28 Jun
2015
28 Jun
'15
3:21 a.m.
0. "... With no evidence of intelligent life other than ourselves, it appears that the process of starting with a star and ending with "advanced explosive lasting life" must be unlikely. This implies that at least one step in this process must be improbable." - https://en.wikipedia.org/wiki/Great_Filter
Hanson/Great_Filter is an excellent reference. So is https://en.wikipedia.org/wiki/Rare_Earth_hypothesis --dan