astronauts. Radar can help control street traffic and assist the police in finding speeding automobiles. Radar sets come in many sizes. A small set, made for use in a guided missile, is not much larger than a coffeepot. The larger sets used to study distant planets may oupy a building many stories high. The size of a radar set depends on the job it is expected to do. But all radar sets, regardless of their size, use th ....