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| | ::Perhaps a reference to the date of 'Jurassic Park'? Not sure exactly when that came out but I think it's in the right range. [[Special:Contributions/108.162.238.189|108.162.238.189]] 14:55, 17 December 2014 (UTC) | | ::Perhaps a reference to the date of 'Jurassic Park'? Not sure exactly when that came out but I think it's in the right range. [[Special:Contributions/108.162.238.189|108.162.238.189]] 14:55, 17 December 2014 (UTC) |
| | :::Hadn't thought of that.. Though after checking, {{w|Jurassic Park}} was released 1993, and I believe set in 1990. Still doesn't seem to tie up.. --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 15:22, 17 December 2014 (UTC) | | :::Hadn't thought of that.. Though after checking, {{w|Jurassic Park}} was released 1993, and I believe set in 1990. Still doesn't seem to tie up.. --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 15:22, 17 December 2014 (UTC) |
| − | ::::I never knew there was ever a space craft called "T-Rex". Learn something new everyday! ;) {{unsigned|Dangerkeith3000}}
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| | The Oldsmobile is probably a reference to the movie ''{{w|Mom and Dad Save the World}}''. The title characters' station wagon was from around that era -- and it ''did'' go into space in the movie. --[[User:Aaron of Mpls|Aaron of Mpls]] ([[User talk:Aaron of Mpls|talk]]) 11:47, 17 December 2014 (UTC) | | The Oldsmobile is probably a reference to the movie ''{{w|Mom and Dad Save the World}}''. The title characters' station wagon was from around that era -- and it ''did'' go into space in the movie. --[[User:Aaron of Mpls|Aaron of Mpls]] ([[User talk:Aaron of Mpls|talk]]) 11:47, 17 December 2014 (UTC) |
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| | :Certainly seems a likely candidate..--[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 17:08, 17 December 2014 (UTC) | | :Certainly seems a likely candidate..--[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 17:08, 17 December 2014 (UTC) |
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| | I did some calculations on the title text, though I'm not sure how correct they are. We can use our standard horse at 450kg, and assuming 9.81m/s<sup>2</sup> gravity (neglecting the slight drop in gravity as it moves up the space elevator), the formula I've used is: | | I did some calculations on the title text, though I'm not sure how correct they are. We can use our standard horse at 450kg, and assuming 9.81m/s<sup>2</sup> gravity (neglecting the slight drop in gravity as it moves up the space elevator), the formula I've used is: |
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| | Now I know there are a lot of assumptions in there, and really the whole formula is backwards, but hey... its a starting point! --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 17:05, 17 December 2014 (UTC) | | Now I know there are a lot of assumptions in there, and really the whole formula is backwards, but hey... its a starting point! --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 17:05, 17 December 2014 (UTC) |
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| − | I think Randall may have been talking to Andrew Hussie --[[Special:Contributions/141.101.106.89|141.101.106.89]] 21:50, 17 December 2014 (UTC)
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| − | https://what-if.xkcd.com/58/
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| − | Getting to space is easy, staying in space is hard.
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| − | The energy required to get to 100km, briefly, is about 1 MJ/kg
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| − | The energy required to stay in low earth orbit is a bit over 30 MJ/kg
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| − | It's tricky to get to low earth orbit with a space elevator, you can go up 200km, but as soon as you let go of the elevator you come down. If you put enough mass at 200km the whole elevator comes down. Not sure which number to use, but I'd go with the 30 MJ/kg, or 15 GJ/horse. So the solar array is about 240kW (averaged over the whole year) and the power plant is 2.5GW. This looks a bit high so maybe the horses don't stay in orbit.
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| − | --[[Special:Contributions/108.162.219.248|108.162.219.248]] 15:49, 18 December 2014 (UTC)
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| − | :It depends on what he means by launch I suppose. I had simply looked at getting to LEO altitude, but staying there once you let go of the cable is a whole different ball game. I believe the only way to get into orbit from a space elevator (lacking additional power) is to go right to geostationary height? Let go anywhere under that altitude and you go into orbital decay.
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| − | :Out of interest, where did you get the 1MJ/kg and 30MJ/kg values? As far as power stations, the new generation twin reactor {{w|Hinkley Point C nuclear power station}} (only know that one because its local to me) is designed to output 3.2GW, so 2.5GW isn't over the top. I would say that 240kW for aback yard solar farm is pretty large, depending on your location and size of back yard. --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 17:11, 18 December 2014 (UTC)
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| − | ::1MJ/kg comes from mgh for 1kg at 100km we get 9.81 * 100,000<br>
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| − | ::30MJ/kg comes from 1/2 mv^2 I happen to know that orbital velocity is about 8km/s so 1/2*8000^2 = 32,000,000
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| − | ::Normally I'd say close enough for goverment work, but in this case NASA probably uses a bit more precision. If you want to be more precision, visit wikipedia "specific orbital energy" and "circular orbit".
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| − | ::If we release a horse from the space elevator at any altitude it will be in orbit, at least until it contacts the earth's atmosphere. It turns out that if we release it at 30,000km (from the earths center = 23,600km altitude) then at perigee the altitude is 100km. High enough that a horse would stay in orbit for a while. Releasing 750 km higher raises perigee to 1000km altitude. So we don't have to go all the way to geostationary orbit, just high enough. But still 23,000km is not LEO.
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| − | ::--[[Special:Contributions/108.162.219.248|108.162.219.248]] 04:32, 19 December 2014 (UTC)
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| − | :::Ok, I'm just about following you I think! So assuming we are launching to orbit, we have to get to 23,600km, at which point gravity is considerably reduced. We definately have to take into account {{w|Space elevator#Apparent gravitational field|change in gravity}} as our horses move up the cable.
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| − | :::I did some maths, and I believe it takes 19.9GJ to get a 450kg horse to 23,600km. That is essentially mgh, but taking into account the change in gravity. At 1 Watt, thats gonna take 631 years. Our 500 horses per year solar plant needs to output 315kW ([http://www.solardaily.com/reports/Independence_Solar_Completes_300_kW_Rooftop_Solar_Array_999.html 300kW solar array on a roof for reference]). Our 10 horses per minute power station would need to output 3.32GW, so a decent nuclear facility. Once the Three Gorges Dam in China is running at full capacity (22.5GW), it could be launching 68 horses per minute. Running constantly at full capacity, we could rid the world of horses (est 58 million) in under two years. --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 11:09, 19 December 2014 (UTC)
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| − | :::I confirmed the height of 23 600 km with my own calculations; my result is about 189 km altitude at perigeum, and 996 km for 24 350 km (750 km higher, as you wrote). My code seems consistent as entering geostationary orbit altitude results in geostationary orbit. Anyway, I think that 19.9 GJ is slightly wrong - [http://www.wolframalpha.com/input/?i=G*earth+mass*450+kg+*+(1%2Fearth+radius-1%2F(earth+radius%2B23600km)) I entered it into Wolfram], and it showet a little more. This results in 350 kW and 3.7 GW for backyard solar panels and power plant, respectively. [[Special:Contributions/162.158.92.100|162.158.92.100]] 22:20, 28 January 2017 (UTC)
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| − | I filled out the remaining fields. I thought about getting the interior capacities of all 1981 Oldsmobile models but doesn't seem worth it. It's clearly a joke so that kind of research doesn't seem necessary.{{unsigned ip|173.245.56.152}}
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| − | '''Arrow of Time'''
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| − | Did anyone else notice the special advert for Xmas gifts? It was up at the top of the main xkcd page yesterday 2014-December-17, but gone today (the 18th). In black, blue and red colored printing it said:
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| − | "The XKCD store Christmas shipping deadline is Friday!<br>
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| − | Once it passes, there is no going back. The arrow of time drags us all<br>
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| − | inexorably forward toward decay and disorder toward the end of all things.<br>
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| − | Toward the empty silence of the grave. ORDER NOW!"
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| − | I thought it was amusing and saved a bitmap. Was kind of surprised that there was no other mention of this here, or on the fora either. {{unsigned ip|108.162.216.171}}
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| − | :I did notice it too, though I've always been a bit disappointed by the limited range of T-shirt comics. None of my favourites are on there. As far as this page mentioning it, it isn't relevant to the comic, so doesn't belong on this page. I don't know of a page on explainxkcd where it would really fit in. --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 11:18, 19 December 2014 (UTC)
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| − | ::Here: [[xkcd#Header_text]] on the [[xkcd]] page on explain. Just finished the transcript for this comic. Note the [[1461: Payloads#Trivia]] above. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 00:58, 30 January 2017 (UTC)
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| − | ::Why not make your own? Here is a fridge magnet, it wasn't too hard to figure out the design tools, [http://www.cafepress.com/cp/customize/product2.aspx?from=CustomDesigner&number=1027311439 Duty Calls magnet] Actual size is a little over 2" x 3" (50 x 75mm)--one problem with the design tools is figuring out the final size for some items. Based on my understanding of the CC license, I have not sold these, but I have given a few to friends. Edit--when something I want is in the XKCD store, of course I buy it there so Randall gets the cash. For example, the large poster sized version of Money on the wall in front of me now came from the XKCD store. It would be really cool if Randall made this fridge magnet (or something similar) available on his site.{{unsigned ip|108.162.216.171}}
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| − | :::I guess part of the reason is that I like the idea of Randall getting the cash from my purchase. --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 14:04, 19 December 2014 (UTC)
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| − | Actually, I find it strange that no explicit mention of Laika or Sputnik 2 is made. --[[Special:Contributions/141.101.75.89|141.101.75.89]] 23:50, 18 December 2014 (UTC)
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| − | I'm pretty sure this has nothing to do with dimensional analysis. Who wrote that part? have you ever actually done dimensional analysis? He's just using a nonstandard unit of measure. Unit conversion is almost -but not entirely- unlike dimensional analysis. {{unsigned ip|108.162.241.5}}
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| − | What's with the mass of squirrel? Apart from marmots, any squirrel weighs way less than a kilogram! {{unsigned ip|108.162.253.150}}
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| − | The T-Rex entry may refer to the Wankel Rex or Devil Rex discovered in 1988. See https://en.wikipedia.org/wiki/Specimens_of_Tyrannosaurus#.22Wankel_Rex_or_Devil_Rex.22:_MOR_555
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| − | PaperDragon-CA [[Special:Contributions/108.162.216.89|108.162.216.89]] 17:57, 30 September 2016 (UTC)
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