Your electronic devices swarm with it; the sun bathes you in it. It's zooming at you from cell towers, microwave ovens, CT scans, mammogram machines, nuclear power plants, deep space, even the walls of your basement. You cannot see, hear, smell or feel it, but there is never a single second when it is not flying through your body. Too much of it will kill you, but without it yo...(展开全部)