{
  "export": {
    "source": "https://urth.darkrealm.vip/thread/urth/1460",
    "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": 1460,
    "subject": "How big the Ship?",
    "messages": 1,
    "voices": 1,
    "first": "1999-03-31T02:05:00+00:00",
    "last": "1999-03-31T02:05:00+00:00"
  },
  "messages": [
    {
      "message_id": "<urth-v0024-0108@digest.urth.net>",
      "from": {
        "name": "m.driussi",
        "address": "m.driussi at genie.com"
      },
      "date": "1999-03-31T02:05:00+00:00",
      "subject": "(urth) How big the Ship?",
      "in_reply_to": null,
      "reply_link": null,
      "blocks": [
        {
          "kind": "text",
          "depth": 0,
          "text": "Today I finally found reason to try and calculate the size of the\nship \"Tzadkiel\" by way of answering the question: if the miracle\neclipse of the Sun by Apu Punchau was caused by the Ship's sails,\nthen how big would it have to be, and how close to Earth, to cause a\ntotal eclipse?\n\n=Angular Diameter=\nThe angular diameter of both Sun and Moon is around one-half a\ndegree. The formula\n\nS = 57.3 x D/R\n\nwhere D is diameter and R is distance from Earth.\n\nSince the Ship is assumed to be in LEO (Low Earth Orbit), and LEO\nranges from 150 to 2000 km, I just plugged in values to see what\nwould happen.  I also converted the diameter into leagues, since the\nleague is the unit Severian uses for very big objects (wall of\nNessus, the cliff in the mountains, etc.).\n\nORBIT      SAIL DIAMETER       DIAMETER IN LEAGUES\n 150 km     1.36 km             0.28\n 300 km     2.71 km             0.56\n 500 km     4.52 km             0.93\n1000 km     9.04 km             1.87\n2000 km    18.08 km             3.74\n\nThese sail diameters are all quite reasonable--in fact, by standards\nof solar sails, they are very modest, since solar sail designs range\nin diameter from 2 km to 400 km.\n\n(FWIW, a sail diameter of 400 km can cause total eclipse at an orbit\nof 44,235 km.)\n\n=mantis="
        }
      ]
    }
  ]
}