I would think radio waves to be quite sensible here compared to other-dimensional ghost-aliens roaming the skies. Given radio waves being the primary marker fo

I would think radio waves to be quite sensible here compared to other-dimensional ghost-aliens roaming the skies. Given radio waves being the primary marker for our own existence and looking at the distance those artificial signals already travelled compared to the size of the cosmos, I believe not having any form of indication for intelligent or any alien life is a surprise.