Originally Posted by Gunk
Everything is radioactive, no?
AFAIK, everything "decays' and releases radiation but to say something is radioactive means that it has to be decaying at least 3-4 times faster than background radiation. Background radiation is basically the radiation being let off by everything decaying, so if you've got say, 40 counts of background radiation over a period of 120 seconds and element A has maybe, idk, 100K counts of radiation, then that's radioactive. Of course, the counts really have nothing to do with the risks associated with the element, the geiger counter could be beeping faster than a GAU12 shoots and the danger level could still be pretty low.