The Tunguska Event is a modern mystery, the type that makes the stuff of science fiction even. The event happened a hundred years ago today, and scientists still talk about it.

So what is the Tunguska Event exactly? Strictly speaking, it was a huge explosion that happened in Russia, and whose effect was felt through Eurasia. There were even reports that people in Asia were able to read newspapers outdoors as late as midnight from the light of the explosion.

Eyewitness accounts confirm that the explosion came from the sky, when a great light split the sky in two. It was a meteor (dun-dun-dunnnn). It may not have touched the ground, but the explosion was so great that eighty million trees were knocked over (see the picture above), and the trees at ground zero were stripped of their bark.

The meteor exploded several thousand feet above the ground, but nevertheless, 40 miles away from the explosion, the heat was enough to make a man feel as if his shirt was on fire. Scientists estimate that the force of the explosion may have been equivalent to as much as 30 megatons, and could easily level a town.

So should we all start living in fallout shelters now? Well, not unless you're really, really paranoid about it. Scientists believe that a Tunguska-sized impact will only enter the atmosphere once every 300 years. And even if it does hit, what are the chances that it'll fall just above your head?