> If it didn't have a physical presence, like it was folding space or something and traveling in a bubble, then it seems very, very strange that an advanced civ

> If it didn't have a physical presence, like it was folding space or something and traveling in a bubble, then it seems very, very strange that an advanced civilization can fold space to effectively travel without any impact on the world, but let the EM radiation that is light/heat leak out. I'm not sure why you're speculating on unknowable alien motives. The only thing that matters is agreeing on whether there is something unusual here that requires an explanation. If it turns out to be aliens, then you can speculate on their motives.