Atmosphere
literally, the air surrounding our planet, and which, as the etymology implies, is, speaking broadly, a "sphere" (not, of course, a solid, but a hollow one). With strict accuracy, it is a hollow spheroid. Its exact height is unknown. At 2.7 miles above the surface of the earth, half its density is gone, and the remainder is again halved for every further rise of 2.7 miles. Some small density would remain at 45 miles high. At 80 miles, this would have all but disappeared. But from sundry observations, made at Rio Janeiro and elsewhere, on the twilight arc, M. Liais infers that the extreme limit of the atmosphere is between 198 and 212 miles. ATMOSPHERIC PRESSURE In the lower strata of the atmosphere, the temperature falls at least a degree for every 352 feet of ascent; hence, even in the tropics, mountains of any considerable elevation are snow-capped. The atmosphere appears to us blue, because, absorbing the red and yellow solar rays, it reflects the blue one. There appears to be no atmosphere around the moon; but the case seems different with the sun, Venus, Mars, Jupiter, and Saturn.
Figuratively, any pervading intellectual, moral, religious, or other influence by which one is surrounded; as in the expression, "He lives in an atmosphere of suspicion."