This paper takes part in the series essay competition of “great science” of Recordunkown.
The search for alien civilization started after human beings stepped out of the earth. For more than half a century, scientists have been searching for alien civilization. Some people may not understand why scientists are so obsessed with the search for alien civilizations? Does alien civilization exist?
In the vast scale of the universe and the 13.8 billion years of the universe, it is difficult for us to doubt the existence of alien civilization. Scientists also believe that the probability of the existence of alien civilization is close to 100%. As for why we are looking for alien civilization, one reason is driven by human curiosity. We want to see if the universe has the same intelligent life as human beings, and what aliens look like?
Another reason is that it has something to do with the progress of human civilization. We all know that although human beings are intelligent civilization and have entered the era of science and technology, we can’t do it if we want to explore the universe. According to the classification standard of cosmic civilization given by scientists, human beings are not even a level one civilization at present, they can only barely count as a level 0.7 civilization.
In fact, it’s easy to understand that human civilization only took about 5000 years to form, and science and technology only developed for hundreds of years. Compared with the billions of years of life history of the earth and the 13.8 billion years of history of the universe, this time is insignificant. If human beings can continue to develop science and technology, as long as we are given enough time, then we can grow into a first-class civilization, a second-class civilization, a third-class civilization and so on.
However, it will take a very long time to achieve such a level promotion, even at the current speed of human science and technology development. According to the estimation of scientists, it may take hundreds of years for us to grow into a first-class civilization. If we want to grow from a first-class civilization to a second-class civilization, it may take tens of thousands of years. With the continuous improvement of the level, the time required is also increased geometrically.
If the earth’s environment has been stable and the universe’s environment has been stable and safe, it will naturally give mankind a long enough development time. However, with the continuous improvement of human cognition, we understand that the universe is not peaceful at all. In 1994, the earth almost came to an end. Fortunately, with Jupiter in front, the terrible comet did not hit the earth.
But will such good luck always accompany the earth and mankind? We can’t believe in luck. We still need to make rapid efforts to develop science and technology. Only when we really become an interstellar civilization can we have the strength to deal with cosmic disasters. Depending on the development of human beings, it takes a long time to become an interstellar civilization. What can we do? At this time, scientists thought of alien civilization.
From the time scale of 13.8 billion years in the universe, theoretically, there should be some advanced civilizations tens of thousands, tens of millions or even hundreds of millions of years ahead of human beings. If we can get in touch with such a powerful civilization and get the help of alien civilization in science and technology, we may be able to turn human beings directly from insects into dragons and become interstellar civilization, which will undoubtedly save human beings up to a few million years of long development time.
Therefore, although Hawking has repeatedly warned mankind to be alert to alien civilization, it still can not extinguish the enthusiasm of scientists to find alien civilization. There are two ways for human beings to search for alien civilization, one is to search for the possible wireless signals of alien civilization in the universe, the other is to search for earth like planets very similar to the earth through continuous observation through telescopes.
According to the various conditions required for the birth of life on earth, scientists believe that the planet environment inhabited by alien civilizations should be similar to ours, with atmosphere, magnetic field, liquid water on the surface and so on. According to this standard, scientists have found many earth like planets, but they have not found a planet that is completely similar to the earth’s environment. There is a huge gap between these planets and the earth’s environment.
The environment of these planets is totally unfit for human survival. If we don’t find the same ecological planet as the earth, does it mean that there is no alien civilization? Of course, scientists will not believe that there is no doubt about the existence of alien civilization. The reason why we have not found anything may be that we are looking for the wrong way and direction.
Human beings look for alien civilization according to the ecological standards of the earth, so there will be many similarities between aliens and human beings in terms of survival conditions, such as the need for water and oxygen for breathing. But have we ever thought that it is not oxygen that aliens may breathe, but other gases? Scientists speculate it could be hydrogen.
Most life on the earth and the survival of human beings need sufficient oxygen. Without oxygen, we can not survive. This is the basic element for human beings to survive on the earth. So how does the earth’s rich oxygen come from? In fact, in the early days of the earth, there was no oxygen. At that time, the atmospheric carbon dioxide dominated the mainstream.
Early life on the earth was anaerobic because there was no oxygen. If this atmospheric structure did not change later, then life on the earth would have evolved and finally breathed carbon dioxide instead of oxygen. But that changed later, with the emergence of a species called cyanobacteria, which changed the earth’s atmosphere.
“Cyanobacteria” can release a large amount of oxygen and absorb carbon dioxide at the same time. As time goes on, the carbon dioxide in the earth’s atmosphere is less and less, and the oxygen is higher and higher, completing the replacement of carbon dioxide and oxygen. With abundant oxygen, the original anaerobic organisms continue to disappear, new life is born, and the breathing gas is oxygen.
The rich oxygen content of the earth is formed by a kind of coincidence, so will the alien civilization planets experience the same atmospheric changes as the earth in the early days? I’m afraid it’s unlikely that each planet’s ecological environment will have its own evolution route. The habitation of alien civilizations may also form its own unique evolution direction. The gas composition of the atmosphere may be very different from that of the earth’s atmosphere.
If the composition of the atmosphere is different, the gases we breathe may be different. We need oxygen, and aliens may need hydrogen. Why do scientists guess it’s hydrogen? This is not a random guess, but a certain basis. We all know that water is the source of life, but don’t forget that water will produce two gases after electrolysis, one is oxygen, and the other is hydrogen. From the molecular weight, there are two hydrogen molecules produced by electrolysis, while only one oxygen molecule.
In addition, what is the most abundant material in the universe? I believe many people know that hydrogen is the most abundant substance in the universe. And scientists found that there are many stars in the universe, there are clouds, these clouds contain a lot of hydrogen. On the whole, the probability of extraterrestrial civilization breathing hydrogen is still very high.
If we change the direction of looking for alien civilizations and choose the direction according to the standard that they need hydrogen to breathe, we may be able to find that many earth like planets meet this standard. The discovery of alien civilization may be just around the corner. As long as we can narrow down the scope of the universal existence of alien civilization and roughly determine which galaxies are likely to have alien civilization, we can concentrate our strength and conduct long-term observation and Research on several key interstellar stars, which may lead to more important discoveries.
We should know that the universe is too big. If we do not narrow down the scope, the probability of finding alien civilization is basically zero, because it is still a distant dream for human beings to realize interstellar exploration. If there are advanced civilizations in some galaxies, we may also hope to observe some particularly magnificent civilization buildings, such as the Dyson sphere.
Of course, it’s only our guess that extraterrestrial civilizations breathe hydrogen. Life is mysterious and complex, and life on earth is just one of many life forms. There must be many differences between extraterrestrial life and earth life. They may breathe oxygen, hydrogen, carbon dioxide or other gases just like human beings.