Earth is a living world, which has bred countless lives on this planet, and is currently the only place where human beings are known to have life.
The reason why the earth can become the only planet with life, in addition to the right space position and the right magnetic field of the right strength, the most important thing is that it is wrapped in a thick atmosphere. If you look at the appearance of the earth from space, you can see that there is a transparent mix of gases around the earth, which is firmly absorbed by the gravity of the earth!
The composition of the atmosphere is mainly composed of nitrogen, oxygen and argon, as well as a small amount of carbon dioxide and noble gases. According to the height, it is divided into five parts: troposphere, stratosphere, intermediate layer, thermal layer and fugitive layer.
Extending upward from the surface is first of all the troposphere, with an average height of about 12 km, the most dense area of the troposphere atmosphere, and also the place where weather phenomena such as rain and snow form. 50 kilometers up from the troposphere is the stratosphere, the stratosphere air is relatively thin, oxygen molecules under the ultraviolet radiation, the formation of a thick layer of ozone, he is like a barrier to protect us from the sun's ultraviolet rays. 85 km upstream from the stratosphere is the middle layer, which is mainly composed of nitrogen and oxygen, and has strong convective motion due to the high rate of vertical decrease in temperature. 800 kilometers up from the middle layer is the thermal layer, the air of the hot layer is highly ionized by the short-wave radiation of the sun, the ionosphere is in the hot layer, the aurora we see is also formed in this layer, after leaving the thermal layer is the final escape layer, although the current escape layer height is 800 km to 3000 meters, but in fact scientists can still detect thin gas molecules at an altitude of 22,000 km from the surface, strictly speaking, the atmosphere currently has no exact height limit.
Although the atmosphere is made up of gases, its total mass is staggering, about 5.5 trillion tons, and most of these gas molecules are "imprisoned" at altitudes of 20 to 30 kilometers under the influence of Earth's gravity. So the farther away from the surface the atmospheric molecules are affected less by the Earth's gravitational pull, physicists count that hundreds of thousands of tons of the outer atmosphere are "stripped" every year, and more importantly, this "atmospheric stripping" has been going on for billions of years.
Many people will wonder why the Earth's atmosphere has not disappeared or thinned for so many years.
The answer is that the earth will "regenerate" more atmosphere every year, such as ocean evaporation, biological activity and volcanic eruptions are the reasons for the production of a large number of gas molecules, such as a tiny gas just released by you, which is also a little bit of a meager force for the earth's atmosphere, so these gas molecules and the earth's annual "escape" atmosphere has formed a dynamic balance relationship, and the earth's atmosphere has not changed much for billions of years.
In fact, the hundreds of thousands of tons of mass and asteroid micrometeorites that the Earth loses every year are almost nothing compared to each other, and the total mass of the Earth will not be significantly reduced or increased by human activities and the escape of atmospheric molecules.