Most impressive about nuclear physics, is knowledge, that in classic rigid matter exists huge-huge emptiness - atom core is just about 1/100,000 of volume of at

Most impressive about nuclear physics, is knowledge, that in classic rigid matter exists huge-huge emptiness - atom core is just about 1/100,000 of volume of atom. And this emptiness is so huge, that to make safety blanket against cosmic particles for interstellar flights (on current level of radiology medicine), need few METERS of solid shield, or hundred KILOmeters of atmosphere. Second important consideration, nuclear fission reactions are very slow if compare to speed of light, this is why possible nuclear bomb, as if cores explode immediately, all nuclear fuel will be just fly out and not react. So, high probability, if SINGLE high energy particle will intersect human body, will nothing happen, this particle will just fly right through body without any visible effects. But even if particle will be so fortunate to directly hit some core in human body, according to rule of impulse saving, this core will also got very high speed and will fly out of body before fission appear (when high energy particles hit core of air at high altitude, they have some time to fission, so on surface usually detected traces of fission).