In the beginning, the Earth was a big "burning rock" that wandered around the Sun. Like all the other planets, the earth is a descendant of our star and is subject to its gravitational pull.
|Photo by Pixabay at Pexels|
The earth had water that could have come from far away frozen in comets. That water, subjected to heat, evaporated and the water particles were trapped by the earth's gravity, circulating in a dense layer around it. And just as the water vapor remained, so did other gases (nitrogen, oxygen, argon and ozone). These combined in different layers at different heights with respect to the surface and according to the density of each one. This probably occurred in 5 stages of which only the first 2 are important in explaining the formation.
In the long run, these gas layers helped to generate the conditions for the planet to sustain life. A little more heat and the vapor and gas particles would be light enough to escape the planet. Any colder and nothing would have moved for a long time.
Now, this is all speculation. The way to be sure that this process was what the planet went through in its formation and that its atmosphere and other layers originated following this pattern is for us to see it on another planet. We would only have to observe a planet in the same position as ours with respect to the Sun (or in the habitable zone) for at least 1 billion years.
Or we could speculate based on the evidence. The bad thing about this is that if we get it right once we think we can always get it right by speculating. And then theories based on fantasies come out. **To avoid that, a good application of science is necessary. Although we cannot avoid human subjectivity and its love for fiction.
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