The big bang theory: Tunguska explosion of 1908

I always enjoy watching documentaries about mysterious and unexplained phenomena that occur on our planet. As such I like watching The Discovery Channel, National Geographic and The Smithsonian Channel as a way of learning about the oddities that have occurred over the history of Earth. One such phenomena is the Tunguska event of 1908. On June 30th, 1908 an enormous(and presumed aerial) blast, possibly the largest explosion in recorded history occurred in Tunguska, Russia, a remote and rugged wooded region located in extreme northern Russia. The explosion, which scientists estimate was one thousand(1000) times more powerful than than the Hiroshima A-bomb, scorched and flattened eighty million trees with a fireball and outwardly radiating shock wave that destroyed an area over eight hundred(800) square miles. Many theories abound as to what caused this colossal blast but one generally accepted scenario is that an asteroid or comet, entering Earth's atmosphere, exploded 5-10 kilometres above the ground which also explains why no crater was ever discovered around the blast area. The Tunguska region itself is so remote and the terrain so difficult that the first research team didn't reach the blast area until 1928, twenty years after the event itself.