From: oliver.jennrich@gmx.net   
      
   Luigi Fortunati  writes:   
      
   > A gelatin sphere in remote space, far from any gravitational field,   
   > maintains its spherical shape because it is in an inertial reference   
   > frame where there are no forces that can deform it.   
      
   Actually, it maintains its spherical shape because of surface tension   
   or other elastic internal forces. Without it, brownian motion would   
   cause diffusion, as can be observed by any gas cloud.   
      
   Even in the case of surface tension and finite temperature, the   
   spherical form would only adhered to 'on average', as the same   
   brownian motion would excite the normal modes of the sphere: the   
   sphere would wobble.   
      
   > But if the gelatin sphere approaches a planet or a star and falls free,   
   > it gets longer, it ovalizes.   
      
   Given that there is a mechanism to exert internal forces (such as   
   said surface tension) on the sphere, most parts of the now ovoid   
   are not in free fall anymore but deviate from the geodesic path due   
   to those internal forces.   
      
   If there is no mechanism to exert such internal forces, as would   
   be in the case of e.g. an ideal gas, all the parts of the cloud   
   would fall freely. But the shape of the cloud would not even be   
   close to an ovoid. At least not for long.   
      
   >   
   > Is this deformation of the gelatin sphere in free fall in a   
   > gravitational field due to the action of a force or not?   
      
   The shape of a body that is held together by internal forces is   
   determined by the balance of the external (tidal) force and the   
   internal forces.   
      
      
   --   
   Space - The final frontier   
      
   [[Mod. note -- Just to be clear, the author is (perfectly reasonably)   
   using a Newtonian-mechanics perspective in which gravitation is a   
   force.  In general relativity we would describe the same situation   
   using slightly different words ("proper acceleration" etc).   
   -- jt]]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)