explain xkcd - User contributions [en]

3023: The Maritime Approximation

2024-12-13T10:09:41Z

172.71.160.92: /* Explanation */

{{comic
| number = 3023
| date = December 11, 2024
| title = The Maritime Approximation
| image = the_maritime_approximation_2x.png
| imagesize = 265x126px
| noexpand = true
| titletext = It works because a nautical mile is based on a degree of latitude, and the Earth (e) is a circle.
}}

==Explanation==
{{incomplete|Created by a SEMICIRCULAR SAILOR - Needs explanation of the origins of the units and constants involved for readers to investigate the confidentiality of the relationship. Also, needs clear explanation of title text. Do NOT delete this tag too soon.}}
Mph ({{w|miles per hour}}) and {{w|Knot (unit)|knot}}s (''nautical miles'' per hour) are both units used to express speed, including that of vehicles. Miles per hour are typically used in the {{w|Miles per hour|US, UK and some smaller countries}} for the speed of cars and other similar vehicles, while knots are used by some sailors or pilots to describe the speed of ships or aircraft. Novice sailors or sailors who spend a lot of time on land may find it helpful to quickly convert between mph and knots. Usually, this is in the form of 1 knot = 1.2 mph, or 1 mph = 0.87 knots (1 knot = 1.85 km/h and 1 km/h = 0.54 knots for metric sailors). [[Randall]] has humorously noticed that π mph ≈ e knots: π mph = [https://www.google.com/search?client=firefox-b-d&q=pi+mph+in+knots 2.72997] knots, {{w|E_(mathematical_constant)|e}} = 2.71828. Despite the claim of the title text, this is a coincidence,{{Citation needed}} since even though knots are based on nautical miles, which are related to degrees of latitude (and thus to π, which is used to describe the circumference of a circle), miles per hour have no relation to either e or π. Furthermore, the title text makes the connection to e by mentioning "Earth (e)" but e is not a commonly used symbol or abbreviation for Earth and even if it were, it has nothing to do with Euler's number e. Randall also conflates "circle" with "sphere" for simplicity, as they both have a radius that can be measured with π.

The equality shown in this strip consists of several different parts:

# The mile (1609.344 m) per hour (mph) is a unit of speed common for motor vehicles in a few countries, such as the United States and United Kingdom.
# The knot is a unit of speed that is one nautical mile (1852 m) per hour, used in nautical contexts.
# π is a number equal to the ratio of a circle's circumference to its diameter, about 3.14159.
# e is Euler's number, the base of the natural logarithm, about 2.71828.

π mph × (1609.344 meters/statute mile ÷ 1852 meters/nautical mile) ≈ 2.729969 knots. The result is only about 0.43% larger than ''e'' knots ≈ 2.71828 knots.

Knots are related to the circumference of the Earth, which can introduce pi, but this is only "useful" if you want to express your speed as a fraction of the radius of earth: 1 knot = 1 nautical mile per hour = 1/60 of a degree of Earth's circumference per hour = 1/21,600 of Earth's circumference per hour = 2π/21,600 x Earth's radius per hour. However, nowadays this is an approximation, because a nautical mile is defined as exactly 1852 m, which is not exactly 1/60 of a degree of Earth's circumference.

Randall has made similar observations of different dimensions that equal each other in the past with comics such as [[687: Dimensional Analysis]], where he compares {{w|Planck Energy}}, the pressure at the earth's core, the gas mileage in a Prius, and the width of the English Channel to Pi. In addition, in [[What If?]], he has compared the mass of Earth to be Pi "milliJupiters," or Pi times the mass of Jupiter divided by 1000, and noted that the volume of a cube with side lengths of one mile is roughly similar to the volume of a sphere with a radius of 1 kilometer. In [[217: e to the pi Minus pi]] and [[1047: Approximations]], Randall gives a lot of similar numerical approximations.
The joke is that it is not exact, but only correct to a certain percentage, unlike {{w|Euler's Identity}}, which is exact, and that's what makes the latter truly remarkable. This isn't helped by the fact that the comic carries the implication that this neat, easy to remember identity is actual useful for sailors, when really, being easy to remember is all it has going for it: it doesn't make calculations any easier, and is impossible to do without a calculator or paper, and doing it on paper is much harder than other conversions, given that Pi and e are both irrational, and transcendental.

The title text furthers the joke that this identity between miles and knots is truly fundamental, and through faulty logic. Whenever Pi shows up in an equation, the claim made by many mathematicians is that there is a circle hiding somewhere in the equations. Randall says that Pi is coming from the fact that nautical miles are based on the fact that the earth is round, and shipping routes over it's surface are circular. He also claims that e is in the equation because of earth.

==Transcript==
:[In a small panel an equation is shown. There is a footnote below the equation:]
:<big>π mph = ''e'' knots*</big>
:<small>*Correct to <0.5%</small>

:[Caption below the panel:]
:The sailor's version of e<sup>iπ</sup>=−1

{{comic discussion}}

[[Category:Math]]

2954: Bracket Symbols

2024-07-04T09:02:25Z

172.71.160.92: /* Explanation */ More about integrales and link to F-Holes

{{comic
| number = 2954
| date = July 3, 2024
| title = Bracket Symbols
| image = bracket_symbols_2x.png
| imagesize = 592x569px
| noexpand = true
| titletext = ’"‘”’" means "I edited this text on both my phone and my laptop before sending it"
}}

==Explanation==
{{incomplete|Created by a ([{《"complicated function"》}]) - Please change this comment when editing this page. Do NOT delete this tag too soon.}} WAKE UP, NERDS! Come explain to me why this is funny!

'The preliminary nerd has arrived and did his best to fix the article.' (Even though I'm not British, I thought it might be funny to reference the comic. {See what I did there?} )

Bracket symbols are meant to put around a text. This comic shows a variety of bracket symbols and Randall's description.
Here is a list of what these symbols may mean as a preliminary to a full proper explanation: (feel free to update or completely replace this)

{| class="wikitable"
|+Descriptions
|-
! Symbols
! Comic text
! Real use
! Explanation
|-
|()
|Regular parentheses for setting stuff aside
|Used to mark side remarks (like explanations) in regular text. Also used in mathematical expressions and programming languages to show the sequence of operations or separate other things like function arguments.
|Normal parentheses. No joke here.
|-
|[]
|Square brackets (more secure)
|Used in regular text to mark still less important remarks, like glosses, omissions, translator and editorial notes etc. In mathematics, often used as outer parentheses for easier visual matching in complicated expressions. In programming languages used to mark specific syntactic elements, like array indexes, lists etc.
|The sharper edges and corners may suggest these brackets hold things in more securely, so the contents is less likely to fall out. They resemble staples used to hold things in place securely.
|-
|{}
|This stuff is expensive so be careful with it
|Rarely used in normal text. In mathematics, sometimes used as third level outer brackets, or in other special notation. In programming languages most often used to denote begin and end of a separate block of code, but other uses are also extant.
|All that graphical detail in the bracket, if manufactured as a physical object, would increase the production cost making it more expensive than "regular" brackets.
|-
|"" or “”
|Someone is talking
|Used to denote speech or citations in normal text. The first version is commonly used in programming languages to denote text that is not a program, such as messages displayed to the user.
|Normal quotation marks. Some languages or communities use different typographical conventions such as „German quotation marks“. See also below for British and French.
|-
|<nowiki>''</nowiki> or ‘’
|Someone British is talking
|British quotation marks. Some programming languages use the first version to denote non-program text.
|British media use these to note when people are talking.
|-
|‹› or <>
|An Animorph is talking
|Angle brackets
|Books like the series {{w|Animorphs}} or science fiction novels use these when a character is communicating nonverbally, for example telepathy.
|-
|«»
|A French Animorph is talking
|French quotation marks. In some languages used for quotes within quotes.
|These symbols are literally called French quotation marks.
|-
|<nowiki>|</nowiki>|
|I'm scared of negative numbers but these sigils will protect me
|
|Absolute indicators used in math to ensure a number is positive (ex. <nowiki>|-69| = 69</nowiki>) therefore protecting you and your equations from them.
|-
|**, __, //
|I have a favorite monospaced font
|
|Markup symbols for text to make it *bold*, _underlined_, or /italic/.
|-
|~~
|I'm being sarcastic and I had a Tumblr account in 2014
|
|Strikethrough markup commonly used on sites like Tumblr to indicate that you don't really mean something you said. This is a somewhat archaic trend, but I still use it...
|-
|[([{()}],)]
|These Python functions are not getting along
|The square brackets denote a mutable [https://docs.python.org/3/tutorial/introduction.html#lists list], the round brackets an immutable [https://docs.python.org/3/tutorial/datastructures.html#tuples-and-sequences tuple] , and the curly brackets a [https://docs.python.org/3/tutorial/datastructures.html#sets set]. It is valid to have nested them like this. [] could also be a slice (a bit of a list or tuple) and {} could be a [https://docs.python.org/3/tutorial/datastructures.html#dictionaries dictionary], but the syntax is wrong for these.
|Random parentheses - Spaghetti code (badly maintained or written) in programming languages including Python will often be badly organized creating a mess of indentations and brackets used to create functions or loops etc.
|-
|⌊⌋
|Help, I'm a mathematician trying to work with actual numbers and they're scary
|
|Mathematical symbols meaning "floor" (i.e. round down to the next lower integer). (Someone else explain the joke!)
|-
|ʃ ʅ
|Why are you trying to read my violin?
|ʃ is the {{w|Integral symbol}} which itself is derived from a {{w|Long s}}. In mathematics it is usually paired with the differential of the variable of integration (e.g., dx). A reverse integral symbol is usually not used in mathematics.
The symbols could also be a lowercase {{w|Esh (letter)}} and its reversed symbol.
|Violins are known for their characteristic {{w|F-hole}}s.
|-
|<nowiki>|⟩</nowiki>
|Don't stop here--this is quantum country
|
|This {{w|Bra–ket notation|notation is used in quantum mechanics}} to notate a vector. This is called a ket, and the mirrored sign <nowiki>⟨|</nowiki> is called a bra. Combining them as bra-ket gives the inner product <nowiki>⟨|⟩</nowiki>.
|}


==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

Bracket Symbols

and what they mean

( ) Regular parentheses for setting stuff aside

[ ] Square brackets (more secure)

{ } This stuff is expensive so be careful with it

" " Someone is talking

' ' Someone British is talking

‹ › An Animorph is talking

« » A French Animorph is talking

| | I'm scared of negative numbers but these sigils will protect me

<nowiki>*</nowiki> * _ _ / / I have a favorite monospaced font

~ ~ I'm being sarcastic and I had a Tumblr account in 2014

[ ( [ { ( ) } ] , ) ] These Python functions are '''''not''''' getting along

⌊ ⌋ Help, I'm a mathematician trying to work with actual numbers and they're scary

ʃ ʅ Why are you trying to read my violin?

| ⟩ Don't stop here--this is quantum country

{{comic discussion}}

[[Category:Language]]
[[Category:Math]]
[[Category:Programming]]

Talk:2942: Fluid Speech

2024-06-06T08:53:11Z

172.71.160.92: nasalized schwa

I've noticed that this doesn't seem to be the case in all languages. For example, when native Polish speakers talk rapidly (even when speaking English), they enunciate every sound accurately in quick succession while flattening out the tone and rhythm of their speech. I wonder if this is because Polish is an inflected language where the grammar of the sentence is determined by endings of words rather than word order. Does anyone know if there have been any studies on this? [[Special:Contributions/162.158.74.49|162.158.74.49]] 23:12, 5 June 2024 (UTC)

:I'm not linguists but based on how many those are, definitely. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 00:10, 6 June 2024 (UTC)

:Russian also has vowel reduction like English and it's a Slavic language like Polish, so I don't think so. Although someone who knows more than me might be able to chip in on whether the effect is stronger in English. [[Special:Contributions/162.158.114.198|162.158.114.198]] 03:24, 6 June 2024 (UTC)

I've just added a very barebones version of an explanation based on what I could understand from the comic. I can tell that the four diagrams depict that of the human mouth but since I am not a linguist, I lack the knowledge of various terms and thus, can't fully explain the comic. I understand what the comic is trying to convey, I just can't explain it. Looking forward to seeing how this progresses. [[User:OmniDoom|OmniDoom]] ([[User talk:OmniDoom|talk]]) 00:22, 6 June 2024 (UTC)

I don't think #4 is a real IPA symbol, but as I am not a linguist, I have no idea. [[Special:Contributions/162.158.91.36|162.158.91.36]] 01:38, 6 June 2024 (UTC)
:/ə̃/ is a {{w|Nasal_vowel|nasalized}} {{w|schwa}} --[[Special:Contributions/172.71.160.92|172.71.160.92]] 08:53, 6 June 2024 (UTC)

The hovertext joke is that every English speaker fully pronounces the first "t" in "Hot Potato". It's at the end of "hot". Nobody says "ha potato". [[User:Nitpicking|Nitpicking]] ([[User talk:Nitpicking|talk]]) 03:01, 6 June 2024 (UTC)

:Unless you mean "the glottal stop should be considered an allophone of <t> at the end of syllables" then yes they do. It's /hoʔ/, not /hotʰ/. [[Special:Contributions/162.158.114.198|162.158.114.198]] 03:24, 6 June 2024 (UTC)

:(Edit conflicted with 162, above, so this is my own reply...) I thought it was that it isn't "ho T'p otato", with the "teh-peh" awkwardness. For me, the natural way to say it is to glottalstop the first T for more "ho'potato" (the other Ts, there I find awkward ''not'' to get the "t>s<" out of, the ">s<"-tail being what makes a full-T not a lazy one). But clearly a different accent involved, as "ha" doesn't work at all for me unless I try to use some sort of (probably awful) Goodfellas-type accent. And my native accent is notoriously good at glottlestopped Ts (that most people misinpersonate badly, by attaching them to the wrong adjacent syllable).
:As for "going to", experimentally holding my finger over the length of my tongue, it seems it barely has to move at all in "going" (the whole tongue wants to rise on the "i", but I can suppress that and do the tone-change from further back, if not straight from the vocal chords). Though continuing through to the "to", with my finger in there, it's no better than "going ku" as I prevent the tongue-tip doing the necessary small movement to fulfil any form of T. I can do better through basic gastromancy, but behind my unmoving jaw and lips (''without'' the finger almost down my throat, of course), I can feel the tongue tip doing it's small but vital "crossing the T" work. [[Special:Contributions/172.70.86.64|172.70.86.64]] 03:53, 6 June 2024 (UTC)
:For me, it's more like "ho'buh-deh-duh" - so none ot the t's get pronounced properly. And I'd drop the n in 'going to' before I dropped the t.[[Special:Contributions/172.70.163.120|172.70.163.120]] 08:22, 6 June 2024 (UTC)

Unless someone's willing to start an "explain explain xkcd", I think this explanation still needs a lot of work to be intelligible to non-linguists (myself included). That aside, I do appreciate whoever took the time to type all that up. [[Special:Contributions/162.158.166.210|162.158.166.210]] 03:31, 6 June 2024 (UTC)
:The current explain reads, to me at least, more like a 102 lecture than an explanation of the comic. I of course have no idea what is in a 101 first week lecture so shrug. (Aside, wth? This keyboard doesn't have a tilda. Copy and paste ftw) [[Special:Contributions/172.71.223.38|172.71.223.38]] 05:51, 6 June 2024 (UTC)
: I think it's fine if you can read/interpret the {{w|International Phonetic Alphabet|IPA}}. If you don't it's utterly incomprehensible. I think we need some examples here as to how the sounds written here are pronounced. Like "sound <x> as in <word>" [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 06:52, 6 June 2024 (UTC)
:: Yeah, except [[2819]] [[Special:Contributions/172.70.163.120|172.70.163.120]] 08:30, 6 June 2024 (UTC)