overview
The universe is vast, and the earth and human beings are as small as dust in the universe. Looking across the entire universe, there are nearly 200 billion galaxies similar to the Milky Way , and within galaxies similar to the Milky Way, there are at least about 200 billion to 400 billion stars similar to the sun.
This means that in the vast universe, there is a high probability that there are civilizations similar to or even higher than the earth. Human beings are very likely not the only life forms in the galaxy, and aliens may really exist.
I believe that most people believe that there are other civilizations outside the earth, and there are aliens besides humans. However, due to the limitations of the times, human understanding and technological level have yet to mature, and humans have never found other civilizations in the universe. living body.
So the question is, since humans have never been able to find aliens, does it mean that aliens do not exist? If it exists, then why have humans never been able to find their "neighbors" in the vast interstellar space?
Aliens do not exist
Since direct and indirect evidence that proves the existence of aliens has never been found, some scientists believe that there is no extraterrestrial civilization in the universe, and aliens do not exist at all. As for some rumors about aliens, the authenticity cannot be confirmed.
For example, a typical alien drives UFO to the earth. In fact, any object flying or floating in the sky can be called a UFO as long as we have not confirmed its nature.
In reality, due to the stereotype caused by movies and TV dramas, many people directly equate UFOs with aliens, which is obviously too absolute.
We should not associate the three letters UFO with aliens when we see them, and make unfounded remarks as a matter of course.
In fact, most UFO incidents are ultimately proven to be natural phenomena. James Oberg, a former employee of NASA (NASA), specifically traced UFO incidents and related clues reported decades ago, and finally found that so-called UFO incidents have their corresponding natural events that can be explained.
Therefore, as to why humans cannot find aliens, some scientists believe that this is because aliens do not exist.
The aliens that cannot be found
One day in 1950, physicist Enrico Fermi was chatting with his colleagues and proposed that based on the age, there should be living planets in the vast universe, and there should be intelligence like human beings. Civilization, and in theory, some civilizations should have become advanced civilizations long ago and have the ability to navigate interstellar space.
Therefore, this winner of the Nobel Prize in Physics asked a soulful question: "Where are the aliens?" This is the Fermi Paradox that has no answer so far.
The "Great Filter" hypothesis
After the Fermi Paradox appeared, the scientific community launched a heated discussion on it, and tried to solve the alien puzzle. The "Great Filter" is a representative theory to answer the Fermi Paradox. , proposed by Robin Hanson, an economist at George Mason University in the United States. This theory explains the conditions that a group of organisms need to meet to become an advanced civilization.
Planetary system theory believes that as long as it is an terrestrial planet in the habitable zone of a star, it has the conditions for the birth of life. Therefore, life is likely to be common in the universe. However, different life planets face different conditions in the process of evolution and development, and will also lead to different destinies.
This is the problem to be studied by the "Great Filter" theory.
Simply put, the "Great Filter" conjecture holds that the evolution and development of life in the universe must go through nine stages or steps. Only after passing these nine stages can we develop step by step from the initial simple life to interstellar civilization. Stage .
Each stage is a threshold. Only after crossing it can you enter the next stage. If you stumble over one of the thresholds, you will be "filtered" out of course, that is, you will die.
On some living planets, life may have only evolved to the multi-cell stage before being destroyed by disasters. They did not cross the filter and were eliminated from the beginning; some living planets may have developed to the stage of intelligent life, but they have not yet. After leaving the home planet, it was destroyed due to a cosmic disaster, and it also did not cross the filter.
There are also some alien civilizations that may have passed all the previous tests and are just one step away from becoming interstellar civilizations, but in the end they were unfortunately eliminated.
Moreover, the Great Filter is divided into nine different stages according to the difficulty. There is an insurmountable gap between each stage. The later stages are more difficult. Only by passing them all can we become a sufficiently advanced civilization. .
But before it becomes an interstellar civilization, no matter how far a civilization’s technological strength develops, it cannot stop the devastating blow of some cosmic disasters.
On countless living planets, it is precisely because of the existence of the Great Filter that countless living planets have reached their end, and no civilization has finally passed through and become an interstellar civilization.
Judging from this theory, the earth is also facing the risk of being "filtered".
"Dark Forest" Law
Like the "Big Filter" theory, the "Dark Forest" is also an explanation of the Fermi Paradox. The " dark forest " law was proposed by Liu Cixin in " Three Body ". This theory believes that once a certain cosmic civilization is discovered, it will inevitably be attacked by other cosmic civilizations.
In the "dark forest" theory, the universe is like a dark forest. In this forest, there are dangers and shadows. Every civilization is a hunter. They sneak in the forest like ghosts, being careful and not daring to alarm others. , because there are many hunters like him in this forest. If one accidentally exposes himself, he will become a prey in the hands of others and be slaughtered by others.
Therefore, from Liu Cixin's point of view, the reason why the aliens did not show up is actually just like us, is afraid of revealing their location and causing death..
Once we launch a signal that can be located into the universe with great fanfare, we will instantly become the target of attack. This is the same for aliens, so no matter what, the aliens will not let us find them.
Therefore, if this theory is used to explain the reason why humans cannot find aliens, it is because alien civilizations do not want to show up for safety reasons.
In this sense, regardless of the level of alien civilization, in fact, like the earth and humans, they have the instinct to seek advantages and avoid disadvantages, and they are also trying their best to avoid exposing themselves and putting themselves in danger.
The zoo hypothesis
The zoo hypothesis was proposed by astronomer John Ball. In essence, it is also an answer to the Fermi Paradox.
This hypothesis believes that in the boundless universe, there are indeed alien life forms. These alien life forms have more advanced technological civilizations and use this to observe the earth.
For some reason, these aliens are unable or unwilling to directly contact humans on the earth, so they can only allow humans to evolve naturally, but the evolution and development of humans are under their observation.
is similar to people observing animals in the zoo, except this time, humans are no longer the ones who keep the animals in cages, but are creatures controlled by aliens on the earth. The animals being observed and monitored have become Humanity himself. And aliens are hidden deeper in the universe, watching our every move from places we can't see.
In summary, regarding the Fermi Paradox, scientists mainly provide three viewpoints to explain it: the "Great Filter" hypothesis, the "Dark Forest" law and the Zoo Hypothesis. Although they cannot prove its scientific nature, they do provide some explanations. The mystery of humans not being able to find aliens provides a lot of room for imagination.
Conclusion
As for why humans cannot find aliens, scientists have tried their best to provide their own explanations. These explanations are not necessarily objective and scientific, but judging from the current human understanding ability, it is necessary to To find an indisputable answer to this is obviously unrealistic.
But there are only things in the world that are not yet known, and there are no things that cannot be known. Humanity’s exploration of the stars and the sea will not stop. As long as science and technology continue to advance, I believe that one day in the future, humans will finally be able to solve this mystery and solve it. The mysterious veil of alien civilization, and the true face of aliens in Lushan.
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