This is showing a slowed version fission. The "invader" lands on an unstable atom causing it to split, releasing one hundred "invaders" than the hundred invader continue the process until there is 1000 than 10000 than 100000 and continues until their is no more atoms to destroy. In chemistry in one "mole" there is 6.02 x 10^23 atoms. In a five hundred pound bomb there is shit ton of atoms to split. This releases a shit ton of energy which destroys everything nearby and pollutes everything with radioactive fall out for a long time.