Oh that's excellent! I hadn't read up on that before. I will do so now. I've heard it used before, usually in context of, "Why is the Earth habitable?" "Because it's in a habitable zone". - and really, that's the only decent answer, even if not fully satisfying tongue emoticon [1]#yay In Research-Mode - thank you smile emoticon References Visible links 1. https://www.facebook.com/hashtag/yay?hc_location=ufi