From: seawasp@sgeinc.invalid.com   
      
   On 7/27/16 3:19 AM, Mikkel Haaheim wrote:   
   > Le dimanche 24 juillet 2016 19:57:11 UTC+2, Sea Wasp (Ryk E. Spoor) a écrit   
   :   
      
   >> 	Oh, the hell it doesn't. On the Arenaverse scale, even more so, because   
   >> instead of the trick we can use today -- put up a satellite and look   
   >> down through what amounts to only a couple miles of sea-level density   
   >> air -- you'd have to look through effectively infinite amounts of such   
   >> air, with accompanying dust, humidity, clouds, etc.   
   >>   
   >   
   > Which limits EM range a little (depending on frequency,   
      
   	Not "a little". With a good telescope in space, I can pick up details   
   on planets millions of miles away.   
      
   	Look through a hundred-plus miles of atmosphere, even pure   
   nitrogen/oxygen and trace gases without a bit of dust in it, you'll be   
   losing definition already noticeably. With humidity, worse. With dust,   
   worse.   
      
   	Space is easy. Air is hard.   
      
      
   > but vastly improves sonar.   
      
      
   	Welll... yes, compared to VACUUM where the range of sonar is zero, yes.   
   But in the air? No. There's a good reason we don't generally use sonar   
   in air; it dissipates at relatively short ranges. Underwater, that's a   
   different thing, but there you've got water, vastly more dense than air,   
   to transmit the signals.   
      
   	In air? No, not even at a few kilometers.   
      
   	And even underwater, sonar's severely limited by all sorts of effects   
   -- boundary layers, multipath, etc. -- which are much less an issue with   
   EM sensing in space.   
      
   >>   
   >> 	For any particular case with unlimited monetary expenditure, perhaps,   
   >> but you're dismissing stuff that we KNOW is a problem as though it   
   >> isn't, which really makes me question how much you know about the   
   >> *practical* limitations and not the theoretical. I work, as I said, with   
   >> multispectral imaging and sensors, some for the military, and our   
   >> experience with such imaging is more a matter of seeing more of its   
   >> limitations than its awesomeness.   
   >   
   > NOW you are beginning to see what I have been talking about.   
      
      
   	Not really. Because in space, my cheapo IR camera can sense you so   
   easily that you'll have to spend many orders of magnitude more trying to   
   hide from it. The person trying to see you will ALWAYS have an advantage   
   in space, while on Earth often the person trying to HIDE has the advantage.   
      
      
   --   
                         Sea Wasp   
                           /^\   
                           ;;;	   
   Website: http://www.grandcentralarena.com  Blog:   
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