Why haven't we discovered an alien civilisation yet? Is earth the only living planet and humans the only intelligent life? That doesn't make sense. Because there is nothing special about earth, and there are billions of earth-like and habitable planets like it in the vast universe. It is unbelievable that alien life exists only on earth when none of these billions of exoplanets exist.
So far, we have not found alien life or alien civilizations, not necessarily because alien life or alien civilizations do not exist, for more reasons. One of the reasons is that the universe is really very big, you know, the diameter of the solar system is measured in light years, the closest exoplanet to our earth, proxima b, is 4.22 light years away from our earth, that is to say, it takes 4.22 years to fly to proxima b at the speed of light, "Slow" Manned spacecraft flight the flight time for a "Slow" Manned spacecraft is even longer. If we did not launch manned spacecraft to these exoplanets, we would not be able to observe them directly with telescopes or probes, and we would not be able to know the details of these planets and whether there is extraterrestrial life or alien civilisations on them.
For humans, the universe is too dimensional for us to see the details of its depths for the time being. For alien civilizations, there may be a similar problem, because not all alien life, alien civilizations will reach a very high level. If there are extraterrestrial beings and civilisations in the vicinity of the earth, and they are still at a relatively primitive level of development, more backward than we are, they would not be able to establish contact with us themselves. It would be as if they were 'trapped' on an island with us, completely unaware of the existence of other life 'on the other side'. Of course, there are also some who believe that earth may be a zoo for advanced alien civilizations to "Keep" Humans in, and that they do not want to be discovered by us humans, so they are hidden away, so naturally we cannot find them.
Scientists reveal four evil alien civilizations
It is also because the universe is so big and there are more exoplanets than we can imagine, so even though we haven't found alien life or alien civilizations yet, some scientists are still worried that if we take the initiative to contact these potential alien civilizations, it may lead to "Extinction", because not all alien life and alien civilizations are good. Not all alien life and civilisations are benign. This is why some scientists have suggested that there may be four evil alien civilizations deep in the universe that would invade our planet if they had the power to do so.
The view of astronomers is that there could be millions of habitable planets in our galaxy, and that there could be evil alien civilizations on at least four of these potentially habitable planets. If these evil alien civilisations reach a certain level of technological development and have the ability to fly interstellar, they could launch an invasion of our planet. What is the situation? Is earth not safe anymore?
Of course, the probability of an invasion of the earth by an alien civilisation is very low and this is not based on astronomical research, but on the "Answer" That researchers have found when they analysed the history of human development. The researchers have analysed the scenario of a war on earth between 1915 and 2022 and concluded that the probability of a future invasion of an alien civilisation by a human civilisation is 0.028% and the probability of an interplanetary invasion is only 0.0014%. Alberto caballero, an academic from the university of vigo in spain, believes that there could theoretically be 15785 extraterrestrial civilizations in the galaxy, of which only 0.22 are evil extraterrestrial civilizations that could come into contact with us humans, and if we include some extraterrestrial civilizations that have not yet mastered interstellar flight, the number would be 4.42.
29 alien civilisations may have discovered earth
This is actually not the first study on the possibility of an alien civilization discovering earth or invading it. In other studies, scientists have repeatedly suggested that alien civilizations may exist and may have even discovered earth. Scientists in the uk, for example, have calculated that there could be 36 alien civilisations in the galaxy that could transmit radio signals like humans. A study by a cornell university team published in the journal nature also suggests that 29 extraterrestrial civilizations may have discovered earth.
The cornell university team identified through their research the existence of 2,034 star systems around the milky way where earth can be observed circling the sun. Of these 2,000+ star systems, 1,715 exoplanets may have discovered earth within the last 5,000 years, and there may be an additional 391 exoplanets where earth can be found within the next 5,000 years. Although we do not yet know if there is alien life on these exoplanets, or if they are habitable, we do not know yet. However, researchers believe that 29 of these exoplanets are in the habitable zone of the star system and could detect earth, as well as radio signals emitted by us humans. Given this one scenario, scientists believe that there may be 29 potentially habitable alien civilisations that have picked up our signals and discovered the presence of earth.
Is earth not safe anymore?
Theoretically, it is indeed more likely that extraterrestrial life exists on planets other than earth, and it is difficult to say whether there is an alien civilisation. This is because a planet needs to have many aspects in order to develop an intelligent civilisation. On earth, there are creatures that have existed for hundreds of millions of years, much earlier than humans, but they are limited in many ways and cannot develop in the direction of intelligence at all. For example, although octopuses have a very high iq and have existed on earth for longer than we have, many people believe that octopuses may be 'extraterrestrial', but the age of octopuses is very short and they die very quickly after mating, so they are unable to pass on some of their best experiences and naturally cannot develop the "Octopus civilization" Could not have developed.
The probability of extraterrestrial life existing, and the probability of an extraterrestrial civilization existing, is very low. If they want to compete for earth's resources, they are perfectly capable of developing the resources they need on other planets where there are no humans and no life, such as the moon for helium-3, europa for water resources, etc.