explain xkcd - User contributions [en]

Talk:3023: The Maritime Approximation

2024-12-13T06:39:18Z

141.101.105.87:

1.609*3.1416926 looks like 1.852*2.718281828
''seems legit'' {{unsigned ip|172.71.124.233|21:37, 11 December 2024 (UTC)}}

I added the basics of an explanation, it definitely needs some work, but it should do as a starting point. Hope I did well! [[Special:Contributions/172.68.22.92|172.68.22.92]] 23:06, 11 December 2024 (UTC)

The knot is exactly 1 nautical mile per hour. Meanwhile π/e ≈ 1.155727, which is close to nm/mi = kt/mph ≈ 1.15078
[[Special:Contributions/172.70.134.135|172.70.134.135]] 23:26, 11 December 2024 (UTC)

This article says one knot is 1.2 MPH, which is true for the number of digits of precision stated. But in context of the claimed precision of 0.5% it would be more helpful to state that one knot is approximately 1.151 MPH. https://en.wikipedia.org/wiki/Knot_(unit) [[Special:Contributions/172.71.159.7|172.71.159.7]] 00:08, 12 December 2024 (UTC)

Transcendental : relating to a spiritual realm. eg "the transcendental importance of each person's soul". Works for me. {{unsigned ip|162.158.186.248|00:09, 12 December 2024 (UTC)}}
:Just as a fun fact, "transcendental" in this case is referring to {{W|Transcendental number}}, which are numbers that cannot be expressed as the root of a polynomial, which basically means they cannot be found using algebra alone. I think the two definitions are related, since these numbers "trancend" the "realm" of numbers which can be found with algebra. [[Special:Contributions/172.68.22.82|172.68.22.82]] 01:04, 12 December 2024 (UTC)

Another maritime approximation: 1 meter/sec nearly equals 2 knots (actual is 1.94384), perhaps there is an actual explanation for this? {{unsigned ip|162.158.155.117|01:36, 12 December 2024 (UTC)}}
:Both the nautical mile and meter derive from measurements of the Earth's circumference, and the number of seconds in an hour is related to the base-60 counting system (as is the number of degrees in a circle), but beyond that it's just how the math works out. 1 nautical mile is (well, was) 1/60 of a degree of latitude. 1 meter is (was) 1/10,000,000 of the distance from the Equator to the North Pole, which is 90°, so that's 9/1,000,000 of a degree of latitude. So 1 m = 27/50,000 nmi. Then, an hour is 3600 s. So 1 m/s = 27∙3600/50,000 nmi/hr. Cancelling, that's 1 m/s = 243/125 nmi/hr, and that fraction is quite close to 2. But there's no real deeper connection.[[Special:Contributions/172.70.115.102|172.70.115.102]] 15:08, 12 December 2024 (UTC)

A better mnemonic, which I actually use: miles→km is Fibonacci. 2miles≈3km, 3miles≈5km, 5miles≈8km, 8miles≈13km, 13miles≈21km, 21miles≈34km, 34miles≈55km, 55miles≈89km, 89miles≈143.23km, Fibonacchi would predict 144km. But at that point, you can just remove some less significant digits anyway. For everything in between, you can estimate how far it is from the nearest Fibonacci numbers, that works pretty well, too. [[User:Fabian42|Fabian42]] ([[User talk:Fabian42|talk]]) 01:54, 12 December 2024 (UTC)
: Yes, similar to this comic the ratio of km to miles (1.6093) is very close to the golden ratio (1.6180) or (1 + sqrt(5))/2. [[Special:Contributions/172.68.54.64|172.68.54.64]] 04:28, 12 December 2024 (UTC)

My favorite one is that pi squared is approximately the acceleration of gravity (9.8 m/s^2). The best part is that is NOT a coincidence. [[Special:Contributions/172.71.183.174|172.71.183.174]] 06:11, 12 December 2024 (UTC)
: How is this not a coincidence? ([[User:Wowitschris|Wowitschris]] ([[User talk:Wowitschris|talk]]) 20:56, 12 December 2024 (UTC))
::It's actually a coincidence, but in a weird sense it almost would not be. When French revolutionaries invented the metric system, they considered defining the meter as the length of a pendulum with a period of one second. If they had done that, g would be exactly pi squared. But it was already known back then that g varies with location, so the actual definition based on earth's circumference was adopted --[[Special:Contributions/141.101.105.87|141.101.105.87]] 06:39, 13 December 2024 (UTC)
Actually the most common form of Euler's identity is e<sup>iπ</sup> + 1 = 0; I find it odd that Randall never writes it that way (see [[179]] and [[2492]] for example).
--[[Special:Contributions/172.69.68.4|172.69.68.4]] 12:47, 12 December 2024 (UTC)
:The form that you wrote and Randal's preferred form are identical. The equations are slightly different, but they are the same <b>form</b>. Other forms would involve using trigonometric functions, infinite series, integrals or ... something else. [[User:Galeindfal|Galeindfal]] ([[User talk:Galeindfal|talk]]) 18:38, 12 December 2024 (UTC)

1306: Sigil Cycle

2024-07-29T06:34:19Z

141.101.105.87: /* Explanation */

{{comic
| number = 1306
| date = December 20, 2013
| title = Sigil Cycle
| image = sigil_cycle.png
| titletext = The cycle seems to be 'we need these symbols to clarify what types of things we're referring to!' followed by 'wait, it turns out words already do that.'
}}

==Explanation==
In {{w|computer programming}}, a variable is a way of storing information temporarily, for use later in the program. There are different types of variables, called {{w|Data type|data types}}, such as integers, strings, characters, and booleans, all of them holding different types of information. Integers hold whole numbers, strings hold text, and so on. Variables traditionally have names that identify their purpose, and a programmer should usually be able to infer from this variable name what type of variable it is. For example, if you want to store the name of the customer in a catalogue service, you might store the text in a string variable called "NameOfCustomer". Because it is fairly clear that names are made up of text, it is logical that this variable would be a string variable - if you didn't have any other information about it.

A {{w|Sigil (computer programming)|sigil}} in computer programming is a symbol that appears before the variable name. It is an alternative method of telling someone who is reading the program code what data type the variable is. Rather than relying on logic, then, to know that NameOfCustomer is a string, you might use a sigil "$" before the variable name, as in $NameOfCustomer, which would specify that the variable can hold text. Sigils can also specify the {{w|Scope (computer science)|scope}} of a variable, which refers to where the variable can be used in a program, and which parts of the program can access that variable. Sigils are useful in some ways because you don't have to refer to previous program code or find where the variable is declared (created) to know what data type it is. They also provide some level typing in languages that do not explicitly declare the type of the variable.

Most {{w|Programming language|programming languages}} have a different method for storing variables, although some languages may use the same variable types under different names. The following are the programming languages referenced in the comic and how they use variables.

;{{w|QBASIC}}
:Variables of type string end with the $ symbol. Other symbols are used (% for integers, ! for single-precision, # for double-precision and, in some versions of BASIC, & for long integers), however the usual QBASIC program will use only the $ symbol and not any of the others, as the default type if no symbol is used is single-precision and that's OK for most numeric uses.

;{{w|C++}}
:Pronounced "see plus plus." Variables are just words with regular letters. It is the name of the language itself that includes symbols.

;{{w|bash (Unix shell)|bash}}
:This is not typically thought of as a full-featured programming language, but a Unix shell. However, the shell command syntax is rich enough to be able to write simple (and sometimes really complex) programs called shell-scripts. In this language, all variable dereferences start with the symbol $.

;{{w|Perl}}
:In Perl, the initial character provides the context of the variable. Scalars (text, numeric and also to references to data) start with the $ character. An @ is for an array. With %, it is a hash (a loose non-sequential array, or 'dictionary' lookup). Functions ''can'' be given a preceding &, but rarely need this in straightforward use. You can use the variables $temp, @temp, %temp and &temp simultaneously and independently. There is also the * (not in a mathematical sense) which identifies a 'glob', a way to fuse or use all those types (and more!) in 'interesting' ways if you have a yen to.
:A block, with {} surrounding some other suitable statement(s), can potentially be typed to (re)interpret the context within. If you have a $reference which currently points to an @array, @{$reference} will let you use it as a direct array. But in simple cases, like that, this can often be shortened to @$reference, as alluded to by the "@$PERL" of the comic. (Just as $$reference would be a valid way to dereference the $reference when it points to $scalar... or even to $anotherReference that itself points to a %hash, in which case you could even use %$$reference for 'direct' access to that. Perl can be complicated, if you let it!)

;{{w|Python (programming language)|Python}}
:Variables are just words with regular letters.

;{{w|Google}}
:Once upon a search query, Google added a social network called "[[918|Google+]]" (pronounced "Google plus") to its many offerings. On this network, accounts were identified and "mentioned" (linked in a message, and sent a notification) with a + prefix. For example, [[Randall]] was "+Randall Munroe". Google+ has been defunct since 2019, but it was active and growing in 2013 when this comic was posted.

;{{w|Twitter}}
:Twitter account IDs are identified by the leading symbol @. When an account is "mentioned" in a tweet using @, it triggers smart behavior. For example, account owners can configure Twitter to forward tweets that mention them. This feature was not present in the early days of Twitter.

;{{w|Hashtag}}s
:In 2007 Twitter users began a convention that a # sign (whose {{w|Number sign|many names}} include the "hash") can be prepended to words to mark them as keywords. Twitter could then be searched for those words. In 2009 Twitter recognized the existence of hashtags and began hyperlinking them. Some other microblogging services followed suit. Google+ eventually added hashtag support as did Facebook.

As is noted by the comic, the use of sigils to indicate types of variables varies between programming languages, from strict enforcement in languages like Perl, to their complete absence in languages like C++ (but see {{w|Hungarian Notation}}). The comic notes that the use of sigils seems to be cyclic, especially if you count things like hashtags as extensions of the pattern.

The title text describes the two competing influences responsible for the cycle: The first impulse finds sigils useful to elucidate the type of the variable, especially when variable names are not very descriptive, while the latter impulse notes that descriptive variable names are much more useful for that purpose, especially in extensible languages where the built-in types form only a small part of the type system.

==Transcript==
:A sinusoidal curve is shown.
:Y axis: Odds that the words I type will start with some weird symbol
:X axis: Time
:Data labels: [at first peak] $QBASIC, [at first trough] C++, [at second peak] $BASH, @$PERL, [at second trough] PYTHON, [at third peak] +GOOGLE, @TWITTER, #HASHTAGS

{{comic discussion}}

[[Category:Line graphs]]
[[Category:Computers]]
[[Category:Internet]]
[[Category:Programming]]
[[Category:Social networking]]
[[Category:Google Plus]]

1305: Undocumented Feature

2024-07-29T06:33:06Z

141.101.105.87: /* Explanation */

{{comic
| number = 1305
| date = December 18, 2013
| title = Undocumented Feature
| before = [[#Explanation|↓ Skip to explanation ↓]]
| image = undocumented_feature.png
| titletext = And it doesn't pop up a box every time asking you to use your real name. In fact, there's no way to set your name at all. You just have to keep reminding people who you are.
}}

==Explanation==
An {{w|undocumented feature}} is a part of a software product that is not explained in the documentation for the product. [[Cueball]] has found such a feature, a chat room intended to ask for help, accessible through the help page of some unnamed old Windows utility. The people who found the chat room started out using it for its intended purpose (helping users of the utility by contacting other users), however as time has passed they have become friends and enter the chat only to talk to each other, with no relation to computer problems.

A {{w|virtual machine}} (or VM) is a computer program designed to emulate the hardware of a full computer. In this case, users of the old chat room create VMs only to have the old operating system installed which included the utility program. They use this setup only to access the old chat room. This is shown in the third panel where [[Cueball]] is using a modern laptop to enter the chatroom (presumably by means of a VM), whereas [[Ponytail]] is most likely using an old computer (as evidenced by the CRT monitor).

A chat room like this must be hosted on some outside server, so the narrator of the comic wonders who runs this server. An obvious thought about this is if and when the server will be shut down, effectively cutting all communication among chat users. Another obvious thought is why the utility author is still maintaining the chat server, since its original purpose of allowing communication between users with problems with the utility program is no longer an issue as everybody has migrated to more modern systems. The comic suggests that the reason for doing this can be a bored {{w|System administrator|sysadmin}}, who is just reading the messages of the chat users and following their lives but never writing anything. This would turn the chat room into a {{w|soap opera}} for the sysadmin.

The {{w|Deep Web}} is a term used to refer to any information which is available online, but is hard to find (usually because there are no links to that information in web pages). The chat room described would be an example of this. From this point on, the comic takes an {{w|existentialist}} turn (a [[220|frequent xkcd trait]]), talking about how life is short, everything has to end, etc.

The last panel is a reference to [http://online.wsj.com/news/articles/SB10001424052702304403804579263371125671670 Facebook's recent announcement] that it would start autoplaying video ads, and the title text refers to YouTube requiring its users to use their real-life identities instead of just nicknames. These last parts of the comics somehow reveal that the point of the whole comic is just to complain about aggressive money-driven policies used by modern social networks in general and Facebook in particular. It is hinted that [[Randall]] would prefer older technologies, where limited resources would forbid autoplaying videos or huge databases with every detail of every user's life.

It's possible that the comic is about an actual chat room (like euphoria.leet.nu/xkcd), but more likely it is a complete invention, since if it were real someone would have been able to trace its origin. However, if it is real, the participants would not want to confirm this in order to protect their privacy.

The title text mentions the simplicity of this chat; even user names do not exist and other users could only be identified by their behavior.

==Transcript==
:[A support window is shown.]
:An old Windows utility has an undocumented feature. If you open "help" and click on the background, you get dropped into a "support" chat room.
:Support Window: Launching support forum...

:[An active conversation between two people is shown.]
:Only a few of us ever found it. But we became friends.

:[Cueball and Ponytail are at computers.]
:We kept launching the program to check in. Eventually some of us were running VMs just to keep accessing it.

:[Another conversation.]
:As the Internet aged, so did we.

:[Three question marks.]
:We don't know who runs the server. We don't know why it's still working so many years later. Maybe we're some sysadmin's soap opera.

:[A group of people are shown in a bubble.]
:It will probably vanish someday, but for now it's our meeting place. Our hideaway.

:[The bubble is now smaller, and some parts of a web are shown.]
:A life's worth of chat,

:[More of the web is shown.]
:Buried in the deep web.

:[A flat landscape is shown with the sun at the horizon.]
:But even if it lasts forever, ''we'' won't. When we're gone, who will remember us?

:[Cueball and Hairy are shown standing together in a bubble.]
:Who will remember this strange little world and the friendships we built here?

:[No panel shown:]
:Nobody.

:[An empty bubble is shown.]
:This place is irrelevant. Ephemeral. One day it will be forgotten.

:[The bubble starts to fade away.]
:And so will we

:[The bubble has almost completely faded away.]

:[The bubble is now completely gone.]

:[Caption inside a new panel:]
:But at least it doesn't have fucking video ads.

==Trivia==
There are many examples of undocumented features in programs written for old versions of Windows, for example:
*When playing {{w|Solitaire (Windows)|Windows Solitaire}} with the "draw three" option, one can [http://www.eeggs.com/items/42178.html draw single cards] by holding <Ctrl+Alt+Shift> while clicking on the card to draw cards.
*When playing {{w|Microsoft Minesweeper|Windows Minesweeper}} in pre-Windows-95 versions, typing "{{w|xyzzy}}" followed by <Enter> and then <Right-shift>, will [http://www.eeggs.com/items/49964.html turn the top left pixel] of the windows background black or white to indicate if the mouse is over a mine or not.
*The first releases of {{w|Windows 95}} allowed one to see the "credits" for Win95 by creating a folder in the desktop and then [http://www.eeggs.com/items/478.html renaming it several times].
*{{w|Microsoft word|Word}} 97 has an embedded pinball game, accessible by a [http://www.eeggs.com/items/763.html weird sequence of strange actions].
*{{w|Microsoft Excel|Excel}} 97 has also an embedded game of a flight simulator, accessible by another [http://www.eeggs.com/items/718.html weird sequence of actions].
*{{w|Microsoft Excel|Excel}} 2000 has an embedded [http://www.youtube.com/watch?v=PGZfuwsvIFQ car racing game].

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Hairy]]
[[Category:Internet]]
[[Category:Philosophy]]
[[Category:Social networking]]
[[Category:YouTube]]
[[Category:Social interactions]]

2936: Exponential Growth

2024-05-23T07:46:53Z

141.101.105.87: Fix floating point rounding issues

{{comic
| number = 2936
| date = May 22, 2024
| title = Exponential Growth
| image = exponential_growth_2x.png
| imagesize = 545x264px
| noexpand = true
| titletext = Karpov's construction of a series of increasingly large rice cookers led to a protracted deadlock, but exponential growth won in the end.
}}

==Explanation==
{{incomplete|Created by a 2^64TH ITERATION OF A BOT - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

{{w|Exponential growth}} is the principle that if you keep multiplying a number by a value larger than 1, you will pretty quickly get very large numbers. Even if you start with 1 and simply double it each time, you'll have a 10-digit number after about 30 iterations.

This principle is often illustrated using the story "Game of Rice". A king of India wished to reward a man for creating a new game of Chess, and told him that he'd grant any wish. The man simply asked for a {{w|Wheat and chessboard problem|grain of wheat to be placed on a chess board and for it to double with each square on the board each day.}} The king granted his strange request and ordered one wheat grain to be placed on the board. The second day two more pieces were placed on the square next to that and the day after four pieces on the next. However, by day 20 there was over 500,000 grains on the board. The king had to dig into his own stock pile to pay his dues. On day 24 the king owed 8 million grains. By day 32 the king owed over 2 billion pieces of grain, at this point he had to give up and offered the man another prize.

Instead of this being a (possibly apocryphal) story, [[Black Hat]] used it literally during a game of chess to annoy his opponent into quitting. Black Hat begins describing the metaphor, only to reveal it wasn't a metaphor at all. Black Hat had been playing actual Chess games, and tried to force his opponent to resign by burying the chess pieces in rice, as implied by the multiple large sacks bluntly labelled 'rice' on his side of the chessboard. This is not the first comic to feature large quantities of rice labelled in this manner - in [[1598: Salvage]], a gargantuan tank of rice has simply the word 'rice' written on the side in equally gargantuan capital letters.

{{w|Garry Kasparov}} is a world renowned Russian chess master. He had the highest FIDE chess rating in the world-one of 2851 points-until {{w|Magnus Carlsen}} surpassed that in 2013 by 31 points. The Kasparov gambit is an opening move in chess.

In 1984-85 Garry Kasparov played {{w|Anatoly Karpov}} in a 5-month-long 48-game championship tournament which was abandoned. In the 1984-85 match Kasparov was losing 4-0 with 6 wins being required to win. Kasparov proceeded to draw 35 times before the match was abandoned.

In a 1985 rematch, Kasparov defeated Karpov for the world championship title, which he retained in their next rematch in 1986.

* First row:
** a1: 1
** a2: 2
** a3: 4
** a4: 8
** a5: 16
** a6: 32
** a7: 64
** a8: 128
* Second row
** b1: 256
** b2: 512
** b3: 1,024
** b4: 2,048
** b5: 4,096
** b6: 8,192
** b7: 16,384
** b8: 32,768
:
* First of each row
:
** c1: 65,536
** d1: 16,777,216
** e1: 4,294,967,296
** f1: 1,099,511,627,776
** g1: 281,474,976,710,656
:
* ...
:
* Eighth row
** h1: 72,057,594,037,927,936
** h2: 144,115,188,075,855,872
** h3: 288,230,376,151,711,744
** h4: 576,460,752,303,423,488
** h5: 1,152,921,504,606,846,976
** h6: 2,305,843,009,213,693,952
** h7: 4,611,686,018,427,387,904
** h8: 9,223,372,036,854,775,808

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[Black Hat is talking to Cueball standing next to him.]
:Black Hat: Exponential growth is very powerful.

:[Closeup on Black Hat. Next to him is an image of the lower left part of a chessboard. The four leftmost squares in the bottom row have grains of rice on them -- one, two, four, and eight grains respectively.]
:Black Hat: A chessboard has 64 squares.
:Black Hat: Say you put one grain of rice on the first square, then two grains on the second, then four, then eight, doubling each time.

:[Black Hat has emptied a bag of rice on a chessboard. There are several bags next to him and a pile of rice already on the table. A frustrated Hairy is walking away, fists clenched.]
:[Caption above panel, representing Black Hat continuing to speak:]
:If you keep this up, your opponent will resign in frustration.
:It's called Kasparov's Grain Gambit. Nearly impossible to counter.

{{comic discussion}}

[[Category:Comics featuring Black Hat]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Hairy]]
[[Category:Chess]]
[[Category:Food]]
[[Category:Comics featuring real people]]