{
  "export": {
    "source": "https://urth.darkrealm.vip/thread/urth/3036",
    "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": "urth",
  "thread": {
    "id": 3036,
    "subject": "Green, argument for orbital eccentricity",
    "messages": 1,
    "voices": 1,
    "first": "2002-03-14T02:30:27+00:00",
    "last": "2002-03-14T02:30:27+00:00"
  },
  "messages": [
    {
      "message_id": "<urth-v0203-350@digest.urth.net>",
      "from": {
        "name": "Michael Andre-Driussi",
        "address": "mantis at siriusfiction.com"
      },
      "date": "2002-03-14T02:30:27+00:00",
      "subject": "(urth) Green, argument for orbital eccentricity",
      "in_reply_to": null,
      "reply_link": null,
      "blocks": [
        {
          "kind": "text",
          "depth": 0,
          "text": "Experiment: build a model in our solar system. Let Blue = Earth, move Venus\nout a bit, rename it \"Ishtar,\" and let's see.\n\nI want Ishtar to orbit within Martyn Fogg's \"Moist Greenhouse\" range, which\nwould be .85 AU to .95 AU for our system.  (\"Moist Greenhouse\" is one step\naway from \"Runaway Greenhouse.\")\n\nSo place Ishtar at .9 AU, with a year of 311 days.\n\nEarth is at 1 AU.\n\nIf we give both planets perfectly circular orbits, then they will be at\ntheir closest point about once every Ishtar year (plus a little), a\nfraction of an Earth year.\n\nWe want an orbit more \"cometary,\" yet we want it to remain within a\nboundary (Moist Greenhouse) more constrained than comets.\n\nIf we give Ishtar an orbital eccentricity of .05 (less than Mars's; about\nwhat Jupiter has), then Ishtar will swing from .855 AU to .945 AU.  It will\ndo this in the course of its year: speeding up as it nears the Sun, slowing\ndown as it reaches the farthest point.\n\nI don't know the formula, but my guess is that Ishtar at apehelion while\nEarth is near (leaving aside Earth's perihelion) would not happen once a\nyear.\n\nStarting both at the closest separation: Day 0\nIshtar arrives back at point on Day 311\nEarth arrives back at point on Day 365\nThey are 54 days out of synch (Earth \"falling behind\"), suggesting that it\nwill take, what, 6.75 years for them to get back into synch?\n\nISHTAR  EARTH\n   0        0\n 311      365\n 622      730\n 933     1095\n1244     1460\n1555     1825\n1866     2190 = 6 years\n2177\n2488     2464 = 6.75 years\n\n\nSomething like that.\n\n=mantis=\n\n\nSirius Fiction\nbooklets on Gene Wolfe, John Crowley\nNow with UPDATES!\nhttp://www.siriusfiction.com/"
        }
      ]
    }
  ]
}