how, exactly,an atom bomb explosion generates a mechanical shockwave capable of flattening concrete buildings?

Question

since nuclear explosions release almost entirely radiant energy,is the mass of matter available(the bomb itself & the surrounding athmosphere)to be expanded by super heating, enough to generate physical pressure-shockwaves capable of destruction comparable to the explosion of several thousand tons of chemical explosives

Answer 1

Basically, it compresses the air because of the rapid heating. If you ever get to see a bomb explode in slow motion in the desert, the shockwaves are very visible. You can even see the moisture in the air condense out.

Answer 2

Whenever an explosion occurs, a vaccuum is formed by the explosion... Depending on the material exploded, or in other words, the magnitude of the explosion, the vaccuum created is bigger, or smaller. The vaccuum is formed because when the explosion occurs, the shockwave (heat realeased) is strong enough to push all matter away from the epicenter. Gunpowder has a pretty small vaccuum, where as TNT has a relatively large one, and atom bombs have a gigantic one. When you say atom bomb I assume you mean fission bomb. (The splitting of atoms, not the forced joining.) You actually get a larger explosion by joining atoms together than you do by splitting them, but I believe this is only because of the fuel to time ratio... that's another story. Basically, the only thing that knocks buildings down when an atom bomb goes off, is a wall of air that has nowhere else to go. The air itself is highly compressed due to the explosion, and will easily topple the brick wall. After the "superheat" is dissipated inside the vaccum, the atmosphere surrounding the compressed air from the explosion pushes all the compressed air back in to the vaccuum. (that's when you think everything is sucked back in... not sucked, pushed) I hope that's what you were lookin' for.