In the episode Unafraid of the Dark in Neil deGrasse Tyson's series Cosmos, Tyson says the following: "Hess had discovered cosmic rays, showers of subatomic particles that crisscross the universe at nearly the speed of light. Without the shielding effect of the Earth's atmosphere, they would be lethal. Some cosmic rays can carry as much energy as a bullet fired from a rifle." If that's true, how did the astronauts who walked on the moon survive? They weren't shielded by the Earth's atmosphere, and the moon does not have an atmosphere to shield them. I know that the astronauts wore those space suits that covered their entire bodies, but I don't think that such space suits were bulletproof.