Free Astronomy Magazine May-June 2024

28 MAY-JUNE 2024 ASTRO PUBLISHING on our planet: we find cultures, to- tally uninterested in what exists be- yond what the naked eye shows, coexisting with cultures that launch themselves into scientific endeavors beyond the limits of the most dar- ing science fiction. Even if there were a “confederation” of particu- larly advanced ETCs, it would be enough for just one of them, in any given era, to decide to act against common values, and the zoo-level ETCs would be aware of the exis- tence of the others. It should be noted that the risk of violating hegemony increases with the num- ber of civilizations involved, so if there were a multitude we would perhaps already be aware of it. Fur- thermore, if the “confederate” ETCs were numerous enough to commu- nicate with each other in a reason- able time, even more numerous would probably be those of zoo- level which, however backward, would nevertheless be able to freely send radio signals into space. We Earthlings have been doing this for several decades: around twenty di- rected messages have been sent so far towards relatively nearby stars and towards the globular cluster M13. The first messages already ar- rived at their destination (Epsilon Eridani and Tau Ceti) in the second half of the 1990s; others are about to arrive (Gliese 581 in 2029 and 2030, Luyten's Star in 2030). If many other ETCs of our level or a little more advanced had acted like us in the last 50,000-100,000 years and continued to do so, the Milky Way would be permeated with arti- ficial radio signals, and although not intentionally sent towards the Earth, they could accidentally speed in our direction. However, this “by- product” of the zoo hypothesis does not seem to be a reality, so much so that from 1960 to today none of the copious SETI experiments have recorded signals that cannot be at- WE DON’T LIKE THE TERM “INVASION”. WE PREFER “GALAXY GENTRIFICATION.” SON, IT’S TIME YOU KNEW THE TRUTH... YOU WERE ABDUCTED. EARTH’S FINAL ALIEN ABDUCTION NOW I’LL JUST TAKE THIS PROBE... IT’S FAKE! IT’S DEMONS! IT’S OUR MILITARY! NOPE! NOT READY YET! tributed to terrestrial technologies or natural sources. While avoiding any radio contact, other revealing clues to the presence of ETCs or Extraterrestrial Intelli- gences (ETIs) could however spread into space, as recalled by Crawford and Schulze-Makuch in their article: “Even if they can hide evidence of their technology (space probes, com- munications traffic and so forth), hiding the large number of inhab- ited planets in the background im- plied by such a scenario would probably prove challenging (unless they are able to bring an astonish- ingly high level of technical sophis- tication to the task). In any case, advanced technological civilizations may find it difficult to hide the ther- modynamic consequences of waste heat production, which is indeed the basis of some current technosigna- ture searches. Moreover, any space- faring civilization is likely to gen- erate a great deal of space debris, and the greater the number of ETIs that have existed in the history of the Galaxy the greater the quantity of debris that will drift into the Solar System, where a determined search may discover evidence for it.” To date, the reality is that no tech- nosignature (or even biosignature) of any kind has been found outside our terrestrial context. All this rein- forces the dominant opinion, ac- cording to which if ETCs exist in our galaxy, they must be extremely rare and unaware of the existence of the others. The Fermi paradox still awaits a consistent answer... !