I remember when I first started blogging, over six years ago, it was considered quite controversial to state that being hit by extraterrestrial objects was a legitimate concern, and one in which we should invest resources to prevent. But over the past few years, evidence continues to accumulate that there have been significant events within historical times that, had the occurred today, could cause millions of casualties. For example, some researchers are now quite confident that if God destroyed Sodom and Gomorrah, He did it with an asteroid.
On the other hand, a half-mile-wide object would make a hell of a bang that should be pretty obvious from orbit today, so one has to be a little skeptical. I’d like to see how they arrived at that diameter.