Atmosphere

Definition of Atmosphere

The atmosphere is described as a “protective shield”, which ensures the continuation of life on the planet, and while it allows beneficial sunlight to reach the earth, it prevents harmful rays and meteors from reaching it, in addition to its influential role in the formation of water.

gas mixture
The atmosphere is an invisible envelope surrounding the planet, and it consists of a group of gases attracted to it by Earth’s gravity, most notably nitrogen by 78%, oxygen by 21%, and a mixture of other gases such as carbon dioxide, argon, helium, and neon by 1% .
The atmosphere also contains water vapor, and a group of small, solid and liquid particles floating called aerosols, including: pollen, volcanic ash, and dust, and 98% of the atmosphere’s mass is located in the first 30 kilometers close to the Earth’s surface.

Atmospheric layers

Troposphere

It is the lower layer of the atmosphere, i.e. the closest layers to the surface of the earth, which is the field of clouds, storms, wind movements, and the geographical and seasonal variation of the climate. This layer pressure and density decrease rapidly with altitude, and the temperature decreases at a constant rate of about (6.5 degrees Celsius per 1 km), that is, it becomes about (20 degrees Celsius below zero) at an altitude of (5.5 km) and the atmospheric pressure drops to (500 millibars) and successively The temperature drops to (minus 57 degrees Celsius) at an altitude of (11 km), this range of the atmosphere, extending from the surface of the Earth to where the temperature stops dropping, is called the troposphere, this name came from the Greek word tropin (Tropein), which means change, and the word (sphere) an envelope, meaning that the troposphere, which means, the changing envelope.

Stratosphere

This atmosphere extends above the troposphere by about 50 km and contains most of the ozone in the layers of the atmosphere. The increase in temperature with height occurs due to the absorption of ultraviolet (UV) rays from the sun. Temperatures in the stratosphere are higher during the summer pole and lower during the winter pole.

By absorbing dangerous ultraviolet rays, stratospheric ozone protects us from skin cancer and other associated health damage, however there are chemicals (called chlorofluorocarbons or freons and halons) that were once used in refrigerators, nebulizers and fire extinguishers which in turn have reduced The amount of ozone in the stratosphere, especially in the polar latitudes, led to the so-called “Antarctic ozone hole”.

Humans have now stopped making most of the harmful CFCs and the ozone hole is expected to eventually recover during the 21st century, but this process is very slow, and currently the stratosphere is the layer of the atmosphere most affected by human activity.

Mesosphere

It is the third layer of the atmosphere, the temperature in the mesosphere decreases with the increase in altitude. This layer cannot absorb heat directly from sunlight due to the presence of a small number of gas molecules in it, and therefore the source of the heat of the mesosphere is the stratosphere, which is directly below it. Thus, the mesosphere is very cold, especially at its summit, where the temperature is about -90 °C (-130 °F).

The air density is very low in the mesosphere, where 99.9% of the mass of the atmosphere is concentrated below this layer. From this number, you can visualize how very low air density and very low pressure also. Imagine if a normal person decided to travel through the mesosphere without wearing the right equipment, this person would be exposed – Unfortunately for him – severe burns caused by ultraviolet rays, because the ozone layer that provides protection from ultraviolet rays is in the stratosphere and not in the mesosphere, in addition to that there will not be enough oxygen to breathe, and the most strange thing is that if the same person decided to travel In this layer, after wearing a special suit that will protect him from ultraviolet rays, he will still be exposed to the phenomenon of blood boiling at normal body temperature due to the severe low pressure.

Thermosphere

Or the so-called thermosphere, the thermosphere is the fourth layer of the atmosphere where the air is very thin, which means that there are much fewer air molecules compared to the other layers. The thermosphere is very sensitive to solar activity and can heat up to 1,500 degrees Celsius or higher when the sun is most active, resulting in the aurora borealis that illuminate the night sky.

Astronauts spend their time in this layer as they orbit the Earth in the space shuttle or inside the space station, and within this layer there is the so-called ionosphere, which is a layer abundant with electrons, atoms, and ionized molecules that extends from 48 kilometers above the surface of the earth to the edge of space i.e. Up to about 965 km overlapping in the mesosphere and thermosphere, one of the most important features of this layer is that it makes radio communications possible.

It is the upper layer of the atmosphere, this layer is very thin and is considered the place where the atmosphere merges in outer space, the exosphere mainly contains atoms of oxygen and hydrogen, but in very small numbers as atoms and molecules rarely collide with each other, these molecules follow ballistic paths , being subject to the influence of Earth’s gravity and some of them escape directly into space.

Exosphere

It is the upper layer of the atmosphere, this layer is very thin and is considered the place where the atmosphere merges in outer space, the exosphere mainly contains atoms of oxygen and hydrogen, but in very small numbers as atoms and molecules rarely collide with each other, these molecules follow ballistic paths , being subject to the influence of Earth’s gravity and some of them escape directly into space.

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