Perhaps these Dyson-sphere-building civilizations only live around red dwarves (because that's where they originated). Red dwarves are dim and hard to detect, e

Perhaps these Dyson-sphere-building civilizations only live around red dwarves (because that's where they originated). Red dwarves are dim and hard to detect, especially when they are far away. A red dwarf with a dyson sphere around it would be even harder to detect.