You can imagine the size of the universe. It is huge. But where are all the aliens? They have not yet been found, but we are almost one hundred percent sure of their existence. So they are investigating us, infecting us, invading us, preparing a plan of destruction, isn't it?
The Fermi paradox lies in the absence of visible evidence of the existence of other intelligent civilizations - on all stars and in all galaxies in the universe. Or do you think that if at least one intelligent civilization could let us know about its existence, it would remain "out of the access zone"?
Either we are on the "black" list, or we really are the most advanced form of life in the universe (scary to think). Even more terrifying can be the fact that we are alone in the universe.
Searching for any extraterrestrial life is arguably one of the most meaningful things we can do as a species. We are ready for contact with aliens. We believe that they can teach us something. But life beyond Earth has not yet been discovered, and Search for Extraterrestrial Intelligence (SETI) specialists are beginning to despair. In any case, the search continues, and scientists are inventing more and more extreme methods for deeper observation of space in order to see glimpses of intelligence on distant stars.
Keplerian SETI candidates
17% of the stars detected by the Kepler telescope hold Earth-sized planets in orbits, highlighting the predominance of small exoplanets in our galaxy.
Some scientists have come to the conclusion that there may be much more potentially habitable zones than we think.
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The basic assumption with which we start thinking is this: our hypothetical neighbors in space develop in a similar way to ours. The lack of visible evidence in space will be a strong argument for this. Although in fact it is unlikely that somewhere outside our solar system, people like us are developing - they go shopping and fight among themselves.
However, in the event of such a coincidence, the alien race would one day have to come to the radio waves. We've been on the air for nearly 120 years (although with the invention of the digital signal, our analogue transmitters will soon go silent), which means that if an extraterrestrial civilization turns the knob of a radio receiver within 120 light years from Earth, it will have a great chance to enjoy our good and bad music and listen to news even 120 years ago. That is, they will find us.
Radio leaks are too unreliable. What if we point the antenna at the stars and “listen” to the broadcast in the hope of catching a signal specially directed in our direction? Since the 1960s, the SETI program has hunted for alien radio signals, but only recently, thanks to the Kepler space telescope, have we been able to more accurately target potentially habitable worlds. This means that everything is just beginning. Although SETI hasn't heard a single signal yet, great things await us in millions of other worlds.
Interference on the air
A radio signal detected by a 100-meter telescope in West Virginia while scanning an exoplanet candidate KOI 817. This is the type of signal that SETI scientists hope to hear from aliens.
While listening to the broadcast, SETI recorded several false signals. As we search in specific narrow ranges (which only certain technologies can generate), terrestrial interference constantly interferes with SETI searches. Fortunately, astronomers are not stupid and know what the difference is between alien signals and Aunt Masha's gossip on the phone.
Traces of strangers on the moon?
The tracks of Apollo and its equipment are still visible on the lunar surface.
But wait. Are we looking for aliens on distant stars, and not on the moon at our side?
Right. While the main goal of SETI's research is focused on finding suspicious radio signals in deep space, it is worth keeping in mind that the Moon will be a very good stopover for aliens who accidentally come to visit us. Searching for traces of aliens on the lunar surface will not seem so stupid to you when you learn that the LRO satellite, which is now flying around the moon, found traces of Neil Armstrong in 1969.
Alien artifacts
Mars Phoenix. Orbital view.
Why stop at the moon? If an evolved form of extraterrestrials has been in our solar system at any time in its entire history, it is possible they have severely inherited.
HP 56948: Twin of the Sun
Forget about "habitable exoplanets" for a minute. How about focusing your efforts on finding stars that are identical in temperature, size, and chemical composition to our sun? After all, this object provides our planet with energy, and all the chemicals that formed our planet came from the protoplanetary disk of our newborn sun 4.5 billion years ago. Let's just look for stars like the Sun.
In 2012, astronomers discovered HP 56948, a "clone" of the Sun, located just 200 light-years away. And although no planets have yet been discovered in its orbit, it is very curious whether such stars could be a potentially habitable zone for alien civilizations. We wrote more about these very zones in the article on binary star systems: suns that revolve around each other, providing a sufficiently large field for the development of alien forms.
Artificial exoplanets
From Kepler's perspective, as he observes the "dips" of light from stars, the telescope analyzes the light curve. Well, since the planets are known to be round, it will be a surprise to get a non-standard light curve. Non-spherical planets do not exist in nature, so as soon as Kepler discovers, for example, a massive pyramid, this may indicate the intrigues of aliens.
What is noteworthy is that there is a separate search program in this direction - the search for extraterrestrial technologies (SETT) and its main difference from SETI is that we are looking for indirect evidence of high technologies in space.
Where has this star gone?
Spiral Galaxy M51: Can You See One Dark Spot?
Could the absence of stars in the galaxy reveal the presence of superintelligent aliens?
In 1964, Soviet astronomer Nikolai Kardashev suggested that some alien civilizations could be so advanced that they would use all the energy coming from the star. These are civilizations of the second type on the Kardashev scale.
How will they do it? For example, by creating a fan-favorite science fiction Dyson sphere around a star. This shell will collect all the energy from the star, thereby hiding it from any outside observer. From our point of view, if we notice darkness in one of the segments of the galaxy, perhaps the aliens are having fun, hiding the stars in huge spheres.
Asteroid eaters
On the streets, they say that humanity is on the verge of turning asteroids into a whole power plant. And although the reality is that most technologies are not yet adapted to mining ore in space, this does not mean that alien civilizations are at the same stage of development.
We know that asteroids are full of valuable materials and that they circle the stars, which means that if someone smarter than us in space, he will come to the same conclusion: you need to take an asteroid, split it and get rich. (Although “getting rich” can be a special feature of human nature). Can we detect debris flying in all directions during the operation of such an orbital mining station? Quite.
Black holes - spacecraft engines
If evolved enough, some aliens could even make their own black holes as small as an atom and weighing millions of tons. If you plug this black hole into the engine, you know how, it will generate a huge amount of gamma rays, which, in turn, will be converted into energy for the spacecraft. According to experts, such a source of energy could be inexhaustible. And as far as we know, the radiation emitted by these artificial black holes would be easy to detect, which means - hello Earthlings, we came in peace.
Aliens, are you still alive?
The SETI search problems lead to various assumptions. One of them is that aliens use radio transmitters. Another is that aliens have always used radio transmitters. The latter is unlikely to be true, unless a very advanced civilization has been broadcasting 24 hours a day for billions of years.
As shown by false SETI results, the signal from outsiders is likely to be inconsistent. But how can we catch it if the life of civilization is too short?
And but the planetary dolphins
Dolphins are intelligent. Perhaps as intelligent as humans. But as far as we know, they don't use radio. What if extraterrestrial intelligence looks like dolphins? Will we never be able to find them until we fly to them on the planet and talk tête-à-tête? This assumption not only sparked a heated debate in SETI, it forced us to rethink the concept of "intelligence" on a galactic scale.
Little green men
Since the universe is silent, some astronomers - prematurely - declared that there is no intelligent life among the stars. From the point of view of science, this is fine, even if it is very shortsighted. But what if an extraterrestrial civilization doesn't want to make contact? What if she is happily doing her job, not wanting to talk to us? Moreover, what if they live so efficiently that too little energy escapes into space to be detected?
Invasion
Movies like Battle Los Angeles and Independence Day have hinted to us that not only are we one step away from an alien invasion, but we also don't really know how to deal with them. Many wondered: why would they invade at all? The answer, of course, is "why not?" But the story about "the engine that could" will surprise no one.
With this in mind, SETI decided to revise its strategy and launched the WETI program - waiting for extraterrestrial intelligence. Then all the programs for finding and communicating with extraterrestrial civilizations will have to be curtailed, and then, hiding our heads in the sand, sit and hope that no one will find us.