There is a fascinating PBS Space Time video[1] about black holes that questions the very existence of whatever is "inside" a black hole.
They point out that as you approach a black hole, your proper time is advancing slower and slower when compared to an observer located far away from the black hole (like us, on Earth). That means that from the point of view of this far observer, nothing happens inside a black hole until an infinite amount of time. In other words, what is inside a black hole is separated from us not by a space-like frontier, but a time-like one. Events behind the event horizon are postponed to "the end of times".
Does it even make sense to say that those events exist, then? Are they any more real than fairy tales or mathematical equations? If not, we can make any speculation we want, including the existence of alien civilizations.
They point out that as you approach a black hole, your proper time is advancing slower and slower when compared to an observer located far away from the black hole (like us, on Earth). That means that from the point of view of this far observer, nothing happens inside a black hole until an infinite amount of time. In other words, what is inside a black hole is separated from us not by a space-like frontier, but a time-like one. Events behind the event horizon are postponed to "the end of times".
Does it even make sense to say that those events exist, then? Are they any more real than fairy tales or mathematical equations? If not, we can make any speculation we want, including the existence of alien civilizations.
1. https://www.youtube.com/watch?v=vNaEBbFbvcY