Word: layering
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Diamond knew that the speed of sound is greater in warm air than in cold air. If a sound wave, rising through the sub-zero temperatures below the upper jet stream, suddenly hit a layer nearly as warm as the earth's surface, the top of the wave front, he figured, would accelerate. The whole front would then bend back earthward and rumble down. Diamond figured that he might be able to bounce a boom off the upper stream, predict its course, and record the boom as it came back to earth, thus helping to confirm his rocket data...
...whose own cornea had become overgrown with scar tissue after an injury. All of the operations were what ophthalmic surgeons call "penetrating transplants" or "full-thickness grafts," for which fresh corneas must be used within 72 hours of the donor's death. When only the outermost layer of the cornea is needed, for a split-thickness graft, an eye can be used after it has been frozen and banked for weeks...
Scientists have been studying this "airglow" layer for more than 40 years, and astronomers were cursing it long before that. Its faint green luminescence, which is probably caused by the recombination of irradiated oxygen atoms, masks dim but fascinating stars from earthbound telescopes. And not until men learned how to climb above that shimmering stratum in spacecraft could observers be sure of its altitude and thickness...
Astronauts John Glenn and Scott Carpenter both looked down on the airglow layer from their soaring Mercury capsules and found it as bright from that vantage point as the earth under a quarter moon. Then, last May, Gordon Cooper took a special camera aloft with him and photographed the airglow as he passed over Australia on his 16th orbit. With color film twice as fast as anything available commercially, he shot a sharply defined green band 16 miles thick, distinct from the blue-white earth some 65 miles below. "It must have been a tremendous experience, seeing this wedding ring...
Though what Cooper saw in the green veil was no surprise to scientists, the astronaut did manage to jolt them with another discovery. As he passed over South America, Cooper caught a glimpse of a thin, barely visible rust-colored layer roughly 70 miles higher than the green stratum he had been searching for. His sighting confirmed an earlier report by Astronaut Wally Schirra, and scientists now suspect the green veil may be topped by a red one made up of photochemically stimulated atomic oxygen...