> there no large artificial structures or billboards anywhere we can see.
I half suspect the aliens who can construct structures large enough to see from lightyears away are by far most likely to be building Dyson Spheres around stars which make them significantly less likely to be seen rather than something we'd notice.
I half suspect the aliens who can construct structures large enough to see from lightyears away are by far most likely to be building Dyson Spheres around stars which make them significantly less likely to be seen rather than something we'd notice.