<human>:  Why did they call the first Soviet nuclear test ‘Tsar Bomba’?
<bot>: The bomb was named after the Russian Tsar Nicholas II, who was assassinated in 1918. The bomb was a hydrogen bomb, and it was the largest ever created by humans. It was tested in 1961 at Novaya Zemlya, and it had a yield of 50 megatons, or 50 million tons of TNT. It was the most powerful weapon ever detonated.