ATMOSPHERE AS A PROTECTIVE COVER AND EARTH The composition of the atmosphere In the atmospheric layer contained a variety of gases. By volume, most types of gas contained in a row is nitrogen (N2) as much as 78.08%, oxygen (O2) as much as 20.95%, 0.93% argon, as well as carbon dioxide (CO2) as much as 0.03% . Various other types of gas are also contained in the atmosphere, but in much lower concentrations, such as neon (Ne), helium (He), krypton (Kr), hydrogen (H2), xenon (Xe), ozone (O3), methane ( CH4) and water vapor (H2O). Among the gases contained in the atmosphere, carbon dioxide and water vapor contained in concentrations that vary from place to place, and from time to time for water vapor. Nitrogen into the atmosphere comes from the remnants of agricultural output and volcanic eruptions, while the expenditure or absorption of nitrogen gas from the atmosphere mainly due to biological processes in plants and sea life. Another gas enough oxygen in the atmosphere is. Oxygen among others, comes from the process of photosynthesis in green leafy plants. Carbon dioxide has a climate that is especially important role because the gas was effective in sorting out the absorption of terrestrial radiation that radiates out, if not, the radiation it will just disappear into the sky. In the process of photosynthesis, plants absorb carbon dioxide from the air and emit oxygen. The existence of the atmosphere that surrounds the entire surface of the earth has a very important significance for the survival of many organisms on earth. Atmospheric functions include: 1. Reduce the solar radiation reaching the Earth's surface during the day and heat loss at night. 2. Distribute water to different areas of the earth's surface. 3. Provide oxygen and carbon dioxide. 4. as a drag meteor that fell to earth. The role of the atmosphere in reducing the solar radiation is very important. If no layer of the atmosphere, the surface temperature of the earth when 100% of radiation received by the Earth's surface will be very high and feared no organisms were able to survive, including humans. In distributing water among regions on the surface of the earth, is seen in the role of the atmospheric hydrological cycle. Without the atmosphere that can hold moisture, the entire surface of the Earth's water will only accumulate in the lowest place. The rivers will run dry, all the water will seep into the sea, so the water will collect in the oceans and seas alone. The distribution of water by the atmosphere provides an opportunity for all living things to grow and expand across the water surface. Atmospheric Layers The atmosphere is composed of several layers, which are named according to the phenomena that occur in layers and can be distinguished based on the change in temperature due to the change in elevation from sea level (elevation). The transition between the layers to one another take place gradually. The layers of the atmosphere are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. 1. Troposphere Troposphere is the lowest layer of the atmosphere, which is at an altitude of 0-17 km above the earth's surface. Thick tropospheric average of 10 km. Equatorial region, the height of the atmosphere about 16 km with an average temperature of 80 C. Troposphere altitude region was about 11 km with average temperature of 54 C-rat, whereas the polar area height is approximately 8 km with an average temperature of 46 C. The density of air is certainly very low. In this vein, almost all types of weather, sudden changes in temperature, wind, pressure and humidity that we experience day-to-day progress. The height of the lowest is the warmest part of the troposphere, due to the Earth's surface absorbs heat radiation from the sun and channel the heat into the air. 2. Stratosphere The second layer of the atmosphere is the stratosphere. The stratosphere is situated at an altitude of between 18-49 km from the earth's surface. This layer is characterized by a temperature inversion process, meaning that higher temperatures increase with the increase in height. Temperature increase based on the height from standstill, which is at the top of the stratosphere is called the stratopause temperatures around 0 C. In the stratosphere there is no more water vapor, clouds or dust atmospheres, and usually the planes that use jet engines flying on this layer to avoid weather disturbances. 3. Mesosphere The third layer of the atmosphere is the mesosphere. Mesosphere is located at an altitude of 49-82 km from the earth's surface. This layer is a protective layer of the Earth from falling meteors or celestial objects beyond. Mesosphere layer is characterized by a decrease in air temperature, average 0.4 C per hundred meters. Decrease in temperature is due to radioactive mesosphere has a negative balance. 4. Thermosphere (ionosphere) The transition from the mesosphere to the thermosphere begins at an altitude of about 81 km. Named thermosphere due to the rise in temperature is quite high at this layer is about 1982 C. This change occurs because the absorption of ultra violet radiation. This radiation causes chemical reactions to form electrically charged layer known as the ionosphere, which can reflect radio waves. Before the advent of the satellite era, this layer is useful to help emit radio waves over long distances. Aurora phenomenon also known as the northern lights or light south happening here. 5. Exosphere or Desifasister Higher, above the ionosphere, there's exosphere. There are no clear boundaries after the ionosphere, the air becomes thinner and thinner and eventually completely empty of air. This area is the exosphere, the transition region between the sky and space. Exosphere lies at an altitude of between 800 - 100 km from the earth's surface. This layer is the layer of heat and air molecules can leave the atmosphere to an altitude of 3150 km from the Earth's surface. This layer is often referred to also by geostationary and interplanetary space. This layer is very dangerous, because it is a scene of devastation meteor from outer space. Maintenance of balance ratio of oxygen in the atmosphere is realized through a perfect recycling system. Humans and animals use oxygen continuously, while they emit carbon dioxide gas, which is toxic to them. Plants, on the other hand, establish a process which is precisely the opposite, and maintain continuity of life by turning carbon dioxide into oxygen. Every day billions of tons of oxygen released into the atmosphere by plants in this way. Now, if humans and animals carry out chemical reactions similar to plants, the earth, in a very short time, will be the planet inhospitable to living things. If both animals and plants produce oxygen, the atmosphere becomes highly flammable and very small spark once will cause a great fire. Finally, with such a scenario, the earth would stay so charcoal. If instead, both plants and animals both produce carbon dioxide, in the atmosphere as a result of oxygen will be depleted quickly, and naturally, all living things would soon meet death because he could not breathe. All this shows that God created the Earth's atmosphere specially for human life.