What is atmosphere ?
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Answer:
An atmosphere is a layer or a set of layers of gases surrounding a planet or other material body, that is held in place by the gravity of that body. An atmosphere is more likely to be retained if the gravity it is subject to is high and the temperature of the atmosphere is low. The total mass of Earth's atmosphere is about 5.5 quadrillion tons, or roughly one millionth of Earth's mass.
Earth's atmosphere has five major and several secondary layers. From lowest to highest, the major layers are the troposphere, stratosphere, mesosphere, thermosphere and exosphere.
Troposphere is the first and densest atmospheric layer.Earth’s troposphere extends from Earth’s surface to, on average, about 12 kilometers (7.5 miles) in height, with its height lower at Earth’s poles and higher at the equator. Most of Earth’s weather happens here, and almost all clouds that are generated by weather are found here, with the exception of cumulonimbus thunder clouds, whose tops can rise into the lowest parts of the neighboring stratosphere.
Stratosphere is the second. Located between approximately 12 and 50 kilometers (7.5 and 31 miles) above Earth’s surface, the stratosphere is perhaps best known as home to Earth’s ozone layer, which protects us from the Sun’s harmful ultraviolet radiation. Because of that UV radiation, the higher up you go into the stratosphere, the warmer temperatures become. The stratosphere is nearly cloud- and weather-free, but polar stratospheric clouds are sometimes present in its lowest, coldest altitudes. It’s also the highest part of the atmosphere that jet planes can reach.
Mesosphere is the third layer.Located between about 50 and 80 kilometers (31 and 50 miles) above Earth’s surface, the mesosphere gets progressively colder with altitude.The very scarce water vapor present at the top of the mesosphere forms noctilucent clouds, the highest clouds in Earth’s atmosphere, which can be seen by the naked eye under certain conditions and at certain times of day. Most meteors burn up in this atmospheric layer. Sounding rockets and rocket-powered aircraft can reach the mesosphere.
Thermosphere is the fourth layer. Located between about 80 and 700 kilometers (50 and 440 miles) above Earth’s surface is the thermosphere, whose lowest part contains the ionosphere ( ions which helps us to communicate with each other) . In this layer, temperatures increase with altitude due to the very low density of molecules found here. It is both cloud- and water vapor-free. The aurora borealis and aurora australis are sometimes seen here. The International Space Station orbits in the thermosphere.
Exosphere is the last layer of the Earth. Located between about 700 and 10,000 kilometers (440 and 6,200 miles) above Earth’s surface, the exosphere is the highest layer of Earth’s atmosphere and, at its top, merges with the solar wind. Molecules found here are of extremely low density, so this layer doesn’t behave like a gas, and particles here escape into space. While there’s no weather at all in the exosphere, the aurora borealis and aurora australis are sometimes seen in its lowest part. Most Earth satellites orbit in the exosphere.
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