[userulluipeste]

Your math is sound, but I don't agree with all your data inputs. Specifically, that only (the engineered) radio signals would pick the attention of an alien civilization. (In fact, I think that Marconi's or most of the subsequent man generated signals, maybe with exception of nuclear detonations and such, were to faint to be picked up even from within the limits of our own planetary system.) The most obvious clue for presence of life, visible from far away, started with the Great Oxygenation Event. That enough should put Earth on anyone's map, and that happened 2 billions years ago. Achieving 100% of light speed is not possible within our current knowledge, but I assume that 20% should be for non life-carrier spacecraft, which at our galaxy's 200ly diameter gives us a cap of around 1'000 years of travel between most of the intra-galactic destinations. Even with a 10'000 technological head-start, a given civilization can devise a system to achieve galactic oversight. If there's indeed someone out there, with such a head-start, we should assume they're already watched our planet closely and maybe even getting a continuous track of our evolution.

As for "we’ve seen no evidence of anything resembling a Kardashev type civilization in the neighborhood", although you're right, it's hardly useful to think in this frame. The available means that we had so far for observing anything in far away space were and still are pretty limited, for even inert phenomena. I'd say that counting on that to spot something sentient, where things are actively engineered, which may as well include engineering for the appearance itself, is overly optimistic.

[lazide]

We’re just getting more and more hypothetical in a complete vacuum of real information though right?

If we’re trying to get something even somewhat defensible, there has to be some grounding on SOMETHING, or it’s all just fantasy.

If they spent 10k ly getting here, and the ungodly amount of energy and time it would take to do 20% of light speed over that distance, and they had since the great oxygenation event to notice us and get here (and have such a technological and energy advantage over us they were able to do it) - then why are they being seen randomly checking out military aircraft (not very smart or subtle it seems?) but never talk to anyone else? And show no other signs of existing?

Not impossible, but seems like a truly massive amount of energy and commitment of time over what far exceeds the timescales life as we know it works on to check out what could just be a puddle full of gooey algae for all they knew. And then potentially just sitting and watching for 100 million or a billion years.

At least seeing radio signals or a double flash from a nuke test means there is something like intelligent life?

[userulluipeste]

"We’re just getting more and more hypothetical in a complete vacuum of real information though right?"

Not really. Both of us were counting on current human knowledge, that our galaxy is this (light years) large, that the maximum speed is that of light and that an exponential amounts of energy is needed for each logarithmic increment of relativistic speed, that there is a working model for life based on what we call organic chemistry, that an atmosphere rich in a highly reactant element that is oxygen can not exist without something continuously producing it and what that could mean for an alien observer, all because, in the slim chance that we are the ones with technological head-start, that should serve as base ingredients for thinking about our long-term future external policy. I'm thinking if we are to become Kardashev type II (and above) civilization, what ought to be the best approach in dealing with an evolving galaxy? But yes, there are also aspects which are hard to think of now in more than hypothetical terms, like what would mean in practical terms to have access to (at least) a star's amount of energy and what it would be worth spending it on. To me, "to check out what could just be a puddle full of gooey algae" looks like a very important objective, and finding something underwhelming should be the desired result, safety wise.