Arriving from Outer Space

Suppose that we were space travellers, visiting the earth from some distant planet. It would be difficult to detect much trace of the atmosphere until we were in the region of the lower part of the orbit of the first Sputnik, say between 200 and 300 miles up. At that distance from the earth the pressure of the atmosphere, which measures the weight of the air above us, is less than one millionth of that on the ground. This means we would be moving in what is called a “vacuum” on earth, for at this level, pressure is lower than that which can be reached by the finest laboratory pumps.

Having passed through the stratosphere, we would enter the atmosphere, or region of weather. Meteorologists are interested in the whole atmosphere, but especially in the troposphere, because it is only in this relatively thin layer that we find weather, that is clouds, fogs, rain, hail and snow.

In general the higher one goes in the atmosphere, the colder the air becomes. This seems odd at first, because by climbing up we are getting nearer to the sun, from which we get all our heat. The explanation is that the rays of the sun are not very effective in heating air directly. Most of the energy in a sun beam passes through clear air with very little absorption. What happens is that the sun’s rays heat the surface of the earth, both the ground and the sea, and it is from the warm surface that the atmosphere receives most of the energy which appears as wind, and causes weather generally.

(Рубцова М.Г., стр. 91)

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