The theory of "Dyson spheres" and the search for alien civilizations
Freeman Dyson proposed the possibility of building a sort of "shell" around a star to capture much of its energy. Such technological structures could indicate the footprint of an extraterrestrial civilization.
When we raise our gaze towards the immense dark blue of the universe that dominates the celestial vault, contemplating the immensity and the myriads of stars that form the Milky Way, it is almost natural to ask ourselves how many possible extraterrestrial civilizations are out there.
The problem is determined precisely by the incredible number of stars that populate our galaxy and trying to identify a possible alien civilization - or if they are trying to communicate with us in some way - is equivalent to looking for the proverbial needle in the haystack.
For this reason, some scientists come to the conclusion that makes more sense to look for "someone" who lives in the vicinity of our solar system, rather than dedicating ourselves to listening or observing stars of planetary systems existing in other galaxies which, even when they seem close, are actually millions of light years away and therefore communicating with aliens is decidedly unrealizable.
If we could observe such distant worlds, we could only hope to find archaeological traces of intelligent extraterrestrial civilizations that have been extinct for millions of years.
Given that it is worth dedicating ourselves to research in our galaxy, some scientists have suggested that a method to find traces of intelligent civilizations in the Milky Way could be to identify some anomalous "structures", so anomalous that cannot be explained with known astronomical processes.
In other words, it would be a matter of finding mega-scale technological structures that could indicate the imprint of an extraterrestrial civilization.
In 1964, Soviet astronomer Nikolai Kardasev classified extraterrestrial civilizations capable of such works as “type II.” Such civilizations would have technological capabilities capable of dwarfing our most advanced energy production systems. How? By capturing all the energy produced by their parent star!
In the early 1960s, physicist Freeman Dyson proposed the possibility of building a sort of "shell" around a star to capture much of its energy. To build such a shell, an amount of matter at least as large as the mass of Jupiter would be needed.
The megastructure would be composed of a system of orbiting satellites capable of harnessing solar energy and then transmitting it to a receiving station. According to Dyson, such a work would guarantee the long survival of a possible alien species, largely satisfying the growing energy needs of a technological civilization.
Dyson's fascinating intuition starts from the assumption that our civilization could one day build similar structures to meet the growing demand for energy, although he never described in detail how such a work could be achieved.
However, since then numerous projects have been proposed to build an artificial structure or series of structures to harness a star's energy. In some cases, it has even been hypothesized to enclose a star in a solid shell of matter, but this is only one of the less plausible variants.
It was Dyson, before Kardashev, who intuited that the search for evidence of the existence of similar structures could lead to the identification of an intelligent extraterrestrial civilization. The existence of such a system built around a star would alter the light emitted, as part of the light would be absorbed by the satellites.
If the attenuation of stellar energy is significant, it could be a clue to the existence of an alien technological megastructure. The problem is that a star shrouded in a cloud of cosmic dust would be very similar to a Dyson sphere.
The NASA image (below) captured with the Wide-field Infrared Survey Explorer may be an example.
The red object in the upper left is a star in the final stage of its life shrouded in dust. However, a survey carried out on 250 thousand infrared celestial sources reveals that almost 17 of these could be the signature of a possible Dyson Sphere, as Richard Carringan of Fermilab explains.
It is likely that an alien super-civilization will expand its colonization to nearby solar-type stars starting from the planetary system of origin. Theoretically, one wouldn't have to look too far after spotting a "Dyson Sphere."
Carringan imagines a grouping of stars colonized by a Type II civilization. This would be detected as an anomalous dark void in the galaxy's disk. These dark voids would be an indication of the "exploitation" of some stars.
In his reflections, Kardeschev also hypothesized the existence of type III civilizations, capable of exploiting the energy of an entire galaxy. But to date, any objective evidence of such technological exploitation is lacking, and it is therefore fair to say that Type III extraterrestrial civilizations either do not exist at all, or at least not yet.
Indeed, it could also be that the aliens simply have no motivation to develop such systems, or are not capable of it, or have budget problems!
