>> We really can't rule anything out, as their motivations, technologies, and requirements are not human. But the quest isn't to detect all alien life, just an

>> We really can't rule anything out, as their motivations, technologies, and requirements are not human. But the quest isn't to detect all alien life, just any. The really alien stuff, the stuff we cannot comprehend, we cannot detect. So we start with the sorts of things we might be able to detect. By doing so we have already made all sorts of assumptions and that is ok because it is the only way forwards. Yes, we might miss a civilization that does not live on a planet with an atmosphere, but that doesn't mean we shouldn't keep looking at atmosphere signatures.