There is no clear boundary between the atmosphere and space. It is thinner and slowly fades into space. Three-quarters of the atmosphere inside the ground is 11 km from the planetary surface. In the United States, people who travel in a height of 80.5 km (50 statute miles) are astronauts. One altitude of 120 km (75 miles or 400000 ~ m) marks the border, where atmospheric effects will be felt during re-entry. The Kármán-line at 100 km (62 miles or 328000 m), is also often used as the boundary between the atmosphere and space. Ionosphere: is the part of the atmosphere caused by solar radiation ionized. It plays an important role in atmospheric electricity and forms the inner edge of the magnetosphere. He has practical significance because among other functions, it affects the radio propagation to distant places on Earth. It is located in the Thermo sphere, and is responsible for the Earth's magnetosphere. Mesosphere: From the Greek word "μέσος" means middle. The mesosphere ranges from about 50 km (160000 m), in the range of 80 to 85 km (265000 - 285000 m), the temperature decreases with altitude. This is also where most meteors burn when in the atmosphere. Stratosphere: From the Latin word "Stratus", ie spreading. The stratosphere extends from the troposphere is between 7 and 17 km (23000 - 60000 ft) range of up to 50 km (160000 ft). Temperature increases with the altitude. The stratosphere contains the ozone layer, the part of the earth's atmosphere contains relatively high concentrations of ozone. "Relatively high" means a few parts per million, much higher than the concentration in the lower atmosphere, but still small in comparison to the major components of the atmosphere. It is especially in the lower part of the stratosphere about 15 to 35 km (50000 - 115000 ft) above the Earth's surface, if the thickness varies seasonally and geographically. Troposphere: From the Greek word "τρέπω" meaning to turn or change. The troposphere is the lowest layer of the atmosphere, it starts at the surface and extends between 7 km (23000 m) at the poles and 17 km (60000 m) at the equator, with some deviations due to weather factors. The troposphere is a large vertical mixing by solar heat at the surface. This heater warms air masses, making it less dense, so that they grow. If an air mass is increasing the pressure on them is so extended, work against the opposing pressure of the surrounding air. Work to be done to expend energy, so that the temperature of the air mass decreases. As the temperature drops, water vapor in the air or ground can consolidate, release of latent heat that further surcharges air mass. This process determines the maximum rate of decrease in temperature with altitude, the so-called adiabatic lapse. It contains approximately 80% of the total mass of the atmosphere. 50% of the total mass of the atmosphere is in the lower 5 km from the troposphere. The atmospheric pressure is a direct result of the total weight of the air above the point at which the pressure is measured. This means that the air pressure varies by place and time, because the amount (weight) of air above the Earth depends on the place and time. The atmospheric pressure increases with altitude, decreasing from 50% at an altitude of about 5.6 km (18000 ft). Equivalent, about 50% of the total mass of the atmosphere is in the lowest 5.6 km. This pressure drop is approximately exponentially, so that the pressure is reduced by about half of all 5.6 km. Because of the changes in the temperature of the atmosphere in the entire column, as well as the fact that gravity starts to fall in large amounts, not a single equation model atmospheric pressure through all the heights (it is modeled in 7 layers exponentially decreasing, in the equations above). Below the turbopause at an altitude of about 100 km (not far from the mesopause), the Earth's atmosphere has a more or less uniform composition (apart from water vapor), as described above, is the homosphere. [5] However, more than 100 km, the Earth's atmosphere begins the composition varies with the altitude. This is primarily because, in the absence of mixing, the density of a gas from falls exponentially with increasing altitude, but at a rate that depends on the molecular weight. So higher mass elements such as oxygen and nitrogen fall faster than lighter elements, such as helium, hydrogen molecular and atomic hydrogen. Therefore, there is a layer, the so-called heterosphere, where the atmosphere is different composition. As the height increases, the atmosphere is characterized by the gradual helium, molecular hydrogen and atomic hydrogen. The exact amount of heterosphere and its layers varies greatly with the temperature. After the loss of hydrogen, helium and other hydrogen-containing gases, from the early earth by the radiation of the sun, primitive Earth was devoid of an atmosphere. The first atmosphere created by outgassing of the gases in the interior of the early earth, which still goes on today in volcanoes. [6] The modern atmosphere is sometimes referred to as "Earth" third atmosphere "to the current chemical composition mainly from two different previous compositions. Original atmosphere was primarily hydrogen and helium. Heat from the molten crust yet, and the sun, and probably a stronger solar wind, broke up this atmosphere. About 4.4 billion years ago, the surface had cooled enough for a crust that are still heavily populated with volcanoes, the released vapor, carbon dioxide and ammonia. This led to the At the beginning of the "second" atmosphere, primarily carbon dioxide and water vapor, with some, but virtually no nitrogen-oxygen. This second atmosphere had about 100 times as much gas as the current atmosphere, but as it cooled much of the carbon dioxide was dissolved in the oceans as carbonate precipitated. later, "second atmosphere" largely contained nitrogen and carbon dioxide. however, simulations run at the University of Waterloo and the University of Colorado in 2005 suggests that it may have had up to 40 % hydrogen. [7] It is generally considered that the greenhouse effect, caused by a high level of carbon dioxide and methane, kept the soil from freezing. one of the earliest species of bacteria was the cyanobacteria. fossil suggests that these bacteria existed in the form of approximately 3.3 billion years ago and were the first oxygen-producing phototropic evolving organisms. they were responsible for the initial conversion of the Earth's atmosphere from an anoxic oxic state to a state (that is, from a state without oxygen to a State with oxygen) in the period from 2.7 to 2.2 billion years ago. Firstly, to carry out oxygenic photosynthesis, they were able to produce oxygen, while sequestering carbon dioxide into organic molecules play an important role in the atmosphere oxygenating. photosynthesis capacity plant would later develop and continue the release of oxygen and carbon dioxide sequestration. Over time was locked excess carbon in fossil fuels, sedimentary rocks (especially lime stone), mussels and animals. Since oxygen was released, it reacts with ammonia to release nitrogen; also would even bacteria convert ammonia into nitrogen. But most of the nitrogen present in the atmosphere, it is clear from sunlight-powered photolysis of ammonia released steadily over the aeons of volcanoes. As more plants appeared, the levels of oxygen increased significantly, while the carbon dioxide levels decreased. At first oxygen in connection with various elements (such as iron), but also oxygen in the atmosphere, leading to mass death and further development. with the appearance of an ozone layer (Ozone is an allotrope of oxygen) forms of life were better before UV radiation. this oxygen-nitrogen atmosphere is the "third atmosphere." 200 to 250 million years ago, up to 35 percent of the atmosphere was oxygen (bubbles of ancient atmosphere were in a Bernstein). this modern atmosphere has a composition, compliance with the oceanic blue-green algae, and geological processes. O2 not stay course in a free atmosphere, but more likely to be consumed (by inorganic chemical reactions, as well as animals, bacteria, plants and even country in the night), while the CO2 ousted by respiration and decomposition and oxidation of organic matter. Oxygen would disappear within a few million years ago by chemical reactions and CO2 dissolves easily in water and would have gone in, if not millennia replaced. both operated by the biological productivity and geological forces seemingly working hand in hand to secure reasonably steady level over millions of years (see Gaia theory). air pollution is a chemical, physical (eg particle), or biological agents, will change the natural properties of the atmosphere in an undesirable way. reduction of the ozone layer in the stratosphere by air pollution (mainly from chlorofluorocarbons substances) has long been considered a threat to human health and ecosystems of the earth. world-wide air pollution is responsible for the large number of deaths and cases of respiratory diseases. air quality standards are enforced , as the Clean Air Act in the United States, the presence of some pollutants. While the major stationary sources are often associated with air pollution, the largest source of emissions is actually mobile sources, mainly in the automotive industry. gases such as carbon dioxide, methane, hydrofluorocarbons, and contribute to global warming, and these gases or excess amounts of some emitted from fossil-fuel burning, were recently by the United States and many other countries (see Kyoto agreement), as pollutants.
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