SETI, the Search for Extra Terrestrial Intelligence, is in the main the scanning of the heavens by radio telescopes for artificial radio signals emitted either deliberately or via leakage from technologically advanced extraterrestrial civilizations. The search has been on again, off again, but mainly on again for over 50 years, without, to date, any positive resolution (you can’t prove a negative, so the hunt continues, in case). Unfortunately, despite their ongoing failure to detect ETI, they rubbish those involved in other types of SETI – like UFOs and ‘ancient astronauts’.
Now some SETI scientists have spend a goodly proportion of their careers, maybe even their entire careers doing their search thing. What that tells me is that way down deep inside, at a scientific gut-feeling even philosophical level, they are convinced that one or more (probably more) advanced extraterrestrial civilizations, our equals or better (probably better) exist. That’s really great!
However, those same https://www.screendaily.com/news/signature-teams-with-red-rock-procam-on-trainee-scheme/5104354.article, when asked if that advanced extraterrestrial civilization(s) might have not only radio technology, but subluminal interstellar spaceflight abilities, well the eyebrows start heading north. To further ask them whether those advanced ET civilizations might have been, and might currently be now, on-site (i.e. – here around Planet Earth), well the eyebrows head up to the North Pole!
So, ET radio transmissions good; but ET visitations bad!
The nasty bit is that subluminal interstellar spaceflight violates no laws of physics; no laws of engineering. The time it takes to boldly go, seek out and explore, even colonize the galaxy our solar system is home to, is but a fraction of the age of our home galaxy. So, if radio ET exists, as SETI scientists must have faith in regarding that premise, then ET interstellar travel, exploration and colonization is equally plausible. SETI scientists can not logically dismiss that plausibility, especially if there’s a reasonable few advanced ET civilizations out there, and keeping in mind it only takes one such bolding going ET civilization to saturate our galaxy with their presence.
Now it needs to be pointed out and re-enforced again, and again, that a visitation to Planet Earth has bugger-all, zip, zilch to do with humans beings currently residing here or ET responding to our own radio leakage. You see that’s the SETI scientist’s argument why ET’s UFOs cannot be here. The signature of our existence here travels into the cosmos via EM radiation at light speed. Translated, our only plausible detectable EM signature is our radio/radar waves, which have only been outward bound for a century of so. So, the maximum radius our ET has to be, in order to know about us is 100 or so light years. But they then have to hop in their UFOs and travel through interstellar space to visit us, so the practical radius shrinks. The two constraints mean that ET would have to be close by, something probably against all the cosmic odds. But that argument is so flawed as to be laughable. This is an egocentric trip personified! ET can only be here because humans are here! Crap!
Humans here are irrelevant to ET being here. The reason Planet Earth gets a visit is that ET was roaming around the stellar neighbourhood doing their Captain Cook or Captain Kirk sticky-beak exploring thing, and our star, our Sun, Sol is one of the better candidates as a bio-friendly mainstream star and one having a home to a planetary system, ably detected by ET before-the-fact in the same manner as we in turn detect extra-solar planetary systems today. So Mr. Spock says to Captain ET, “Sir, Sol isn’t very far out of our way to take a look at the planetary regime, especially as how I’ve spectroscopically detected potential biological signatures of oxygen and methane in the atmosphere of one of the planets.” And so ET’s starship zeros in for a closer look, and our Mr. Spock exclaims, “Sir, hey wow, that third rock from Sol has a biosphere. Fascinating! Let’s catalogue that!”
Okay, so that conversation took place 300 million years ago. That interesting data point now pointed the way and reason for numerous follow-up visits, visits that might be continuing right through to the present day. The critical thing (apart from humans having nothing to do with ET’s initial visit) is that once that data-point was noted and logged it could in turn be communicated to other advanced ET’s out there. By now, over 300 million years or so, maybe more, maybe less, since first visit (hardly first contact) the whole bloody galaxy knows about Sol, her third rock outwards, and that biosphere!
Okay, having dismissed the improbable humans-are-responsible for ET being here non-argument, one need ask, without human influences, how often can we expect, on average, Captain ET and crew to show up?
The physicist Edward U. Condon, in his very own summary to the report of the team of investigators who looked into the UFO issue under a government (USAF) contract, never ruled out the possibility of extraterrestrial visitors, only that 10,000 years between visits was a minimum figure. That’s in the report that he gave the thumbs down to regarding the UFO ETH (extraterrestrial hypothesis). UFOs today – no; visits by ETI every 10,000 years was okay, enough time for them to get from there to here. On the other hand, noted astronomer and exobiologist (now termed an astrobiologist) Carl Sagan thought 100,000 years between visitations was a reasonable ballpark figure.
Now, depending on who’s calculations you accept, whether you’re an optimist or a pessimist, an interstellar boldly going ET civilization should have come across Planet Earth, on average, every 10,000 according to Condon , which is an order of magnitude more frequent that the 100,000 years given by Sagan . It has been pointed out, and it’s certainly true, that given the age of our Planet Earth, it would be Royal Flush times 1000 odds if a first visit just happened to have, well happened, in our lifetime. But, and here’s where the SETI scientist’s position becomes untenable, our planet, at 4.5 billions years of age (far younger than the age of our galaxy) should have received somewhere between 45,000 (Sagan) visits overall and 450,000 (Condon) visits overall by ET. Our SETI scientist would say that our “now” falls between the visitations -those gaps when ET is doing his interstellar boldly going thing somewhere else.
What the SETI scientist fails to come to terms with, fails to grasp, doesn’t quite have the smarts to understand and accept, is the once Planet Earth has been found, the first of those 45,000 or 450,000 expected visits, while certainly isn’t going to be in our “now”, the second, third, fourth, etc. visit will no longer reflect ‘on average’, something hinted at earlier.
I would have to assume, that ET, from the first visit, all those years ago (thousands, millions, even billions of years ago) wouldn’t have tagged Planet Earth as just another hunk of planetary debris, unworthy of any ongoing interest. From the get-go, Planet Earth would have showed unusual traits – an atmosphere, not so much; a lithosphere, not so much; a hydrosphere, yes indeed, very much; but especially a biosphere, very, very, very much.