What tech are you thinking of? Remember it's not just the distance but the speed. How would we course correct a relativistic object once the target was close enough to estimate the desired change?
Well, you do that with the same kind of engines that propels them at relativistic speed. Anyway, it's not a target and forget situation, because relativistic ships get a (relatively) lot of drag in space.
> Well, you do that with the same kind of engines that propels them at relativistic speed.
Which don't exist except as fantasy, and even most of the fantasy ones wouldn't work for targeting adjustments.
To me the most likely back of the napkin answer to the Fermi paradox is that aliens are elsewhere in time. The Milky Way galaxy is about 100,000 light years across but about 13.5 billion years old. So it’s like 135,000x deeper in the time direction than the distance direction. We’re in the light cones of all the stars we can see, and as far as we know, we can’t get out of them. If a civilization ended even 100 years…
This is the L constant of the Drake equation. Probably the hardest to find a value for until we've actually discovered other intelligent life or remains of such. The confounding part of it is that we can only guess at things that may end a civilization so completely that it will never recover. Things like the so called Great Filters, natural extinctions like impact events or gamma ray bursts, or other more speculative things that prevent expansion. The tricky part is that our existence seems to fly in the face of such events so far, is that mere luck or do all forms of intelligent life have enough sense to navigate around these problems? The last and most paradox defining part of the problem is that even if the tiniest fraction of civilizations can evade these filters then they should eventually be everywhere in the galaxy. Assuming the Copernican principle that we are not at a special place in the universe or time then there should have already been ample opportunity for such civilizations to develop and hence Fermi's question "Where is everybody?".
Civilizations are only detectable for a short period of time. Once they understand physics, they no longer need radio waves or Dyson spheres or to travel through what we call spacetime.
Why wouldn't they need megastructures and travel once they understood enough physics?
Space and time may be emergent, we don't know, all we do know is that our current model of physics is missing something. Quantum Gravity for example and We don't know what happens inside a black hole either.
Maybe I lack imagination, but I can only see as a constant selective pressure leading to a specie with interstellar space plans (we still haven't) the biped-on land evolution that took place on earth, and I can only see earth-like planet hosting avanced life.
To me the most likely back of the napkin answer to the Fermi paradox is that aliens are elsewhere in time. The Milky Way galaxy is about 100,000 light years across but about 13.5 billion years old. So it’s like 135,000x deeper in the time direction than the distance direction. We’re in the light cones of all the stars we can see, and as far as we know, we can’t get out of them. If a civilization ended even 100 years…
That and the fact that civilizations probably only broadcast EM radiation out into the void for a short period of time before they start getting into energy efficiency and switch over to more efficient communication technologies.
Even with a dark forest, one would have territorial threats announced to the rest of the world.
Examples:
Blow a star up and make it project a unique territorial mark.
Make a diamond lighttower, beaming threatening messages to probable green zones, to lure unsuspecting enemies in.