The nuclear bomb is the worst weapon created by man until now. It has the power to destroy an entire city, killing millions of people. It destroys everything inside a 21 km radio. It leaves radiation that causes cancer and it damages the environment. The only two times that we have seen its extermination were during World War II, in Hiroshima and Nagasaki.
During phase one of an explosion, a ball of plasma appears and grows into an enormous fireball with a radius of 1 km. The ball is so hot that everything inside it is evaporated. The ball creates an intense flash of light that blinds everyone who sees it. The heat of the flash produces a thermal pulse that burns everything closer than 13 km from the origin.
The second phase begins after a few seconds. A powerful hurricane of air destroys everything inside a radius of 21 km. Nothing survives the explosion. Every building falls down with the people in it.
During the Cold War, Russia and the United States were frighteningly close to destroying each other with nuclear bombs. We have to be aware of the danger of nuclear bombs.