Many scientists involved in the search for extraterrestrial civilizations are sure that sooner or later humanity will come into contact with aliens living somewhere in the Milky Way. Unfortunately, experts cannot predict how they will look and how they will treat people, but they can predict the level of their technological development. "Lenta.ru" talks about the latest research in which scientists tried to predict an approximate portrait of an alien civilization that will someday come into contact with us.
Technology decides everything
Any civilization that has reached such a technological level that interstellar travel is feasible for it should become noticeable to astrophysicists. But the "silence" of space, which formed the basis of the Fermi paradox, hints that there are no developed civilizations in the vicinity of the solar system. So far, scientists have not found a single meaningful sign that humanity is not alone in the Milky Way.
First of all, you need to understand what exactly to look for. Scientists are interested in civilizations that are potentially capable of contact, which means they must leave technosignatures - signs of the presence of technologies that are visible from a great distance and which cannot be hidden. With the help of statistical analysis, you can predict what humanity will notice first. If we assume that in the Milky Way there really is someone other than humanity, and these someone are at different stages of technological development, then we can even approximately determine who we will face in the first place. This will not necessarily be direct contact, but we can be convinced of the existence of an extraterrestrial civilization with the help of astronomical observations.
Dyson Sphere of Many Rings
It is reasonable to assume that the nature of the contact largely depends on the technological capabilities of another civilization. The same factor will determine the very attitude of humanity towards fellow humans: it is one thing when we communicate with those who are at the same stage of development, and another thing when we find a civilization much older than ourselves. The longer an intelligent life exists, the more technological capabilities it is likely to have, including the ability to establish contact.
It remains only to understand with whom mankind is more likely to face. According to theoretical models, even if it is naive to assume that the Milky Way is full of young civilizations, and the old and ancient are rare, the probability of contact is proportional to the age of the civilization. That is why focusing on the search for technologies similar to ours will not lead to success.
Scientists have come to a consensus that the very success of SETI depends on how durable alien civilizations are, moreover, they are durable in the technological sense. Technosignatures must have existed for thousands or even millions of years. Perhaps even the civilization that gave birth to them will disappear, just as the ancient Egyptian culture that built the Great Pyramids disappeared. For example, aliens could leave behind interstellar beacons or launch probes that continue to roam space. Such probes are hypothetically capable of replication, that is, making copies of themselves, and can spread throughout the galaxy.
What are SETI projects
SETI (Search for Extraterrestrial Intelligence) refers to any research aimed at finding extraterrestrial intelligence and making contact with it. Scientists have been studying SETI since 1959, trying to identify radio signals at a wavelength of 21 centimeters and a frequency of 1420 megahertz. It is believed that any technologically advanced civilization will try to establish contact on this frequency, but so far the search has not been crowned with success, although thousands of stars have been scanned. Currently, SETI projects are usually funded by private funds, and researchers remain optimistic that contact will be established in the coming decades.
The authors of the study, published in the arXiv preprint repository, categorized the possible types of technosignatures by their duration. Type A can reach the age of a thousand years, which is comparable to the time of the technological development of earthly civilization. Type B can survive as long as a biological species - about a million years. Finally, Type C has been around for at least a billion years.
The most durable technosignatures may not necessarily be built by high-level civilizations. For example, intelligent species that have just mastered off-planet flights can leave space debris, pollute the atmosphere with persistent pollutants, or send interstellar probes powered by chemical rocket engines. People have not yet produced technosignatures of type A, if we consider radio signals or traces of industrial activity in the Earth's atmosphere, but the probes Voyagers, Pioneers and New Horizons are capable of becoming technosignatures of type B and even C in the distant future. To type C also includes more exotic objects such as lighthouses or megastructures like the Dyson sphere.
Extinct and prosperous
Any technosignature that we can detect statistically should have existed for a very long time - about a million years. We may also come across younger technosignatures, but only if they are widespread in the Milky Way. Therefore, it is more rational to expect that if we can observe signs of the existence of another civilization, then technologically it will be very different, and its level of development will be much higher than ours. Moreover, a significant part of potentially detectable technosignatures in the Milky Way most likely belongs to civilizations that have already become extinct. This means that contact with "aliens" will be more reminiscent of archeology, only instead of a shovel - telescopes capable of discerning traces of already extinct activity.
The authors emphasize that in order to successfully search for aliens, it is necessary to abandon anthropocentrism and give preference to identifying megastructures, lighthouses and interstellar probes, which could have been created by a type II civilization according to Kardashev, or even developed artificial intelligence left after its creators. Such signs are much less common than type A technosignatures, but they are easier to detect precisely due to their durability.
It is worth remembering that for a developed civilization that has existed for millennia, transitional signatures (atmospheric pollution and climate change) are already unacceptable, since they limit the time of its life. Going into space, exploring interplanetary routes, building gigantic structures capable of accommodating hundreds, thousands or even millions of living beings is a logical step for aliens who are going to exist for a very long time. Therefore, there remains a rather high chance that humanity will come into contact with a still living civilization that has managed to survive and reach incredible technological heights.
Classic SETI searches, which seek to identify familiar technologies such as narrow-band radio signals and optical laser pulses, have been unsuccessful over 60 years of observations.While it cannot be said that aliens cannot use these means of communication, it must be recognized that a high-tech civilization can use a different type of space communication. Quantum communication is preferred for safety and efficiency. Looking in the sky for light "beacons" that are clearly visible, but practically useless in themselves, can be a waste of time. Most likely, the aliens send each other narrowly focused signals that are unlikely to be intercepted by accident, unless they are directed directly to Earth.
The Ringworld is another hypothetical astro-engineering structure
However, according to Michael Hippke, humanity could already record a weak signal from a technologically advanced civilization that has mastered quantum communications, it is just that the existing approach is not able to recognize them. Aliens can deliberately choose a covert communication channel to go unnoticed by more primitive intelligent beings. In addition, the interstellar quantum network may result from the achievement of "quantum supremacy" by advanced civilizations and will serve such exotic purposes as distributed quantum computing. In addition, quantum communication channels are protected from eavesdropping and are capable of transmitting more information per unit of time than conventional ones. Therefore, it is natural to expect that a civilization with which we can establish contact will use quantum technologies.
True, to capture quantum signals, you need to have quantum receivers - and they don't exist yet. At the same time, Hippke believes that the available equipment is sufficient to find signs of quantum entanglement of photons in the light of stars, albeit with the destruction of the information contained in them. Perhaps we should use a new approach, and the Universe will cease to be silent, although the search for quantum signals will be very laborious.
Physicist Stephen Hawking warned that looking for aliens is a dumb idea, since we don't know for sure if they will be friendly. Science popularizer Michio Kaku is convinced that the Earth should remain in the shadows, because the risk is too great. The fact that a hypothetical civilization would be technologically more advanced poses a potential threat to us, even if the aliens themselves are not intentionally hostile. No one knows exactly what social, economic and existential consequences such contact will have for us. It is also not known what role other people's technologies will play. An encounter with an extraterrestrial probe that accidentally entered the solar system may be limited to observations at a distance, or it may end in disaster if such a probe is capable of "multiplying".
Allen antenna array used for SETI
When it comes to artificial intelligence, the situation can become even more dangerous. Philosopher Nick Bostrom predicts that in the future, humanity will be able to build a machine superintelligence that will surpass the human brain in everything. This entails new threats, which, according to some experts, are fundamentally insurmountable: a person, by definition, will not be able to contain superintelligence. Assuming that advanced aliens have already crossed this line, we get a frightening picture that any old and technologically advanced civilization that humanity is likely to encounter is actually controlled or even made up entirely of AI.
In another pessimistic scenario, called a SETI attack, even a radio signal that encodes a malicious message or instructions to create hostile systems can be dangerous. A similar scenario was described by astronomer and cosmologist Fred Hoyle in his science fiction novel Andromeda.
In any case, it would be a mistake to extrapolate human behavior to an alien mind. Unfortunately, there are still too many unknowns in the search for extraterrestrial intelligence, and so far only science fiction writers feel comfortable coming up with various scenarios of contact.