{ "export": { "source": "https://urth.darkrealm.vip/thread/urth/922", "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": 922, "subject": "slow black hole", "messages": 1, "voices": 1, "first": "1998-07-05T19:55:00+00:00", "last": "1998-07-05T19:55:00+00:00" }, "messages": [ { "message_id": "", "from": { "name": "m.driussi", "address": "m.driussi at genie.geis.com" }, "date": "1998-07-05T19:55:00+00:00", "subject": "(urth) slow black hole", "in_reply_to": null, "reply_link": null, "blocks": [ { "kind": "text", "depth": 0, "text": "prion,\n\nYou saw-bird, you: a slow black hole could be used to \"stellificate\"\na jovian world like Jupiter.\n\nSecretly we'll call this the \"2010: Odyssey Two\" scenario, but in public\nwe reference Martyn J. Fogg's TERRAFORMING (1995) and the notes therein\nfrom his 1989 paper, \"Stellifying Jupiter: A First Step to Terraforming\nthe Galilean Satellites,\" published in JBIS.\n\n\"Identifying three principal assumptions crucial to its feasibility:\n\n\"1. Primordial black holes exist, are detectable and occur in a range\nof masses in the Solar System.\n\n\"2. It will become possible to maneuver low-mass black holes and embed\nthem within planets.\n\n\"3. Accretion onto the hole occurs at the Eddington limit, with a\nrelatively high rest mass to energy conversion efficiency in the\ninfalling material.\n\n\"I examined all three of these assumptions in detail in my original\npaper. Suffice it to say here that it is thought possible that\nprimordial black holes, of a wide range of masses, could have been\nformed in the Big Bang. None have yet been detected and so their\nexistence has yet to be proved, or non-existence disproved. Although\nthe smallest of them (up to an initial mass of ~10^12 kg) would have\nevaporated by now due to the emission of Hawking radiation, holes\nuseful for the purpose of stellification would be about a million\ntimes more massive than this and would have undergone very little\nchange since the origin of the universe . . . .\n\n\"Assumption 3 is particularly important, as the hole must not eat up\nthe planet it has stellified too quickly and should convert as much\nof the accreted mass as possible into energy that escapes in the form\nof radiation. The Eddington limit applies when the accretion rate is\nvery great. The luminosity produced by the accretion process exerts\na pressure on the infalling plasma and tends to retard the flow. The\nphoton force acts almost entirely on electrons but gravity works\nequally well on electrons and protons. Hence electrons move outward\nin relation to protons creating and electric field that trasfers the\nphoton force from electrons to protons. The luminosity ultimately\napproaches a critical value known as the Eddington limit:\n\n\"L = {4(Pi)(G)(M)(m

)(c)}/sigma ~ 6.35 (M)\n\nwhere M is the mass of the hole, m

is the proton mass, and\nsigma is the total electron scattering cross-section (6.57 x\n10^-29 m^2). When the accretion luminosity rises above L, the\nradiation pressure becomes large enough to prevent any further\ninflow. Accretion is thus self-regulated\" (TERRAFORMING, p. 463).\n\n[mantis note: I'm using \"< >\" brackets to denote subscript.]\n\n\"Potentially therefore, a small black hole could provide a power\nsource for the interior of a stellified planet such as Jupiter that\noperates more efficiently than the processes in the core of the Sun.\nIt is emphasized, however, that the accretion process is still\nclouded by a great deal of uncertainty, especially where accretion\nonto microscopic black holes is concerned. It is possible that the\nradiation released by accretion from such a dense medium as the\ninterior of a planet may itself be swallowed by the hole, as the\ndiffusive velocity of the radiation relativeto the matter may be\nexceeded by the matter's infall velocity. In this extreme case,\naccretion is unimpeded by any `back reaction' and calculations\nsuggest that Jupiter would vanish =in less than a human lifetime=!\"\n(TERRAFORMING, p. 464).\n\n[mantis note: gratuitous italics at the very end is my own\naddition. \"Less than a human lifetime\" is assumed to mean something\ngreater than \"less than a mayfly's lifetime\"; human lifetime having\nan outer edge of what, 70 or 100 years.]\n\nInteresting enough, in the section on \"Asteroengineering,\" which\ninvolves modifying our sun to avoid the disasterous red-giant phase,\nthe focus is on papers (1990 and 1993) by Martin Beech, looking at\nfive techniques, including my favorite \"Accretion onto a central\nblack hole\" with the application \"Luminosity determined by\ncontrolled accretion onto a small black hole at the stellar core\"\n(TERRAFORMING, p. 458).\n\nThese starry-eyed engineers! Where =do= they get their fantastical\nideas?!\n\n=mantis=" } ] } ] }