Pound for pound, the cosmic or gamma ray is probably the most dangerous. It is an electromagnetic ray that has an extremely high frequency and an extremely short wavelength or period. (Frequency and wavelength are inversely proportional.Always.) These electromagnetic phenomena are generated at the sub-atomic level.
Nuclear reactions or decay generates these little guys, as can subatomic particle interaction. And because they are of such high energies, they can shred the covalent bonds of the molecules that are the building blocks of living tissue. The have exceptional power to penetrate, and, because of their energies, can do a lot of damage.
One photon of these heavy gamma rays can dissociate a whole flock of chemical bonds as it passes through a body and then can come right out the other side with no difficulty. A crime scene investigator who is down with physics would call it an electromagnetic through and through.wiki.answers.com»