From: g_d_pusch_remove_underscores@xnet.com   
      
   husoway@hotmail.com (Voyager) writes:   
      
   > Hmm, sorry the question was not clear.. Let me try again. Imagine you   
   > are on a space ship traveling towards earth. You would be looking at a   
   > sphere, correct ?, as you approach the planet. If you were to pass by   
   > earth, since you obviously cannot go thru it, you would be passing by   
   > each side of the planet, under it or above it right? I mean there is   
   > no other way. I realize the concept of side, top or bottom is our way   
   > of things here on earth but still, I think even traveling thru space,   
   > they would hold true in some way. I mean you pass by objects, or above   
   > or below them. I would think!   
      
      
   Then you would be thinking wrongly. There is no "up" in space. There is no   
   "down" in space. There is no "above" or "below" in space. There is no   
   "to the left side of" or "to the right side of" in space. Any concept based   
   on or derived from an up/down dichotomy is totally meaningless in space,   
   since it is implicitly based on the assumption that you are sitting on a   
   planetary surface in a noticible gravitational field which you are not,   
   instead of in free-fall.  The only conventional spatial relationship   
   that makes sense in space is "near by." The only spatial orientation   
   relationships that make sense are _RELATIVE_ orientations.   
      
      
   > So if you are in the space craft and you are approaching earth, how does   
   > your orientation stay correct no matter what part of the sphere you   
   > proceed to and enter thru the atmosphere?   
      
   It does =NOT= happen "automatically." You need to make observations of your   
   approach trajectory and the _RELATIVE_ orientation of your spacecraft with   
   respect to the planet, and then fire your attitude-control rockets to   
   spin your spacecraft around until you have _FORCED_ the relative orientation   
   of your spacecraft with your approach vector to have the correct attitude   
   for atmospheric entry. If you do not _FORCE_ the spacecraft to have the right   
   orientation for atmospheric entry, your spacecraft will most likely burn up.   
      
      
   > Hope this makes sense!   
      
   Sorry, you will need to totally abandon all your planet-centered notions of   
   spatial orientation such as "up" and "down" to understand what navigating   
   in space is like, first.   
      
      
   -- Gordon D. Pusch   
      
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