I found this video: https://youtu.be/mr7FXvTSYpA, where some hypotheses are formulated about the characteristics that should define a civilization much more advanced than ours (the human civilization); They are presenting three grades of evolution, and they categorize them based on the level of expertise in the use of energy, and the amount of it that a civilization is capable of manage and take profit of.
With all due respect, I think that this projection about the future of possible existing civilizations seems too simplistic, I will explain myself:
Thinking that the next evolutionary level is characterized by a greater ability in generating or consuming energy is a very linear thought. This is like, in ancient times, humankind usually thought that the cause for a new nature phenomena was due to some new Gods, since the existing ones were already dealing with some other things; It’s like imagining that cars may go faster, just by putting larger and larger engines, without changing its technology in radical, completely new ways.
I’d rather tend to think (I don’t like the word “believe”), because of the knowledge we humans have, that in the case of a more advanced civilization, a really big evolutionary leap must have been happened; It must have been so huge that we can’t even reach to imagine how it could have been.
They must have biologically changed so much, that maybe they are not living beings as we know them now. Perhaps, once you reach a critical point for a particular knowledge, you choose to exist in another different reality (no longer in this universe), which may be just as the initial step to reach another “complete” existence (in lack of a better word). Perhaps that is the reason why it is so difficult to find some other civilisations out there. Because simply, they are no longer here in this actual universe (or the actual part we know about it).
And if they’re still in, it’s maybe in a way so unimaginably different, that we can not perceive it, something similar (but more rich and complex), to the ‘n-dimensional’ universe that appears in many theories and movies.
The essence of existence is maybe so different compared to that we know (“only” the universe), that for those civilizations we are absolutely and infinitely insignificant, much more than the way we compare ourselves to bacterias.
And although our knowledge of existence is, for the time being, very limited, I hope that someday we could be capable and ready to learn more about the one and only truth about existence. I hope that this could become true, due tho the big jump we made in the last 200 years thanks to the scientific and technological progress.