Individually doing atmospheric analysis for every planet in the galaxy is probably an impossible task for a civilisation confined to a single solar system. Listening for signals is something our civilisation already does. If we discover radio signals from a primitive civilisation in the next star system over there’s a non-zero chance we’d panic and try to wipe them out.
That’s the risk that dark forest theory is talking about. Maybe the threat comes from a civilisation dedicated to wiping out intelligent life that just hasn’t found you yet, maybe it just comes from your nearest neighbor. Maybe there’s no threat at all. The risk of interplanetary war is still too great to turn on a light in the forest and risk a bullet from the dark.
And while knowing this, why do we still not choose to just observe and be as quiet/ non existant as possible?
Unless they have been actively and vigorously scouting for us with FTL travel, our earliest radio transmissions, even if we assume they’re somehow still recognizable and not totally lost in the background noise of space, have only made it about 126 light years or so from earth (and honestly our very earliest ones probably wouldn’t be recognizable from very far at all, Marconi’s radio was of course pretty crude, it was our first time playing with radios, so we can probably chop a good 20+ light-years off of that easily if we’re being realistic)
Now that encompasses some 60,000 or so stars, which is a tiny speck of the observable universe, and depending on how you fill out the Drake equation that could be a whole lot of aliens out there listening, or literally no one. And only about half of them, assuming no FTL travel or communication, would have had a chance to get a response to us by now (if they even wanted to) since their response would have to travel at or below C.
If they’re in the Milky Way or nearby intergalactic space and have bothered to point instruments at us that are far beyond the capabilities we have on earth now today within the last 300,000 years, they may know that homo sapiens exist, but they’d need to be within 3000 light years to know that we entered the bronze age, and within about 200 to know that we’ve even started playing with electricity (and counting on them looking specifically at us is a real long-shot)
Parts of the Andromeda galaxy, at best, is maybe aware that Australopithecus evolved. Any further out and no one has any clue that anything really resembling humans at all is here.
Now that sort of isolation does give us a bit of security in case there is a xenocidal race that would like to wipe us out somewhere in the universe, unless we’re very unlucky we probably have a long time before we have to worry about them even knowing we’re here, and at least that long again until they can do anything about it (unless they do have FTL travel) so probably not something we actually need to be concerned about, again unless we get really unlucky the sun dying in a couple billion years is probably a more pressing concern.
I think it’s likely we’re the first and oldest advanced civilization in the universe, which means we’ll likely always have a technological advantage to the tune of 100+ thousand years head start. It’s entirely plausible that we are the future’s xenocidal species.
But why would evil aliens wait for intelligence to evolve and be a potential threat when they could just destroy every biosphere before life can produce intelligence?
We can’t really pretend to understand the thoughts or motivations of aliens, after all, they are completely alien to us.
We can’t understand their culture, but we can understand their reasoning. Assuming their technology doesn’t break physics and they evolved via natural selection then they will have had the same universal pressures shaping them that we did. Namely that one individual can’t know and do everything so at least some cooperation is necessary to reach space and they will use math and logic to solve technical problems.
Starting with the assumptions that they use math and aren’t suicidal you can eliminate a lot of the proposed fermi paradox solutions because they propose in some form or another that an advanced race that’s also stupid just appeared fully formed. Or the whole race suddenly gets a case of the stupids.
I mean, we’re talking from the position of a race where a whole lot of us have evolved to have a serious case of the stupids and in a frightening number of cases we’ve put some of the biggest stupids in charge of running the show.
Looking at ourselves, it’s not too hard to imagine a race of religious zealots who view other intelligent life an an abomination to be destroyed but are fine leaving lesser life forms alone.
A good point, and the fact that we dont see evidence of solarsystems being wiped out when we look into space makes me hopefull that super high intellegence is fundamentaly incompatible with agression