Some estimates put it at 100 kilotons, which would be five times more powerful than Fat Man, the bomb dropped on Nagasaki by the US in 1945 and which killed 70,000 people instantly. But it still pales in comparison to the largest man-made explosion ever on Earth - the Soviet Union's Tsar Bomba - King of Bombs - detonated in 1961 in the height of the nuclear arms race. That hydrogen bomb unleashed a staggering power of 50,000 kilotons, or 50 megatons.