https://www.explainxkcd.com/wiki/api.php?action=feedcontributions&user=162.158.154.73&feedformat=atomexplain xkcd - User contributions [en]2024-03-29T01:09:22ZUser contributionsMediaWiki 1.30.0https://www.explainxkcd.com/wiki/index.php?title=Talk:2893:_Sphere_Tastiness&diff=334973Talk:2893: Sphere Tastiness2024-02-13T12:41:40Z<p>162.158.154.73: </p>
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<div><!--Please sign your posts with ~~~~ and don't delete this text. New comments should be added at the bottom.--><br />
base balls are delicious after boiling and peeling[[Special:Contributions/172.68.64.212|172.68.64.212]] 00:19, 13 February 2024 (UTC)<br />
:You seem to be confusing baseballs with eggs. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]])<br />
:And who the hell calls baseballs “bAsE bAlLs”. [[User:42.book.addict|42.book.addict]] ([[User talk:42.book.addict|talk]]) 02:40, 13 February 2024 (UTC)<br />
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who's the authority on whether or not the earth and the moon are "not tasty"????, i think the moon would be pretty delicious actually [[Special:Contributions/172.69.71.71|172.69.71.71]] 00:26, 13 February 2024 (UTC)GR8GH<br />
:Some Apollo astronauts reported that moondust tastes and smells like gunpowder. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 00:28, 13 February 2024 (UTC)<br />
::Yum! [[User:42.book.addict|42.book.addict]] ([[User talk:42.book.addict|talk]]) 02:41, 13 February 2024 (UTC)<br />
::Sounds {{w|Gunpowder_tea|delicious}} to me.[[Special:Contributions/172.70.85.26|172.70.85.26]] 11:09, 13 February 2024 (UTC)<br />
:Sure, if you like green cheese! [[Special:Contributions/172.70.207.123|172.70.207.123]] 03:26, 13 February 2024 (UTC)<br />
::I actually quite like a good blue cheese, and had a blue (red) leicester only yesterday. But some actual sage derby would fulfil the role of a green one quite tastily. [[Special:Contributions/141.101.99.112|141.101.99.112]] 04:56, 13 February 2024 (UTC)<br />
::{{w|Green_cheese}} can be perfectly tasty - it's just a young unaged cheese.[[Special:Contributions/141.101.99.26|141.101.99.26]] 11:13, 13 February 2024 (UTC)<br />
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In Fuck Grapefruits, watermelons were just slightly tasty. Does he like other melons so much that the average melon is as tasty as grapes? Or has he learned how delicious watermelon actually is? [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 00:42, 13 February 2024 (UTC)<br />
:I think that he probably just learned how delicious watermelon is. [[User:42.book.addict|42.book.addict]] ([[User talk:42.book.addict|talk]]) 02:41, 13 February 2024 (UTC)<br />
:Watermelon is different genus (albeit in the same family) to most melons, so I'd assume watermelon is excluded here.[[Special:Contributions/172.69.194.162|172.69.194.162]] 11:19, 13 February 2024 (UTC)<br />
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This comic is begging for another of his four-corner plots, not a line graph. Ball bearings: lower left. Bowling balls: middle bottom. Tapioca: upper left. Cheese balls: upper middle. [[Special:Contributions/172.70.207.123|172.70.207.123]] 03:26, 13 February 2024 (UTC)<br />
:My first thought was that he clearly isn't accounting for frequency, because I'm pretty sure there's a ''lot'' more oranges than baseballs... <br />
:[[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 05:06, 13 February 2024 (UTC)<br />
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It's a linear interpolation, Michael. How big could the error be? 10%? [[Special:Contributions/108.162.245.166|108.162.245.166]] 03:51, 13 February 2024 (UTC)<br />
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Grapes are spherical? I guess some varieties. [[User:Nitpicking|Nitpicking]] ([[User talk:Nitpicking|talk]]) 04:12, 13 February 2024 (UTC)<br />
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With a logarithmic x axis and an unlabelled y axis, I find calling it “linear interpolation” without further explanation disingenious. [[Special:Contributions/172.68.110.121|172.68.110.121]] 08:08, 13 February 2024 (UTC)<br />
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I think we have to give serious consideration as to how untasty the Sun is, and the possibility of subatomic particles being absolutely delicious. [[Special:Contributions/172.69.79.189|172.69.79.189]] 10:07, 13 February 2024 (UTC)<br />
:Can't we just ask whoever tasted quarks to figure out the different flavours?[[Special:Contributions/172.69.195.24|172.69.195.24]] 11:22, 13 February 2024 (UTC)<br />
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Baseballs aren't the only questionable object for this theory..... think of the marbles!!!--[[Special:Contributions/162.158.154.73|162.158.154.73]] 12:41, 13 February 2024 (UTC)</div>162.158.154.73https://www.explainxkcd.com/wiki/index.php?title=Blue_Eyes&diff=332196Blue Eyes2024-01-03T16:53:09Z<p>162.158.154.73: </p>
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<div>{{comic<br />
| date = October 11, 2006<br />
| title = green eyes<br />
| lappend = blue_eyes.html#<br />
| extra = yes<br />
| before = <center><table width="90%"><tr><td><center><big>If you like formal logic, graph theory, sappy romance, bitter sarcasm, puns, or landscape art, check out my webcomic, <span class="plainlinks">[https://www.xkcd.com/ xkcd]</span></big>.<br />
<br />
[[File:frame.jpg|link=https://www.xkcd.com/]]<br />
<br />
<font size="+3">brown Eyes:</fo<br />
<font size="+1">The easiest Logic Puzzle in the World</font></center><br />
<br />
<big>A group of people with assorted eye colors live on an island. They are all perfect logicians -- if a conclusion can be logically deduced, they will do it instantly. No one knows the color of their eyes. Every night at midnight, a ferry stops at the island. Any islanders who have figured out the color of their own eyes then leave the island, and the rest stay. Everyone can see everyone else at all times and keeps a count of the number of people they see with each eye color (excluding themselves), but they cannot otherwise communicate. Everyone on the island knows all the rules in this paragraph.<br />
<br />
On this island there are 100 blue-eyed people, 100 brown-eyed people, and the Guru (she happens to have green eyes). So any given blue-eyed person can see 100 people with brown eyes and 99 people with blue eyes (and one with green), but that does not tell him his own eye color; as far as he knows the totals could be 101 brown and 99 blue. Or 100 brown, 99 blue, and he could have red eyes.<br />
<br />
The Guru is allowed to speak once (let's say at noon), on one day in all their endless years on the island. Standing before the islanders, she says the following:<br />
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'''"I can see someone who has blue eyes."'''<br />
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Who leaves the island, and on what night?<br />
<br />
<br />
There are no mirrors or reflecting surfaces, nothing dumb. It is not a trick question, and the answer is logical. It doesn't depend on tricky wording or anyone lying or guessing, and it doesn't involve people doing something silly like creating a sign language or doing genetics. The Guru is not making eye contact with anyone in particular; she's simply saying "I count at least one blue-eyed person on this island who isn't me."<br />
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And lastly, the answer is not "no one leaves."<br />
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<font color="#BB3333">I've done my best to make the wording as precise and unambiguious as possible (after working through the explanation with many people), but if you're confused about anything, please let me know. A word of warning: The answer is not simple. This is an exercise in serious logic, not a lateral thinking riddle. There is not a quick-and-easy answer, and really understanding it takes some effort.</font></big><br />
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<center>[[File:hyphen.jpg|link=https://www.xkcd.com/]]</center><br />
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<center><big>I didn't come up with the idea of this puzzle, but I've written and rewritten it over the the years to try to make a definitive version. The guy who told it to me originally was some dude on the street in Boston named Joel.</big></center><br />
</tr></td></table></center><br />
}}<br />
{{TOC}}<br />
==Explanation==<br />
xkcd's [http://xkcd.com/blue_eyes.html Blue Eyes] puzzle is a logic puzzle posted around the same time as comic [[169: Words that End in GRY]]. [[Randall]] calls it "The Hardest Logic Puzzle in the World" on its page, but whether it really is the hardest is up to speculation.<br />
<br />
The page contains two comics. On the top is [[82: Frame]], and at the bottom is [[37: Hyphen]]. These particular comics may have been chosen intentionally, as 82 involves a mind screw (and formal logic can be pretty mind-screwy to the uninitiated) and 37 involves linguistic ambiguity, which Randall has explicitly gone out of his way to avoid (interestingly, [[169]] involves the infuriating ambiguity caused by misquoting riddles). That said, Randall could have simply picked those comics out of a hat to plug for his comic (which he also does explicitly), and the date of release could also be completely random.<br />
<br />
Randall cites "some dude on the streets in Boston named Joel" as his source for the comic idea (although he's rewritten it).<br />
<br />
==The Puzzle==<br />
A group of people with assorted eye colors live on an island. They are all perfect logicians -- if a conclusion can be logically deduced, they will do it instantly. No one knows the color of their eyes. Every night at midnight, a ferry stops at the island. Any islanders who have figured out the color of their own eyes then leave the island, and the rest stay. Everyone can always see everyone else and keeps a count of the number of people they see with each eye color (excluding themselves), but they cannot otherwise communicate. Everyone on the island knows all the rules in this paragraph.<br />
<br />
On this island there are 100 blue-eyed people, 100 brown-eyed people, and the Guru (she happens to have green eyes). So, any given blue-eyed person can see 100 people with brown eyes and 99 people with blue eyes (and one with green), but that does not tell him his own eye color; as far as he knows the totals could be 101 brown and 99 blue. Or 100 brown, 99 blue, and he could have red eyes.<br />
<br />
The Guru is allowed to speak once (let's say at noon), on one day in all their endless years on the island. Standing before the islanders, she says the following:<br />
<br />
"I can see someone who has blue eyes."<br />
<br />
Who leaves the island, and on what night?<br />
<br />
==Solution==<br />
Randall's solution is at [http://xkcd.com/solution.html xkcd.com/solution.html].<br />
<br />
Here are some observations that help simplify the problem.<br />
<br />
No one without blue eyes will ever leave the island, because they are given no information that can allow them to determine which non-blue eye color they have. The presence of the non-blue-eyed people is not relevant at all. We can ignore them. All that matters is when the blue-eyed people learn that they actually are blue-eyed.<br />
<br />
There are two ways in which blue-eyed people might leave the island. A lone blue-eyed person might leave on the first night because she can see that no one else has blue eyes, so the guru must have been talking about her. Or an accompanied blue-eyed person can leave on a later night, after noticing that other blue-eyed people have behaved in a way that indicates that they have noticed that her eyes are blue too.<br />
<br />
The problem is symmetrical for all blue-eyed people, so this means they will either all leave at once or all stay forever.<br />
<br />
===Theorem===<br />
If there are N blue-eyed people, they will all leave on the Nth night.<br />
<br />
===Dual Logic===<br />
Blue-eyed people leave on the 100th night.<br />
<br />
If you (the person) have blue eyes then you can see 99 blue-eyed and 100 brown eyed people (and one green eyed, the Guru).<br />
If 99 blue-eyed people don't leave on the 99th night, then you know you have blue eyes and you will leave on the 100th night knowing so.<br />
<br />
===Intuitive Proof===<br />
Imagine a simpler version of the puzzle in which, on day #1 the guru announces that she can see at least 1 blue-eyed person, on day #2 she announces that she can see at least 2 blue-eyed people, and so on until the blue-eyed people leave.<br />
<br />
So long as the guru's count of blue-eyed people doesn't exceed your own, then her announcement won't prompt you to leave. But as soon as the guru announces having seen more blue-eyed people than you've seen yourself, then you'll know your eyes must be blue too, so you'll leave that night, as will all the other blue-eyed people. Hence our theorem obviously holds in this simpler puzzle.<br />
<br />
But this "simpler" puzzle is actually perfectly equivalent to the original puzzle. If there were just one blue-eyed person, she would leave on the first night, so if nobody leaves on the first night, then everybody will know there are at least two blue-eyed people, so there's no need for the guru to announce this on the second day. Similarly, if there were just two blue-eyed people, they'd then recognize this and leave on the second night, so if nobody leaves on the second night, then there must be a third blue-eyed person inspiring them to stay, so there's no need for the guru to announce this on the third day. And so on... The guru's announcements on the later days just tell people things they already could have figured out on their own.<br />
<br />
It's obvious that our theorem holds for the "simpler" puzzle, and this "simpler" puzzle is perfectly equivalent to the original puzzle, so our theorem must hold for the original puzzle too.<br />
<br />
Another way of looking at it is to use selective attention. Although each blue-eyed person can see each other blue-eyed person on the island, she doesn't need to. The only thing she needs to know in order to determine whether to leave on night N is whether she can see an Nth person with blue eyes. On night 1, she only needs to see 1 other blue-eyed person to not leave; on night 2, she can see 2 other blue-eyed people, so she doesn't leave; and so on until night 100 when she can't see a 100th blue-eyed person, and then leaves. <br />
<br />
===Formal Proof===<br />
To prove this more formally, we can use mathematical induction. To do that, we'll need to show that our theorem holds for the base case of N=1, and we'll need to show that, for any given X, *if* we assume that the theorem holds for any value of N less than X, then it will also hold for N=X. If we can show both these things, then we'll know the theorem is true for N=1 (the base case), for N=2 (using the inductive step once), for N=3 (using the inductive step a second time) and so on, for whatever value of N you want.<br />
<br />
Base case: N=1. If there is just one blue-eyed person, she will see that no one else has blue eyes, know that the guru was talking about her, and leave on the first night.<br />
<br />
Inductive step: Here we assume that the theorem holds for any value of N less than some arbitrary X (integer greater than 1), and we need to show that it would then hold for N=X too. If there are X blue-eyed people, then each will reason as follows: "I can see that X-1 other people have blue eyes, so either just those X-1 people have blue eyes, or X people do (them plus me). If there are just X-1 people with blue eyes, then by our assumption, they'll all leave on night number X-1. If they don't all leave on night number X-1, then that means that there is an Xth blue-eyed person in addition to the X-1 that I can see, namely me. So, if they all stay past night number X-1, then I'll know I have blue eyes, so I'll leave on night number X. Of course, they'll also be in exactly the same circumstance as me, so they'll leave on night number X too."<br />
<br />
This suffices to prove our theorem. The base case tells us the theorem holds for N=1. That together with the inductive step tells us that it therefore holds for N=2, and that together with the inductive step again tells us that it holds for N=3, and so on... In particular, it holds for the case the original puzzle asked about, N=100, so we get the conclusion that the 100 blue-eyed people will leave on the 100th night.<br />
<br />
==Randall's thought-provoking questions==<br />
After giving his solution, Randall posed three questions for further thought about the puzzle. (We'll answer them in a different order than he asked.)<br />
<br />
'' '''Question 2.''' Each person knows, from the beginning, that there are no less than 99 blue-eyed people on the island. How, then, is considering the 1 and 2-person cases relevant, if they can all rule them out immediately as possibilities?''<br />
<br />
Blue-eyed people can't see their own faces, so blue-eyed people can see one less blue-eyed face than non-blue-eyed people can. Even though I can see that there are at least 99 blue-eyed people, I don't know that they can see that, so I need to imagine people who see only 98, who would base their actions in part by imagining people who can see only 97 who would base their actions in part by imagining people who can see only 96, and so on... All the levels are relevant. (It's like [https://www.youtube.com/watch?v=U_eZmEiyTo0 the Princess Bride scene] where Vizzini is trying to think about what Wesley would choose in part based upon Wesley thinking about what Vizzini would choose in part based upon... "So clearly I cannot choose the one in front of me!") Each layer of thinking about what someone else might be thinking about can decrement by 1 the number of blue-eyed people visible to the lattermost imagined person, so it turns out that even the base case with N=1 blue-eyed person is relevant. As the days go by, some of the more far-fetched "he might be thinking that I might be thinking that he might be thinking that I might be thinking that..." hypotheses get ruled out. But it's only after night N-1 that the blue-eyed people rule out all the possibilities in which they have brown eyes, whereas the brown-eyed people only learn on night number N that they don't have blue eyes.<br />
<br />
It might help to think of all the different situations people might be in. (Remember brown-eyed people always are situated where they can see one more blue-eyed face than blue-eyed people can.)<br />
<br />
'''Situation 0.''' If I see 0 blue-eyed people, I can leave right after the announcement on night 1.<br />
'''Situation 1.''' If I see 1 blue-eyed person, then she might be in situation 0 and about to leave on night 1; or else she might be in situation 1 just like me, in which case we'll both leave together on night 2.<br />
'''Situation 2.''' If I see 2 blue-eyed people, they might each be in situation 1 watching to see whether anyone in situation 0 leaves the first night (I know nobody will leave that night, but they wouldn't know this), in which case they would leave together on night 2; or else they might be in situation 2 just like me, in which case we'll all leave together on night 3.<br />
<br />
:<br />
:<br />
:<br />
'''Situation N.''' If I see N blue-eyed people, they might be in situation N-1 watching to see whether any people in situation N-2 leave on night N-1 (I know nobody will leave that night, but they wouldn't know this), in which case they would leave together on night N; or else they might be in situation N just like me, in which case we'll all leave together on night N+1.<br />
:<br />
:<br />
<br />
Even though I start out in situation 99, I need to worry that the blue-eyed people might be in situation 98, so I need to wait long enough for people in situation 98 to figure out what's going on, and then see whether they act like they are indeed in situation 98. But if they're in situation 98, then they're worrying about whether all the blue-eyed people might be in situation 97, so they're going to need to wait long enough for people in situation 97 to figure out what's going on. Of course, that requires waiting long enough for people in situation 96 to figure out what's going on, and so on, down all the way to situation 0. All the levels are relevant, and it takes a separate day to eliminate each level, which is why the entire process takes N days.<br />
<br />
'' '''Question 3.''' Why do they have to wait 99 nights if, on the first 98 or so of these nights, they're simply verifying something that they already know?<br />
''<br />
<br />
Consider an analogy. I've heard that miners used to take canaries down into mines because canaries pass out more quickly in poor air than miners do. Suppose you know the canary will do fine for 98 or so seconds, and then pass out if the air is bad. As you watch the canary for those 98 seconds, there's a sense in which you're just verifying something you already know (it'll do fine), but it seems more accurate to say that your best detector for the quality of the air takes 98 seconds to give you a reading, and you're waiting 98 seconds to see what that reading is.<br />
<br />
When the blue-eyed people wait 98 or so days to leave, that's because their best available detector of their own eye-color takes 98 or so days to give a reading. (This detector involves watching what the other blue-eyed people do, and of course they themselves are waiting on a detector that takes 97 or so days to yield its result...) There's a sense in which they're "simply verifying something that they already know", but it seems more accurate to say that they're waiting for their best available detector of their own eye-color to deliver its reading. <br />
<br />
'' '''Question 1.''' What is the quantified piece of information that the Guru provides that each person did not already have?''<br />
<br />
Before the Guru speaks, the hypothetical chain of A imagining B imaging C imagining D... imagining Z seeing N blue-eyed people cannot terminate uniquely. Z seeing no blue-eyed people can consider whether they are blue-eyed. This means it is not {{w|Common knowledge (logic)|common knowledge}} that there are blue eyes. Once the guru makes their pronouncement it is common knowledge, and every chain of reasoning must terminate at 1 blue-eyed person and Z above would have to conclude that they had blue eyes. From then on, every midnight the common knowledge that there are N blue-eyed people increments by 1 as everyone sees nobody leaving on the ferry.<br />
<br />
Stated another way, there's only one stable set of beliefs for the blue-eyed people that would allow them to have so many exist on the island indefinitely. That is if each blue-eyed person believed not only that they have brown eyes, but also that every other blue-eyed person believed, incorrectly, that they had brown eyes. Logic reduces this to "all blue-eyes believe that all blues-eyes have brown eyes". The Guru eliminates that particular possibility.<br />
<br />
Another straightforward way to understand why the Guru's information is important is thus. Each blue-eyed person knows two sets of information: what the actual situation is on the island (both now and in the past), and what would happen in a hypothetical situation. Each blue-eyed person then needs only to compare the actual situation to a known hypothetical one, and if it matches up, then they take the corresponding action. Consider this: If there were only one blue-eyed person, and the guru never made the announcement, she would not leave on day 1 because she would not know that N is greater than or equal to 1. Now let's add a second blue-eyed person. Blue-eyes 2 would not be able to inductively determine whether or not to leave on night 2, because blue-eyes 2's knowledge of whether or not to leave on night 2 is dependent on what blue-eyes 1 does on night 1 if and only if blue-eyes 1 knows what to do on night 1. If blue-eyes 1 doesn't know that N is greater than or equal to 1, then blue-eyes 1 doesn't know what to do on night 1. So, her lack of leaving gives blue-eyes 2 no new information, since it was an uninformed action and blue-eyes 2's inductive reasoning was dependent on blue-eyes 1 knowing what to do, and so the inductive process never takes off for the hypothetical situation. This means a hypothetical situation for N people cannot be induced. As such, blue-eyes 100 does not have certain knowledge of the hypothetical situation that would occur on nights 99 and 100, and so even though she knows N = either 99 or 100, she can't take action on either of those nights, because she has no certain hypothetical situation to compare reality to, and as such cannot have certainty about the actions she should take.<br />
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==Trivia==<br />
The web page which contains the puzzle has no {{w|CSS|style sheet}}. The font size of the heading and subheading is increased with deprecated HTML tags, rather than with heading tags. The way the page is displayed therefore depends on the browser's settings. Despite this fact, due to a similarity of default settings between computers, most computers will display the page with a white background, black text, and the {{w|Times New Roman}} font. However, it has two line breaks after every paragraph instead of HTML paragraph breaks, meaning that paragraph spacing will not vary between browsers, relative to the font size.<br />
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{{comic discussion}}<br />
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[[Category:My Hobby]]<br />
[[Category:Multiple Cueballs]]<br />
[[Category:No title text]]<br />
[[Category:Comics with lowercase text]]</div>162.158.154.73https://www.explainxkcd.com/wiki/index.php?title=Talk:301:_Limerick&diff=331095Talk:301: Limerick2023-12-19T01:25:42Z<p>162.158.154.73: I found proof!</p>
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<div>Wow, I just stumbled across this comic via the "Random" button, and I realized that I haven't looked at Slashdot in over a year... Feels good to be free! Now back to obsessively reloading Reddit... [[Special:Contributions/173.245.55.210|173.245.55.210]] 20:40, 5 November 2013 (UTC)<br />
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Limericks are not anapestic trimeter, the meter in most limericks (including this one) is an amphibrach. {{unsigned ip|141.101.104.23}}<br />
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The problem is that there's no fake comment you could add to YouTube that's so stupid it ''couldn't'' have been seriously posted by one of the common members there. — [[User:Kazvorpal|Kazvorpal]] ([[User talk:Kazvorpal|talk]]) 22:48, 3 November 2019 (UTC)<br />
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I found someone who posted to every song in an album some variation of "Is this music?" Two of the songs were spoken word, and one was entirely instrumental, but the first song is a relatively normal punk song. I am almost completely sure they were joking. (The album is Made in a Day by Maki Yamazaki on thevoidsings youtube channel).[[Special:Contributions/162.158.154.73|162.158.154.73]] 01:25, 19 December 2023 (UTC)</div>162.158.154.73https://www.explainxkcd.com/wiki/index.php?title=Talk:2319:_Large_Number_Formats&diff=193441Talk:2319: Large Number Formats2020-06-14T11:44:26Z<p>162.158.154.73: </p>
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<div><!--Please sign your posts with ~~~~ and don't delete this text. New comments should be added at the bottom.--><br />
<br />
Wouldn't Lincoln be:<br />
Two score and nine score and six score and fourteen score and seven score and one score and eighteen score and two score and three score score and four? [[Special:Contributions/162.158.155.194|162.158.155.194]] 11:25, 14 June 2020 (UTC)<br />
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I've added the way I'm familiar with (Polish) to the "normal person in Europe outside of UK" caveat, but I think this still might be over-generalization to say that all Europe outside UK uses "." separator; I've actually never seen it used, but I've seen "'" used, even though I have no connection whatsoever with Switzerland. [[Special:Contributions/162.158.154.175|162.158.154.175]] 11:13, 13 June 2020 (UTC)<br />
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: Yes. We also use the single apostrophe as a thousands separator in Sweden. And in Excel we use the semicolon in formulas, since the comma is used for decimals. <br />
[[User:Embridioum|Embridioum]] ([[User talk:Embridioum|talk]]) 22:18, 13 June 2020 (UTC)<br />
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Would love an explanation of the scientist avoiding rounding one. Would make sense to me with 2.525997..., but as 2.5997... I'm at a loss! {{unsigned ip|198.41.238.106|22:19, 12 June 2020 (UTC)}}<br />
: Truncating the number just before a digit less than 5 so that the final digit is not rounded up. (I do this all the time, and, I am a scientist.) {{unsigned ip|108.162.216.172|00:48, 13 June 2020 (UTC)}}<br />
(The above was posted (anonymously?) seconds before I could get mine in, so here it is in the original format.)<br />
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This is probably completely irrelevant but it seems Randall made a small typo when trying to show a "Scientest trying to avoid rounding up."<br />
I assume it should be 2.525997*10^13. It seems he left out a 5 and a 2 and I say such because whether he forgot the 52 or 25 is up for debate.<br />
<br />
Relevant screenshot: [[https://i.imgur.com/NrvOivy.png]]<br />
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Also, if I'm just being completely daft and am missing something completely, please feel free to criticize me harshly and I'll go back to my little hideyhole. [[Special:Contributions/108.162.237.24|108.162.237.24]] 22:21, 12 June 2020 (UTC)<br />
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: In reality, a scientist would probably say 6.416*10^13 cm. (Although possible counterpoint, this comic is really about the ''number'' 25,259,974,097,204, not the distance 25,259,974,097,204 inches.) [[Special:Contributions/172.69.33.207|172.69.33.207]] 22:47, 12 June 2020 (UTC)<br />
:: Centimetres are not an SI unit. it would be 6.416*10^11 m [[Special:Contributions/172.68.255.14|172.68.255.14]] 01:51, 13 June 2020 (UTC)<br />
::: Depends on field. It can easily be 35.67 light minutes. Or 2140 light seconds if you insist on SI units. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 22:11, 13 June 2020 (UTC)<br />
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I believe the "2.5997" was intentional, or at least I thought it was when reading it. At first I thought it was a typo, but Randall calls that number "Scientist ''trying'' to avoid rounding up" which makes me think Randall intentionally made that "mistake" as if the scientist had accidentally forgotten the first two digits (25) and used the remainder of the number (259974...), rounding it to "2.5997x10^13" [[User:Kirypto|Kirypto]] ([[User talk:Kirypto|talk]]) 23:03, 12 June 2020 (UTC)<br />
: Randall fixed it! [[User:Gvanrossum|Gvanrossum]] ([[User talk:Gvanrossum|talk]]) 05:43, 13 June 2020 (UTC)<br />
:: Looks like that was just a typo, Randall replaced it with a new version. [[User:Natg19|Natg19]] ([[User talk:Natg19|talk]]) 02:55, 13 June 2020 (UTC)<br />
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As a (not so?) old British person, I approve. Let the Trillions come around later, when it's ''worth'' increasing the prefix to "level 3". Don't waste them on the more petty numbers. [[Special:Contributions/162.158.155.122|162.158.155.122]] 23:13, 12 June 2020 (UTC)<br />
:I'm also a not-so-old British person, and therefore use the short-scale as a matter of course. But, although I'm too young to ever have used the long scale, I regret its passing, for all that. On a visual level, if a million gives us a chunk of six zeroes, there's a simple elegance to the "bi-", "tri-", "quad-" (etc.) prefixes numerating two chunks, three chunks, four chunks, etc. From a less visual, more linguistically neat perspective, if you've got a million^2, a million^3, a million^4 and so on, then using "bi" to mean two, "tri" to mean three, "quad" to mean four makes sense...because that's what those things mean.[[User:Yorkshire Pudding|Yorkshire Pudding]] ([[User talk:Yorkshire Pudding|talk]]) 10:32, 13 June 2020 (UTC)<br />
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;"Engineering" notation omitted?<br />
I find it somewhat strange that Randall doesn't offer '''25e12''' or any of those variants ('''25.259...*10^12'''). I feel like a lot of "non-normal" people would map billion to E12 instead of requiring a single digit to the left of the decimal point. shrug [[User:JohnHawkinson|JohnHawkinson]] ([[User talk:JohnHawkinson|talk]]) 23:09, 12 June 2020 (UTC)<br />
: Honestly I thought "engineering" notation was a myth invented by HP's calculator division. But I'm personally offended that the programmers' notation 25_259_... was omitted. Maybe Randall still uses Python 2. :-) [[User:Gvanrossum|Gvanrossum]] ([[User talk:Gvanrossum|talk]]) 05:47, 13 June 2020 (UTC)<br />
::Well, just because HP's calculator division invented something doesn't mean it's a myth. They do have the power to invent things and had the market penetration for their names to have power and influence the world; but for sure, having used HP calculators in high school affected how I thought about numbers in college. But I think anyone who works with SI prefixes on a regular basis and reports results using them will appreciate "engineering" notation given the direct correspondence. And, of course, it also corresponds to how "normal" people use write numbers in the millions/billions/trillions, as this comic shows…which was the point… [[User:JohnHawkinson|JohnHawkinson]] ([[User talk:JohnHawkinson|talk]]) 12:03, 13 June 2020 (UTC)<br />
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"What's an inch?" [[Special:Contributions/162.158.62.119|162.158.62.119]] 23:18, 12 June 2020 (UTC)<br />
: The imaginary nano-scale multiple of the speed of light times Planck's constant. Which, dimensionally, would seem to be kg.m³/s²? [[Special:Contributions/162.158.154.73|162.158.154.73]] 00:15, 13 June 2020 (UTC)<br />
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As an article pointed out to me the other day that seemed obvious after it was said it's a non-tariff trade barrier used as American protectionism that doesn't get tariffed back. {{unsigned ip|172.69.63.81|00:10, 13 June 2020 (UTC)}}<br />
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Can someone explain the set theory notation? {{unsigned ip|172.68.255.14|01:56, 13 June 2020 (UTC)}}<br />
: You can use only sets to construct the natural numbers, see https://en.wikipedia.org/wiki/Natural_number#Constructions_based_on_set_theory - {{unsigned ip|172.68.215.76|02:20, 13 June 2020 (UTC)}}<br />
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It seems nobody has pointed out that the power of 10 in the title text is really just the log(x) of the number, which is in fact very common in scientific contexts -> log(25,259,974,097,204) = 13.4024 [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 02:31, 13 June 2020 (UTC)<br />
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The alternative would be for him to write 10^13.402432900872993447734410070128 (Rounded up). Notation that produces a longer string of digits than the original number seems useless on all fronts but somehow even more fun. I like the current explanation, though. It was insightful, IMO. -B- [[Special:Contributions/162.158.106.126|162.158.106.126]] 17:14, 13 June 2020 (UTC)<br />
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We have kept the olden ways here in the north. Miljon (10^6), miljard (10^9), biljon (10^12), biljard (10^15). Also, "biljard" is the same word as the game of pool in Swedish.<br />
[[User:Embridioum|Embridioum]] ([[User talk:Embridioum|talk]]) 07:17, 13 June 2020 (UTC)<br />
:Another thing an Older British Person might argue about is Billiards, the cue-and-ball game. Often, among all the vaiations, it was the three-ball version (white and white-spot cueballs, for each player, and red ball as the common target) on either pocketted or non-pocketted tables (the former mostly as a sop to using an unmodified snooker table) or, explicitly, Bar Billiards with target holes and obstacle pegs (quite common as early coin-operated pay-to-play tables). Only by succumbing to the americanism was Pool (usually 15-ball, spots+stripes+8ball) ever called billiards. Well, ''I'' thought that was interesting... [[Special:Contributions/162.158.159.136|162.158.159.136]] 12:49, 13 June 2020 (UTC)<br />
::"Why sure I'm a billiard player, certainly mighty proud to say, I'm always mighty proud to say it. I consider that the hours I spend with a cue in my hand are golden." -Harold Hill [[Special:Contributions/108.162.216.60|108.162.216.60]] 14:34, 13 June 2020 (UTC)<br />
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Also Italian uses the long scale for large numbers, and also in Italian the word for the game of pool coincides with 10^15. Albeit I have to say that I've never heard anyone use bilione and biliardo referring to numbers. We usually stop at miliardo, saying things like "un milione di miliardi" when we need to say those large numbers, or use the scientific notation. --[[Special:Contributions/172.68.198.106|172.68.198.106]] 09:04, 13 June 2020 (UTC)<br />
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While we're on different languages, how about this one: 1262998704860-vingt-quatre - French person. --[[User:IByte|IByte]] ([[User talk:IByte|talk]]) 11:11, 13 June 2020 (UTC)<br />
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:Russian uses the short scale, like million, billion, trillion, quadrillion, etc. But it calls a billion a milliard, and a thousand milliards is a trillion. Why? [[Special:Contributions/172.69.68.195|172.69.68.195]] 18:09, 13 June 2020 (UTC)<br />
:: Sounds to me like Russia 'inherited' Milliards from its usage by trade partners at one point in time when that was a number people were starting to want to use seriously, but adopted the short-Trillion from a later time when (different) people were needing to discuss higher values and adopt terms for these into their own tongue. If you check the chequered history of what-means-what (before Short and Long scales were mad3 at least self-consistent among their adherents) you could reasonably blame/credit many different sources for each development. [[Special:Contributions/162.158.158.249|162.158.158.249]] 01:03, 14 June 2020 (UTC)<br />
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Why *that* number? OK, so it's a big number (well, maybe not compared to all the other numbers). One oddity is that the prime factors are:<br />
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2 2 7 11 82012902913<br />
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7 11? Subliminal advertising? If you turn the big prime upside-down calculator style, you get: eigzogzlos8<br />
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I'm surprised that 5 and 23 are missing. In fact, that's almost suspicious.<br />
: I think you're overthinking this, or maybe you got nerdsniped. Randall probably just chose a large number with different digits and being a fan of space, this one worked for him. [[User:Bischoff|Bischoff]] ([[User talk:Bischoff|talk]]) 08:40, 14 June 2020 (UTC)<br />
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I thought in all or most of Europe the thousands separator was a space not a dot. --[[Special:Contributions/162.158.238.4|162.158.238.4]] 03:09, 14 June 2020 (UTC)<br />
: That's actually something interesting I learned from this explanation. I always assumed everyone either used commas (US and UK) or dots (pretty much the rest of at least Europe, never thought much about other continents in this regard) and grouped them in threes. Apparently I was very wrong. The Indian system of grouping digits looks a bit confusing to me, but apparently it corresponds well to their language. [[User:Bischoff|Bischoff]] ([[User talk:Bischoff|talk]]) 08:32, 14 June 2020 (UTC)<br />
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Please refrain from using new sections in the comment section! --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 06:43, 14 June 2020 (UTC)<br />
: What's so bad about them? At least in a comic like this one, where people are actually discussing/commenting on different aspects of the comic, I find sections very helpful to keep track of different conversations. [[User:Bischoff|Bischoff]] ([[User talk:Bischoff|talk]]) 08:22, 14 June 2020 (UTC)<br />
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Re: Software developer, the "power" operand varies wildly across programming languages, some do indeed use ^, some go for ** and some have to resort to something like a pow(x,y) function, but in the languages/dialects I use most the ** operator binds closer than (has order of precedence over) the * operator, so x*10**y would not be (10x)<sup>y</sup> as currently suggested in the Explanation. But ^ is the bitwise operator (lower precedence than *), so would do something even more 'interesting' to the result. Now, obviously, different codes for different coves and all - but I'm dredging my memory for all kinds of obscure scripting languages I've not used for years (what does COBOL do..? Forth is Reverse Polish. Lisp(is(more(Forward(Polish))))) not sure which one Randall is basing it on (if it's not just geek-sniping at its finest). [[Special:Contributions/141.101.107.234|141.101.107.234]] 10:47, 14 June 2020 (UTC)<br />
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Speaking as a set theorist, I'd also describe that number as "Pretty small, just slightly bigger than 1." [[Special:Contributions/162.158.154.73|162.158.154.73]] 11:44, 14 June 2020 (UTC)</div>162.158.154.73https://www.explainxkcd.com/wiki/index.php?title=Talk:2319:_Large_Number_Formats&diff=193312Talk:2319: Large Number Formats2020-06-13T00:15:16Z<p>162.158.154.73: /* Actual scientist: */</p>
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== Scientist avoiding rounding ==<br />
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Would love an explanation of the scientist avoiding rounding one. Would make sense to me with 2.525997..., but as 2.5997... I'm at a loss!<br />
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(The above was posted (anonymously?) seconds before I could get mine in, so here it is in the original format.)<br />
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This is probably completely irrelevant but it seems Randall made a small typo when trying to show a "Scientest trying to avoid rounding up."<br />
I assume it should be 2.525997*10^13. It seems he left out a 5 and a 2 and I say such because whether he forgot the 52 or 25 is up for debate.<br />
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Relevant screenshot: [[https://i.imgur.com/NrvOivy.png]]<br />
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Also, if I'm just being completely daft and am missing something completely, please feel free to criticize me harshly and I'll go back to my little hideyhole. [[Special:Contributions/108.162.237.24|108.162.237.24]] 22:21, 12 June 2020 (UTC)<br />
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In reality, a scientist would probably say 6.416*10^13 cm. (Although possible counterpoint, this comic is really about the ''number'' 25,259,974,097,204, not the distance 25,259,974,097,204 inches.) [[Special:Contributions/172.69.33.207|172.69.33.207]] 22:47, 12 June 2020 (UTC)<br />
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I believe the "2.5997" was intentional, or at least I thought it was when reading it. At first I thought it was a typo, but Randall calls that number "Scientist ''trying'' to avoid rounding up" which makes me think Randall intentionally made that "mistake" as if the scientist had accidentally forgotten the first two digits (25) and used the remainder of the number (259974...), rounding it to "2.5997x10^13" [[User:Kirypto|Kirypto]] ([[User talk:Kirypto|talk]]) 23:03, 12 June 2020 (UTC)<br />
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As a (not so?) old British person, I approve. Let the Trillions come around later, when it's ''worth'' increasing the prefix to "level 3". Don't waste them on the more petty numbers. [[Special:Contributions/162.158.155.122|162.158.155.122]] 23:13, 12 June 2020 (UTC)<br />
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== "Engineering" notation omitted? ==<br />
<br />
I find it somewhat strange that Randall doesn't offer '''25e12''' or any of those variants ('''25.259...*10^12'''). I feel like a lot of "non-normal" people would map billion to E12 instead of requiring a single digit to the left of the decimal point. shrug [[User:JohnHawkinson|JohnHawkinson]] ([[User talk:JohnHawkinson|talk]]) 23:09, 12 June 2020 (UTC)<br />
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==Actual scientist: ==<br />
"What's an inch?" [[Special:Contributions/162.158.62.119|162.158.62.119]] 23:18, 12 June 2020 (UTC)<br />
: The imaginary nano-scale multiple of the speed of light times Planck's constant. Which, dimensionally, would seem to be kg.m³/s²? [[Special:Contributions/162.158.154.73|162.158.154.73]] 00:15, 13 June 2020 (UTC)<br />
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As an article pointed out to me the other day that seemed obvious after it was said it's a non tarrif trade barrier used as American protectionism that doesn't get tarrifed back</div>162.158.154.73https://www.explainxkcd.com/wiki/index.php?title=Talk:1788:_Barge&diff=193269Talk:1788: Barge2020-06-12T12:30:40Z<p>162.158.154.73: </p>
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Any reason why the background is black in this one? [[Special:Contributions/162.158.234.34|162.158.234.34]] 16:35, 20 January 2017 (UTC)<br />
:Black background...huh? [[User:GoonPontoon|GoonPontoon]] ([[User talk:GoonPontoon|talk]]) 18:27, 20 January 2017 (UTC)<br />
::The xkcd Browser Android app, at least, uses black outside the rectangular comic image for this one instead of the usual white. It usually does that for dark-background comics like [[312]]. I don’t know if it gets the color from the site somehow or uses its own heuristics, but either way this isn’t the first time it’s made the “wrong” choice. --[[Special:Contributions/162.158.78.148|162.158.78.148]] 18:40, 20 January 2017 (UTC)<br />
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When did the fine print at the bottom of the xkcd homepage change? [[Special:Contributions/162.158.122.102|162.158.122.102]] 18:08, 20 January 2017 (UTC)<br />
:A few weeks ago, exactly when I'm not sure.<br />
:Actually, [[footnote|for quite a while]] [[User:Jacky720|That's right, Jacky720 just signed this]] ([[User talk:Jacky720|talk]] | [[Special:Contributions/Jacky720|contribs]]) 21:22, 20 January 2017 (UTC)<br />
::Where do we put this kind of information on this wiki? Very funny but not so great as the one about the humour --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 23:16, 20 January 2017 (UTC)<br />
:::A sorry did not understand that the link was to a page on this site: [[footnote]]. Thanks. Have made a link to this page from the page on ([[xkcd]]). --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 14:21, 23 January 2017 (UTC)<br />
::::But much worse the [[xkcd warning]] has also been removed. So sad. Made the page for it. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 15:13, 23 January 2017 (UTC)<br />
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What exactly would cause a rocket to explode when it lands on this trick-barge (and into water)? [[Special:Contributions/141.101.105.48|141.101.105.48]] 08:52, 23 January 2017 (UTC)<br />
:If the computer thinks it landed on a solid barge, it will turn off the engine, and the rocket will tip over, crash into the remaining hull, and explode. If the computer does not think it landed, the engine will enter the water and either go out (tip over, explode) or cause a steam explosion followed by a fuel tank explosion. [[User:Chrullrich|Chrullrich]] ([[User talk:Chrullrich|talk]]) 10:26, 23 January 2017 (UTC)<br />
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I'm not sure it is intended to be destructive, so much as scaling up of the everyday. You know how satisfying it is when you open a new jar of coffee or spread and get to punch the paper seal with a spoon? Randall has previously referred to these little pleasures, like cleaning the dryer fluff in https://xkcd.com/1346/ . [[Special:Contributions/141.101.98.244|141.101.98.244]] 09:32, 23 January 2017 (UTC)<br />
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:I do not think I would take any pleasures engaging in violence against pinnipeds made of compressed wood cellulose, especially with a metallic eating utensil. Fresh dryer fluff is another story while the spread depends on the magazine. [[Special:Contributions/162.158.69.9|162.158.69.9]] 11:38, 23 January 2017 (UTC)<br />
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Actual SpaceX launch was a couple of weeks ago: should we mention it?</div>162.158.154.73https://www.explainxkcd.com/wiki/index.php?title=Talk:2291:_New_Sports_System&diff=190321Talk:2291: New Sports System2020-04-10T10:55:30Z<p>162.158.154.73: Kriegspiel</p>
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Note that the title text goes at the end of the explanation, not within the transcript section. I've removed it twice now. [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 00:41, 9 April 2020 (UTC)<br />
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I really want to see this happen now :D [[Special:Contributions/172.68.174.128|172.68.174.128]] 01:18, 9 April 2020 (UTC)<br />
:Alright, who programs the VR software and who organises the tournament? :D [[User:Fabian42|Fabian42]] ([[User talk:Fabian42|talk]]) 03:17, 9 April 2020 (UTC)<br />
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I find myself wondering how easy it would be to merge the video feeds from the different players, so viewers can see everyone as if it were a traditional match. If each arena has a camera in the same place, it shouldn't be that hard to isolate parts of the image which are different from a static image; but I'm not sure what would be the best method for determining which player is in front when they overlap. I guess you need some method of tracking the players' positions in any case, to work out who's touching the ball. Would the technology used for home VR be easily adaptable to a full size stadium? - [[User:Angel|Angel]] ([[User talk:Angel|talk]]) 10:50, 9 April 2020 (UTC)<br />
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Another way to do it: Each player has their own ball. But only one of the balls is "live" at any given time. Maybe it lights up or something. If another ball contacts the live one, it changes places, allowing you to effectively "tackle" the player who's in possession. Would mean that ball physics are more realistic, while still maintaining the confusion. Maybe also give the players little shock collars to let them know if they collided with another player. (Is running through another player a foul in basketball?) - [[User:Angel|Angel]] ([[User talk:Angel|talk]]) 10:55, 9 April 2020 (UTC)<br />
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:And that's just got me thinking that [[wikipedia:BASEketball|BASEketball]] would be entirely playable in this form - [[User:Angel|Angel]] ([[User talk:Angel|talk]]) 11:13, 9 April 2020 (UTC)<br />
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This reminds me very much of the chess variant [https://en.wikipedia.org/wiki/Kriegspiel_(chess) Kriegspeil]. [[Special:Contributions/162.158.154.73|162.158.154.73]] 10:55, 10 April 2020 (UTC)</div>162.158.154.73https://www.explainxkcd.com/wiki/index.php?title=1093:_Forget&diff=1496891093: Forget2017-12-22T18:58:00Z<p>162.158.154.73: /* Transcript */</p>
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<div>{{comic<br />
| number = 1093<br />
| date = August 10, 2012<br />
| title = Forget<br />
| image = forget.png<br />
| titletext = 'Baby Got Back' turned 20 this year. My favorite nostalgia show is VH1's 'I Love The Inexorable March of Time Toward the Grave That Awaits Us All.'<br />
}}<br />
<br />
==Explanation==<br />
The median age in {{w|USA}} is currently about 37 years. Assuming that you must be at least five years old to remember a cultural event later, this means that anything that happened more than thirty-two years ago is remembered by a minority of people today. This applies to any event prior to 1980, so here in 2012, the majority of Americans are too young to remember the Seventies. However, according to census estimation the median will raise in the future, so instead of a 32 years gap between event and the moment when most people can't remember it, the gap becomes 35 years (implying a median of some 40 years).<br />
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'''2013: The Carter presidency''' {{w|Jimmy Carter}} was the {{w|President of the United States}} from 1977-1981. He lost all popularity after he was viewed as mishandling several crises during his presidency, including the {{w|Three Mile Island accident}}, the {{w|Iran hostage crisis}}, and the "{{w|stagflation}}" of the late 1970s. According to Wikipedia, his decisions to reinstate registration for the draft and his decision to boycott the {{w|1980 Summer Olympics}} in Moscow (over the 1979 Soviet invasion of Afghanistan) helped contribute to his defeat in the 1980 Presidential campaign.<br />
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'''2014: The Reagan shooting''' References the 1981 {{w|Reagan assassination attempt|assassination attempt}} on the then American president, {{w|Ronald Reagan}}.<br />
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'''2015: The Falkland Islands War''' This is in reference to the {{w|Falklands War|brief outbreak of hostilities}} between the {{w|UK}} and {{w|Argentina}} over the {{w|Falkland Islands|Falkland Islands (Islas Malvinas)}} located off the shore of Argentina claimed by both but controlled by the UK. Even to this date, tensions remain high over the ownership of these islands, and while many people alive today weren't alive to witness it, it nevertheless remains present in the collective psyche of both nations.<br />
<br />
'''2017: The first Apple Macintosh''' The {{w|Macintosh}} was a line of computers created by {{w|Apple Inc.|Apple}}, first introduced in 1984, with the {{w|Macintosh 128K}}.<br />
<br />
'''2018: New Coke''' References a public relations blunder that the Coca Cola corporation undertook in attempting to reformulate its cola recipe, the new formula called {{w|New Coke}} popularly. The public backlash so shook the company that they reintroduced the original recipe as {{w|Coca-Cola Classic}} within 3 months. New Coke was eventually rebranded from Coca-Cola to Coke II, and then discontinued. Coca-Cola Classic has quietly been rebranded back to simply Coca-Cola, as it originally was. The "New Coke" introduction is considered one of the biggest PR blunders from a major company ever.<br />
<br />
'''2019: Challenger''' The {{w|Space Shuttle Challenger|Challenger}} was a {{w|NASA}} space shuttle, which was launched in 1986, but {{w|Space Shuttle Challenger disaster|exploded}} 72 seconds into its flight, killing everyone aboard, including {{w|Christa McAuliffe}}, a teacher selected to be the first teacher in space.<br />
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'''2020: Chernobyl''' Refers to the 1986 meltdown of a {{w|Chernobyl|nuclear power plant}} in the {{w|Ukranian SSR}} (then a part of the Soviet Union). The meltdown forced the nearby city of {{w|Pripyat}} to be abandoned, and it remains a ghost town today.<br />
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'''2021: Black Monday''' Refers to the 1987 {{w|Black Monday (1987)|day}} of the largest one-day {{w|stock market}} drop in history.<br />
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'''2022: The Reagan presidency''' {{w|Ronald Reagan}} was an American president from 1981 to 1989, and was a generally well received president known for ending the Cold War, oversaw the {{w|Iran–Contra affair}}, {{w|Invasion of Grenada|invading Grenada}}, and issuing forth a number of new {{w|Reaganomics|economic policies}}.<br />
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'''2023: The Berlin Wall''' Refers to the {{w|Berlin Wall|barrier}} surrounding the western-controlled part of {{w|Berlin}}. It was erected by the {{w|East Germany|East German}} Government in 1961 to stop illegal emigration to West Berlin-the western-controlled enclave after the ending of the Second World War. After a friendly revolution in 1989, emigration to West Berlin (and West German in general) was granted suddenly and very surprisingly again on November 9, 1989. The following rush of people to the Wall from East (to cross the border) and from West (to welcome friends and relatives) in that night coined the figurative "Fall of the Wall", preceding the actual reunion of Germany in 1990 and (almost) complete demolition of the Wall.<br />
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'''2024: HammerTime''' Refers to a refrain in {{w|MC Hammer|MC Hammer's}} 1990 hit song {{w|U Can't Touch This}}; [[Randall Munroe]] makes reference to this song elsewhere in his comics, too (specifically [[108: M.C. Hammer Slide]] and [[210: 90's Flowchart]]).<br />
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'''2025: The Soviet Union''' Refers to a country emerging after the end of {{w|World War I}}. It became the cold-war adversary of the United States after the end of {{w|World War II}} and only collapsed in 1991.<br />
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'''2026: The LA Riots''' Refers to the {{w|1992 Los Angeles riots|massive riots}} occurring at the release of the verdict acquitting the officers accused of the {{w|Rodney King}} beatings in 1992.<br />
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'''2027: Lorena Bobbit''' Refers to the {{w|John and Lorena Bobbitt|woman}} who {{w|emasculated}} her husband in 1993.<br />
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'''2028: The Forrest Gump release''' ''{{w|Forrest Gump}}'' was a 1994 drama starring {{w|Tom Hanks}} as a mentally disabled man, telling his spectacular life story. The movie had a highly successful release, and remains one of the greatest films of all time.<br />
<br />
'''2029: The Rwanda Genocide''' Refers to the 1994 {{w|Rwandan genocide}}, where an estimated 800,000 people were killed.<br />
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'''2030: OJ Simpson's Trial''' The {{w|O. J. Simpson murder case|O.J. Simpson trial}} was a famous criminal case during which {{w|O.J. Simpson}}, a professional football player, was {{w|acquitted}} of the murder of {{w|Nicole Simpson}} and {{w|Ronald Goldman}}. He was later arrested and jailed for other crimes, including armed robbery and kidnapping.<br />
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'''2031: Clinton's reelection''' {{w|Bill Clinton}} was the American president from 1993 to 2001. He won his second term in the {{w|United States presidential election, 1996|1996 presidential election}}. During his second term, he faced controversy during an {{w|impeachment}} trial, for which he was acquitted, and a large number of pardons he made on his last day of office. Clinton was a generally favoured president, exiting his presidency with a high approval rate.<br />
<br />
'''2032: Princess Diana''' {{w|Princess Diana}} was a famous {{w|Commonwealth}} princess who made headlines after her 1997 {{w|Death of Diana, Princess of Wales|death}} in a car crash.<br />
<br />
'''2033: Clinton's impeachment''' In 1998, the American {{w|Congress}} voted to {{w|Impeachment of Bill Clinton|impeach}} then-president Clinton, based on allegations that he {{w|Lewinsky scandal|lied}} about relations with a {{w|Monica Lewinsky|White House intern}}. He was later acquitted.<br />
<br />
'''2034: Columbine''' Refers to the 1999 {{w|Columbine High School massacre}}, where 13 people were killed by a {{w|Eric Harris and Dylan Klebold|pair of shooters}}.<br />
<br />
'''2035: Forgot About Dre''' Refers to the {{w|Grammy}} winning 2000 song, "{{w|Forgot About Dre}}," by the rapper {{w|Dr. Dre}}. In it, Dre complains that his accomplishments have been purposefully ignored and forgotten; ironically, at some point in the future Dre's complaints about being forgotten will, themselves, be forgotten.<br />
<br />
'''2036: 9/11''' Refers to the {{w|9/11}} event, in 2001, where terrorists crashed two planes into the {{w|World Trade Center}} towers, in {{w|New York}}. Two other planes crashed that day: one into the {{w|The Pentagon}}, and one in a field outside of {{w|Shanksville, Pennsylvania}} (presumably on its way to crashing into the Capitol Building).<br />
<br />
'''2037: VH1's I love the 80s''' ''{{w|I Love the '80s (U.S. TV series)|I Love the '80s}}'' was a 2002 nostalgia TV series by {{w|VH1}}. This will make the 1980s doubly forgotten; not only will people not remember the decade, they will not remember the famous retrospective of people remembering the decade.<br />
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'''2038: A time before Facebook''' Refers to the online social media site, {{w|Facebook}}, launched in 2004.<br />
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'''2039: VH1's I love the 90s''' ''{{w|I Love the '90s (U.S. TV series)|I Love the '90s}}'' was a TV series airing in 2004.<br />
<br />
'''2040: Hurricane Katrina''' {{w|Hurricane Katrina}} was a devastating 2005 hurricane that hit {{w|New Orleans}}, killing almost 2000 people and causing 81 billion dollars in damage.<br />
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'''2041: The planet Pluto''' {{w|Pluto}} is a {{w|dwarf planet}} in our solar system. Up until 2006, Pluto was considered to be a planet.<br />
<br />
'''2042: The first iPhone''' {{w|Apple}}'s first iPhone was released in 2007.<br />
<br />
'''2043: The Bush presidency''' {{w|George W. Bush}} was the American presidency from 2001 to 2009. He was criticized for the wars on {{w|War in Afghanistan (2001%E2%80%93present)|Afghanistan}} and {{w|Iraq War|Iraq}}, poor handling of Hurricane Katrina, and seeing the United States enter a recession. His approval peaked after the 9/11 attacks, but had fallen to historical lows by the end of his second term, making him one of the least liked US presidents.<br />
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'''2044: Michael Jackson''' Refers to the {{w|Michael Jackson|pop singer}} who died of drug overdose in 2009.<br />
<br />
'''2045: Trying to say Eyjafjallajökull''' Is a reference to a volcano in {{w|Iceland}} that {{w|Eyjafjallajökull#2010 eruptions|erupted}} in 2010. The eruption threw volcanic ash several kilometres up in the atmosphere, which led to air travel disruption in northwest Europe for six days.<br />
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'''2046: The Arab Spring''' Refers to the {{w|Arab Spring|wave of revolutions}} that began in late 2010, where many Arabic nations overthrew leaders and started civil wars, with many nations converting to democracies.<br />
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'''2047: Anything embarrassing you do today''' Refers to the fact that in 35 years, the majority of Americans will not have been around on this date.<br />
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The title text is in reference to the vastly over-saturated programming on VH1 dedicated to the history of the TV universe.<br />
<br />
==Transcript==<br />
:'''When Will We Forget?'''<br />
:Based on US Census Bureau ''National Population Projections''<br />
:Assuming we don't remember cultural events from before age 5 or 6<br />
<br />
:By this year: The majority of Americans will be too young to remember:<br />
:2012: The seventies<br />
:2013: The Carter presidency<br />
:2014: The Reagan shooting<br />
:2015: The Falkland Islands war<br />
:2016: ''The return of the Jedi'' release<br />
:2017: The first Apple Macintosh<br />
:2018: New Coke<br />
:2019: ''Challenger''<br />
:2020: Chernobyl<br />
:2021: Black Monday<br />
:2022: The Reagan presidency<br />
:2023: The Berlin Wall<br />
:2024: HammerTime<br />
:2025: The Soviet Union<br />
:2026: The LA Riots<br />
:2027: Lorena Bobbit<br />
:2028: The ''Forrest Gump'' release<br />
:2029: The Rwanda Genocide<br />
:2030: OJ Simpson's Trial<br />
:2031: Clinton's reelection<br />
:2032: Princess Diana<br />
:2033: Clinton's impeachment<br />
:2034: Columbine<br />
:2035: ''Forgot About Dre''<br />
:2036: 9/11<br />
:2037: VH1's ''I love the 80s''<br />
:2038: A time before Facebook<br />
:2039: VH1's ''I love the 90s''<br />
:2040: Hurricane Katrina<br />
:2041: The planet Pluto<br />
:2042: The first iPhone<br />
:2043: The Bush presidency<br />
:2044: Michael Jackson<br />
:2045: Trying to say ´´Eyjafjallajökull``<br />
:2046: The Arab Spring<br />
:2047: Anything embarrassing you do today<br />
<br />
{{comic discussion}}<br />
<br />
[[Category:Charts]]<br />
[[Category:Comics to make one feel old]]</div>162.158.154.73https://www.explainxkcd.com/wiki/index.php?title=1885:_Ensemble_Model&diff=1449941885: Ensemble Model2017-09-05T11:20:05Z<p>162.158.154.73: </p>
<hr />
<div>{{comic<br />
| number = 1885<br />
| date = September 4, 2017<br />
| title = Ensemble Model<br />
| image = ensemble_model.png<br />
| titletext = I'm in talks with Netflix to produce an alternate-universe crime drama about the world where sliced bread was never re-legalized, but it's going slowly because they keep changing their phone numbers and the door lock codes at their headquarters.<br />
}}<br />
<br />
==Explanation==<br />
{{incomplete|Requires descriptions of each entry. Do NOT delete this tag too soon.}}<br />
<br />
An {{w|ensemble forecasting|ensemble model}} is a combination of multiple, similar models to show a wider range of possible outcomes. The graphs on the left are tracks of predictions from multiple models. In this comic, Randall starts out describing actual changes that ensemble models show, but sinks into absurdity, describing strange alternate universes and scenarios that likely would not be necessary in an actual model.<br />
<br />
The upper graph looks like one plotting global temperatures with time using different scenarios, like this one: https://www.ipcc.ch/publications_and_data/ar4/wg1/en/figure-spm-5.html<br />
The bottom right graph is a typical hurricane path-prediction graphic.<br />
<br />
Not all of the outcomes are serious. They are explained below:<br />
;…rain is 0.5% more likely in some areas<br />
Historical rain data are used to estimate the probability of rainstorms of a certain size and duration occurring, e.g. the {{w|Flood Studies Report|Flood Studies Report}} in the UK. [[Randall]] here is suggesting that an alternate universe exists where these estimates are higher (and presumably lower) in some areas, and that the estimates of rainfall in this alternate universe is accounted for within ensemble modelling in our own universe. This sort of change in prediction is frequently used when accounting for 'worst case scenarios' in the design processes of structures such as dams. However, the figures to the left appear to indicate time-dependent models, which are typically physics based, e.g. {{w|Large eddy simulation|Large Eddy Simulation}} models or other atmospheric process based models. In those sorts of models, likelihood of rain is usually a prediction rather than a parameter, but might be used as a parameter in a second iteration.<br />
<br />
;…wind speeds are slightly lower<br />
A usual parameter.<br />
<br />
;…pressure levels are randomly tweaked<br />
A very vague but otherwise understandable parameter.<br />
<br />
;…dogs run slightly faster<br />
This is where the comic diverges from reality; there is no reason to have the locomotion speed of dogs as a parameter.<br />
<br />
;…there is one extra cloud in the Bahamas<br />
This situation is most likely too specific and subtle a difference to be useful to the model.<br />
<br />
;…Germany won WWII<br />
"What if Germany won World War II" is a {{w|Hypothetical Axis victory in World War II|very popular}} subject for {{w|alternate history}} stories.<br />
<br />
;…snakes are wide instead of long<br />
<br />
;…Will Smith took the lead in ''The Matrix'' instead of ''Wild Wild West''<br />
Actor {{w|Will Smith}} famously turned down the lead role of {{w|Neo (The Matrix)|Neo}} in ''{{w|The Matrix}}'', instead taking the role of Captain James T. West in the widely-panned action-comedy ''{{w|Wild Wild West}}''. The role of Neo ultimately went to {{w|Keanu Reeves}}. For a more detailed discussion of how the cinematic world would have been different had Smith taken the role, see [https://moviepilot.com/posts/2481780 "How Will Smith Turned Down "The Matrix" - And Blew A Chance To Change Hollywood Forever."]<br />
<br />
;…swimming pools are carbonated<br />
A simple calculation reveals this as a serious {{w|Greenhouse effect|greenhouse}} problem. In the United States there are not less than 5,000,000 private owned pools. Conservatively assumed a volume of 25,000 liters per pool gives 125 billion liters of carbonated soda. According to Wikipedia the U.S. sales reached around 30 billion bottles of water in 2008 (including non carbonated water) which is surely much less than all the pool water. While all those bottles are not considered to have an impact on the green house effect this scenario is getting even worse. Open a bottle of carbonated water and fill the content into glasses. More or less soon the sprinkling is over, meaning you have to open the next bottle and so on. In a pool at the bottom the pressure is high enough to hold the carbon dioxide but on the surface it behaves like the glass. So, while a glass needs new carbonated water every two hours, or ten times per day, let's say it's three times per day for the pool which leads to one thousand times per year. The total number in this scenario would be 125 trillion liters of carbonated soda, ejecting carbon dioxide, per year. But stop: The carbon dioxide used for artificial carbonated water is taken from the air and because of the pressure at the bottom of the pool it doesn't release all back this should have a positive effect. But as Randall has shown in {{what if|88|Soda Sequestration}} this effect would be minimal.<br />
<br />
;…sliced bread, after being banned in January 1943, was never re-legalized.<br />
{{w|Sliced bread}} was in fact {{w|Sliced bread#1943 U.S. ban on sliced bread|banned in the US}} for about two months in early 1943, as a supposed wartime conservation measure. The issue was not the bread itself, but that the pre-sliced loaves required a heavier {{w|wax paper}} wrapping to prevent them from drying out too quickly.<br />
<br />
The title text suggests that [[Randall]] has been pitching an absurd "alternate-universe crime drama" to {{w|Netflix}}. He indicates that a breakdown in communication has occurred between them, though he does not assume directly assume responsibility for this situation. It is nonetheless clear that Netflix has zero interest in the pitch, and so Randall has become overzealous in pushing his idea, to the point that Netflix employees are changing their numbers (presumably they can't block his number because he has resorted to calling from many different phones). He has even taken to infiltrating Netflix's corporate headquarters using ill-gotten security codes, which is definitely illegal{{Citation needed}}, much like [[Elaine]]'s "meetings" with Steve Jobs in [[1337: Part 3]].<br />
<br />
However, it is clear that Netflix is uninterested and is attempting to prevent Randall from contacting them (or trespassing into the building).<br />
<br />
==Transcript==<br />
:[Inside this single panel comic the header on top reads:]<br />
:In an ''ensemble model'', forecasters run many different versions of a weather model with slightly different initial conditions. This helps account for uncertainty and shows forecasters a spread of possible outcomes.<br />
<br />
:[To the left side a picture shows several gray overlapping swirling lines emitted from a point, then gradually diverging rightwards. Below are two smaller pictures; the first shows the lines connected to several loops and in the second it's still a similar figure to the above but moving into the opposite direction with the point emerged to a spiral.]<br />
<br />
:[The text right to the pictures reads:]<br />
:'''Members in a typical ensemble:'''<br />
:A universe where…<br />
:…rain is 0.5% more likely in some areas<br />
:…wind speeds are slightly lower<br />
:…pressure levels are randomly tweaked<br />
:…dogs run slightly faster<br />
:…there's one extra cloud in the Bahamas<br />
:…Germany won WWII<br />
:…snakes are wide instead of long<br />
:…Will Smith took the lead in ''The Matrix'' instead of ''Wild Wild West''<br />
:…swimming pools are carbonated<br />
:…sliced bread, after being banned in January 1943, was never re-legalized.<br />
<br />
{{comic discussion}}<br />
<br />
[[Category:Science]]</div>162.158.154.73