Where are all the galactic super-civilisations, and why can’t we see any?
Basically, the universe is old enough and vast enough that, even with the delays we’re talking about for light and other signals to reach Earth (let alone objects), we still should be able to detect the energy signatures of advanced, potentially spacefaring, civilisations somewhere. Except we can’t. And yes, we sure are looking.
This is part of something called the Fermi paradox, incidentally, which is the disconnect between how many stars in the universe should be able to support intelligent life (lots), versus how many we’ve actually managed to confirm to do so (one).
The hopeful answers to the Fermi paradox are things like “we aren’t looking in the right place/for the right thing” and “they’re hiding from us a la the Prime Directive”. The less encouraging ones are things like “we really are alone” and “spacesharks“…