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A microwave oven uses radio energy to produce heat in substances such as food. Today’s household microwave ovens consist of an electronic device called a cavity magnetron which produces microwave energy, a waveguide that guides the energy in the right direction, and a metal enclosure, which traps that energy until absorbed by food or another material.
Every day tens of thousands of people board airplanes to travel from one place to another. These flights, thousands of which take off and land daily, are among the safest forms of travel. Although airplane crashes are tragic and headline grabbing, the fact is the sky is a very safe place to be. But how, with so many airplanes in the air, does air travel maintain such a good safety record? The answer is, in large part, air traffic control, the complex system of directing planes and telling them how high or low to fly, and when and where to land safely.
Guided missiles were one of Germany’s most important technical achievements during World War II. Rockets and missiles have been part of warfare since the late 1700s. In 1812, for example, the song The Star Spangled Banner made reference to “the rocket’s red glare.” Throughout the 19th century and into the early 20th, experimenters in many nations hoped to turn simple rockets into weapons or, in some cases, as a way to travel into outer space.