From: jack.bohn64@gmail.com   
      
   Paul Colquhoun wrote:   
      
   > That's not the only difference. Ringworld is mind-bogglingly huge, with   
   > the star located at the center, and shadow rings for day-night cycles.   
   >    
   > Orbitals are much smaller, down to single planet sized surface areas,   
   > (or less) and orbit the star like a normal planet would.   
   >    
   > I can't remember how they did the day-night thing. Maybe shutters on an   
   > enclosing roof structure?   
      
   A brief look says that its spin is not in the plane of its orbit.  So, like an   
   inside-out planet, we'd see the sun rising and setting, but we are actually   
   turning towards and away from it.  I'm having trouble visualizing this; had to   
   sight along a ring-   
   shaped object towards a light to get some idea: the sun will be "going down"   
   all afternoon, but won't actually sink below the horizon, but go behind the   
   ring somewhere near it.  At the same time we will see in the east half the   
   ring lit, and that half    
   will rise and circle around the sky until the front of it meets the western   
   horizon, and the sun will peek out from around the ring in the east.    
   Actually, a lot of the lit ring will be visible in the sky in the mornings and   
   evenings.  It will be    
   brighter than the Moon per unit area because of the higher albedo and its   
   closeness.  We would see the sun to the north or south of where the ring would   
   be in the sky, except the equinoxes.  (I'm trying to work this out: the sun   
   appears to drift across    
   the fixed stars over the year, say one degree a day; the point where the   
   rotation of the ring crosses the ecliptic also drifts... at the same rate in   
   the opposite direction? so one edge of the ring should appear to cross the   
   half degree of the sun's face    
   in a quarter day?)  We know total eclipses, when natural and rare, cause   
   excitement.  I'm thinking two a year, especially when someone can be seen as   
   responsible for them, would be thought of as an annoyance.  So design the   
   orbital matching the thickness    
   to the radius such that it's visual size is half its sun's.  Noticeable, but   
   not disruptive.   
      
   Which brings me to the question of what ignorant natives would make of the   
   shape of the world.  On Ringworld it was a table with an arch from which the   
   sun hung on a golden thread.  Here they might quickly work out that their arch   
   is closer than their    
   sun.  Also, being closer, the details on the rest of the ring would be   
   visible:  their far side might be as close as our Moon is.  How far around   
   would you have to go before you could look back and see the "map" of your home   
   there in the sky?  The view    
   of any close orbitals visible in the sky might give the answer right then.    
   (But why would an orbital fall into barbarism with others close?  Malevolence?)   
      
   --    
   -Jack   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)