Our planet is surrounded by an immense layer of gases, the atmosphere. It is around the earth and is maintained through the pull of gravity. It is about 1000 km thick.
It is the layer of air that surrounds the earth. Some facts illustrate the existence of a space containing air from the ground:
- when breathing, we remove oxygen gas from this layer;
- when an airplane takes off, it must have sufficient speed to be able to support itself in the air;
- when jet aircraft at high altitudes are stabilized because they are at a level of the atmosphere where there is little turbulence.
The atmosphere is very important for life on the planet. It mitigates the effects of solar radiation on the Earth, contributes to maintaining an ideal temperature for the development of life, prevents our planet from being directly hit by large meteorites.
The atmosphere has five distinct layers: troposphere, stratosphere, mesosphere, thermosphere and the exosphere.
There is no boundary between one layer and another. Its characteristics gradually change.
It is the air layer that goes from the ground up to approximately 12 km in height. In it there are polluting gases and dust. It is in this layer that clouds, winds, rain, snow form and thunder and lightning happen.
It is in the troposphere that living beings draw oxygen gas (O2) and produce carbon dioxide (CO2) to perform photosynthesis and release oxygen.
It is the layer that begins where the troposphere ends. There is almost no oxygen, air is thin (little oxygen gas; air molecules are too far apart), temperatures are around -50 ° C, so there is no life in this layer. The predominant gas is nitrogen (N).
In the stratosphere, there are no clouds, no storms. This is where jet planes sail.
There is a layer that surrounds the stratosphere, the ozone layer. Ozone gas (O3) is very important to our planet because it absorbs all the ultraviolet radiation (UV rays) that reaches the earth. UV rays are harmful to health because in large quantities alter the constitution of the cells of living beings, causing cancer.
It has approximately 80 km and its temperatures can reach -120ºC. In this layer, meteorological surveys are made through probe balloons that cross the other layers until they reach the mesosphere.
Thermosphere or Ionosphere
It is approximately 640 km above the earth's surface. Its temperature increases with altitude reaching 1000ºC.
In it pass meteorites (rocky or metallic bodies that come from the cosmic space) that catch fire when entering the thermosphere due to the friction with the air. They are the so-called “shooting stars”. Some meteorites can reach the earth's surface. In the thermosphere, two phenomena happen: the northern lights and the southern lights.
The aurora borealis and aurora austral are luminescent phenomena, that is, the emission of light occurs. They happen in the atmosphere of the northern and southern hemispheres. In them are located two magnetic poles of the earth. The particles emitted by the sun interact with the particles of the thermosphere and under the action of the earth's magnetic field produce bright and multicolored bands.
When this phenomenon happens in the northern hemisphere, we call it the northern lights. When this phenomenon happens in the southern hemisphere, we call it the aurora austral.
The thermosphere is also known as the ionosphere because there are many ions (electrically charged particles) in it.
Last atmospheric layer, where the air is very thin. It starts at an altitude of approximately 500 km and goes up to over 1000 km in altitude. It is the limit of the atmosphere and the cosmic or outer space.
The predominant gas in this layer is hydrogen (H2). There is a great variation in temperature, where during the day it can reach 2000ºC and at night about -270ºC.