What would happen

millions of degrees. “If you’re within that, you’re dead,” Schlegelmilch says. According to an online simulation created by Alex Wellerstein at the Stevens Institute of Technology (it’s interactive, scary and fun; go to nuclearsecrecy.com/nukemap/), a 10-kiloton bomb would produce a fireball with a radius of 150 to 200 metres.

SHOCK WAVE

After the fireball comes the shock wave or air blast. If detonated in the air, that same 10-kiloton bomb would destroy most buildings and kill nearly everyone within 600 m of ground zero. The effect is reduced by 23 per cent if the detonation occurs on the ground. The shock wave weakens from there but can still take out residential buildings and cause mass casualties two to two-and-a-half times the initial spread of the shock wave, according to Wellerstein’s projections.

RADIATION

If you survive the fireball and shock wave, now you have to avoid the radiation. Exposure within 1 200 m of that 10-kiloton bomb, Wellerstein shows, will kill up to 90 per cent of people without medical treatment. For 400 m past that, your chances of survival increase but you’ll get third-degree burns, which you probably won’t feel, because the radiation also kills your pain receptors.

FALLOUT

If the attack comes from the ground, dirt and debris are irradiated and shot into the air by the explosion, forming the classic mushroom cloud. Winds can carry the radiation, called nuclear fallout, from that cloud tens or hundreds of miles away, depending on the size of the bomb and the strength of the wind. As it falls back to Earth, it sickens more people.

A nuclear explosion that occurs on the ground creates a smaller shock wave than an airburst, but also sends a mushroom cloud of radioactive material into the air, where it is carried for miles by the wind. 1 Fireball 2 Initial shock wave 3 Weakened...