From: ram@zedat.fu-berlin.de   
      
   quadi  wrote or quoted:   
   >Of course, though, the Ptolemaic geocentric solar system is not disproved   
   >by this.   
      
     Basically, all coordinate systems are on equal footing as long   
     as you can link them with diffeomorphisms. So yeah, you can   
     pick a system where Earth always has the coordinates (0,0,0),   
     meaning it's "at rest", but you can't use one where Earth is   
     flat, since there's no diffeomorphism that turns a sphere into   
     a plane or a surface built from one.   
      
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