ATMOSPHERE

ATMOSPHERE

The earth is surrounded by the atmosphere, which is the body of air or gasses that protects the planet and enables life. Most of our atmosphere is located close to the earth's surface where it is most dense. The air of our planet is 79% nitrogen and just under 21% oxygen; the small amount remaining is composed of carbon dioxide and other gasses. There are five distinct layers of the earth. Let's look at each, from closest to farthest from the earth.

                The layer of the atmosphere closest to the earth is the troposphere. This layer is where weather occurs. It begins at the surface of the earth and extends out to about 4-12 miles. The temperature of the troposphere decreases with height. This layer is known as the lower atmosphere.

      The envelope of air which surrounds the earth from all sides is called atmosphere is held due to the gravitational pull of the earth. The Earth's atmosphere is more than just the air we breathe. It's also a buffer that keeps us from being peppered by meteorites, a screen against deadly radiation, and the reason radio waves can be bounced for long distances around the planet.  The outer layer of the atmosphere is called exosphere which extended up to an altitude of 2000km above the sea level.

   All gases of the atmosphere combined together constitute air. Atmosphere contains 78%nitrogen, 21% oxygen and remaining 1 % consists of argon, carbon dioxide, neon, helium, ozone and hydrogen. Air also contains water vapor and particles of dust.  In the lower layer of the atmosphere, the ratio of different gases remains relatively constant but the percentage of water vapor goes on changing. Clouds float in the lowest part of the atmosphere called troposphere. The air gets thinner, as we go above the surface of the earth. The lowest is the troposphere, which is the layer that provides most of our weather. It contains about four-fifths of the Earth's air, but extends only to a height of about 11 miles (17 kilometers) at the Equator and somewhat less at the Poles. The name comes from a Greek word that refers to mixing. And mixing is exactly what happens within the troposphere, as warm air rises to form clouds, rain falls, and winds stir the lands below. Typically, the higher you go in the troposphere, the colder it gets. Above the troposphere is the stratosphere. It extends to a height of about 30 miles (50 kilometers) and includes the ozone layer, which blocks much of the sun's harmful ultraviolet rays. The stratosphere is warmer than the troposphere because of the energy from the ultraviolet light absorbed by the ozone. At its base, the stratosphere is extremely cold, about -110 degrees Fahrenheit (-80 degrees Celsius). At its top, the temperature has risen back nearly to freezing. Next comes the mesosphere. In this layer, the air temperature drops again, down to nearly -180 degrees Fahrenheit (-120 degrees Celsius) at the top. Meteors generally burn up in the mesosphere, which extends to a height of about 52 miles (85 kilometers). This is why the Earth's surface isn't pocked with meteor craters, like the moons