From: andekl_no@saaf_spam.se   
      
   Henry Spencer  wrote:   
      
   > In article <031107000104234.07Nov03$rookswood@suburbian.com>,   
   > John Savage   wrote:   
   > >>Also - those X-rays can't reach the ground - Earth's atmosphere is   
   > >>equivalent of roughly 10 meters of water...   
   > >   
   > >Curious. So if I sunbaked on the bottom of a 1 metre deep swimming pool,   
   > >(with a suitable snorkle) I should expect to get sunburnt almost as   
   > >severely as when lying on the deck (if we can disregard for the moment   
   > >the not insignificant reflection at the air-water interface)?   
   >   
   > No, these are two different issues.   
   >   
   > To stop X-rays, you basically need mass.  Most any kind of mass is as good   
   > as any other kind; essentially nothing is transparent to X-rays.  So that   
   > extra 1m of water does not add very much more shielding against X-rays.   
      
   Actually - 1 meter of water roughly reduces hard x-rays by a factor of 5   
   to 10 depending on energy. Of course, since virtually no solar x-rays   
   reach ground level it doesn't make a lot of a difference on those ...   
      
   But OTOH as you mention, sunbaking is about UV, not x-rays ...   
      
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