According to AI, an equivalent would be roughly when Google maps shows you 10mi/20km reference scale.
Turning off the labels, aliens would probably assume that the world is naturally full of green stuff that is dealing with some strange grey infestation.
> aliens would probably assume that the world is naturally full of green stuff that is dealing with some strange grey infestation.
I think they would draw the correct conclusion, actually. I know it's popular to compare humans to mold or cancer or whatever these days, but this kind of thing is both unrealistic and insulting to the aliens, who by the definition of the scenario are at least as smart as we are, quite probably more.
Our nighttime view of the planet has dramatically changed in the past 100 years and is increasing. They would instantly see us using electricity and could possibly see our satellites.
I wonder if there are conscious ants and similar small infrastructure-builders running around on the ground with the exact same ideas. "Of course the big-beings-in-the-sky recognize our tracks here are major roads and agricultural areas, they must understand we're intelligent"
Heh, your flip remark leads to an interesting observation: I think the most obvious signature of "abstract intelligence" is suboptimality. An alien would look at an agricultural grid and wonder, what possible natural process would divide something into squares rather than hexagons? Even without knowing what they are or how they form, it's hard to imagine anything that would prefer such a high energy configuration. Such stupidity implies a system oddly bounded in its ability to optimize, which implies a feeble biological brain trying to do something "on purpose" rather than a natural process.
Turning off the labels, aliens would probably assume that the world is naturally full of green stuff that is dealing with some strange grey infestation.