X-ray observations of outer space are usually made from orbiting platforms. Yet radio and optical astronomy seems to work pretty well. I got to thinking that it seems odd for the highest energy electromagnetic radiation to be so well blocked by earth's atmosphere...I would have thought: more energy the more radiation gets thru...but apparently not. Seems like the highest energy radiation (X-rays,gamma rays, and some UV) from space are blocked in the upper atmosphere protecting us from genetic damage; I would have thought it would take more dense atmosphere to block the most energetic radiation; again, apparently not: There is a nice diagram here: http://en.wikipedia.org/wiki/File:Atmospheric_electromagnetic_opacity.svg What's the mechanism(s) that accounts for this absorption?? Is it the upper atmosphere that also blocks high energy radiation emitted from earth??