It is possible that we are looking for the wrong traces of extraterrestrial civilizations. According to a study published recently by Oxford astrophysicist Brian C. Lacki, the mistake has been in looking for active technological signatures. That is, signals derived from extraterrestrial technologies that have been emitted directly. These signals are lost over time. On the other hand, technological signatures that passively act on the light of a star are easier to detect. And the best thing is that, if you can’t find them, you could always search in the middle of the lunar regolith. This all sounds very crazy, but it actually makes sense.
Active or passive signatures? That’s the question. Traditionally, search projects for extraterrestrial civilizations, like SETIhave focused on the detection of possible radio signals coming from their technologies. These are not signals emitted on purpose so that we can find them, but rather the result of their own technological activity.
The problem, according to Lacki in his study, is that, if they have followed an evolution similar to ours, they may not be broadcasting on the radio for more than 100 years. We ourselves have been replacing emissions in this range with fiber optics or satellites with directed emissions and very little “noise” that can reach “intergalactic gossip.” What leads us to think that they continue century after century using the same technologies? They may continue to emit, but no longer in radio waves that disperse into space. The Oxford astrophysicist proposes changing this position by searching for passive technosignatures. That is, signatures derived from the interaction of smart technologies with starlight.
three types. There are three types of passive technosignatures: obscuring, flashing and diffusing. The former act in a similar way to an exoplanet passing in front of its star. When a large object, such as an artificial satellite, passes in front of a star, it temporarily obscures it. This could be confused with an exoplanetbut the idea is to look for concealments with unconventional shapes, that do not resemble anything known.
In the case of flashing signatures, they would be those produced by devices with mirrors aimed at concentrating the star’s light. As if they had their own solar plants. At some point, these types of mirrors could generate flares observable from Earth. Finally, the diffusion signatures would spread the light in all directions, so that a fainter change would be observed, in the form of a color modification in the light spectrum.
What if they are no longer there? If it is already difficult to find other intelligent civilizations, it would be even more difficult to find one that is contemporary with ours. We may simply find technosignatures of a civilization that has already died. In that case, or even if the technologies have simply been abandoned for another reason, there would no longer be intelligent beings in charge of maintaining the devices, so their orbit would end up shifting and they could collide with each other. If this happens, it is possible that very small fragments will be generated, which this scientist calls technograins.
They are so small that the star’s gravity is not able to attract them any more than the stellar winds push them away. Therefore, they would end up swept away from their neighborhood and become a cloud of dust that our solar system could eventually encounter on its journey through the galaxy.
The Moon comes into play. If all of the above occurs, Lacki considers that it could be that some of that dust settles on the Moon, where there is no wind nor are there geological processes that alter the surface, so it could remain for a long time. Therefore, for him, one way to look for technosignatures would be to inspect the lunar regolithlooking for dust that appears to have a technological origin. That, perhaps, could lead us to some intelligent civilization that has gone unnoticed by us.
In short, according to the curious perception of this scientist, when trips to the Moon become more common than anecdotal, we could have an easier time finding technosignatures. Of course, for this, fewer telescopes and more sieves.
Images | Leo Visions (Unsplash)
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