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Atmosphere

Posted by Chris Shrestha

Atmosphere

Life on earth exists only because of atmosphere. It is like a blanket around the Earth, protecting it from the sun and providing the necessary conditions in which animals and plants can live. It is basically a blanket of air wrapped around the earth. This air is a mixture of two gases, Nitrogen (four-fifth) and Oxygen (one-fifth).

The atmosphere is made up of five main layers: the troposphere, the stratosphere, the thermosphere, the mesosphere and the exosphere. The air gets thinner as you go higher, which is why climbers usually take oxygen with them when climbing high mountains. The troposphere is the only layer in which living things can breathe normally. Now let us go in detail about each of the layers. Exosphere is the top layer of the atmosphere and sits about 560 miles above earth. The air is very thin and gas molecules are constantly exiting into space. The thermosphere on the other hand sits about 280 miles above the earth. It is the hottest layer, as the few air molecules absorb radiation coming from the Sun. The Mesosphere is about 50 miles above the ground. It is very cold here with temperatures less than -150 degree Celsius. The lower part is warmer because it picks up heat from the stratosphere just below. Stratosphere is up to about 30 miles above the ground. The temperature in this layer warms from above -76 degree Celsius at the bottom to just above freezing at the top. It contains Ozone, a gas that absorbs harmful ultraviolet rays from the sun. Finally the last one, Troposphere. Here the weather conditions happen in the bottom layer of the atmosphere. This layer stretches up 12 miles from the ground at the equator and about 6 miles at the poles.

The atmosphere not only provides us with oxygen to breathe. It shields us from the Sun’s harmful rays. Some of these are reflected are reflected by various layers such as the stratosphere and the clouds. Other rays have their energy absorbed and spread out through the atmosphere. The gas ozone occurs thinly in the stratosphere and absorbs most of the Sun’s dangerous ultraviolet rays.

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