On Sunday, August 20, 2017 at 6:29:13 PM UTC-5, Mr Anderson wrote:   
   > So, I asked a question on Quora lately about it, but did not get any   
   satisfying answers yet, so I bring it here, for more professional look.   
   > We all know that asteroid belts from movies are complete BS, but, I was   
   thinking if there could temporarily exist a cluster of small planetoids, in   
   which standing on one of them, you actually can see others, at let's say a few   
   kilometers distance.   
   > I want to put such thing on orbit of my setting's main planet, and I don't   
   know how plausible is it. In my fantasy-sf world, such cluster is used as a   
   hub for further space travel and material base for creating spaceships.    
   > Also, I want to know how long such thing could survive, even if it's short,   
   a few thousands years time, and it would be nice if someone could tell me if   
   that would be stable or would spit planetoids in all directions.   
      
   It depends.   
      
   If a cluster of rocks have matching orbits, they'll stay together, more or   
   less, until something perturbs their paths.  But if they're very big, they'll   
   also tend to coalesce together under the influence of gravity.  Again   
   depending on how big, the    
   impacts might give you one bigger asteroid or lots of little gravel.   
      
   Asteroids can certainly be in orbital relationships with each other, as Greg   
   Goss observes.  In _principle_ you could have several co-orbiting asteroids,   
   just like you can have double, triple, or n-le star systems.  But in practice,   
   the more asteroids in    
   the group the sooner you'll likely get a collision or an ejection, or the   
   cluster will pass a planet and get messed up that way.   
      
   So the answer is yes, it sort of could exist, but probably not for long and   
   being in orbit around a planet would make it worse because of tidal effects,   
   among other things.  OTOH, if you put the cluster in the forward or trailing   
   Trojan point of a larger    
   world, it might actually last a little longer there, though I wouldn't swear   
   to that.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)