technology or civilization doesn't require our recognition, it exists or not regardless.
Our combustion-based technology is rather a fluke of having a huge amount of one-time crude oil reserves. Other planets won't necessarily have that.
Our combustion-based technology is rather a fluke of having a huge amount of one-time crude oil reserves. Other planets won't necessarily have that.
As for combustion, indeed, other planets may not have it. So how do you propose that they would start to develop a technology which would lead to building spaceships?
Some stories very much are about aliens who use tech or have civilizations that are very very alien to us.