Civilization-crippling asteroids. A pretty scary concept of course, but a far-fetched one.

At least that’s what all of us—even the most ardent sci-fi fans among us—would like to think.

               Don’t be so sure. A research report published in the science journal Nature now suggests that asteroids of up to 20 km wide could presently strike Earth—at a rate of one every decade or two.

               Such impacts would be comparable to the one that hit the Russian city of Chelyabinsk this February. That strike released the equivalent of 500,000 tons of TNT of energy—causing injuries to 1,000 people and substantial damage.

               Hopefully, scientists will have devised an early-warning detection system by the time the next big space-chunk hits us.
But if not…just another reason to take an umbrella outside.