(urth) grumble at wolfe comment made attached to guardianarticle

[Gerry Quinn]

I forgot about that.

But one or both could have an elliptical orbit.

Again, I don't know whether precession would make this unrealistic or not.  And 35000 leagues is incredibly, dangerously close for two Earth-sized planets.

But in terms of basic mechanics, a series of conjunctions should be possible (for story purposes, I think it would probably be sufficient if the series lasted a few centuries).

- Gerry Quinn


  ----- Original Message ----- 
  From: Jack Smith 
  To: The Urth Mailing List 
  Sent: Wednesday, February 09, 2011 3:29 AM
  Subject: Re: (urth) grumble at wolfe comment made attached to guardianarticle


  I like this explanation, but I don't think it would work.  For bodies in orbit around a central body, the orbital period is directly proportional to the distance or radius from the central body.  So if Green orbits in 6/7 of a Blue year, then Green must be 6/7 of Blue's distance from the sun.  If Blue is 90 million miles from the sun, then Green must orbit at  77 million miles radius, which makes Green 13 million miles from Blue at closest approach.  But we know that at conjunction the 2 planets are only 35,000 leagues (105,000 miles) apart (In Green's Jungles, ch. 15).


  On Tue, Feb 8, 2011 at 9:38 PM, Gerry Quinn <gerryq at indigo.ie> wrote:


    It can work if they have circular orbits that are quite close together, so that Green orbits their star in 6/7 of a Blue year.  Green will go around the star slightly faster than Blue, so that Blue is falling further and further behind.  After 6 Blue years, Blue will have made 6 orbits, while Green will have made 7 and caught up on Blue from behind.

    I don't know if two large planets with such similar orbital radii  would be stable, but anyway it would fit the conjunction schedule, and Green would be a bit hotter than Blue (their temperatures would also depend on atmospheric composition).

    - Gerry Quinn

      ----- Original Message ----- 
      From: Jack Smith 
      To: The Urth Mailing List 
      Sent: Wednesday, February 09, 2011 1:47 AM
      Subject: Re: (urth) grumble at wolfe comment made attached to guardianarticle


      "BTW, is there a consensus on the exact relation of the planets Blue and Green? Do they orbit one another as a single system, or do they orbit the sun on opposite sides, as do Earth and Gor?" 


      They can't orbit each other or orbit on opposite sides of the sun because Blue and Green  are farther apart and then get closer at conjunction.  Conjunction occurs every 6 years (OBW, Ch 7), and Blue's year seems to be about the same as a year on the Whorl.


      I'm not sure how Blue and Green move to produce this conjunction.  If they are about the same distance from the sun but in different orbital planes, they could at times be closer or more distant but conjunction would occur twice a year.  Perhaps Blue's orbit is circular and Green's is more eliptical, resulting in the 6 year interval, but I haven't been able to figure how this would work.



    _______________________________________________
    Urth Mailing List
    To post, write urth at urth.net
    Subscription/information: http://www.urth.net




  -- 
  Best wishes,
  Jack



------------------------------------------------------------------------------


  _______________________________________________
  Urth Mailing List
  To post, write urth at urth.net
  Subscription/information: http://www.urth.net
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.urth.net/pipermail/urth-urth.net/attachments/20110209/13828792/attachment-0004.htm>