{
  "export": {
    "source": "https://urth.darkrealm.vip/thread/whorl/809",
    "note": "Exported from an unofficial mirror of a public mailing list. Copyright in each message remains with the person who wrote it.  Email addresses are obscured as `user at host`, the form the original archive published. This file was rebuilt from parsed fields rather than retained headers, so it is faithful in content but not byte-exact.",
    "addresses": "obscured as 'user at host'"
  },
  "archive": "whorl",
  "thread": {
    "id": 809,
    "subject": "out of plane and kidney bean orbits",
    "messages": 1,
    "voices": 1,
    "first": "2000-04-05T13:48:31+00:00",
    "last": "2000-04-05T13:48:31+00:00"
  },
  "messages": [
    {
      "message_id": "<whorl-v0010-0301@digest.urth.net>",
      "from": {
        "name": "Michael Andre-Driussi",
        "address": "mantis at sirius.com"
      },
      "date": "2000-04-05T13:48:31+00:00",
      "subject": "(whorl) out of plane and kidney bean orbits",
      "in_reply_to": null,
      "reply_link": null,
      "blocks": [
        {
          "kind": "text",
          "depth": 0,
          "text": "Another problem with using a highly eliptical orbit (better known as\norbital eccentricity) on a scale using significant fractions of an\nAstronomical Unit is that the world will have gross \"seasonal\" effects as\nit moves closer and further from the primary.  (Seasonal in quotes because\nour seasons are all just a result of axial tilt rather than the Earth\ngetting closer and further from the sun.)\n\nOut of plane orbit.  This avoids the problem of gross seasonal effects, but\nthere is still the familiar problem that the orbits will intersect at two\npoints rather than just one, and it is hard to see how \"six local years\"\ncould figure in any immediately helpful way: both worlds will have the same\norbit, and thus the same orbital speed, more or less (as I understand it).\n\n(I think) one visual effect would be that (from the northern hemisphere)\nthe out-of-plane planet would look like a star in the north above the\nprimary (in fact, would it be visible?  Even \"daystar\" and \"evening star\"\nVenus/Mercury are within the plane: at right angles, an out-of-plane planet\nwould compete directly with the primary, and that is no contest!), then it\nwould loom large over a few months, then it would sink below the horizon\nand vanish for half a year; then it would come back up, like a giant\nplaying peek-a-boo, and begin shrinking as it climbed up to that point\nabove the primary.\n\nOh, wait!  It would be a crescent near the primary, then\nhalf-light/half-dark at the mid-way point, then full (or dark) at encounter\n(depends on if it is coming long or short; if dead on, then half/half is\nmaximum): its time as a visual disk would only be at or near the encounter,\nif at all.\n\nKidney-bean orbits.  These are weird, all right.  Easier for me to see in\ncases of big gravity wells, like multiple star systems.  Or a similar thing\nwith smaller scale: asteroids doing the gravity dance between Jupiter, Sun,\nand Earth, etc. But Blue and Green are similar Earth-like planets.\n\nAll this reminds me of Jack Vance's THE DRAGON MASTERS, where the alien\n\"star\" Coralyne comes close to planet Aerlith every once in a while, and\neach time waves of grephs come over to mess with the humans.\n\n(But of course, there was an sf magazine in the '30s or '40s that had a\nstory about devil-like aliens swimming down from a moon or a world.  Was it\na cover story?  Well, there was an illustration--probably was a cover.  Has\nanybody found that magazine; know the name of that story?  It was a major\ninspiration for the Short Sun, but that's another story for another time.)\n\n=mantis=\n\n\n\n*This is WHORL, for discussion of Gene Wolfe's Book of the Long Sun."
        }
      ]
    }
  ]
}