"On a long enough timeline, the survival rate for everyone drops to zero." -Tyler Durden This is essentially the message of [link=http://blogs.discovermagazine.com/badastronomy/]Bad Astronomer[/link] Phil Plait's wonderful book "Death from the Skies! The Science Behind the End of the World." The book came out in 2008, the paperback, with a slightly changed title, perhaps because of slow sales, in 2009, but I didn't find this little gem until a few months ago. I advise you to get hold of a copy now. If you're looking for a cheerful, matter of fact discussion of all manner of potentially cataclysmic and human-life ending astronomical events, and why wouldn't you be, this is the book for you. Each chapter is devoted to a different potential catastrophe, ranging from nearby supernovae (not likely) to catastrophic asteroid impacts (very likely on the time frame of human civilization) to gamma ray bursts and wandering black holes, invasion by intelligent extraterrestrial life and finally the end of the solar system and the ultimate death of the universe on time scales when even protons may start to decay. Among the interesting arguments Plait makes is that developing the technology now to change the course of dangerous asteroids would be money well spent, perhaps more useful for us, in terms of cost-benefit, than heavy spending on anti-terrorism/homeland security. I'm not qualified to judge the likelihood Plait suggests for a Tuguska-size meteoroid airburst over a large metropolitan area, but I think preparation for diverting asteroids would be a hugely fun way to spend NASA dollars.