The more a black body is hot right, the more likely it is to radiate energy. But since macro heat is molecular motion, it figures radiation may be caused simply by motion. Under what circumstances, does an atom in a hot black body radiate energy? I would like to know if it's just general increased probabilty, or if it's when the hot atom collides with another atom in the body. Is it more correct to say the radiation is more directly due to the increased atom bumping in hot bodys? If it's due to bumping, then it can still be argued that it may as well be increased probabilty. Since photons are particles. A body traveling at speed with respect to a photon source will experience more bumps and so radiate more energy.