College Uneducation

1. An atmosphere (New Latin atmosphaera, created in the 17th century from Greek ?tµ?? [atmos] "vapor"[1] and sfa??a [sphaira] "sphere"[2]) is a layer of gases surrounding a planet or other material body of sufficient mass[3] that is held in place by the gravity of the body. An atmosphere is more likely to be retained if the gravity is high and the atmosphere's temperature is low.
Earth's atmosphere, which contains oxygen used by most organisms for respiration and carbon dioxide used by plants, algae and cyanobacteria for photosynthesis, also protects living organisms from genetic damage by solar ultraviolet radiation. Its current composition is the product of billions of years of biochemical modification of the paleoatmosphere by living organisms.
The term stellar atmosphere describes the outer region of a star, and typically includes the portion starting from the opaque photosphere outwards. Stars with sufficiently low temperatures may form compound molecules in their outer atmosphere.

2. The atmosphere is divided into five layers.* It is thickest near the surface andthins out with height until it eventually merges with space. The layers fromlowest to highest : - The Troposphere (up to 10 km) It's the atmosphere thatsurrounds us. On top of that comes... - The Stratosphere; (10-50 km) Verylittle oxygen or water vapor. Aircraft fly in the lower stratosphere. This isalso where the ozone layer exists. On top of that comes.. - The Mesosphere;(50-80 km) This is where most meteors burn up, because the density is higherthan the outer layers. On top of that comes.. - The Thermosphere; (80-650 km)Practically a vacuum. Includes the ionosphere (auroras) as well as space stationorbits. On top of that comes... - The Exosphere (500-2000 km ) The farthest anyof Earth's atmosphere exists.Based on charged particles and not necessarily gasmolecules, some atmospheric models combine the Exosphere into the Thermosphere,making the outermost layer the Magnetosphere, a vast region where atmosphericions interact with the solar wind in space.* Names of 11 defined layers, some of which comingle with the basic 5. The names of these levels are Troposphere,Tropopause (upper boundary), Ozone Layer, Stratosphere, Stratopause (upperboundary), Mesosphere, Mesopause (upper boundary), Thermosphere (andIonosphere), Thermopause (upper boundary), Exobase (lower boundary), Exosphere.

3. Layers of the 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...
Troposphere:
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.

Stratosphere: Above the troposphere is the stratosphere, which extends to about 30-35 miles above the earth's surface. Temperature rises within the stratosphere but still remains well below freezing.

Mesosphere: From about 35 to 50 miles above the surface of the earth lies the mesosphere, where the air is especially thin and molecules are great distances apart. Temperatures in the mesosphere reach a low of -184°F (-120°C). The stratosphere and the mesosphere are the middle atmosphere.
Thermosphere:
The thermosphere rises several hundred miles above the earth's surface, from 50 miles up to about 400 miles. Temperature increases with height and can rise to as high as 3,600°F (2000°C). Nonetheless, the air would feel cold because the hot molecules are so far apart. This layer is known as the upper atmosphere.
Exosphere:
Extending from the top of the thermosphere to 6200 miles (10,000 km) above the earth is the exosphere. This layer has very few atmospheric molecules, which can escape into space.
4.
Layers Elevation Temperature Composition
1) The troposphere is the first layer above the surface and contains half of the Earth's atmosphere. Weather occurs in this layer.
2) Many jet aircrafts fly in the stratosphere because it is very stable. Also, the ozone layer absorbs harmful rays from the Sun.
3) Meteors or rock fragments burn up in the mesosphere.
4) The thermosphere is a layer with auroras. It is also where the space shuttle orbits.
5) The atmosphere merges into space in the extremely thinexosphere. This is the upper limit of our atmosphere.