The SETI (Search for Extra-Terrestrial Intelligence) program consists in detecting the presence of advanced civilizations in other star systems. SETI considers it likely that these civilizations will emit electromagnetic signals strong enough to be detected on Earth, particularly in low-galactic frequency bands such as those around 1.4 GHz.
Since the 2000’s, recordings have diversified in terms of frequencies and optics. With the end of government funding, the American private sector had to take over, and the public was invited to participate in 1999 with a downloadable distributed computing program called SETI@home, an initiative of the University of Berkeley, whose total computing power, when the number of users peaked, surpassed the power of the best supercomputers in operation worldwide.
For the analysis of the electromagnetic spectrum around 1.4 GHz, SETI@home took advantage of the enormous computing power of millions of NVIDIA graphics cards and the thousands of CUDA computing units present on their GPUs, which often exceeds by a factor close to 20, those with Intel or AMD CPU processors.
SETI@home, including its version on the BOINC scientific platform, analyzed data from the Arecibo radio telescope for more than a decade without conclusive results. Before shutting down, however, it did identify several candidate signals that did not repeat themselves sufficiently to be considered evidence of an extraterrestrial civilization. The first-ever candidate was the powerful WOW signal, picked up in 1977 for 72 continuous seconds by the Big Ear radio telescope.
The SETI protocol requires that a captured signal must not only be of a very narrowband and therefore of an artificial nature, but also be detected by different radio telescopes in order to eliminate false candidates due to human activity, like satellite or military activity. Pollution of the electromagnetic spectrum has become a major problem for SETI programs, especially since Elon Musk went live with Starlink. In addition, SETI does not observe all frequencies, in all directions, or 24/7, which makes it likely that signature technologies will be missed. It is hoped that technological advances and the development of AI algorithms can increase the chances of detection of a repetitive nature, spaced out over time, including in old data.
The Fermi paradox is perfectly illustrated by SETI research, which, despite decades of research in the radio frequency spectrum, has not been able to highlight the presence of extraterrestrial civilizations or any signature of advanced technology. This paradox postulates that since possible aliens could have appeared millions of years ago, they would have had plenty of time to colonize the entire galaxy, so their non-presence, including on Earth, tends to demonstrate their non-existence.
Is stellar discretion beneficial?
Robin Hanson, one of the experts on this research, recently tried to explain this lack of results with the so-called "grabby aliens" theory, which can be translated as "invasive aliens" and defined as a global threat due to potential predatory and highly invasive stellar species.
He previously explained the Fermi paradox with the existence of several large filters preventing the easy appearance of life, leading to advanced civilizations, as well as their long-term survival. Many events could cause this: self-destruction by nuclear weapons, supernova radiation, the appearance of extreme weather conditions on their home planet, NEO impacts triggering extreme volcanic eruptions and then sudden glaciations.
It can be considered that in many cases, the degradation of their native biosphere will push civilizations to seriously explore their immediate stellar environment with interplanetary probes in order to allow a migration and perpetuation of their species on several planets compatible with their biological characteristics. An advanced civilization could detect photosynthesis existing on Earth from very large stellar distances to place it on a list of candidate planets to be explored with probes, but would not be able to see our activity in the electromagnetic spectrum from beyond 100 light years.
As evolved biological life is not easy to preserve for very long space voyages, it is very likely that the selection of host planets will be dedicated to robotic AIs that can autonomously repair themselves, or even reproduce themselves, like Von Neumann probes. They could discreetly assess the aggressiveness of the civilizations detected and, after a sufficient period of observation, move on to physical contact between biological intelligences of the same emotional sensibility.
This possibility will be subject to a minimum compatibility of the physical environment (pressure, differences in gravity, composition of atmospheres, biological risks, transmission of viruses, etc.) The alternative is a minimized contact with the help of advanced AI capable of understanding new languages and gestures, of presenting oneself with appearances that do not induce reactions of rejection or hostility. Communication, even on a human scale, including between people close to each other, sometimes quickly comes up against a sum of misinterpretations and cultural differences. This doesn’t seem like the most effective solution. AIs on earth have no real intelligence at this point and are just algorithms optimized for some specific and highly repetitive tasks, including learning.
Communication between certain intelligent life forms could be problematic, totally outside the scope of their consciousness and the senses attributed to them by evolution. It may also be that in the very long term, biological life is too fallible. It cannot adapt in different environments, and stellar expansion of civilizations is largely the result of AI migrating inside Von Neumann probes.
Our Universe could be made up of multitudes of deadly and often static biological civilizations that can't communicate with far more resilient AIs exploring their worlds. Nor do these AI have complex forms of communication as their ‘primary directive’, nor do they have the capacity to engage in such an advanced dialogue.
The Hart-Tipler conjuncture postulates that the non-detection of such Von Neumann-type probes in our environment reinforces the hypothesis of a very limited number of civilizations in the Milky Way. However, humanity is probably not the first civilization to appear in our galaxy, given the age of the Milky Way, which is mostly made up of stars much older than our sun. We should therefore statistically note the existence of an ecosystem of civilizations much older and more advanced than our own.
It seems realistic to postulate the existence of a majority category of rather discreet civilizations and another very expansionist and more scientifically advanced whose signature technologies would be much more visible. The activity of our civilization on Earth, for example, remains very undetectable, even in our nearby stellar environment. The researchers then tried to assess how quickly highly expansionist civilizations would become visible across their entire galaxy, as well as their relative numbers compared to those that chose to be much more discrete.
Conquest
It is estimated that it will take four billion years for a technological civilization to appear on a planet with many favorable conditions. Other researchers favor the assumption that the majority of truly advanced civilizations will appear much later, despite the average age of generations of stars in the Milky Way that can produce heavy metals and all the components found on Earth.
According to some recent calculations, only one galaxy out of a million contains an "invasive and noisy" civilization because it is far ahead of all the others and can thus develop rapidly on all the millions of solar systems that constitute it without opposition. If such a civilization emerged early in a given galaxy, it would probably no longer allow others to thrive there, and very large areas under its control would appear there. More precisely, it is possible that there will be a period beyond which the new civilizations could no longer expand, because they would be prevented from doing so by older, far superior civilizations. It is considered likely that in approximately 10 billion years, all of our galaxy's space will be completely colonized.
The simulation suggests that even if only one in 1,000 or 10,000 civilizations becomes "invasive and noisy," the final colonization of large galaxies could stabilize around 100 major civilizations, each of those having absorbed the other, less powerful civilizations, or exploiting their resources by force for industrial purposes, just like the hit sci-fi film series "Star Wars."
Setting the parameters of the simulation a certain way, it appears possible that 50% of our galaxy is already under the control of major civilizations, and that it is just our current technological level that does not allow us to detect them. This semi-control situation may have already materialized in 100,000 to 30 million galaxies. Our technological means would still be very far from being able to detect such a situation of galactic semi-control, and it is possible that we would have to wait another 200 million years before entering the sphere of expansion of a noisy civilization. One possible conclusion from this study is that the SETI search is unlikely to find anything in the immediate future.
A variant of this statistical study is that our galaxy does not yet host such a noisy civilization or will definitely be devoid of one. It even argues that it is possible that by the time life has disappeared from the Earth, within a few million years, no major techno-signature will still have reached our planet.
The "invasive aliens" hypothesis generates criticism, because it contains the assumption of galactic imperialism, which may be a bias due to our own behaviors. Historically, imperialism has been dictated by the need for access to resources, religious conceptions, etc. In a huge star field, things could be very different and absolutely not comparable to human expansion on Earth or that of an ant colony in a forest.
The Galileo Project
However, we cannot exclude particularly exacerbated expansion behavior on the part of some distant species, at least in an initial stage. It is conceivable that the will to expand over millions of years and enormous distances could be inhibited by social or evolutionary changes. The behavior of non-expansionist civilizations could be very different, our planet could be in a zone where only a discrete control system is active, which the controversial phenomenon of UAP evokes quite well at first glance. This phenomenon also reinforces the probability of the feasibility of interstellar travel and reinforces the hypothesis of stellar expansion mentioned.
One could deduce that scientific initiatives such as Avi Loeb's Galileo project will have a much better chance than the many SETI projects to highlight the presence of advanced signature technologies by targeting not deep space, but by installing automated sensors in our near-Earth environment. Unfortunately, the main obstacle for this type of project is still their private and non-governmental funding, because while multi-sensor platform technologies have matured, their deployment in large numbers is still quite expensive. Avi Loeb of Harvard University, for example, has so far only been able to deploy three multi-sensor capture platforms, which limits the potential success of his project. In the case of a consensually recognized positive result, its author would certainly be awarded a Nobel Prize.
Main picture: Image by Michel Bertolotti for Pixabay
