In Siberia in 1908, a huge explosion came out of nowhere

Over 100 years after the most powerful explosion in documented history, researchers are still trying to figure out exactly what happened. By Melissa Hogenboom.
Read more: http://www.bbc.com/earth/story/20160706-in-siberia-in-1908-a-huge-explosion-came-out-of-nowhere?source=Snapzu