Fermi paradox

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The Fermi Paradox , or The Fermi Paradox , named by the Enrico Fermi physicist, is a real contradiction between the lack of evidence and the high probability for the existence of extraterrestrial civilizations. The basic points of the argument, made by physicists Enrico Fermi (1901-1954) and Michael H. Hart (born 1932), are:

• There are billions of stars in a galaxy similar to the Sun, and many of these stars are billions of years older than the solar system.
• With a high probability, some of these stars have Earth-like planets, and if the Earth is distinctive, some may have developed intelligent life.
• Some of these civilizations may have developed interstellar travel, a move that Earth is investigating now.
• Even at the currently planned interstellar travel velocity, the Milky Way galaxy can be fully traveled in a few million years.

According to this line of thought, Earth should have been visited by space aliens. In an informal conversation, Fermi noted there was no convincing evidence of this, prompting her to ask, "Where is everyone?" There have been many attempts to explain the Fermi paradox, especially which shows that intelligent space life is very rare or suggests the reason that such a civilization has not contacted or visited Earth.

Video Fermi paradox

Base

The Fermi paradox is a conflict between scale arguments and probabilities that seem to support the intelligent life that is common in the universe, and the lack of evidence of intelligent life that ever appears anywhere other than on Earth.

The first aspect of the Fermi paradox is the function of the scale or large number involved: there are about 200-400 billion stars in the Milky Way (2-4 ÃÆ'â € "10 ¹¹ ) and 70 sextillion (7ÃÆ' â €" 10 ²² ) in the observed universe. Even if intelligent life occurs only on a small part of the planet around these stars, there may still be a large number of extant civilizations, and if the percentage is high enough it will produce a large number of civilizations still in the Milky Way. This assumes the principle of mediocrity, in which the Earth is a distinctive planet.

The second aspect of the Fermi paradox is the probability argument: given the ability of intelligent life to overcome scarcity, and its tendency to colonize new habitats, it seems likely that at least some civilizations will advance technologically, search for new resources in outer space, and colonize their own star system and , then, the star system around it. Since there is no significant evidence on Earth, or anywhere else in the known universe, another intelligent life after 13.8 billion years of the history of the universe, there are conflicts that require resolution. Some examples of possible resolutions are that intelligent life is less rare than we thought, that our assumptions about the general development or behavior of intelligent species are flawed, or, more radically, that our current scientific understanding of the nature of the universe itself is quite incomplete..

The Fermi paradox can be asked in two ways. The first is, "Why are not there aliens or their artifacts found on Earth, or in the Solar System?" If the interstellar journey is possible, even the "slow" type is almost within the reach of Earth technology, it only takes 5 million to 50 million years to colonize the galaxy. It is relatively short on a geological scale, let alone a cosmological one. Because there are many stars older than the Sun, and since intelligent life may have evolved elsewhere, the question then becomes why galaxies have not been colonized. Even if colonization is impractical or undesirable for all extraterrestrial civilizations, large-scale exploration of galaxies can be made possible by probes. This may leave artifacts detected in the Solar System, such as probe old or proof of mining activity, but nothing has been observed.

The second form of the question is "Why do not we see signs of intelligence elsewhere in the universe?" This version does not consider interstellar travel, but includes other galaxies as well. For distant galaxies, travel time may explain the lack of foreign visits to Earth, but well advanced civilizations can potentially be observed over most of the observable size of the universe. Even if such civilizations are rare, the scale of the argument suggests they must exist somewhere at some point during the history of the universe, and since they can be detected from afar over long periods of time, many more potential sites for their origin are in various observations we. It is not known whether the paradox is stronger for our galaxy or for the universe as a whole.

Logical basic critic

The Fermi paradox has been criticized for being based on improper use of propositional logic. According to a 1985 paper by Robert Freitas, when recast as a statement in capital logic, the paradox no longer exists, and does not carry a probative value.

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History and name

In 1950, while working at Los Alamos National Laboratory, Fermi had a casual conversation as she walked toward lunch with her colleagues Emil Konopinski, Edward Teller and Herbert York. The men discussed a spate of recent UFO reports and a cartoon of Alan Dunn who pridefully blamed the city's waste loss on foreign criminals. Conversations shifted to another subject, until lunchtime Fermi suddenly exclaimed, "Where are they?" (alternatively, "Where is everyone?"). Teller recalled, "The result of the question is the general laughter because of the strange fact that apart from the Fermi question coming from clear blue, everyone around the table seemed to understand at once that he was talking about extraterrestrial life." Herbert York recalled that Fermi followed up his comments with a series of calculations about the possibility of Earth-like planets, the likelihood of life, the likelihood of rise and duration of high technology, etc., and concluded that we should have been visited. past and repeatedly.

Although Fermi's name is most often associated with paradox, he is not the first to ask questions. The previous implicit mention is by Constantine Tsiolkovsky in an unpublished manuscript from 1933. He notes "people deny the existence of intelligent beings on the planets of the universe" because "(i) if such a creature exists, they will visit Earth, and (ii)) if such a civilization exists then they will give us a sign of their existence. "This is not a paradox for others, who regard this as the absence of ET, but it is for him, for he himself is a very believer in life beyond the earth and possibly space travel. Therefore, he proposed what is now known as the zoo's hypothesis and speculated that mankind is not yet ready for higher beings to contact us. That Tsiolkovsky himself may not be the first to discover the paradox suggested by the references mentioned above for the reason of others to deny the existence of extraterrestrial civilizations.

Michael H. Hart published in 1975 a detailed examination of the paradox, which has since become a theoretical reference point for most of the research on what is now sometimes known as Fermi-Hart paradox . Geoffrey A. Landis preferred the name on the grounds that "while Fermi is credited with the first question, Hart is the first to conduct a rigorous analysis that shows that the problem is not trivial, and also the first to publish the result." Robert H. Gray argues that the term Fermi Paradox is wrong, because he thinks this is not a paradox or because of Fermi; he preferred the name of Hart-Tipler argument, acknowledging Michael Hart as the originator, but also a substantial contribution from Frank J. Tipler in expanding Hart's argument.

Other names closely related to Fermi questions ("Where are they?") Include Great silence , and silentium universi (Latin for "the silence of the universe"), although this refers only to one part of the Fermi Paradox, that we see no evidence from other civilizations.

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Drake Equation

The theory and principles in the Drake equation are closely related to the Fermi paradox. This equation was formulated by Frank Drake in 1961 in an attempt to find a systematic way to evaluate the various probabilities involved in the existence of alien life. Speculative equations consider the rate of star formation in galaxies; star fraction with planets and number of stars that can be habitable; fractions of the planets that promote life; a fraction that develops intelligence lives; fractions that have intelligent life of detectable technology; and finally the length of time such communicating civilizations can be detected. The underlying problem is that the last four terms are completely unknown, so statistical estimates are impossible.

The Drake equation has been used by optimists and pessimists, with very different results. Original encounters, including Frank Drake and Carl Sagan, speculate that the number of civilizations is almost the same as the lifespan in a few years, and there may be between 1000 and 100,000,000 civilizations in the Milky Way galaxy. In contrast, Frank Tipler and John D. Barrow used pessimistic numbers and speculated that the average number of civilizations in the galaxy is much less than one. Virtually all arguments involving the Drake equation suffer from the effects of overconfidence, a common error of probabilistic reasoning about low probability events, by guessing a certain number for possible incidents whose mechanisms are not yet understood, such as the possibility of abiogenesis on Earth-like planets, with estimates of current possibilities varying in many hundreds of orders of magnitude. An analysis that takes into account some of the uncertainties associated with this lack of understanding has been done by Anders Sandberg, Eric Drexler and Toby Ord, and points out that with very high probability, the abundant intelligent civilizations in our galaxy or mankind alone in the universe are seen, with lack of observation of intelligent civilization pointing towards the last option.

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Empirical project

There are two parts of the Fermi paradox that depend on empirical evidence - that there are many potentially habitable planets, and that we see no evidence of life. The first point, that many suitable planets exist, is the assumption in Fermi's increasingly enlarged time with the discovery of many extrasolar planets, and models predicting billions of inhabitable worlds in our galaxy.

The second part of the paradox, that we see no evidence of extraterrestrial life, is also an active field of scientific research. These include attempts to discover indications of life, and efforts that are specifically geared towards finding intelligent life. This search has been done since 1960, and some are in progress.

Mainline astronomy and SETI

Although astronomers usually do not search for extraterrestrials, they have observed phenomena that they can not immediately explain without placing intelligent civilizations as their source. For example, pulsars, when first discovered in 1967, are called small green men (LGM) because of the exact repetition of their pulses. In all cases, the explanation without the need for intelligent life has been found for such observations, but the possibility of discovery remains. The proposed example includes the mining of an asteroid that will change the appearance of debris disks around the star, or spectral lines from the disposal of nuclear waste in stars. An ongoing example is the ordinary transit light curve of KIC 8462852, where natural interpretation is not entirely convincing. Although it is most likely a natural explanation will emerge, some scientists are investigating the possibility of long distance that it could be a sign of foreign technology, like a bunch of Dyson.

Electromagnetic emissions

Radio technology and the ability to build radio telescopes are considered a natural advancement for technological species, theoretically creating effects that may be detected through interstellar distance. Careful search for non-natural radio emissions from space can lead to the detection of alien civilizations. The sensitive external observers of the Solar System, for example, will record intense radio waves intensely for G2 stars due to television broadcasting and telecommunications on Earth. In the absence of a clear natural cause, foreign observers may conclude the existence of terrestrial civilization. But it should be noted that the most sensitive radio telescopes currently available on Earth will not be able to detect non-directional radio signals even at a fraction of a light year, so it can be questioned whether such signals can be detected by extraterrestrial civilizations. Such signals can be by-products of accidental civilization, or deliberate attempts to communicate, such as Arecibo messages. A number of astronomers and observatories have attempted and tried to detect such evidence, largely through the SETI organization. Several decades of SETI analysis have not revealed very bright or meaningful repetitive radio emissions.

Direct planetary observation

Detection and classification of exoplanets is a highly active sub-discipline in astronomy, and the first terrestrial planet found in the star habitable zone was discovered in 2007. New constraints in extrasolar detection methods, and use of existing methods from space (such as Kepler Mission, launched in 2009) began detecting and characterizing Earth-sized planets, and determining whether they were in their star-worthy zone. Such an observational enhancement allows us to better measure how a potentially habitable world in general is.

Obstacle about interstellar probe

Self-replicating probes can dig out the Milky Way's galaxy in a million years. If even one civilization in Milky Way tries this, the probe can spread throughout the galaxy. Another speculation for contact with an alien probe - which will try to find a human - is an alien Bracewell probe. Such a hypothetical device would be an autonomous space probe whose purpose was to seek and communicate with foreign civilizations (as opposed to the Von Neumann probe, usually described as pure exploration). This is proposed as an alternative to bringing a slow-speed dialogue of light between very distant neighbors. Instead of competing with long delays of radio dialogue will suffer, an artificial intelligence housing inquiry will look for alien civilizations to communicate closely with the found civilizations. The findings of such an investigation must still be transmitted to the civilization of the house at the speed of light, but an information-gathering dialog can be done in real time.

Attempt to find alien probe

Direct exploration of the Solar System has resulted in no evidence showing visits by their aliens or probes. Detailed exploration of the field of the Solar System where resources will be abundant may not yet produce proof of alien exploration, although the whole Solar System is very wide and difficult to investigate. Attempts to signal, attract, or activate the hypothetical Bracewell probes around Earth have not been successful.

Guess about star-scale artifacts

In 1959, Freeman Dyson observed that every development of human civilization constantly increases its energy consumption, and, he suspects, civilizations may try to exploit most of the energy generated by a star. He proposed that the Dyson ball could be a possible means: the shell or cloud of objects lining the star to absorb and harness the radiant energy as much as possible. Achievements such as astroengineering will drastically alter the observed spectrum of the involved stars, altering at least some of the normal emission lines from the natural star atmosphere to black body radiation, perhaps with a peak in the infrared. Dyson speculates that advanced alien civilizations may be detected by examining the spectrum of stars and looking for such changing spectra.

There have been several attempts to find evidence of the existence of Dyson balls that will change the spectra of their core stars. Direct observations of thousands of galaxies have shown no explicit proof of construction or artificial modification. In October 2015, there was some speculation that the light pattern of the KIC 8462852 star, observed by the Kepler Space Telescope, could be the result of Dyson ball construction.

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Hypothetical explanation for paradox

Large Filter Hypothesis

The Fermi paradox can be explained by a variant of Great Filter Hypothesis, which argues that in order for intelligent life to occur and to create a certain civilization, a very unlikely event, called a "great filter" needs to occur, essentially "filtering" the possible location of intelligent life to planets that "win the cosmic lottery", that is where unlikely events occur. The most commonly accepted probability low case is abiogenesis: the spontaneous generation of the first self-replicating molecular compound by randomly occurring chemical processes. Another proposed large filter is the emergence of eukaryotes or meiosis (both known to have taken billions of years to evolve from the first on Earth) or some of the steps involved in brain evolution that are capable of breaking complex logical deductions.

Space life is rare or absent

Those who think that intelligent (almost) intelligent extraterrestrial life may not argue that the conditions necessary for the evolution of life - or at least the evolution of biological complexity - are rare or even unique to Earth. Under this assumption, called the rare Earth hypothesis, the rejection of the principle of mediocrity, the complex multicellular life is considered highly unusual.

The Rare Earth Hypothesis argues that the evolution of biological complexity requires a number of coincidental situations, such as galactic habitable zones, central stars and planetary systems that have required characters, decent decent zones, the right terrestrial planets, the advantages of a gigantic guardian like Jupiter and large natural satellites, conditions necessary to ensure the planet has a magnetosphere and tectonic plates, lithosphere chemistry, atmosphere, and oceans, the role of "evolutionary pumps" such as massive glacial and rare bolide impacts, and anything that causes eukaryotes, sexual reproduction and Cambrian explosions.

No other smart species appear

It is possible that even if complex life is common, intelligence (and consequently civilization) is not. Although there are remote sensing techniques that may detect planets that live independent of technological signs, none of them have the ability to know if there is intelligent life detected. This is sometimes referred to as the problem of "algae vs. alumni".

Smart alien types lack advanced technology

It could be that while foreign species with intelligence exist, they are primitive or have not yet reached the level of technological advancement necessary to communicate. Along with the non-intelligent life, such a civilization will also be very difficult for us to detect, a brief visit by an inquiry, a journey that will take hundreds of thousands of years with today's technology. To the skeptics, the fact that in the history of life on Earth only one species has developed civilization to a point capable of space and radio technology, lends more confidence to the idea that advanced technological civilization is rare in the universe.

It is the nature of intelligent life to destroy itself

It is an argument that technological civilizations usually or usually destroy themselves before or soon after developing radio or space technology. Possible ways of extermination are many, including unintentional wars, contamination or environmental damage, resource depletion, climate change, or artificial intelligence that are not well designed. This general theme is explored both in fiction and in scientific hypotheses. In 1966, Sagan and Shklovskii speculated that technological civilizations would tend to destroy themselves within a century developing communicative capabilities of interstellar or mastering self-destructive tendencies and surviving over a span of billions of years. Self-annihilation can also be seen in thermodynamics: as far as life is a disordered system that can defend itself against the tendency of interference, "external transmission" or communicative phase of interstellar may be the point at which the system becomes unstable and self-sufficient. -destructs.

It is the nature of intelligent life to destroy others

Another hypothesis is that intelligent species beyond a certain point of technological capability will destroy other intelligent species when they arise. The idea that something, or someone, might destroy intelligent life in the universe has been explored in the scientific literature. A species may do such destruction from expansionist motives, paranoia, or aggression. In 1981, cosmologist Edward Harrison argued that such behavior would be a wise move: an intelligent species that has overcome its self-destructive tendencies may see other species that are depressed on galaxy expansion as a threat. It has also been argued that a successful foreign species will become a superpredator, just like humans.

Periodic extinction by natural events

New life may usually die from warming or cooling on their planet. On Earth, there are many major extinction events that destroyed most of the living complex species at the time; the extinction of dinosaurs is the best known example. This is thought to be caused by events such as the impact of large meteorites, large volcanic eruptions, or astronomical events such as gamma ray bursts. Perhaps such extinction events are common throughout the universe and periodically destroy the intelligent life, or at least its civilization, before the species is able to develop technology to communicate with other species.

Inflation hypothesis and youth argument

Cosmologist Alan Guth proposes a multiverse solution to the Fermi paradox. This hypothesis uses the probability distribution of synchronous gauges, with the result that the young universe is much larger than the older (with the ^{10 37} factor for every second of age). Therefore, on average in all universes, the universe with civilization almost always has only one, the first of which develops. However, Guth notes "Perhaps this argument explains why SETI has not yet discovered the signal from alien civilization, but I find it more plausible that it is merely a symptom that the probability distribution of synchronous gauges is not correct."

Intelligent civilizations are too far apart in space or time

Perhaps a non-colonial colonizing foreign civilization exists, but that they are too far away for meaningful two-way communication. If two civilizations are separated by several thousand light-years, it is possible that one or both of these cultures may become extinct before meaningful dialogue can be established. Human search may be able to detect their presence, but communication will remain impossible due to distance. It has been suggested that this problem may be somewhat corrected if contact/communication is made through the Bracewell probe. In this case at least one partner in exchange can obtain meaningful information. Or, civilization can only broadcast its knowledge, and submit it to the recipient to make what they get out of it. This is similar to the transmission of information from ancient civilizations to the present, and mankind has done similar activities like the Arecibo message, which can transfer information about the Earth's intelligent species, even if it never produces a response or does not produce a time response to mankind accept it. Perhaps archaeological evidence from past civilizations can be detected through space observation.

A related speculation by Sagan and Newman shows that if another civilization exists, and transmits and explores, their signals and probes have not yet arrived. However, critics have noted that this is impossible, as it requires human progress that has taken place at a very special point in time, while the Milky Way is in transition from empty to full. This is a fraction of the galactic lifespan under the assumptions and ordinary calculations generated from them, so the possibility that we are in the middle of this transition is considered low in paradox.

Lack of resources to spread physically across the galaxy

Much speculation about the ability of foreign cultures to colonize other star systems is based on the idea that interstellar travel is technologically feasible. While current physics understanding overrides the possibility of a faster journey from light, it appears that there are no major theoretical barriers to the construction of "slow" interstellar ships, although the engineering required is far beyond our present capabilities. This idea underlies the concept of the Von Neumann probe and the Bracewell probe as a potential proof of space intelligence.

However, it is possible that current scientific knowledge can not precisely measure the feasibility and cost of colonization between stars. The theoretical hurdles may not yet be understood, and the resources required may be so great that they do not allow any civilization to do so. Even if inter and colonization travel is possible, they may be difficult, leading to a colonization model based on percolation theory. Colonization efforts may not occur as an unstoppable urge, but rather as an uneven tendency to "spread" outward, in a recent slowdown and cessation of effort because of the huge cost to be incurred and the hope that the colony will inevitably developing a culture and civilization from them. own. Therefore, colonization can occur in "groups", with large areas remaining not colonized at one time.

If exploration, or reserve of a home system disaster, is the primary motive for expansion, then perhaps mind optimization and similar technology can reduce the desire to colonize by replacing physical travel with much cheaper communication. Therefore, the first civilization may have physically explored or colonized the galaxy, but subsequent civilizations found it cheaper, faster, and easier to travel by contacting existing civilizations rather than physically exploring or traveling alone. This leads to little or no physical travel at the present time, and only directed communications, which are hard to see except to the intended recipient.

Man has not been there long enough

The human ability to detect intelligent extraterrestrial life has existed only for very short periods - from 1937 onwards, if the invention of radio telescopes was taken as a limiting line - and Homo sapiens was a recent geologist. type. The whole period of modern human existence to date is a very short period on a cosmological scale, and radio transmissions have just been propagated since 1895. Thus, it remains possible that humans are not long enough and do not make themselves detectable enough to be discovered. by space intelligence.

We are not listening properly

There are several underlying assumptions of the SETI program that can lead to lost signal seekers. Extraterrestrials may, for example, transmit signals that have very high or low data rates, or use unconventional frequencies (in our terms), which will make them difficult to distinguish from background noise. Signals can be sent from non-primary order star systems we search for with lower priority; the current program assumes that most of alien life will orbit stars like the Sun.

The biggest challenge is the large size of radio search required to search for signals (effectively covering the whole of the visible), limited amount of resources committed to SETI, and the sensitivity of modern instruments. SETI estimates, for example, that with highly sensitive radio telescopes such as the Arecibo Observatory, Earth television and radio broadcasts can only be detected at distances up to 0.3 light-years, less than 1/10 the distance to the nearest star. Signals are much more easily detected if signal energy is limited to a narrow frequency range, or directed to a particular part of the sky. Such signals can be detected in the range of hundreds to tens of thousands of light-years distances. However, this means that the detector must listen to the appropriate frequency range, and be in the region of the space where the file is being sent. Many SETI searches assume that extraterrestrial civilizations will broadcast deliberate signals, such as Arecibo messages, to be found.

Thus to detect alien civilization through their radio emissions, Earth observers need more sensitive instruments or should expect for favorable circumstances: that broadband radio emissions from foreign radio technology are much more powerful than ours; that one of the SETI programs is listening to the correct frequency of the proper space region; or aliens deliberately send a focus transmission to our general direction.

Civilizations broadcast detectable radio signals for only a short time

Perhaps alien civilizations can be detected through their radio emissions for only a short time, reducing their chances of seeing them. The usual assumption is that civilizations are transcending radio through technological advances. However, even if the radio is not used for communication, it can be used for other purposes such as the power transmission of a solar powered satellite. Such use may remain visible even after broadcast emissions are replaced by less-observed technologies.

More hypothetically, advanced alien civilizations may evolve beyond broadcasting altogether in the electromagnetic spectrum and communicate with technologies not developed or used by humans. Some scientists have hypothesized that advanced civilization can send neutrino signals. If such signals exist, they can be detected by a neutrino detector that is now being built for other purposes.

They tend to isolate themselves

It has been argued that some advanced beings can break away from physical form, create a massive artificial virtual environment, transfer themselves into this environment through mind uploading, and actually exist in the virtual world, ignoring the external physical universe.

It may also be the intelligent alien life developing an "increasing disinterest" in their outer world. Perhaps any moderately advanced society will develop a very attractive medium and entertainment well before the capacity for advanced space travel, and that the level of attractiveness of these social tools is doomed, because their inherent complexity is diminished, to overtake any desire for effort complex and expensive. such as space exploration and communication. After an advanced civilization becomes capable of mastering its environment, and most of its physical needs are met through technology, various "social and entertainment technologies", including virtual reality, are postulated to be the key drivers and motivations of that civilization.

They are too foreign

Another possibility is that human theorists have underestimated how many alien lives may be different from those on Earth. Foreigners may be psychologically unwilling to try to communicate with humans. Perhaps human mathematics is parochial to Earth and not shared by other life, although others argue this can only apply to abstract mathematics because mathematics related to physics must be similar (in result, if not in method).

Physiology may also cause communication barriers. Carl Sagan speculates that alien species may have a process of thinking of order of magnitude slower (or faster) than we are. The messages broadcast by the species may seem like random background noise to us, and therefore undetectable.

Another notion is that technological civilization always experiences the singularity of technology and achieves its post-biological character. Such hypothetical civilizations may have advanced drastically enough to make communication impossible.

Everyone listens, nothing transmits

The alien civilization may be technically able to contact Earth, but only listen rather than transmit. If all, or even most, civilizations act in the same way, the galaxy can be full of civilizations that want to be contacted, but everyone is listening and no one is transmitting. This is called SETI Paradox .

The only civilizations that we know of, ourselves, do not explicitly transmit, except for a few small attempts. Even these efforts, and of course efforts to expand them, are controversial. It is not even clear we will respond to detected signals - the official policy in the SETI community is that "[no] responding to signals or other evidence of space intelligence should be sent until appropriate international consultations have taken place." However, given the potential impact of any reply, it may be very difficult to get a consensus on "Who speaks for Earth?" and "What should we say?"

Earth accidentally not contacted

The zoo's hypothesis states that intelligent extraterrestrial life exists and does not contact life on Earth to allow its evolution and natural development. This hypothesis can be broken down under the uniformity of motive defects: all that is required is a culture or a single civilization to decide to act contrary to the imperative within our detection range for it to be aborted, and the likelihood of such violation increases with the number of civilizations.

The analysis of time between arrivals between civilizations in the galaxy based on general astrobiological assumptions suggests that early civilizations will have a commanding lead over later arrivals. Thus, it may have defined what we call the hypothesis zoo through force or as a galaxy/universal norm and the "paradox" generated by the founding effect of the culture with or without the continued activity of the founder.

Earth is intentionally isolated (planetarium hypothesis)

The idea associated with the zoo hypothesis is that, beyond a certain distance, the perceived universe is a simulated reality. The planetarium hypothesis speculates that a creature may have created this simulation so that the universe looks empty from another life.

Malicious to communicate

Alien civilizations may find it too dangerous to communicate, either to us or to them. After all, when very different civilizations have met on Earth, the results are often a disaster for one side or the other, and the same may be true for interstellar contact. Even contacts at a safe distance can cause infection by computer code or even the idea itself. Perhaps a wise civilization actively conceals not only from Earth but from all people, for fear of other civilizations.

Perhaps the Fermi paradox itself - or its foreign equivalent - is the reason for every civilization to avoid contact with other civilizations, even if there are no other obstacles. From the point of view of any civilization, it is impossible for them to be the first to make the first contact. Therefore, for this reason, it is possible that earlier civilizations faced fatal problems with first contact and did so should be avoided. So perhaps every civilization is silent because of the possibility that there is a real reason for others to do so.

Liu Cixin's novel, The Dark Forest, speaks of such a situation.

The simulation theory

Similar to the Planetarium hypothesis, it is theorized that the reality we perceive is a simulation created by more intelligent beings. The creator of this hypothetical simulation may have deliberately expelled life other than what has been found on Earth, or has not yet introduced it to humans in the simulation. It is also possible that they themselves are more intelligent human beings, who have not yet come into contact with aliens.

They are here undetected

It is possible that an advanced civilization to travel among the stars can visit or observe our world while remaining undetected or unrecognized.

They are not recognized here

Most residents believe that at least some UFOs are aliens driven by aliens. While most of these are unknown or false interpretations of worldly phenomena, some remain confusing even after the investigation. The consensus scientific view is that although they may be unexplained, they do not rise to a convincing level of evidence.

Source of the article : Wikipedia