My understanding is there is not a such thing and humans, if we want to go interstellar, are going to have to accept that those humans and probably all their offapring are gone forever.

> there is not a such thing

Yet. Or, as the good science communicators like to say, "as far as we know / as far as our current understanding goes". Looking back in history, almost everything we're taking for granted today was both dreamed by the pas era's "futurists" and deemed impossible by their skeptics. Only time (hah!) will tell, I guess.