Doomsday in Tunguska

On June 30, 1908, one of the biggest explosions in history rocked a forested region in Siberia. The theories of what happened are as widespread as the damage the fireball caused. Some speculate asteroids, space aliens and black holes were the culprit. Others focus on the earth, pinning the blame on everything from subterranean volcanoes to acclaimed physicist Nikola Tesla. Join the ongoing investigation over what caused one of the biggest explosions in history.