Image: Carolina Ibáñez de Aldecoa Marín (@carwaro).
Experimental science bases one of its pillars on evidence. Some of this evidence is easy to obtain and we can even be first-rate witnesses of it. At other times this is not possible.
Such is the case of the microscopic world (cell biology, atomic and molecular physics, quantum, etc.) and the macroscopic (stars, galaxies, quasars, black holes, for example). In these scenarios we can no longer “see” directly with our own eyes. Certainly, we can resort to instruments that again adapt the light to our retinas (with microscopes and telescopes mainly). However, we still cannot “see”, for example, the cholesterol molecules in a blood test. Nor can we observe possible oceans on distant planets in our own galaxy.
The only tool available to science in these cases is the use of so-called “markers”. A marker is an indirect but unequivocal witness to the presence of something or the occurrence of a fact .
For example, the presence of GHC in the urine is a marker for pregnancy, even though this hormone is too small to be seen directly. In the biomedical field we would be talking about a “biomarker”. In astrophysics, the light spectrum of a star can be used as a marker to determine the composition of the atmosphere of an exoplanet orbiting the first.
Logically, we have the same (null) options of admiring that distant world for ourselves (not even with the most powerful of telescopes). Exoplanet detection itself also makes use of the signature left by a star’s light evolution over time. The well-known “transit methods” and “radial velocity” are therefore “astromarkers” of the presence of new worlds.
The SETI (Search for extraterrestrial intelligence) discipline also defines its own markers: techno-markers. These are “snitches” for the existence of technologically advanced alien civilizations.
The 21 centimeter line for hydrogen is perhaps the best known (used, for example, in Carl Sagan’s fantastic novel “Contact”). Another one proposed in 2015 by Jason T. Wright (from NASA’s Nexus for Exoplanet System Science Institute), is related to the pattern of light that we would observe if artificial megastructures (such as Dyson spheres) eclipse their own star.
And the most recent technomarker of all is the one presented by Dr. Socas (from the Instituto de Astrofísica de Canarias) in his scientific article “Possible Photometric Signatures of Moderately Advanced Civilizations: The Clarke Exobelt”.
According to Socas, it would be possible to appreciate measurable variations in the light curve of a star, when it is transited by an exoplanet that was surrounded by an entourage of artificial satellites. This set of geostationary devices is what is known as “Clarke’s belt” (defined by the great British popularizer and writer).
In addition, another point in favor of this techno-marker is that it implies “active maintenance” by the host planet of the belt. Otherwise, the artificial satellites would end up falling on the planet or colliding with each other, as has already happened in our case. Earth already has its own (and growing) Clarke belt.
Who knows if some extraterrestrial cilivization is already “marking” us as a “candidate planet to host intelligent life”.
Dr. Alberto Corbi Bellot. Higher School of Engineering and Technology (ESIT) – International University of La Rioja (UNIR) Institute for Educational Research, Innovation and Technology (Unir iTED).
