From: rmarsh@xtra.co.nz   
      
   In message <2ohtqiFabqfpU1@uni-berlin.de>, "nostradamus"   
    wrote:   
      
   >        Is it not contradictory for cosmologists to state that   
   >Star Trek is rubbish because you cannot hear expolsions   
   >in a vaccum and then say that space is full of gasses?   
      
   Yes and no.  Space is "full" of gases at a very low density.  As such,   
   it's not a pure vacuum, but it's pretty damn close.  At that density   
   there is no sound, just a few particles getting pushed about by the   
   concussions and vibrations that make sound in an atmosphere.   
      
   For there to be sound, there have to be enough particles that they   
   bounce back and forth off each other.  In space, when the side of your   
   space station gets dinged, the vibrations might knock a few particles,   
   but they just fly off into the dark and may not hit another particle   
   for metres, or kilometres, or AUs, or light years.   
      
   Even the "gas clouds" that are dotted about the place are too thin to   
   carry sound.  Nebulae aren't visible because they are dense, but   
   because they are huge.  It only takes a single 1nm particle every   
   cubic centimetre to be completely opaque at a thickness of ten light   
   years.   
      
   --   
   R.G. "Stumpy" Marsh.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)