Tsar Bomba, or the King of Bombs, was the largest nuclear bomb ever detonated. It produces an explosion equivalent to 50 megatons of TNT. By comparison, the atomic bomb dropped on Hiroshima was equivalent to 13 kilotons of TNT. That means that Tsar Bomba, called "Big Ivan" in Russia, was almost 4,000 times more powerful than the Hiroshima bomb. It was a test explosion, detonated on 30 October 1961, in Novaya Zemlya, an Arctic archipelago. The size of the fireball was 4.6 km (2.8 mi) across, and would have destroyed everything in a 26.3 kilometer (16.3 mi) radius. "Big Ivan" left a massive crater which is observable today by satellite.
The Tsar Bomba was tested during a time of Cold War tension, when the United States was developing its ICBM missile systems and engaging in the Operation Dominic nuclear tests on the Pacific islands. The USSR needed to demonstrate its might, and originally planned a 100 megaton nuclear test. It was scaled back to 50 megatons to minimize fallout because it was calculated that winds would blow the dust cloud across northern Russia. The effects were astonishing.
Tsar Bomba was a huge bomb, about the size of a car. The USSR's heaviest carrier plane had to be modified in order to carry it. The bomb was outfitted with a special slow parachute, to give the plane time to travel a substantial distance away before the bomb was detonated. When the bomb exploded, the fireball was so tall that it touched the part of the sky where the plane was upon release. The mushroom cloud it produced was 60 km (37 mi) tall, almost seven times higher than Mount Everest, and 30-40 km wide.
If it were used in an actual war, Tsar Bomba would have been considered highly inefficient, but psychologically intimidating. At the time, USSR missile guidance systems were not at all perfect, and could miss their target by as much as 10 km (6.2 mi). The USSR government wanted a weapon that could destroy a city entirely even if it landed several miles away from it. That weapon was the Tsar Bomba.