We often say: The universe is huge, and there are no wonders. In the vast space of the universe, there are only things we have not seen, and nothing that does not exist. Any event of small probability that is magnified to the entire universe will become an inevitable event.
Therefore, from the perspective of the universe, the existence of alien civilizations is also inevitable. If this is the case, theoretically there should be a large number of alien civilizations in the universe, but why is there no one to contact us? I believe that many of my friends have thought about such doubts, and scientists have also put forward a variety of conjectures. In fact, there are mainly two reasons.
One reason is that the probability of the birth of civilization is very low. With the continuous improvement of human cognition of life, modern science believes that the origin of life does not have high requirements for planets. As long as a planet has enough liquid water and geothermal energy, Probability can give birth to life.
There are many planets in the universe that meet this condition. Even in the solar system, there are many other planets that meet this condition besides the earth. For example, Europa has a large amount of liquid water outside of its ice layer, and There is also ground heat. Scientists have enough reasons to suspect that Europa may have given birth to life, which shows that life may be universal in the universe.
Although life is very common in the universe, it is very difficult to finally form civilization through evolution. Not to mention intelligent life, even complex life with preliminary consciousness is not so easy to be born.
For a planet to evolve into intelligent life, it needs to meet very harsh conditions. Scientists have established a habitable planet model based on the ecological situation of the earth. According to this model, scientists have found that for the birth of intelligent life, the planet needs to have the following six factors.
1. To be in the habitable zone of the galaxy. This is the most important external condition for the planet. Only in the habitable zone can it obtain suitable light and heat requirements, and a large amount of liquid water can exist on the surface of the planet.
2. A large amount of liquid water. Water is the source of life. This is a fact without doubt. There are more than millions of various organisms on the earth, and most of the components of biological cells are water. For example, 70% of human tissue is water.
Without water, life on earth cannot complete the subsequent series of evolutionary evolution, cannot evolve to a higher level of life, and cannot give birth to intelligent life human beings. Although the conditions for the birth of life do not necessarily require the participation of water, after the birth of life, if you want to continue to evolve into a higher life, then the participation of a large amount of liquid water is an inevitable condition. For example, life may be born in the environment of Mars, but because there is no large amount of water, even if life is born, it cannot continue to evolve and can only exist in the form of primitive microorganisms.
3. The atmosphere. The atmosphere is very important to life on a planet. We all know that the universe is not peaceful and safe. There are many dangerous things that can threaten life, such as asteroid impacts and various kinds of radiation in the universe.
Asteroid impacts are very common in the solar system, as we can see from the large number of craters on the moon, and the Earth’s history has also encountered asteroid impacts many times. However, due to the presence of the atmosphere, these asteroids will friction and burn with the atmosphere before they hit the ground and finally decompose and disappear.
Without the protection of the atmosphere, life on earth might have been destroyed for many times, and there would be no biological world as it is now. The cosmic radiation is more lethal to life. Although many lives can survive in the harsh environment of the planet, in the face of cosmic radiation, almost no life can directly resist. The atmosphere can effectively block and absorb most of the cosmic radiation and protect the planet’s ecological environment.
4. A strong magnetic field. There are two main functions of the magnetic field. One is to block all kinds of radiation in the universe. You must know that in a galaxy environment, the radiation of stars is very strong. For example, the sun’s radiation, and besides the atmosphere, another effective thing that can withstand this radiation is the magnetic field.
Another function of the magnetic field is to form a stable ecological circulation system. The earth is a world of magnetic field. The existence of magnetic field gives the earth a perfect and stable ecosystem. Only a perfect and stable ecosystem can give life enough time to evolve and evolve, and hope that a smart civilization will eventually be born.
5. The guardianship of a larger planet. We all know that in a star system, in addition to planets, there will be a large number of asteroids and other material debris. The orbit of the planet is very stable, as long as the star does not undergo major changes, there will be no chaos in the planetary system.
And those large numbers of asteroids and other material fragments are not so stable, they often go out of orbit and move towards the habitable zone. If a living planet is not guarded by a large planet in front of it, there is a high probability that it will be hit by asteroids frequently, leading to the end of the evolution of life.
It is precisely because of the protection of the giant Jupiter that life can complete the evolution of 4 billion years and finally give birth to human civilization. We must know that in 1994, thousands of people witnessed a cosmic event that had never been seen before in human history, and that was the comet “Shoemaker-Levi 9” and the largest planet in the solar system—— Jupiter collided.
Without the protection of Jupiter, this comet would collide with the earth, and the final result would be the complete destruction of the earth’s ecology and the end of all life.
6. There must be a satellite with a large mass around us. A large mass satellite is very important for a living planet. The existence of a large mass satellite can change the rotation of the planet to a large extent, so that it has a More adapted to the rotation speed of life evolution.
The existence of massive satellites can also effectively stabilize the ecology on the planet’s surface and form a very good ecosystem. It is precisely because of the existence of the moon that the earth has a stable and beautiful ecological environment and can complete the 4 billion-year evolution of life.
The above are the six factors that a planet needs to have an intelligent civilization. In the universe, there are very few planets that can meet these six difficulties at the same time, so the birth of intelligent civilization is not easy, but even so, the vast universe also tells us that the number of alien civilizations should be very large. of.
But there is still no extraterrestrial civilization to contact us, here we have to think of another reason, that is distance. Distance will hinder communication. This is what we all know. The vast universe uses light years as the basic unit. The neighbor of the solar system is the Biling galaxy, which is 4.2 light years away. At the speed of the existing spacecraft of mankind, it takes a few minutes to reach. One hundred thousand years.
It takes a long time for the development of a civilization to realize such an interstellar shuttle. Prior to this, alien civilizations wanted to contact us only through radio signals, but until now we have not really received signals from alien civilizations. One reason for this may be the use of different civilizations. The signal mode is different.
For example, alien civilization uses gravitational waves to propagate signals, while humans use electromagnetic waves. There are two signal modes that are not two at all. Naturally, it is impossible to truly communicate. We cannot receive signals from alien civilizations, and alien civilizations cannot receive signals from humans. Only when the signal patterns of the two civilizations are the same or similar can they receive and communicate with each other.
Distance may be the main reason why we cannot communicate with alien civilizations. From the perspective of the cosmic scale and the harsh conditions required for the birth of civilization on the planet, it is also very normal that the galaxy has only one civilization. If this is the case, then the alien civilizations we can communicate with need to come from other galaxies outside the Milky Way, such as the Andromeda Galaxy.
Although the Andromeda Galaxy is a neighbor of the Milky Way, it is also millions of light-years away from us. If it is a light-speed radio wave signal, it will take at least millions of years to propagate to the solar system. This time is very long for a civilization. In addition, whether the wireless signal can travel so far without dissipating is also a question.
No matter what, human beings will never stop exploring extraterrestrial civilization. We can only hope that the signals of extraterrestrial civilization can be received by us. After human beings have the ability to navigate between stars, we can take the initiative to explore other galaxies. At that time, I believe that discovering alien civilizations will not be too difficult.