The Tsar Bomba, detonated by the Soviet Union in 1961, is the most powerful nuclear bomb ever tested. It had a yield of about 50 megatons, making it approximately 3,000 times more powerful than the bomb dropped on Hiroshima. The explosion created a fireball visible from 1,000 kilometers away, and its shockwave circled the Earth three times. The bomb was so powerful that it was scaled down from its original design to reduce fallout.