RT Nick Szabo (@NickSzabo4)Radically concentrating matter like that would mean either (a) they aren't accessing most of their stars' energy, or (b) the smaller surfaces are correspondingly hotter and brighter. If they are using most of their galaxies' stellar energies the waste heat signature will have the same watts/square meter of waste heat either way over their overall region, whether from a large total area of dim surfaces or a small total area of bright surfaces. If they are radiating fewer watts then ...