There are eight planets in the solar system, and they revolve around the sun like eight notes, and their orderly appearance is like playing a beautiful symphony.
However, when we get to know each planet, you will find that these planets are not wonderful at all, at least for life, their environment is very scary.
They're either too hot, or they don't have an atmosphere, or they're just giant gas giants with only Earth— a blue solar system planet that has everything so moderate that it eventually gave birth to life.
However, The Earth's environment has not always been so moderate, and it has been very "violent" and risky.
So, how did the Earth form? Why did it "stand out" among these planets and become the cradle of life?
This image is a good description of the early solar system, source: NASA/JPL-Caltech
How did the Earth form?
While we can't see the formation of the solar system with our own eyes, there is now a wealth of evidence, as well as a wealth of computer simulations, that Earth, like other planets in the solar system, was formed by a mixture of dust and gas from the early solar system.
About 4.6 billion years ago, our solar system was just an area of dust and gas clouds called solar nebulae, which could have been disturbed by external forces (such as nearby supernovae) or could have evolved on their own, eventually causing these clouds of dust and gas to begin to rotate.
Under the action of gravity, the center begins to collapse, the material condenses together, and as it becomes larger and larger, the strong pressure allows nuclear fusion to occur, and the early sun appears.
The Sun pockets most of the material in the solar system, but there is still a small part — about 0.2 percent of the matter still rotates , only then they have a central point , the Sun.
These substances vary slightly in size and speed, and the difference in speed causes these early substances to collide with each other and glue together.
Eventually, they go from tiny dust particles to boulders, into boulders, and then into larger "asteroids."
The mass of the "asteroid" is large enough that its gravitational pull can affect the surrounding dust and gas, which causes more and more material to condense together, and the "asteroid" is getting bigger and bigger, and early planets begin to appear.
In the early days of the solar system, the eight planets had many "asteroids" of different sizes in their orbits, but one thing was the same as it is now, that these planets close to the sun were rocky planets, and away from the sun were gas giants with rocky cores, because the strong solar wind prevented the planets close to the sun from maintaining more gas.
The Moon may have formed as a result of an early collision, NASA/JPL-Cal
In the early solar system, the planets were not "orderly" at all, they collided and attacked each other, and the formation of the moon was most likely caused by the collision of an "asteroid" the size of now Mars and an early Earth.
When the solar system began to stabilize, the Earth and the other seven planets, as well as other solar system objects, took shape, and the Earth became the largest rocky planet in this early material "scramble".
So why do scientists now tell such a story about the formation of the solar system?
In fact, the key evidence is meteorites. Meteorites are brought to Earth in a variety of ways, and some of them carry information from the early solar system.
When the solar system stabilized, the story of the solar system turned to the evolution of the planets themselves, and although all the planets underwent similar processes in the early days, their own evolution varied, eventually resulting in only Earth having life.
The early Earth's environment was very harsh
The early Earth was not "moderate" at all, in fact it was so hot that all the material on Earth was molten. There are several factors that contributed to the heat of the early Earth:
Illustration: Comparison of the Early Earth and the Modern Earth
The first part comes from gravitational contraction.
As small pieces of rock and metal accreted, the early Earth became larger, heavier, and hotter at the same time.
That's because the Earth's interior is becoming more and more stressed by gravity, a process that generates heat, just as we now squeeze gases to produce heat.
The second part comes from radioactive decay.
Early in Earth's history, there were many radioactive elements with short half-lives that decayed into stable materials long ago, but they initially released a lot of heat and heated the earth.
The third part is impact.
Like we said earlier, the early days of the solar system were an unstable system, asteroid impacts were very common, and studies now show that Earth suffered very violent impacts in the first 500 million years.
This impact generates "huge amounts" of heat, which is also constantly heating the earth.
With the blessing of these "three fires", everything on the early Earth melted, but this state gave the Earth its first chance to change itself.
In the molten state, the heavier material on the earth sinks into the core, while the lighter material "floats" to the surface, which forms the current structure of the earth: the core, the mantle, the crust.
As for why this structure has completely changed the earth, the reason is that it can maintain the atmosphere.
It is well known that the Earth now has an atmosphere thanks to its magnetic field, which blocks the solar wind, which comes from the material collected by the early Earth, nickel-iron, melts and sinks into the core.
Because the early Earth was "destroyed" by the solar wind, its atmosphere was gradually produced after it had its own magnetic field, which occurred after the Earth gradually cooled.
Volcanic eruptions, as well as comet impacts, gave Earth an early atmosphere dominated by water vapor and carbon dioxide.
When the earth cools down again— when water is able to exist on the surface in liquid form— the earth begins to rain, and because the earth is very hot and constantly evaporates the water, it is a rain that lasts a long time.
Eventually the ocean formed, the fate of the earth was completely changed, and life appeared in the water.
Finally: Why is there life only on Earth?
Some scientists have proposed the concept of habitable zones (which is now widely accepted) in which planets can have liquid water, which is necessary for life.
The Earth occupies a perfect position in the solar system, and in its orbit, both perihelion and aphelion point are in such a habitable zone, which is a necessary condition for its emergence of life.
But why is Mars, also in the habitable zone, dead silent?
Note: Earth and Mars in the habitable zone
The reason is that the atmosphere of Mars is extremely thin, and the "culprit" that causes this situation is the magnetic field, mars loses its magnetic field at some stage, and the solar wind makes it no longer able to maintain a sufficient atmosphere, as well as liquid water.
Mars spins about the same speed as Earth, and considering that they form much the same way they form from each other, the loss of the magnetic field on Mars is intriguing, which some scientists think may be because Mars is too small, which makes its core cool faster.
Earth, on the other hand, is the planet of the solar system that rotates just right, orbits just right, and "heads" just right, and finally there are so many colorful lives and us here.