Quote Originally Posted by Dannon Oneironaut View Post
A quote from Wikipedia:

The Tunguska event was a large explosion, possibly caused by a meteoroid or comet, in what is now Krasnoyarsk Krai, Russia in June 1908. Night skies as far away as London were markedly brighter for several evenings. Unsupported theories regarding the event include the impact of a miniature black hole or large body of antimatter, ball lightning, a test by Nikola Tesla of the apparatus at Wardenclyffe Tower, and a UFO crash.[12][43][44] Another theory is that the explosion was caused by a piece of Biela's Comet from 1883.[45]
So basically, no one knows what cause the Tunguska event.