We have already discussed the so-called Fermi paradox. In short, its essence is that if there were at least one more technologically advanced civilization capable of interstellar flights in our Galaxy, it would have “occupied” the entire (or almost the entire) Milky Way long ago, and we would have observed undeniable signs of its presence. Of course, here you may mention numerous witnesses of UFOs or strange archaeological findings that are considered signs of “paleocontacts” … but all these evidence cannot be considered indisputable, if only because they are not present in our lives permanently or at least repeatedly, so the question of the reality of an extraterrestrial mind remains unanswered.
Pessimists among scientists offer the simplest solution to this paradox: they admit that we are alone on our “star island” (and perhaps within the entire Local Group). This does not rule out the possibility that other advanced civilizations capable of crossing interstellar distances will arise in the future or have existed in the past, but for some reason have declined or disappeared altogether. Until recently, most of the scientific community tended to share this opinion, but the large number of exoplanets detected in recent decades and the discovery of some patterns in the evolution of living matter have added arguments to enthusiasts of the search for extraterrestrial intelligence.
Here it should be explained why we limit ourselves in our reflections only to the Local Group. As is known from the General Theory of Relativity, the highest speed that can be developed in our universe is the speed of light in a vacuum (299,792 km/s), and only photons (quanta of electromagnetic radiation that do not have a so-called rest mass) are capable of this. It is theoretically possible to accelerate material bodies to such a speed, but it will require enormous energy, so it is generally accepted that interstellar travel will be carried out ten times slower — that is, at a speed of 0.1 c (about 30 thousand km/s), which is a very optimistic assumption. This will allow us to reach the nearest stars in 40-100 years. Meanwhile, crossing the Milky Way (its full diameter), would take us as much as a million years.
As you know, interstellar distances (unless we are talking about double or multiple stars) are tens and hundreds of thousands of times greater than interplanetary distances: for example, the nearest star Proxima Centauri is located 90 thousand times farther from the Sun than the planet Neptune. The situation is approximately the same when we shift to intergalactic distances. The nearest non-Local Group galaxy, NGC 300, is 6 million light-years away, so moving at a speed of 0.1c, we’ll get there in as much as 60 million years. These are completely different scales of space and time, besides, we should not forget that thanks to the cosmological expansion of the Universe, objects at a distance of a billion light years are already moving away from us at a speed only slightly less than 0.1 c, so we simply will not catch up with them. Of course, it is possible to imagine a highly developed civilization that managed to overcome any distances almost instantly… but it is better to postpone considering such a version until the end of the article. Now let’s try to list the explanations of the Fermi paradox offered by those who are not inclined to consider humanity the only intelligent race of the Milky Way.
Modern technological civilization has existed for no more than a couple of thousand years — this is an incredibly short time by the scale of the universe. However, we have already encountered many problems created by humanity itself and capable of destroying us or at least “rolling back” to a primitive level, which does not involve the possibility of interstellar travel. If such troubles lie in wait for the majority of developed civilizations, it is not surprising that none of them has ever paved its road into the “bigger Galaxy”. In addition, external factors are looming over us, which do not depend on human activity, but would produce a similar detrimental effect on our future (collision of the Earth with an asteroid or comet, unpredictable fluctuations in solar activity, etc.).
It is also possible that an intelligent species, even after reaching the level of technological civilization, still will not be able to leave its own planet due to some peculiarities of its representatives. Imagine that dolphins or other creatures that need large volumes of water for normal life have reached the required level of development on Earth. How will they “pull” themselves into space? Another option was described in several fantastic stories — thinking plasmoid formations in the atmospheres of gas giants. It will be easier for them to go on an interstellar journey together with their own planet, which is not completely impossible, but requires much more knowledge and effort than building and launching a spaceship (even a very large one).
The outer space is harsh
As a matter of fact, humanity has now “detached from the Earth” by a tiny distance by galactic standard — just the radius of the Moon’s orbit. Astronauts who flew to the Moon spent up to 12 days outside the atmosphere and radiation belts of our planet, which protect us from high-energy particles wind and cosmic rays, and managed to receive sufficiently high doses of radiation during this time. Interplanetary travel will last ten times longer, and there this problem will be even more acute. Of course, methods of protecting people from the dangerous effects of outer space are constantly being improved, but during interstellar flights, this task will become many times more difficult.
If a spacecraft moves through the Galaxy at the already mentioned speed of 0.1 c, the relative speed of all matter in the environment, from individual atoms to particles of interstellar dust, will be approximately the same. When they collide, a huge amount of energy will be released: for example, a “meeting” with a grain of sand 1 mm in size (and weighing about 2 mg) will lead to an explosion with energy of almost a billion joules, that is, more than 200 kg in TNT equivalent. And during tens of years of space travel, not one or two such grains of sand will come across the path of our starship. There is still no effective defense against such “bombing”, and it is not known whether it is possible at all. This factor also puts galactic expansion into great doubt, or at least will slow it down a lot, because after each flight to the nearest star with a habitable planet, we will actually have to build a new “vehicle”.
The right of the first intelligence
An interesting explanation of the Fermi paradox was proposed by several astronomers, among whom was Stanford University professor Laurence Bracewell. In general, it can be summarized as follows: our Galaxy is already 10-11 billion years old. Initially, a large part of its population consisted of hot massive stars, whose active existence lasts no more than a few hundred million years. From hydrogen and helium (the main chemical elements of the early universe) they synthesize in their cores the heavier elements needed to form rocky terrestrial planets, then explode as supernovae and scatter these elements into interstellar space. Later, those elements enter the regions of star formation, where stars are condensed with planetary systems that are already suitable for the origin and development of living organisms of the types known to us.
All of these processes occur at roughly the same rate throughout the Milky Way, eventually leading to the appearance of intelligent species — and it just so happened that humanity itself became the first such species. That is, our “brothers in mind” almost certainly already exist, but… they are still too young. And even if we are about the same “age”, they and we still need some more time to go out into interstellar space and meet.
But let’s imagine a civilization that managed to overcome all the problems associated with interstellar flights and began the gradual colonization of the Galaxy. Who said that its representatives will be like people and address us in a language that we can understand? When Earth scientists discuss the search for extraterrestrial life, they almost always talk about self-replicating structures based on carbon chains and biochemical reactions in aqueous solutions. Such a concept was even labeled “hydrocarbon chauvinism”, but the truth is that we have not yet encountered examples of living matter organized according to other principles, and we do not even know what these principles might be. Perhaps “alien intelligence” has long existed alongside us, we just cannot distinguish its bearers from “inanimate nature”. Or maybe they themselves don’t want to catch our eye.
The principle of non-interference
Why do we suppose that aliens who arrived in the solar system and noticed the presence of an intelligent race on the third planet from the sun would immediately rush to get to know us? Even within the borders of our native Earth, humanity has enough examples of the negative consequences of the contacts of societies with different levels of development. A civilization that has learned to travel between the stars will probably be intelligent enough to protect Earthlings (and possibly themselves) from such “culture shock.” Most likely, its representatives will watch us without revealing their presence in any way, until they decide that we are already “ripe” to meet them.
Now let’s return to the idea of “almighty” aliens who have learned to move at a speed much faster than light. Of course, the level of their technology will allow them not only this: they will also be able to remain invisible or perfectly disguise themselves as objects, birds, animals, people… Without much effort, they will learn human languages, protect themselves from a possible threat from earthly viruses and bacteria. It will be difficult for them to refrain from interfering in some important socio-historical events… All these scenarios have already been described many times in various fantastic works and conspiracy theories, and in fact we cannot completely exclude them from consideration. The only way to ever discover representatives of such a “super-civilization” is to constantly deepen our knowledge of the surrounding world, to look for apparent inconsistencies and interesting patterns in it. Perhaps the day will come when the aliens decide that humanity is finally “ripe” for safe contact with them, and then we’ll learn about the existence of “big brothers in mind”.
But for now, it looks like the humans are “the biggest brothers” around — at least within our Galaxy.