{ "export": { "source": "https://urth.darkrealm.vip/thread/whorl/449", "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": 449, "subject": "The Physics and Dimensions of the Whorl", "messages": 2, "voices": 2, "first": "1997-10-07T13:03:58+00:00", "last": "1997-10-07T14:54:35+00:00" }, "messages": [ { "message_id": "", "from": { "name": "John Eric Ivancich", "address": "ivancich at eecs.umich.edu" }, "date": "1997-10-07T13:03:58+00:00", "subject": "(whorl) The Physics and Dimensions of the Whorl", "in_reply_to": null, "reply_link": null, "blocks": [ { "kind": "text", "depth": 0, "text": "Hi Everyone,\n\nI'm going to try to pin down the radius and the circumference of the\nWhorl with some physics calculations. Now it's been more than a\ndecade since I've had a physics course, so I hope someone will check\nmy work.\n\nBefore I start, I would like to point out two things. GW was a\nmechanical engineer, so he could have done the same calculations, and\nprobably armed with nothing but a slide rule. Second, GW, in his\nanswers to the WHORL, said he didn't know what the dimensions of the\nWhorl were.\n\nAssumption #1\n-------------\n\nGravity in the Whorl is about the same as that on Earth/Urth. Gravity\nis measured by the acceleration rate towards the ground. On Earth (at\nsea level, at 45 degrees latitude) it is 9.80616 meters per second per\nsecond. Since most of us are probably more comfortable thinking in\nterms of miles per hour, that would be 78986 miles per hour per hour.\n\nBasic Relationships\n-------------------\n\nFrom the rate of acceleration we can determine the relationship\nbetween the velocity at the inner surface of the Whorl and the radius\nof the inner space of the Whorl.\n\n v*v\n r = --- ; \"radius equals velocity-squared over acceleration\"\n a\n\nSince we know \"a\", all we need is a good estimate of \"v\", and then we\nhave \"r\".\n\nAlso recall the basic relationship between circumference and radius.\n\n c = 2 * pi * r\n\nAssumption #2\n-------------\n\nWe have some clues about the velocity of the inner surface of the\nWhorl due to information we have about the floaters.\n\nIn Nightside, pp. 196-7 (mass paperback version used for all page\nreferences) Silk, while returning to the city in Blood's floater\nmentions the trip had taken hours on donkeys. On p. 204, while in the\ncity, Silk says it had been less than a half an hour since he'd left\nBlood's compound.\n\nIf a donkey travels at 5 mph (guess), and it took them 3 hours (guess)\nto get to Blood's estate, then it's a distance of 15 miles. When\nreturning in the floater it took them 30 minutes, so the floater was\ntraveling at 30 miles per hour. If the donkey travels faster, or the\ndonkey-time were longer, or they spent some time in the city before\nSilk mentioned the half an hour, then the floater traveled faster. I\nthink it's safe to say, though, that the floater wasn't going any\nfaster than 60 mph.\n\nFurthermore, that speed is safe, as there were no warnings of \"vector\nunacceptable\".\n\nAssumption #3\n-------------\n\nIn Calde, pp. 303-6, they (Silk, Hyacinth, Oosik, Quetzal, Xiphias,\nthe surgeon, and a driver) try to speed away in the floater as the\npterotroopers are attacking. They achieve an unacceptable vector, and\nthey, along with objects within the floater, start to float. This can\nonly mean that they completely counter-acted the velocity of the\nWhorl, negating its gravity effects.\n\nIf we can figure out how fast they were going (and assuming a strictly\nsoutherly direction, p. 306) we know the velocity of the inner surface\nof the Whorl.\n\nThey're in a city street filled with people. That would seem to put\nan upper-limit on their speed. But the speed must also be\nsignificantly greater than the typical speed the floater travels at,\nsince apparently they experience no significant altered-gravity\neffects at the typical speed.\n\nIt thus seems to me, then, that the floater was traveling maybe in the\nrange of 150 to 200 mph, when they lost the effect of gravity. Let's\nassume the larger.\n\nCalculation #1\n--------------\n\nOK folks, here we go. Are you sitting down???\n\n 200 * 200\n r = --------- = 0.5 miles ; diameter = 1 mile ; circumference = 3.14 miles\n 78986\n\nSeems we have a problem, huh?\n\nWhat if the velocity is 400 mph -- which seems beyond reasonableness.\n\n 400 * 400\n r = --------- = 2 miles ; diameter = 4 miles ; circumference = 12.5 miles\n 78986\n\nAnd we still have problems.\n\nCalculation #2\n--------------\n\nLet's try it the other way. Let's go from radius to velocity:\n\n v = sqrt(r * 78986)\n\nOn May 5, 1997, mantis posted to the WHORL estimating the radius of\nthe Whorl as being between 72 miles and 344 miles (I took the liberty\nof converting from leagues to miles).\n\nAt 72 miles, the velocity at the inner surface would be 2400 mph.\n\nAt 344 miles, the velocity would be 5200 mph.\n\nWhile these figures seem more reasonable for the dimensions of the\nWhorl, the floater could never approach these speeds, particularly in\ncity streets, and thus they could never have significantly\ncounter-acted the gravity effect.\n\nConclusion\n----------\n\nGW took significant artistic license. Although maybe he'd blame it on\nHorn and Nettle...\n\n\nEric\n(ivancich at eecs.umich.edu)" } ] }, { "message_id": "", "from": { "name": "Michael Straight", "address": "straight at email.unc.edu" }, "date": "1997-10-07T14:54:35+00:00", "subject": "Re: (whorl) The Physics and Dimensions of the Whorl", "in_reply_to": "", "reply_link": "subject", "blocks": [ { "kind": "quote", "depth": 1, "text": "On Tue, 7 Oct 1997, John Eric Ivancich wrote:\nCalculation #1\n--------------\n\nOK folks, here we go. Are you sitting down???\n\n 200 * 200\n r = --------- = 0.5 miles ; diameter = 1 mile ; circumference = 3.14 miles\n 78986\n\nSeems we have a problem, huh?" }, { "kind": "text", "depth": 0, "text": "\"THE RINGWORLD IS UNSTAAABLE! THE RINGWORLD IS UNSTAAAABLE!\"\n\n-Rostrum" } ] } ] }