Whether there is an alien civilization outside the earth is a topic that is often discussed, but it is not discussed enough and there is no answer.
If we want to explore whether there is extraterrestrial life, we must first determine the principle of the formation of life. Contemporary scientists believe that every life is actually a “chemical product”. The formula for the formation of this “chemical product” is uncertain. However, it needs three elements: energy, chemical elements and liquid water.
Liquid water is well suited for evolution because molecules can melt in water to form more complex structures. Take the earth as an example. Deep in the earth’s oceans, there are cracks in the earth’s crust. Such an environment is conducive to chemical reactions, which makes it easier for atoms to form various molecules.
This is why the earth’s first life came into being. Some people speculate that the earth’s earliest cells were born in magmatic water. At first glance, you must wonder how hot magmatic water can give birth to life? It’s good not to burn to death.
But in fact, the deeper scientists study, the more they discover how tenacious life is.
The earth’s microorganisms can not only survive on the top of snow mountains, but also exist in trenches with thousands of tons of pressure. Even in vacuum simulators, microorganisms can survive without oxygen. Therefore, compared with these environments, the magmatic water environment is not too bad.
It is generally believed that life on earth was born 4 billion years ago. At that time, the earth’s environment was far worse than it is now. Not only volcanoes erupted frequently, but also asteroid storms hit the earth for 100 million years. Even so, life was born soon.
Since life on earth is so tenacious, we can’t help but believe that other livable planets are likely to have similar life. Therefore, according to the three necessary conditions for the existence of life, the livable planets were selected one by one.
The first condition is energy. Solar energy is very common. It’s not necessary to say that. However, it’s worth mentioning that although some stars are far away from stars, they can also obtain energy. For example, the satellites of some gas giant planets, although they are far away from the stars and cannot get light, get energy because of the pull of giant planets. Jupiter’s moon Europa is a case in point, with its undersea volcanoes emitting liquid water and chemicals.
The second condition is chemical elements, but there are too many elements that can give birth to life. They can be found everywhere in the galaxy, so there is no need to say more.
The third condition is liquid water. Current research shows that there are 500 billion earth like planets in the Milky Way alone that may have liquid water, and the whole universe is as high as 10 to the twentieth power, that is, one.
Since so many planets are likely to have life, the existence of extraterrestrial life is almost inevitable. Just now, we calculated which planets may have extraterrestrial life from the perspective of space. Next, we will discuss it from the perspective of time.
Before the birth of the earth, the universe was already 10 billion years old, during which life is likely to be pregnant. When the earth no longer exists, the last star can still survive for 100 trillion years, during which the breeding of life will not stop.
From the beginning of the birth of the universe 14 billion years ago, millions of years after the birth of the universe, the temperature was so high that it could burn everything. At this time, there was no life. About 7000 years later, the temperature dropped, and the huge hydrogen cloud formed the earliest star under the action of gravity.
The stars at that time were quite different from those at present. However, no life could witness them, because the elements produced by the big bang were only hydrogen, helium and lithium, while the elements that could give birth to life were all produced in the stellar nucleus. Therefore, only after the explosion of the first batch of stars could cosmic life appear.
So some people speculate that, about 13.7 billion years ago, these elements that can give birth to life were combined for the first time. However, some people’s conjecture is more bold. They think that 15 million years after the big bang, the temperature of the universe will drop to 24 degrees Celsius, which is suitable for the birth of life.
And they also hypothesized that during this period, there was a kind of “super dense space region” in the universe, which would not only form stars and planets, but also form a lot of liquid water, from which the first life might be born.
If this hypothesis is true, there may be a life as old as the universe in the deep of the universe. They were born 10 billion years earlier than human beings. What will they evolve into in these 10 billion years? It’s really hard to imagine.
Xiaobian thinks that our time is very precious, because we all know that the universe will eventually become invisible because of the expansion of space and time, and the night sky will become dark. At that time, the civilization will certainly wonder what the universe was like in the past. For us, we only need to look up at the sky to know the answer. How lucky it is!
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