explain xkcd - User contributions [en]

2492: Commonly Mispronounced Equations

2021-07-26T18:37:30Z

162.158.158.175: /* Explanation */ explain sohcahtoa

{{comic
| number = 2492
| date = July 21, 2021
| title = Commonly Mispronounced Equations
| image = commonly_mispronounced_equations.png
| titletext = "Epsihootamoo doopsiquorps" --the Schrödinger equation for the hydrogen atom
}}

==Explanation==
{{incomplete|Created by a LAGRONJ EYSIBARYMOODMOOSIOYLERSIBRYMOOAMOOBAMOOSIMASIBRSIQORTFAHMOOVYFAHMOOVY. Please mention here why this explanation isn't complete: the elided equation in the incomplete notice needs explanation. It would be interesting for more people to weigh in on personal history eliding equations. Do NOT delete this tag too soon.}}

This comic is a collection of very commonly used physics and mathematical equations, along with their "correct" pronunciations. Equations are normally voiced out loud either by their names ("Mass–energy equivalence") or by saying the parts out loud using normal linguistic rules ("E equals M C squared"). This comic instead asserts that equations are meant to be said out loud like words, using their own set of phonic rules.

Though this premise may seem absurd, sometimes this kind of pronunciation is used as an abbreviation or a mnemonic device. For example, the equation A=Pert used for compound interest is commonly taught and pronounced as the "pert" equation, while SOH-CAH-TOA, spoken as one word, is used as a mnemonic for the definitions of the main trigonometric functions: sine = opposite/hypotenuse, cosine = adjacent/hypotenuse, and tangent = opposite / adjacent.

Some nerds have both the trait of using equations as commonly as others might chat, and of finding it entertaining to make up new funny sounds ("input", "pwn"). Saying the equations more rapidly can speed up work or make work seem more enjoyable. This phenomenon is called {{w|elision}}.

The pronunciation given for F=ma is the same as the actual pronunciation of FEMA, the acronym for the {{w|Federal Emergency Management Agency}}.

{| class="wikitable"
!Equation
!Pronounciation
!Explanation
|-
|{{w|Newton's law of universal gravitation}}
|Fuh-''JAM''-er
|F, gravitational force, is pronounced /f/. G, the gravitational constant, is prononounced as a soft G /dʒ/. The m's (mass 1 and 2) are both pronounced /m/, and the r (radius) is pronounced /r/. The numbers are unpronounced.
|-
|{{w|Mass–energy equivalence}}
|''EM''-cah-too
|E, energy, is pronounced as a short E /e/, m (mass) is pronounced /m/, c is pronounced as a hard C /k/, and the exponent "2" is pronounced "two".|
|-
|{{w|Pythagorean theorem}}
|at-''BOOT''-coot
|The side length "a" is pronounced as a short a. The side length "b" is pronounced /b/. The hypotenuse "c" is pronounced as a hard "c" /k/. Each exponent 2 is pronounced /t/ for "two", and the vowel sound /u/ of "two" is used as the filler vowel sound.
|-
|{{w|Area of a circle}}
|''APP''-er-too
|A, the area, is pronounced as a long a. Pi is pronounced /p/. R is pronounced /r/. 2 is pronounced "two". For added bonus, this becomes very similar to the word "aperture", which can be described as just the area of a circle.
|-
|{{w|Entropy_(information_theory)|Shannon entropy}}
|Ha-''SPLOG''-pee
|H, entropy, is pronounced /h/. The minus sign is unpronounced. Sigma, the summation sign, is pronounced /s/. The first pᵢ is pronounced /p/ with the subscript i unpronounced. log, the logarithm function, is pronounced "log" (like a piece of lumber). The second pᵢ is pronounced /pi/, where the subscript i makes the long e sound /i/.
|-
|{{w|Schrödinger equation}} for hydrogen
|Epsihootamoo doopsiquorps
|The form of the Schrödinger equation intended seems to be '''Eψ''' ''"epsi"'' = − '''(ℏ2/2μ)''' ''"hootamoo"'' '''∇2ψ''' ''"doopsi"'' - ('''q'''2/4πε'''0r)ψ''' ''"quorps"'' – pronounced, it seems, with a silent 4πε. (μ is mu, ψ is psi, ∇ is the {{w|Nabla_symbol|nabla or del symbol}} and pronounced /d/ here.).
|}

List of equations:
* {{w|Newton's law of universal gravitation}} ( F = G(m₁m₂/r²) )
* {{w|Mass-energy equivalence}} ( E = mc² )
* {{w|Pythagorean theorem}} ( a² + b² + c² )
* {{w|Area of a circle}} ( A = πr² )
* {{w|Entropy_(information_theory)|Shannon entropy}} and {{w|Diversity_index#Shannon_index|Shannon index}} ( H = -Σpᵢlog(pᵢ) )
* {{w|Ideal gas law}} ( PV = nrt ) -- sometimes said "PIV-nert" as a mnemonic, but according to Randall, this is a "mispronunciation".
* {{w|Euler's identity}} ( e^(iπ) = -1 )
* {{w|Newton's_laws_of_motion#Newton's_second_law|Newton's 2nd law of motion}} ( F = ma )
* {{w|Wave equation}} (c would conventionally be c²) ( ∂²u/∂t² = c(∂²u/∂x²) )
* {{w|Derivative#Definition|Derivative}} ( f'(x) = lim(h→0) (f(x+h)-f(x))/h )
* {{w|Quadratic formula}} ( x = (-b±√(b²-4ac))/2a )
* (title text) {{w|Schrödinger_equation#Hydrogen_atom|Schrödinger equation for the hydrogen atom}} ( Eψ = -∇²ψ(ℏ²/2μ) - ψ(q²/4πε₀r) )

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
[Each equation is bordered, with a pronunciation guide beneath.]

Commonly Mispronounced Equations

'''Row 1'''

F = G m₁m₂/r² 
FUH-'''''JAM'''''-ER

E = mc² 
'''''EM'''''-CAH-TOO

a² + b² = c² 
AT-'''''BOOT'''''-COOT

'''Row 2'''

A = πr² 
'''''APP'''''-ER-TOO

H = -Σpᵢlog pᵢ 
HA-'''''SPLOG'''''-PEE

PV = nrt 
'''''PAV'''''-NURT

'''Row 3'''

e^iπ = -1 
'''''EYE'''''-PIN

F = ma 
'''''FEE'''''-MAH

∂²u/∂t² = c ∂²u/∂x² 
'''''DOOT''''' CAH-'''''DOOX'''''

'''Row 4'''

f'(x) = lim h→0 f(x+h) - f(x) / h 
'''''FAX'''''-LIM-OH '''''FAX'''''-UH-FOX

x = -b ± √(b² - 4ac) / 2a 
ZA-'''''BO'''''-BA FAK-'''''TOH'''''-AH

{{comic discussion}}
[[Category:Physics]]
[[Category:Math]]
[[Category: Language]]

2492: Commonly Mispronounced Equations

2021-07-22T20:26:51Z

162.158.158.175: /* Explanation */ Explain Schrödinger equation joke.

2359: Evidence of Alien Life

2020-09-15T10:06:56Z

162.158.158.175: /* Explanation */

{{comic
| number = 2359
| date = September 14, 2020
| title = Evidence of Alien Life
| image = evidence_of_alien_life.png
| titletext = Both too cautious AND not cautious enough: "I'm skeptical that those are aliens, so I'm going to try pulling off their masks."
}}

==Explanation==
{{incomplete|Created by an APPROPRIATELY CAUTIOUS ALIEN BOT. ''Needs a table explaining each panel of the alignment chart like other such comics''. Do NOT delete this tag too soon.}}
This comic depicts a table of possible responses to new information on the possibility of alien life. It is presented in table form, with the columns representing three categories of reaction to new evidence, and the rows representing the strength of new evidence, increasing down the table. Each intersection then shows a small scenario of what the response would be. The left and right-hand column scenarios are hyperbolic in either their acceptance or denial. The center column represents a reasonable course of action.

This comic was a reaction to [https://www.nytimes.com/2020/09/14/science/venus-life-clouds.html the discovery of phosphine gas on Venus]. {{w|Phosphine}} is a molecule whose presence in the Venusian atmosphere came as a surprise. Light breaks phosphine down, meaning something must be producing it. However, there is no known abiotic mechanism on Venus that would produce the gas in the quantities observed. The phosphine could therefore be a sign of life on Venus, but more evidence is needed. Venus was also an unexpected place to find a possible sign of life - although it was {{w|Venus in fiction|a common pulp fiction setting in the early 20th-century }}, the arrival of the space probe era dashed hopes that the hidden surface might be, say, an exotic jungle. More recent efforts at finding life in the Solar System have mostly focused on Mars and various ice moons with suspected {{w|Ocean#Natural_satellites|subsurface oceans}}.

The title text refers to an action which is simultaneously too cautious and not cautious enough: the speaker is skeptical that aliens exist, which is usually an appropriate belief, except that presumably Megan and Cueball are in the situation presented in the bottom row, where aliens have landed right in front of them. Rather than modifying his belief (presumably it's Cueball, who was the one to approach the aliens in the other panels), he expresses an intention to approach the alleged aliens and attempt to remove their masks. He believes that he will expose a human wearing a costume, perpetrating a {{tvtropes|ScoobyDooHoax|"Scooby-Doo"-style hoax}}, but no matter what the outcome is, he's acting rashly. If the beings before him are aliens, he will be initiating a very aggressive first contact and will likely receive a violent response, and even if the alien is not violent, Cueball might end up removing an environmental apparatus that is protecting it from Earth's environment (or vice versa). On the other hand, even if the "aliens" really are fakes, Cueball might end up injuring someone who is just playing a harmless joke (and who'd want to keep ''some'' kind of mask on to reduce the spread of {{w|COVID-19}}.

The destruction of human governmental buildings is a common trope in science fiction films, as a way of aliens removing the ability of humanity to co-ordinate a response to an attack. The United Nations building is [https://nypost.com/2017/12/11/former-uk-official-reveals-plan-in-case-of-alien-invasion/ allegedly] the co-ordination centre for a worldwide response to an extraterrestrial incursion. However, since popular culture in the USA currently doesn't pay much attention to the United Nations, in American movies it is more commonly the White House that gets blown up by aliens.

The "alien probe" asteroid might refer to {{w|'Oumuamua}}, which passed through the Solar System in 2017. 'Omuamua's {{w|trajectory|hyperbolic trajectory}} indicated interstellar origin. Because of the unusual elongated shape suggested by its {{w|albedo}} (the object was never visualized as more than a point source of light) and indications of a slight non-gravity related acceleration, there were many wild speculations about 'Omuamua's origin, including it being an alien probe similar to the one presented in the science fiction classic {{w|Rendezvous_with_Rama|Rendezvous with Rama}}.

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

The comic is laid out like a grid, with implements down the left-hand side (Weak Evidence of Alien Life/ Promising Evidence/ Definite Evidence) and the type of "reaction" across the top (Not Cautious Enough / Appropriately Cautious/ Too Cautious). The grid illustrates the "match-ups".

From the top left corner, going from left to right, top to bottom, with each first item being on its own line in the grid, the squares are as follows:

Row 1: Cueball, looking through a telescope

Weak Evidence of Alien Life/Not Cautious Enough: Cueball - "That asteroid is probably an alien probe"
 
Weak Evidence of Alien Life/Appropriately Cautious: Cueball - "This asteroid is weird and we should take a closer look; It's not aliens"
 
Weak Evidence of Alien Life/Too Cautious: Cueball - "This asteroid appears to be far away, but it could also be nearby and just very small"

Row 2: Ponytail, holding a tablet or pad with "V" on it, approaches Cueball

Promising Evidence/Not Cautious Enough: Ponytail to Cueball - "They found life on Venus!"
 
Promising Evidence/Appropriately Cautious: Ponytail to Cueball - "Theses molecules might be produced by life or by weird high-heat chemistry"
 
Promising Evidence/Too Cautious: Ponytail to Cueball - "There is growing evidence that the atmosphere on Venus contains molecules"

Row 3: Flying saucers descend on Earth

Definite Evidence/Not Cautious Enough: Cueball - "I'm going to go give those aliens a hug!"
 
Definite Evidence/Appropriately Cautious: Cueball - "Oh wow, aliens! Should we try to communicate?"
 
Definite Evidence/Too Cautious: Megan - "The energy beams vaporizing the United Nations could be a possible biosignature"

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]

Talk:2357: Polls vs the Street

2020-09-10T00:54:44Z

162.158.158.175:

Love the title text! [[User:Fwacer|Fwacer]] ([[User talk:Fwacer|talk]]) 23:56, 9 September 2020 (UTC)

I Edit Conflicted with someone (2 minutes too late, after quite a bit of typing, then half a dozen Captcha submissions - just two to put ''this'' text in). If anyone wants to review my attempt, I'm HTML-commenting it in this gap...

...I already knew I'd have to Wikilink some bits, and can see at least one typo. Maybe I'll integrate some into what's there now, myself but probably not tonight. [[Special:Contributions/162.158.158.241|162.158.158.241]] 00:39, 10 September 2020 (UTC)
:(Self-reply) Looking into it, I must have been editing for a whole hour, actually. Didn't feel like it, but given there wasn't even a transcript when I started (but the BOT had been replaced) I must have been. And I want paying for all the Captcha responses I'm asked for. It seems I'm either being 'a useful idiot' for slavishly helping the Algorithm, or I am far better(/worse?) at identifying traffic lights, crosswalks, motorbikes, traffic and bicycles than "the man on the street" that pre-populated the Captcha knowledgebase thresholds... [[Special:Contributions/162.158.158.175|162.158.158.175]] 00:54, 10 September 2020 (UTC)

199: Right-Hand Rule

2019-12-18T21:39:30Z

162.158.158.175: "Limiting for a rule that is meant to make math and physics problems easier" makes it seem as though females are more in need of help with math and physics than males.

{{comic
| number = 199
| date = December 20, 2006
| title = Right-Hand Rule
| image = right_hand_rule.png
| titletext = To really expand your mind try some noncartesian porn. Edwin Abbot Abbott has nothing on "Girls on Girls in Tightly Closed Nonorientable Spaces"
}}

==Explanation==
The {{w|right-hand rule}} is a mathematics and physics trick to learning how to find the {{w|cross product}} of two Cartesian vectors in three dimensions. First, position your right arm in the direction of the first vector (in the example diagram in the comic, this is to the left). Then, curl your fingers in the direction of the second vector (out of the page/screen, in the example). Now point your thumb perpendicular to the other fingers, and it will point in the direction of the cross product of those two vectors (upwards, in the example). Note that reversing the order of the two vectors also reverses the direction of the cross product.

The book rule is an actual alternative to the right hand rule that might be useful to some physics students doing exercises out of their textbooks. However, it would give incorrect results with books in languages that are read from right to left, as well as most Jewish prayer books.

The gun rule also technically works, but it would be extremely impractical, expensive, and dangerous to use and fire a loaded gun every time you want to find the result vector. It would also be very awkward to hold the gun in line with the vectors. It also assumes that the safety latch is consistently on the same side of all guns; if a gun was made with the safety latch on the other side, then it would give incorrect results.

The body rule is for males only, which limits the number of people who are able to use this rule. With the right arm oriented along one vector and the legs along the second, the result vector is found along the penis of the person, which is conveniently erected by watching porn.

The title text refers to {{w|Edwin Abbott Abbott}}, author of the book Flatland, a story about a two-dimensional world.

{{w|Orientability}} is a property that refers to a space with continuously varying {{w|surface normal}}s, which are essentially just vectors that are perpendicular to the surface of the space. Nearly every space commonly encountered is orientable; this is likely why the porn is referred to as mind expanding and superior to Edwin Abbot Abbott's work.

==Transcript==
:[Picture of a right hand with fingers curved, thumb pointed away, with axes drawn to demonstrate the right-hand rule of physics.]
:Alternatives to the Right-Hand Rule in vector multiplication:
:[A slightly-open book with labeled axes drawn on.]
:Book Rule: Open the front cover along the first vector and the back cover along the second. The result vector is along the spine, out the top.
:[A handgun with axes.]
:Handgun Rule: Point the grip along the first vector and rotate it so that the second vector is on the safety latch side. Fire. The result vector is toward the bullet holes.
:[A person with right arm extended.]
:Body Rule (males only): Point your right arm along the first vector and your legs along the second, then watch some porn.

{{comic discussion}}
[[Category:Math]]
[[Category:Physics]]
[[Category:Comics featuring Cueball]]

1676: Full-Width Justification

2019-10-13T15:51:25Z

162.158.158.175: Removed unnecessary length of word "space".

{{comic
| number = 1676
| date = May 4, 2016
| title = Full-Width Justification
| image = full_width_justification.png
| titletext = Gonna start bugging the Unicode consortium to add snake segment characters that can be combined into an arbitrary-length non-breaking snake.
}}

==Explanation==
The comic refers to an irritating problem in laying out text to fit from margin to margin, the problem of {{w|justification (typesetting)|justification}}, where you want multiple-line text to line up on the left side (common), the right side (less common), or both sides, which is commonly called full justification. This strip is dealing with how to make text fit such that it lines up on both sides while still looking good. Sometimes, as with a shorter word between two long words like "relationship between [[:wikt:deindustrialization|deindustrialization]]," there's no universal good way to make the typography work. It is a difficult problem to make text look good and be easily legible especially in a narrow space, with the biggest issue being how to handle words that are too long to fit nicely.

The comic shows several solutions to this problem, some realistic and others less so, but each partly or wholly unsatisfying.

"'''Giving up'''" essentially means not attempting full justification for a particular line, which means it will not fit with the rest of the layout.

"'''Letter spacing'''" involves an conspicuously large amount of whitespace between letters, suggesting a reading where each letter is a word until the reader recognizes what is intended. This method is in somewhat common use in newspaper and magazine layout, where it is generally known by the name "tracking" (distance between all letters) and "kerning" (distance between particular pairs of letters that fit together easily). However, letter spacing is unavailable for justification purposes in some languages (such as German), in which it is used for emphasis, as italics are in English.

"'''Hyphenation'''" is confusing because it requires suspended recognition of the full word, confusing the eye into seeing, in the given case, the non-words "deindus" and "trialization". This creates difficulty in both pronouncing and parsing the word. Moreover, the decision of when and where to hyphenate is non-trivial, particularly for automated text layout; for example, breaking a word and leaving only two "orphaned" letters on the following line is generally considered an illegal hyphenation. Nevertheless, hyphenation is a very common means of handling extreme cases.

"'''Stretching'''" appears visually unnatural and unfamiliar, and may present technical difficulties in rendering.

Adding "'''filler'''" words is generally undesirable: in the worst case, the meaning may be unintentionally altered, or the tone might be rendered too informal, as in the given example, and even in the best case, the text becomes less concise and potentially more difficult to read. Automation is also difficult. However, filler words added by a human, especially the original author of the text, are the least visually conspicuous, and may be the most practical solution in some scenarios.

Finally, adding a decorative image like "'''snakes'''" (but not necessarily snakes in particular) to fill the extra space is a justification practice of significant historical interest (it was particularly common for illuminated manuscripts in the medieval era and remained prominent until the invention of the printing press) but little modern relevance. There may be a particular absurdity to using a snake as it can be read as a word, such as "the relationship between snake deindustrialization" as would be done similar to a {{w|rebus}}.

In modern text layout programs, some combination of the above strategies may be used to achieve the most visually consistent effect. For example, in one case, hyphenation might be the best option to split a very long word, while another line might be too long by only one or two letters, in which case the program could apply a very slight degree of extra letter spacing, too small for the average reader to notice.

The title text suggests that in order to facilitate the "snakes" method of "solving" the problem, the {{w|Unicode Consortium}}, the organization in charge of the common text standard {{w|Unicode}}, should add "snake-building characters" (similar in concept to the existing {{w|Box Drawing}} block), to allow variable-length snake images to be used as filling. Currently, there are at least six snake characters in Unicode, not including at least ten more Egyptian hieroglyphs that represent specific snakes, some in specific combination with other hieroglyphs: [http://unicode-search.net/unicode-namesearch.pl?term=SNAKE]
*[https://codepoints.net/U+1DC2 U+1DC2]   <big>᷂</big>   <big>[S᷂]</big>
**A diacritical {{w|combining character}} used in Americanist phonetic notation to indicate lenis (weak) articulation.
*[https://codepoints.net/U+2E92 U+2E92]   <big>⺒</big>
**A {{w|CJK character}} which might be interpreted as "snake".
*[https://codepoints.net/U+8675 U+8675]   <big>虵</big>
**Another CJK character meaning "snake".
*[https://codepoints.net/U+86C7 U+86C7]   <big>蛇</big>
**Another CJK character meaning "snake".
*[https://codepoints.net/U+1D9DC U+1D9DC]   <big>𝧜</big>
**One of the poorly-supported characters in the {{w|signWriting|signwriting block}}.
*[https://codepoints.net/U+1F40D U+1F40D]   <big>🐍</big>
**An {{w|emoji}} snake.

One of the hieroglyphs ([https://codepoints.net/U+13192 U+13192 EGYPTIAN HIEROGLYPH I009A]) is described in [https://mjn.host.cs.st-andrews.ac.uk/egyptian/unicode/tablemain.html source documents] as HORNED VIPER CRAWLING OUT OF ENCLOSURE, so it is literally a snake-building character.

"Non-breaking" in the title text refers to a similar process as zero-width joiners and no-break HTML and CSS; the whole snake would shift down if it were too wide to fit on a given line. This suggestion would likely be rejected; the Unicode consortium is very specific about which characters are added{{Citation needed}}, and always require a good reason{{Citation needed}} before adding a character or set of characters to the standard. Strange decisions by the consortium have previously been referenced in [[1253: Exoplanet Names]], [[1513: Code Quality]], and [[1525: Emojic 8 Ball]].

Within an hour or two of this comic being published, a thread on the subject started on the Unicode Consortium’s official Unicode Mailing List. As of two days later, it’s still running.

==Transcript==
:Strategies for full-width justification

:[Below the caption is a column with six boxes, each showing a different "strategy" for justification which is annotated beside it. Here the annotation is written at the top and the text below. The top and bottom of the text is cut of in the middle, but as it can be "read" this is written anyway. Only for hyphenation does an extra word appear at the end. In the last with snakes, a snake is drawn to cover the entire spaaace from the end of between to the right border.]

:Giving up
::their famous paper
::on the relationship
::between
::deindustrialization
::and the growth of

:Letter spacing
::their famous paper
::on the relationship
::b  e   t   w   e  e   n
::deindustrialization
::and the growth of

:Hyphenation
::their famous paper
::on the relationship
::between deindus-
::trialization and the
::growth of ecological

:Stretching
::their famous paper
::on the relationship
::<big><big><big>between</big></big></big>
::deindustrialization
::and the growth of

:Filler
::their famous paper
::on the relationship
::between crap like
::deindustrialization
::and the growth of

:Snakes
::their famous paper
::on the relationship
::between 🐍 [a snake filling the gap]
::deindustrialization
::and the growth of

==Trivia==
*The full text (with alternate changes) reads:
::''...their famous paper on the relationship between [crap like]/[ 🐍 ] deindustrialization and the growth of [ecological]...''
*An approach not depicted is to treat justification as part of a spherical typesetting strategy which allows words to move between lines even where this is not locally optimal. Its net effect in a case like this is to pull words from the previous line for use as filler. This approach is used by {{w|TeX}}.
*In Arabic, it is common to stretch the lines connecting letters as a relatively elegant and satisfying resolution to this problem. This trick is called "{{w|kashida}}" (كشيدة). There does in fact exist a Unicode character, U+0640: (ـ), to help with this: using it to extend "كشيدة" would result in something like "كـــــشـــيـــدة" (which, incidentally, looks a lot like a snake).
*Jim Chapman, developer of Windows 10 e-reader app Freda, has implemented snake-justification in the app, now available on the [https://www.microsoft.com/store/apps/9wzdncrfj43b Windows Store]. For best results, use the 'settings' screen to switch 'hyphenation' to 'no', 'use snakes' to 'yes', and choose a large font size (33 or so). Then pick a book with long words and justified text, and read it in a narrow window.
*The comic has been discussed on the [http://www.unicode.org/mail-arch/unicode-ml/y2016-m05/0004.html Unicode Mailing List].
*The typesetting system [http://www.sile-typesetter.org/ SILE] implemented snake justification on the same day the comic was published.
*"Line Fillers" depicting animals (including snakes) were widely used in [http://www.medievalcodes.ca/2016/04/line-fillers.html medieval book art].

{{comic discussion}}
[[Category:Animals]]
[[Category:Unicode]]