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Earth's Multilayered Atmosphere

There are Layers in Space which Serve as Barriers to Gases and Radiations and so They Protect the Earth from the Many Dangers That Exist in Space

There is a mixture of gases in the atmosphere which is around the earth that is held in place by the earth's gravity.

The invisible mixture of nitrogen, oxygen, argon, carbon dioxide, and water vapor protects our planet from harmful radiation and makes life on earth feasible.

The atmosphere's density decreases with its height or distance from the earth; however, not at a uniform or consistent rate. Above approximately 90 kilometers, or 55 miles, the air is extremely rarefied, but it extends thousands of miles above the earth.

Different layers of atmosphere are distinguished by the levels of their temperatures:

  • The troposphere extends 18 kilometers, or 11 miles, above the earth.

    It is warmed by solar rays re-radiated from earth's surface.

    This causes convection currents that bring changes in the weather.

    Temperature in the troposphere decreases with height to -60°C, -76°F, but in the stratosphere it rises close to the freezing point.

  • The stratosphere, which is just above the troposphere, extends to 50 kilometers, 30 miles.

    It contains ozone, which absorbs ultraviolet rays from the sun.

  • In the next layer above the stratosphere, is the mesosphere, which extends to 80 kilometers, 50 miles, above the earth and it is here that the temperature drops to -113°C, or -173°F.
  • The previous three layers form the lower atmosphere.
  • In the more rarefied upper atmosphere, temperature rises, reaching 227°C, 441°F, even at night where thermosphere and exosphere meet 450 kilometers, 280 miles, above the earth.
  • The upper atmosphere absorbs much of the harmful radiation and as it does this, it produces electrically charged particles called ions.
  • In this region, called the ionosphere, layers of greater ion concentration (the D, E, and F layers) exist, although they vary daily or seasonally.
  • Humans use the the ions to bounce radio waves around the earth.
  • Farther out in the ionosphere are two Van Allen Belts (Inner Van Allen belt and Outer Van Allen belt), which are zones of radiation concentration.
—Compiled from information located at
Reader's Digest Illustrated Encyclopedic Dictionary, Volume One, A-K;
The Reader's Digest Association, Inc.; Pleasantville, New York; page 117.
This entry is located in the following unit: sphero-, spher-, -sphere- (page 7)