Word: layering
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Long radio waves can be used to send code and voice across the oceans because they are deflected downward by ionized layers in the atmosphere, and therefore follow the curve of the earth. They cannot be used for television chiefly because they do not offer a wide enough band of frequencies. The shorter waves, including those that are used for TV, pass through the ionized layer and are lost in space...
...long-range study of the upper atmosphere. Part of the "air glow" (the faint glow of the night sky) comes from sodium atoms that absorb solar energy during the day. At night they give off this energy as yellow sodium light. Scientists do not know how high the "sodium layer" is. Nor do they know how the sodium got into the top of the atmosphere. Some think it came from outer space; others suspect that it originated as fine particles of sea salt that were carried upward...
...humans grow older, the innermost layer (intima) of the arteries, ordinarily a thin, smooth membrane, tends to roughen and thicken in a process that may be compared to what happens when deposits of lime accumulate inside a water pipe. This change in the arterial wall is known generally as atherosclerosis...
...push it faster than 600 m.p.h. at 40,000-ft. altitude. These characteristics make it a medium bomber, although its Navy sponsors, for fear of antagonizing the Air Force's Strategic Air Command and the Navy's own airplane-carrier partisans, prefer to call it a "mine layer." Portable Base. If the SeaMaster proves out as its friends hope, it will add a new dimension to long-range air warfare. It will need no elaborate, fixed and vulnerable bases. Instead, it can establish itself in any sheltered body of water within 1,000 miles of the enemy target...
...years old when one of its invading conquerors decided to make it a place of splendor. The Mongol Emperor Kublai, grandson of Genghis Khan, ordered the building of Green Mount, a hill that was dotted with evergreens brought from far and wide by imperial elephants, paved with a layer of green copper ore and topped by a green pavilion. Marco Polo reported in wonderment: "The great Khan caused all this to be made for the comfort of his spirit...