Nuclear weapons have shaped global politics for decades, but their destructive power is almost impossible to comprehend. From the bomb that devastated Hiroshima in 1945 to the Soviet Union’s abandoned plan for a 100 megaton superweapon, each step in nuclear development pushed humanity closer to unimaginable destruction.Here’s a look at six of the most powerful nuclear bombs ever built or tested, ranked from smallest to largest.Hiroshima: The Bomb That Changed HistoryThe first nuclear weapon used in warfare remains one of the deadliest.On August 6, 1945, the United States dropped “Little Boy” over Hiroshima during World War II. The uranium bomb had a yield of approximately 15 kilotons and instantly changed the course of history.The explosion killed an estimated 80,000 people, while tens of thousands more later suffered from radiation exposure and long term health complications.Temperatures near the blast zone reportedly reached around 300,000 degrees Celsius (540,000 degrees Fahrenheit), roughly 300 times hotter than the temperature used for cremation. Buildings were vaporized, fires spread rapidly, and entire neighborhoods disappeared within seconds.It remains a grim reminder of what even a relatively small nuclear weapon can do.North Korea’s 2017 Nuclear TestMore than 70 years later, nuclear weapons had become far more powerful.In 2017, North Korea conducted its largest ever nuclear test, with estimates placing the blast somewhere between 140 and 328 kilotons. Many researchers believe the explosion was around 250 kilotons, making it roughly 16 times more powerful than the Hiroshima bomb.The exact yield remains debated because North Korea has never publicly confirmed the weapon’s full capabilities. What scientists do know is that the detonation triggered a 6.3 magnitude earthquake, and seismic monitoring stations around the world detected the blast.The test reignited fears about North Korea’s rapidly advancing nuclear program.B 83: America’s Most Powerful Active Nuclear BombThe B 83 nuclear bomb remains one of the most powerful weapons in the U.S. arsenal.With an estimated yield of 1.2 megatons, the bomb would unleash catastrophic damage across a massive area. Within roughly 6 kilometers (3.7 miles), blast waves could generate winds reaching 255 kilometers per hour (158 mph). Anyone within 21 kilometers (13 miles) could suffer temporary flash blindness from the intense burst of light.Within an 8 kilometer (5 mile) radius, severe third degree burns would be likely. Closer to ground zero, the destruction becomes even more extreme, with violent shockwaves capable of leveling structures and causing fatal injuries.Despite its immense power, hundreds of B 83 bombs have remained in the U.S. stockpile for years.Castle Bravo: America’s Largest Nuclear TestIn 1954, the United States detonated Castle Bravo at Bikini Atoll in the Marshall Islands.The bomb produced a staggering 15 megaton explosion, around 1,000 times more powerful than the bomb dropped on Hiroshima. Scientists had badly underestimated its power, and the explosion was roughly two and a half times stronger than expected. The fallout spread across nearly 18,000 square kilometers (7,000 square miles), contaminating nearby islands and exposing the crew of a Japanese fishing boat.The blast created a mushroom cloud stretching roughly 39.6 kilometers (24.6 miles) into the sky and carved a massive crater into the ocean floor. The disaster sparked global outrage and intensified opposition to nuclear testing.Tsar Bomba 50: The Largest Nuclear Explosion Ever TestedIn 1961, the Soviet Union detonated Tsar Bomba, the most powerful nuclear weapon ever tested. The hydrogen bomb delivered an astonishing 50 megaton blast over Novaya Zemlya in the Arctic.Commissioned by Nikita Khrushchev, the bomb weighed around 27 tons and required a specially modified aircraft to transport it. The explosion created a shockwave so powerful that it reportedly knocked the bomber aircraft downward by nearly 900 meters (3,000 feet) before the pilots regained control.The blast flattened structures hundreds of kilometers away and remains the largest human made explosion in history.Tsar Bomba 100: The Bomb Too Dangerous to BuildAs terrifying as the 50 megaton Tsar Bomba was, it was originally supposed to be even worse. Soviet planners initially envisioned a 100 megaton version of the weapon. The design called for additional uranium layers that would have dramatically increased the explosion’s power.But Soviet scientists reportedly feared the bomb would create catastrophic radioactive fallout across large parts of the USSR. There was another major problem, the weapon was simply too large. It was so heavy that transporting it by missile or aircraft would have been nearly impossible, and any pilot tasked with delivering it would likely have faced a one way mission.Even during the Cold War, some weapons were considered too dangerous to exist.