Question: I suppose it’s implicitly assumed that FTL travel is physically impossible even for extremely advanced civilizations, are there reasons to feel relatively secure in our belief that aliens will not have discovered some sort of exotic or unknown physics that allows them to achieve that?
Question: I suppose it’s implicitly assumed that FTL travel is physically impossible even for extremely advanced civilizations, are there reasons to feel relatively secure in our belief that aliens will not have discovered some sort of exotic or unknown physics that allows them to achieve that?
Yes, I assume it. If not true, they must be here.
No.
Exactly. FTL is allowed even by relativistic mechanics (who know what allows quantum gravity?), although time travel paradoxes ensue.