Because their residues rise with much more force than most conventional bomb explosions, forming a kind of jet of matter. When an atomic bomb is detonated, it produces a bubble of very hot gas, violently heating the air around it. As this air that has become hot is lighter than the air in the atmosphere, the bubble rises. It’s an effect similar to sinking a volleyball in a pool. When you push it into the water and let go, the ball is thrown out, as it is much lighter than the entire mass of water surrounding it. In nuclear explosions, the gas bubble rises at speeds of hundreds of kilometers per hour, taking tons of air and dust with it.
This jet of matter forms the rod of the atomic mushroom, but, in a few seconds, it loses energy and cools down a little. With the lower temperature, the vaporized material is no longer so light and stops rising frantically, spreading to the sides. The dust, then, mixes with water droplets that are suspended in the atmosphere, creating a gigantic cloud, which is the head of the mushroom. The height the formation reaches depends on the force of the explosion. “The bombs of the Second World War created mushrooms about 8 kilometers high”, says physicist Philip Morrison, from the Massachusetts Institute of Technology (MIT), in the United States.
READ TOO
How did the Hiroshima atomic bomb work?
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– What was the biggest atomic explosion in the world?
– What would happen if a nuclear bomb fell on São Paulo?
ATOMIC GIANT
The mushroom of a hydrogen atomic bomb tested by the United States in 1952 reached 17 kilometers in height in 90 seconds. After five minutes, the big cloud reached 41 kilometers!
MAXIMUM TEMPERATURE
The hot air bubble formed by the explosion – and which rises, creating the mushroom – reaches a temperature of tens of millions of degrees Celsius
ANNIHILATING POWER
Some atomic bombs already tested had a power of 10 megatons, equivalent to 10 million tons of dynamite. The record is 70 megatons, a destructive power almost 5,000 times greater than that of the atomic bomb dropped by the Americans on the city of Hiroshima, Japan, in 1945.