On the 30th June 1908 an explosion with the combined energy of 2000 Hiroshima bombs rocked the region of Tunguska in Central Siberia and felled over 6,000 square km of trees. The explosion could be heard from as far as 1,000km away. Eye witnesses saw a long object fall from the sky which was illuminated in a blue-white light. A 20km high column of light was followed by a black-mushroom shaped cloud. It has been reported that for the next three nights it was so bright across all of Europe that you could read a newspaper outdoors.