From one of my comments at the second link:e "The key to this kind of endeavor is to forget about the specific structures that might exist (e.g. the various variations on Dyson spheres) and think about what we would actually see — surfaces. Surface [and illumination] engineering has some very specific but universal goals, especially involving thermal and optical efficiency (for heat radiation, illumination, reflection, etc.)The universal quest for efficiency should lead to some very blatant spectroscopic si ...