do exist, but that's not background radiation. They wind up way out in the microwave range, as joecrouse said, but that means they are pretty low power.
What's meant by "background radiation" is generally the background of the types of radiation that are of major health concern. I'm sure alpha particles are included-- that's the single most common thing people mean when they say "radiation." Alpha particles are helium nuclei: two protons, two netrons, and no electrons. IIRC, *all* elements have some rate of decay, just the ones you don't think of as radioactive have *really* long half-lives, meaning that their decay events are on average a very long time apart. But manure occurreth, so every once in a while you do get an alpha particle emitted from your pen or the car across the parking lot, or there's just a teensy bit of tritium (heavy water) in your coffee, etc. That's background radiation.
There is also some background level of gamma rays-- high-energy electromagnetic waves (i.e. ultra short-wavelength light) that can cause mutations at high levels. Stars put out a certain amount of this stuff in the ordinary course of things (thus the term cosmic rays), and some of it makes it here, although the photons are pretty spread out by the time they come this far.
There's lot's more to it, of course. I even know a tiny fraction of the lots more. But that's a quickie look at it. swell clicky |
