yo balkans and other things that might generate heat signature, but the argument is there maybe veryspecific heat signature of civilization, of technological life. this is really a long reach, okay? the interesting thing about it is that if we take this question really seriously, it's actually the kind of thing we should be doing. we should be thinking about. to come back to your earlier question about how we going to evaluate our true significant universe, well, it's going to be a technological achievement rather than a philosophical one i think. >> host: when you conclude the book was sort of a subtle distinction between the uniqueness and significance, could you explain this sort of, the line you're walking a at the end we need to leaders what to think about all of this? >> guest: yeah. so i think i'm pretty honest in the book about saying, look, this is my personal take. i've tried to pull together all these different threads, trying to express where do i get to, what do i think beyond certain -- and part of what helps me get to the conclusion is that i often talk about how life