On June 30,1908 the inhabitants of Nizhne-Karelinsk, a small village in central Siberia, saw a bluish white streak of fire cut vertically across the sky to the north-west. What began as a bright point of light lengthened over a period of ten minutes. When it reached the ground it shattered to form a monstrous cloud of black smoke. Seconds later there was a terrific roaring detonation that made many of the buildings tremble. Little had the villagers realized, they had witnessed the greatest natural disaster in the earth's recorded history. If the object had landed a few hours later, it could have destroyed St. Petersburg, London or New York. Even if it had landed in the sea, tidal waves might have destroyed whole coastal regions.
Some claim that what fell was no average meteor. Reports described how the ground had opened up to release a great pillar of fire and smoke which burned brighter than the sun. A man plowing in an open field felt his shirt burning on his back, and others described being badly sun burnt on one side of the face but not the other. Many people claimed to have been made temporarily deaf by the noise. Yet, shockingly, not a single person had been killed or seriously injured. Whatever the object was that produced the explosion had landed in one of the few places on earth where its catastrophic effect was minimized. The day the entire human race had escaped the greatest disaster in its history, and had not even been aware of it.
To this day, no one can answer what exactly the object that came down exactly was. After eight decades plus, extensive testing, we can only wonder what really happened that day in question.
Professor Alexis Zolotov (the leader of the 1959 expedition to Tunguska) calculated that, whatever the object was, it was about 130 feet in diameter, and exploded about three miles above the ground with a force of 40 megatons, 2,000 times greater then the atomic bomb dropped on Hiroshima.
Unexplained Mysteries: Tunguska Explosion