On June 30, 1908, a massive explosion tore through the air above a remote forest in Siberia, Russia. This was the Tunguska Event, and it remains the largest impact event on Earth in recorded history. Witnesses described a fireball brighter than the sun trailing across the sky, followed by a blast so powerful it knocked people off their feet 40 miles away. The heat was so intense that one man felt as if his shirt was on fire. Here is the mind-blowing part: there was no impact crater. Scientists b