{ "export": { "source": "https://urth.darkrealm.vip/thread/urth/3025", "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": 3025, "subject": "Leagues and gravity", "messages": 8, "voices": 7, "first": "2002-03-11T20:08:14+00:00", "last": "2002-03-12T18:13:29+00:00" }, "messages": [ { "message_id": "", "from": { "name": "Jerry Friedman", "address": "jerry_friedman at yahoo.com" }, "date": "2002-03-11T23:52:42+00:00", "subject": "(urth) Leagues and gravity", "in_reply_to": null, "reply_link": null, "blocks": [ { "kind": "quote", "depth": 1, "text": "--- Michael Andre-Driussi wrote:\nAssuming that Lune Diameter = 2160 miles, and Orbit = 150,000 miles . .\n." }, { "kind": "text", "depth": 0, "text": "...\n\nWhere did you get 150,000 miles?\n\nAnyway, you got me thinking about Green-Blue celestial mechanics. Stop\nme if this has all been done.\n\nWe're pretty sure Green is not a satellite but rather another planet\nwith a slightly smaller orbit, so that it comes into conjunction\nevery six years (if I remember correctly), right? Also, Green has\nhigher gravity than the moon--otherwise the narrator would have told\nus at least once how the first thing he as Horn noticed was floating\nevery time he tried to take a step. I can hardly imagine Green has\nless than half the gravity of Earth and the same density. Using those\nassumptions gives it 1/8 the Earth's mass. (Calculations available on\nrequest.)\n\nLet's also believe Incanto quoting one Gagliardo when he says the\nclosest approach of Green to Blue is 35,000 leagues. If these are\nthe same leagues in the afterword to _The Sword of Lictor_, namely\nabout three miles, then that's 105,000 miles. For comparison,\nsomebody on the first visit to the Red Sun Whorl says a league is\n7000 steps. If these are half the Roman pace of which the 5000-foot\nRoman mile was a thousand, then that's 7000*2.5 = 17,500 feet ~ 3.31\nmiles. Using that latter number, Green's closest approach is about\n1.87 x 10^8 meters.\n\nWe can now determine that the maximum force that Green exerts on Blue\nat conjunction is about 8.5 x 10^21 N. For comparison, the force the\nsun exerts on the Earth is about 35.3 * 10^21 N. In other words,\nGreen is going to mess up Blue's orbit something fierce--and much\nmore if it has more than half the Earth's gravity. Mere storms and\ntides are nothing. Blue is going to mess up Green's orbit even more.\nI doubt the system would be stable for more than one or two\nconjunctions.\n\nSo did I make a mistake? Are we supposed to infer something from this\ndiscrepancy? Or is this another case of Wolfe's not letting science\nget in the way of the story? The problem with the latter is that if\nhe can get away with anything, the kind of deductions he apparently\nexpects readers to make become problematic--which is the difficulty\nwe're having with the Blue/Ushas conjecture.\n\nJerry Friedman" } ] }, { "message_id": "", "from": { "name": "Dan'l Danehy-Oakes", "address": "ddanehy at siebel.com" }, "date": "2002-03-12T00:10:49+00:00", "subject": "RE: (urth) Leagues and gravity", "in_reply_to": "", "reply_link": "subject", "blocks": [ { "kind": "text", "depth": 0, "text": "Jerry Friedman wrote, and I'm going to snip and cut mercilessly to\navoid a 90% quoted posting..." }, { "kind": "quote", "depth": 1, "text": "I can hardly imagine Green has less than half the gravity of Earth\nand the same density ... 1/8 the Earth's mass. " }, { "kind": "quote", "depth": 1, "text": "Let's also believe Incanto quoting one Gagliardo when he says the\nclosest approach of Green to Blue is 35,000 leagues. ... that's \n105,000 miles ... Green's closest approach is about 1.87 x 10^8 m." }, { "kind": "quote", "depth": 1, "text": "... the maximum force that Green exerts on Blue at conjunction is about\n8.5 x 10^21 N. Green is going to mess up Blue's orbit something fierce" }, { "kind": "quote", "depth": 1, "text": "I doubt the system would be stable for more than one or two \nconjunctions." }, { "kind": "quote", "depth": 1, "text": "So did I make a mistake? " }, { "kind": "text", "depth": 0, "text": "Not, so far as I can tell, in your math." }, { "kind": "quote", "depth": 1, "text": "Are we supposed to infer something from this discrepancy? " }, { "kind": "text", "depth": 0, "text": "Possibly. My immediate guess would be that Gagliardo was actually\nclueless about the actual distance between the two worlds at, uh,\nperigreen. (No falcon around about this.) It's probably safe to \nguess that the astronomy and astrophysics of the Short Sun\ncolonists is pretty primitive." }, { "kind": "quote", "depth": 1, "text": "Or is this another case of Wolfe's not letting science get in\nthe way of the story? " }, { "kind": "text", "depth": 0, "text": "This is probably heretical, given his engineering background and\nalmost fanatical attention to detail, but ... I have never really \nthought of Wolfe as the kind of Clement-ish worldbuilder who sits \ndown and calculates all the astrophysics of a system before he \nstarts writing. In fact, I could be wrong, but I'm pretty sure \nthat this is the first Lupine text where the actual mechanics of a \nstar system really affected the plot in any significant way - \ncertainly the mechanics of the St Croix system isn't very germane \nto the plot of _Fifth Head_!) " }, { "kind": "quote", "depth": 1, "text": "The problem with the latter is that if he can get away with\nanything, the kind of deductions he apparently expects readers\nto make become problematic--which is the difficulty we're\nhaving with the Blue/Ushas conjecture." }, { "kind": "text", "depth": 0, "text": "The problem we're having with the Blue/Ushas conjecture is that\nsome people on this list, who shall go nameless, like the idea\nso much that they will hang on to it in the face of any amount\nof contradictory evidence. Heck, _I_ like this theory. It would\nresolve a number of irritating problems in the Sun books. But\nin fact it simply does not work for eighty-'leven reasons." } ] }, { "message_id": "", "from": { "name": "Andy Robertson", "address": "andywrobertson at clara.co.uk" }, "date": "2002-03-11T20:08:14+00:00", "subject": "Re: (urth) Leagues and gravity", "in_reply_to": "", "reply_link": "subject", "blocks": [ { "kind": "text", "depth": 0, "text": "----- Original Message -----" }, { "kind": "quote", "depth": 1, "text": "From: \"Jerry Friedman\" \n\nSo did I make a mistake? Are we supposed to infer something from this\ndiscrepancy?" }, { "kind": "text", "depth": 0, "text": "It is clearly signalled that Green causes massive tides on Blue.\n\nYou are right in saying that such an orbital system would be unstable.\n\nBlue would have even more massive effects on Green, of course, sending it\nall over the place.\n\n\nIs there a solution?\n\n\nI favour the idea that Wolfe started off with Blue/Green just being two\nplanets in an alien system.\n\nWhen his hero got to Blue, he started to play with the idea that Blue/Green\njust *might* be Ushas/Lune.\n\nIt is only at this point that we learn that Green comes even closer to Blue\nthan the moon does to the Earth today - something which may signal that\nGreen is a torn-away moon.\n\n\nI think Blue/Green are in such unstable, temporary, orbits because they are\na young configuration - one which was formed when Lune was torn away from\nUshas by the White Fountain.\n\n\n hartshorn" } ] }, { "message_id": "", "from": { "name": "Grant Peacock", "address": "grantpeacock at yahoo.com" }, "date": "2002-03-12T00:49:37+00:00", "subject": "Re: (urth) Leagues and gravity", "in_reply_to": "", "reply_link": "subject", "blocks": [ { "kind": "quote", "depth": 1, "text": "Anyway, you got me thinking about Green-Blue celestial mechanics. Stop\nme if this has all been done." }, { "kind": "text", "depth": 0, "text": "Yeah I once posted some similar thoughts, although I didn't do any math.\n\nHave you considered the possibility that the narrator is accustomed to gravity\nless than 1 g? I'm assuming the whorl was designed to prepare people for Blue. \nThe fliers in the whorl are perhaps more realistic in a .5g environment.\n\nOur moon exerts a stronger force on Earth than our Sun does. I say this because\ntides are only a bit more extreme during a full moon. (I forget the terminology. \nWhat are neap tides??) So I would guess there must be something wrong in your\ncalculations. \n\nI think you are surely right that the orbits are unstable, even if the force\nexerted by Green on Blue is a small percentage of that exerted on Earth by the\nmoon. This means that the arrangement is a new one. For those who believe the\nBlue=Ushas theory, what must have happened was that the white fountain grabbed\nLune out of orbit as it came lumbering in and made into a planet.\n\nDoes the white fountain literally move through space into the system, or does it\njust magically appear?" }, { "kind": "quote", "depth": 1, "text": "We're pretty sure Green is not a satellite but rather another planet\nwith a slightly smaller orbit, so that it comes into conjunction\nevery six years (if I remember correctly), right? Also, Green has\nhigher gravity than the moon--otherwise the narrator would have told\nus at least once how the first thing he as Horn noticed was floating\nevery time he tried to take a step. I can hardly imagine Green has\nless than half the gravity of Earth and the same density. Using those\nassumptions gives it 1/8 the Earth's mass. (Calculations available on\nrequest.)\n\nLet's also believe Incanto quoting one Gagliardo when he says the\nclosest approach of Green to Blue is 35,000 leagues. If these are\nthe same leagues in the afterword to _The Sword of Lictor_, namely\nabout three miles, then that's 105,000 miles. For comparison,\nsomebody on the first visit to the Red Sun Whorl says a league is\n7000 steps. If these are half the Roman pace of which the 5000-foot\nRoman mile was a thousand, then that's 7000*2.5 = 17,500 feet ~ 3.31\nmiles. Using that latter number, Green's closest approach is about\n1.87 x 10^8 meters.\n\nWe can now determine that the maximum force that Green exerts on Blue\nat conjunction is about 8.5 x 10^21 N. For comparison, the force the\nsun exerts on the Earth is about 35.3 * 10^21 N. In other words,\nGreen is going to mess up Blue's orbit something fierce--and much\nmore if it has more than half the Earth's gravity. Mere storms and\ntides are nothing. Blue is going to mess up Green's orbit even more.\nI doubt the system would be stable for more than one or two\nconjunctions.\n\nSo did I make a mistake? Are we supposed to infer something from this\ndiscrepancy? Or is this another case of Wolfe's not letting science\nget in the way of the story? The problem with the latter is that if\nhe can get away with anything, the kind of deductions he apparently\nexpects readers to make become problematic--which is the difficulty\nwe're having with the Blue/Ushas conjecture.\n\nJerry Friedman\n\n__________________________________________________\nDo You Yahoo!?\nTry FREE Yahoo! Mail - the world's greatest free email!\nhttp://mail.yahoo.com/\n\n-- " } ] }, { "message_id": "", "from": { "name": "Roy C. Lackey", "address": "rclackey at stic.net" }, "date": "2002-03-12T06:26:37+00:00", "subject": "Re: (urth) Leagues and gravity", "in_reply_to": "", "reply_link": "subject", "blocks": [ { "kind": "text", "depth": 0, "text": "Andy Robertson opined:\n[snip]" }, { "kind": "quote", "depth": 1, "text": "When his hero got to Blue, he started to play with the idea that Blue/Green\njust *might* be Ushas/Lune.\n\nIt is only at this point that we learn that Green comes even closer to Blue\nthan the moon does to the Earth today - something which may signal that\nGreen is a torn-away moon.\n\n\nI think Blue/Green are in such unstable, temporary, orbits because they are\na young configuration - one which was formed when Lune was torn away from\nUshas by the White Fountain." }, { "kind": "text", "depth": 0, "text": "And Grant Peacock added:" }, { "kind": "quote", "depth": 1, "text": "I think you are surely right that the orbits are unstable, even if the\nforce\nexerted by Green on Blue is a small percentage of that exerted on Earth by\nthe\nmoon. This means that the arrangement is a new one. For those who believe\nthe\nBlue=Ushas theory, what must have happened was that the white fountain\ngrabbed\nLune out of orbit as it came lumbering in and made into a planet." }, { "kind": "text", "depth": 0, "text": "I don't want to get into the Blue=Ushas debate, but Lune didn't go anywhere.\nIt came up as usual--only much brighter--the first night after the flood,\nand seemed to behave itself in its customary manner thereafter. See the last\nparagraph of Chapter XLV of URTH." }, { "kind": "quote", "depth": 1, "text": "Does the white fountain literally move through space into the system, or\ndoes it\njust magically appear?" }, { "kind": "text", "depth": 0, "text": "It moved through space--Sev watched it get brighter as it came nearer.\n\n-Roy" } ] }, { "message_id": "", "from": { "name": "Michael Straight", "address": "straight at email.unc.edu" }, "date": "2002-03-12T15:48:42+00:00", "subject": "Re: (urth) Leagues and gravity", "in_reply_to": "", "reply_link": "subject", "blocks": [ { "kind": "quote", "depth": 1, "text": "On Mon, 11 Mar 2002, Grant Peacock wrote:\nI think you are surely right that the orbits are unstable, even if the force\nexerted by Green on Blue is a small percentage of that exerted on Earth by the\nmoon. This means that the arrangement is a new one. For those who believe the\nBlue=Ushas theory, what must have happened was that the white fountain grabbed\nLune out of orbit as it came lumbering in and made into a planet." }, { "kind": "text", "depth": 0, "text": "But every version of the Blue=Ushas theory I've seen at least admits a\nvery long time between Severian and the Short Sun Books (long enough for\nNeighbor civilization to rise and fall), which is probably too long for\nsuch unstable orbits.\n\n-Rostrum" } ] }, { "message_id": "", "from": { "name": "matthew.malthouse", "address": "matthew.malthouse at guardian.co.uk" }, "date": "2002-03-12T17:58:19+00:00", "subject": "Re: (urth) Leagues and gravity", "in_reply_to": "", "reply_link": "subject", "blocks": [ { "kind": "quote", "depth": 1, "text": "On 12/03/2002 15:48:42 Michael Straight wrote:\nOn Mon, 11 Mar 2002, Grant Peacock wrote:" }, { "kind": "quote", "depth": 2, "text": "I think you are surely right that the orbits are unstable, even if the\nforce\nexerted by Green on Blue is a small percentage of that exerted on Earth\nby the\nmoon. This means that the arrangement is a new one. For those who\nbelieve\nthe\nBlue=Ushas theory, what must have happened was that the white fountain\ngrabbed\nLune out of orbit as it came lumbering in and made into a planet." }, { "kind": "quote", "depth": 1, "text": "But every version of the Blue=Ushas theory I've seen at least admits a\nvery long time between Severian and the Short Sun Books (long enough for\nNeighbor civilization to rise and fall), which is probably too long for\nsuch unstable orbits." }, { "kind": "text", "depth": 0, "text": "For this it doesn't matter if Blue=Ushas or not: any of the explanations\nrequires a system stable enough for the history of the Neighbours etc and\nso far I don;t think we've come up with a mechanical solution that would\nbe.\n\n\nMatthew" } ] }, { "message_id": "", "from": { "name": "Jerry Friedman", "address": "jerry_friedman at yahoo.com" }, "date": "2002-03-12T18:13:29+00:00", "subject": "Re: (urth) Leagues and gravity", "in_reply_to": "", "reply_link": "subject", "blocks": [ { "kind": "text", "depth": 0, "text": "Mantis: thanks for answering my distance-to-Lune question so\nunequivocally!\n\n--- Grant Peacock wrote:\n[I wrote]" }, { "kind": "quote", "depth": 2, "text": "Anyway, you got me thinking about Green-Blue celestial mechanics. " }, { "kind": "quote", "depth": 1, "text": "Stop\nme if this has all been done.\nYeah I once posted some similar thoughts, although I didn't do any math.\n\nHave you considered the possibility that the narrator is accustomed to\ngravity\nless than 1 g? I'm assuming the whorl was designed to prepare people\nfor Blue. \nThe fliers in the whorl are perhaps more realistic in a .5g environment." }, { "kind": "text", "depth": 0, "text": "Reasonable, though we can hang-glide on Earth and the Fliers'\npropulsion modules could easily be far in advance of our\ntechnology. Anyway, wouldn't the narrator or Hoof say something about\nhow heavy they felt on the Red Sun Whorl? Maybe you don't feel the\nlocal gravity in astral projection, but if so, they should notice that\nthe Urth folk walk as if they were nailed to the ground (if nothing\nelse)." }, { "kind": "quote", "depth": 1, "text": "Our moon exerts a stronger force on Earth than our Sun does. I say this\nbecause\ntides are only a bit more extreme during a full moon. (I forget the\nterminology. \nWhat are neap tides??) So I would guess there must be something wrong\nin your\ncalculations. " }, { "kind": "text", "depth": 0, "text": "Tidal force decreases as the cube of the distance, not the square, so\nthe gravitational force of the sun on us is almost 200 times that of\nthe moon, even though the tidal force of the moon is something like\nthree or four times stronger than that of the sun.\n\n(Spring tides, at the full and new moon, are the strongest; neap tides,\nat the quarters, are the weakest.)" }, { "kind": "quote", "depth": 1, "text": "I think you are surely right that the orbits are unstable, even if the\nforce\nexerted by Green on Blue is a small percentage of that exerted on Earth\nby the\nmoon." }, { "kind": "text", "depth": 0, "text": "It's got to be *more*--Green comes much closer to Blue than the moon\ndoes to Earth, and it's surely more massive. Anyway, we agree on the\ninstability." }, { "kind": "quote", "depth": 1, "text": "This means that the arrangement is a new one. For those who\nbelieve the\nBlue=Ushas theory, what must have happened was that the white fountain\ngrabbed\nLune out of orbit as it came lumbering in and made into a planet." }, { "kind": "text", "depth": 0, "text": "Rostrum (I think) answered that point.\n..." }, { "kind": "quote", "depth": 2, "text": "Let's also believe Incanto quoting one Gagliardo when he says the\n..." }, { "kind": "text", "depth": 0, "text": "Oops. I meant Inclito, of course.\n\nJerry Friedman" } ] } ] }