explain xkcd - User contributions [en]

128: dPain over dt

2024-01-01T13:46:06Z

172.70.38.94: xkcd volume 0 cipher, deciphering, and explanation of its text

{{comic
| number = 128
| date = July 14, 2006
| title = dPain over dt
| image = dPain_over_dt.png‎
| titletext = You laugh to keep from crying, you do math to keep from crying...
}}

==Explanation==

Another one of the math-love relationship comics, a mathematical depiction of pain as a {{w|differential equation}} is shown. It is hoped that ''dPain/dt'', or the rate of pain (in this case, shrinking), decreases quickly so that the pain will vanish quickly. He's hoping the value for ''d'' will not be larger than a few days or some weeks. Assuming that ''How much she's still in my life'' is a constant [Megan], [https://www.wolframalpha.com/input/?i=dP%2Fdt+%3D+%28-k1*P%2BG%29*%281%2F%281%2Bexp%28-%28t-k2%29%2Fd%29%29%29 solving the differential equation] leads to the following solution (with unknown ''c1''):
: <math> Pain(t) = {c_1 \left(e^{k_2/d} + e^{t/d}\right)}^{-dk_1} + \frac{[\text{Megan}]}{k_1}</math>

If ''k1'' was positive or if ''k2'' was a large value, the value of ''dPain/dt'' would approach zero. Ideally, ''k1'' would be "How much she's in my life"/''Pain'' (we assume both these values are positive), while ''k2'' would ideally be extremely large. Either of these scenarios approach what would be a situation where the value of ''dPain/dt'' is close to zero. But we don't know the meaning of ''k1'' or ''k2''; these variables are just unpredictable.

In the title text, [[Randall]] changes the famous "laugh to keep from crying" statement to math.

==Transcript==
:dPain/dt = (-k1 Pain + [Image of Megan]) (1/(1 + e ^ -(t-k2)/d))
:''k''1=?
:''k''2=?
:[Image of Megan]=How much she's still in my life
:Please let ''d'' only be a few days... or weeks
:I guess there's some kind of a cutoff after years, where it stops mattering and we can be friends. Do I want that?
:Is ''k''1 positive? Is ''k''2 large?
:Will I ever stop feeling like this?

==Trivia==
* In ''[[xkcd: volume 0]]'', some braille is displayed prominently below the comic:
<pre>⠊⠞⠀⠞⠁⠨⠑⠎⠀⠍⠕⠗⠑⠀⠞⠊⠍⠑⠀⠞⠓⠁⠝⠀⠽⠕⠥
⠑⠭⠏⠑⠉⠞⠀⠃⠥⠞⠀⠇⠑⠎⠎⠀⠞⠓⠁⠝⠀⠽⠕⠥⠀⠋⠑⠁⠗⠲</pre>
*Decoding this gives:
**"IT TAKES MORE TIME THAN YOU EXPECT BUT LESS THAN YOU FEAR."
***This seems to be a message from Randall about breakups such as this one, assuring them that it will not last forever.

{{comic discussion}}
[[Category:Analysis]]
[[Category:Romance]]
[[Category:Comics featuring Megan]]

Talk:2762: Diffraction Spikes

2023-04-15T00:40:33Z

172.70.38.94:

I tried to make an initial explanation, but then someone beat me to it and I made a fool of myself on the page trying to add a comment where it didn't go. I fixed it, but I am ashamed ;~; [[Special:Contributions/172.69.34.15|172.69.34.15]] 23:31, 12 April 2023 (UTC)
:It's all good. As long as you learn from it, and we learn what useful things you want to say, nothing at all to worry about... All power to your typing fingers! [[Special:Contributions/172.70.85.66|172.70.85.66]] 00:15, 13 April 2023 (UTC)
Exoplanets nevertheless exist because, alongside the visible diffraction spikes that chop them up, there are invisible defraction [sic] spikes that reassemble them. [[Special:Contributions/162.158.158.136|162.158.158.136]] 00:32, 13 April 2023 (UTC)
:Pretty sure gravity causes the pieces to drift back together. [[Special:Contributions/172.69.58.86|172.69.58.86]] 20:33, 13 April 2023 (UTC)

Why does the spike slice the planet instead of the planet breaking the tip off the spike? Are the spikes like enormous light sabers? [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 00:43, 13 April 2023 (UTC)
:The spikes are stellar artifacts of distant observers, with all the mass of the star behind them. The Sun hardly moves much if you dunk the Earth into it, why should the exoplanet move the spike? At best you'd get a similar effect to karate chopping a stream of water from a hose. [[Special:Contributions/172.71.150.175|172.71.150.175]] 04:49, 13 April 2023 (UTC)
::Please stop dunking the Earth into the Sun.[[Special:Contributions/172.71.242.172|172.71.242.172]] 08:11, 14 April 2023 (UTC)
:Adding to 172.71...'s point, the spikes are made of star, so it will be incandescent gas with plasma corona. How do you "break" a gas?

Is it inspired by some movie that features this "spike pointing on some person" effect? I remember seeing one, but I don't seem to remember its name. [[User:Unreliable Connection|2659: Unreliable Connection]] ([[User talk:Unreliable Connection|talk]]) 02:07, 13 April 2023 (UTC)

:This comic also reminded me of fractal images. [[User:Memo Spike Connector|2503: Memo Spike Connector]] ([[User talk:Memo Spike Connector|talk]]) 09:06, 13 April 2023 (UTC)

:Is there also some joke here about double vision (if you cross your eyes you will see two planets), you use lens occlusion to see expolanets? ([[garbled]])) 10:55, 14 April 2023 (UTC+1)

From an edit comment "(Refractor telescopes (using only lenses) don't give refraction spikes, reflector telescopes (using mirrors) do.)". Yeahbut, nobuf... It's just the struts, also mentioned, that are the key. You can build pure-refractor telescopes that still have struts (probably not optimal, but a design option) and therefore spikes. And you can make one with mirrors and ''no'' struts (more complicated and less of a practical shape for most mounting/launching purposes) which would therefore be spikeless. [[Special:Contributions/172.70.162.160|172.70.162.160]] 12:00, 13 April 2023 (UTC)

:Some telescopes get diffraction spikes from the shape of the mirror. The JWST is a notable example of this. --[[Special:Contributions/172.71.178.186|172.71.178.186]] 14:13, 13 April 2023 (UTC)
::It's the sharp, angled edges that provide interference patterns (a set of "one-sided diffractions", rather than two-sided ones around an obstruction). A full round mirror on its own would not produce any spikes. Nor if the light from the edge areas cannot possibly reach the sensors, but that would mean less use of the mirror(s) they took great pains to send up there. And the secondary mirror ''has'' struts (in a Y-shape, I think, for technical reasons), thus why there's two minor spikes (actually six, but four are aligned to be hidden within the major spikes) as well as the hexagon-edge-induced set of six. Which also helps you understand in which orientation (or which two possibilities) the JWST was, in order to make any images you see from it.
::But this is already over-explained, really. You ''can'' design a mirror set to a avoid spikes, but with other technical compromises/etc. And above is correct, in that refractive telescopes can find themselves showing spikes (struts, if so designed, and other internal angles that may intrude into the light-path's edge). [[Special:Contributions/172.71.242.86|172.71.242.86]] 17:27, 13 April 2023 (UTC)
:Diffraction spikes are also caused by window screens, dirty or scratched windscreens, and other optical blemishes. Given the relative scarcity of telescopes these are what most people have actually encountered.[[Special:Contributions/172.70.38.94|172.70.38.94]] 00:40, 15 April 2023 (UTC)

The transcript is very long... Too long : as of now, 2055 characters. That "transcript" section is intended for people who can't see the image (blind people for example), so it should be almost as fast to read as it is for you to look at the comic. There is really no need the exact angles of the diffraction spikes or anything, just a description of what's happening so that we can get the joke. You should not try to write a vectorization of the image, there are automated tools for that. [[Special:Contributions/172.71.122.208|172.71.122.208]] 18:04, 13 April 2023 (UTC)
:The comment speaks to the difficulty of creating a transcription of an image that is meaningful to a person who cannot access the image. It would be good to hear from such folk about this.[[Special:Contributions/172.70.110.215|172.70.110.215]] 22:15, 13 April 2023 (UTC)

Why is the asteroid belt mentioned in the explanation? [[Special:Contributions/172.71.222.129|172.71.222.129]] 19:13, 13 April 2023 (UTC)k
:If "all stars" have diffraction spikes, then there should be no planets around Sol. We exist, so Sol must be an exception to "all stars". But the asteroid belt (chopped-up planet(s)) also exists, so perhaps Sol had diffraction spikes sometime in its history. Yes, there's a real, and satisfactory, explanation for the Solar System's Jovian asteroid belt. But, context.[[Special:Contributions/162.158.154.150|162.158.154.150]] 21:58, 13 April 2023 (UTC)

I guess this refers to a solar storm predicted to go on in 2023, which does great damage to the earth's atmosphere like a spike. [[User:ClassicalGames|ClassicalGames]] ([[User talk:ClassicalGames|talk]]) 06:07, 14 April 2023 (UTC)
:{{Actual citation needed}} ...are you going by solar maxima? The weak 2014 one, and the 9-14 years we can generally get between them, makes 2023 off at the ''earliest'' of expectations... Perhaps 2025 is more likely.
:And we get maybe a few days warning of "a solar storm" (CME) that might happen to come our way. Carrington Events are rare, though, and even when 3+ CMEs a day happen (slightly after sunspot maximum, and up from the low frequency of one every five days), we're such a small target that it's still more or less the same amount of total dumb-luck (15-20x a fraction of a chance with a far greater (negative) order to it). [[Special:Contributions/172.70.86.153|172.70.86.153]] 20:42, 14 April 2023 (UTC)

2456: Types of Scientific Paper

2021-04-28T20:51:59Z

172.70.38.94: /* Explanation */

{{comic
| number = 2456
| date = April 28, 2021
| title = Types of Scientific Paper
| image = types_of_scientific_paper.png
| titletext = Others include "We've incrementally improved the estimate of this coefficient," "Maybe all these categories are wrong," and "We found a way to make student volunters worse at tasks."
}}

==Explanation==
{{incomplete|Created by a RESEARCH DEPARTMENT ON A LUNCHBREAK. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}
In this comic, Randall describes categories of scientific papers with somewhat humorous generalized titles.

{| class="wikitable"
|+Breakdown of Papers
|-
|Paper Title
|Explanation
|-
|We put a camera somewhere new
|
|-
|Hey, I found a trove of old records! They don't turn out to be particularly useful, but still, cool!
|
|-
|My colleague is wrong and I can finally prove it
| This title refers to the occasional rivalries between scientists within a field, which can push them to seek proof that they, and not their colleague, are correct.
|-
|The immune system is at it again
|
|-
|We figured out how to make this exotic material, so email us if you need some
|
|-
|What are fish even doing down there
|
|-
|This task I had to do anyway turned out to be hard enough for its own paper
|
|-
|Hey, at least we showed that this method can produce results! That's not nothing, right?
|
|-
|Check out this weird thing one of us saw while out for a walk
|
|-
|We are 500 scientist and here's what we've been up to for the last 10 years
|
|-
|Some thoughts on how everyone else is bad at research
|
|-
|We scanned some undergraduates
|
|}

Trivia: As of now, this comic's title text misspells volunteers as volunters. This may be intentional (WE might be the volunteers).

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
Types of Scientific Paper

We put a camera somewhere new

Hey, I found a trove of old records! They don't turn out to be particularly useful, but still, cool!

My colleague is wrong and I can finally prove it

The immune system is at it again

We figured out how to make this exotic material, so email us if you need some

What are fish even doing down there

This task I had to do anyway turned out to be hard enough for its own paper

Hey, at least we showed that this method can produce results! That's not nothing, right?

Check out this weird thing one of us saw while out for a walk

We are 500 scientist and here's what we've been up to for the last 10 years

Some thoughts on how everyone else is bad at research

We scanned some undergraduates

{{comic discussion}}

2456: Types of Scientific Paper

2021-04-28T20:51:26Z

172.70.38.94: /* Explanation */

{{comic
| number = 2456
| date = April 28, 2021
| title = Types of Scientific Paper
| image = types_of_scientific_paper.png
| titletext = Others include "We've incrementally improved the estimate of this coefficient," "Maybe all these categories are wrong," and "We found a way to make student volunters worse at tasks."
}}

==Explanation==
{{incomplete|Created by a RESEARCH DEPARTMENT ON A LUNCHBREAK. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}
In this comic, Randall describes categories of scientific papers with somewhat humorous generalized titles.

{| border="1"
|+ TODO Fill me
! Category !! Explanation
|-
! We Put a Camera Somewhere New
| Explain
|-
! Hey, I found a trove of old records!
| TODO
|-
! Hey, I found a trove of old records!
| TODO
|-
! Hey, I found a trove of old records!
| TODO
|-
! Hey, I found a trove of old records!
| TODO
|-
! Hey, I found a trove of old records!
| TODO
|-
! Hey, I found a trove of old records!
| TODO
|-
! Hey, I found a trove of old records!
| TODO
|-
! Hey, I found a trove of old records!
| TODO
|-
! Hey, I found a trove of old records!
| TODO
|-
! Hey, I found a trove of old records!
| TODO
|-
! Hey, I found a trove of old records!
| TODO
|}

{| class="wikitable"
|+Breakdown of Papers
|-
|We put a camera somewhere new
|
|-
|Hey, I found a trove of old records! They don't turn out to be particularly useful, but still, cool!
|
|-
|My colleague is wrong and I can finally prove it
| This title refers to the occasional rivalries between scientists within a field, which can push them to seek proof that they, and not their colleague, are correct.
|-
|The immune system is at it again
|
|-
|We figured out how to make this exotic material, so email us if you need some
|
|-
|What are fish even doing down there
|
|-
|This task I had to do anyway turned out to be hard enough for its own paper
|
|-
|Hey, at least we showed that this method can produce results! That's not nothing, right?
|
|-
|Check out this weird thing one of us saw while out for a walk
|
|-
|We are 500 scientist and here's what we've been up to for the last 10 years
|
|-
|Some thoughts on how everyone else is bad at research
|
|-
|We scanned some undergraduates
|
|}

Trivia: As of now, this comic's title text misspells volunteers as volunters. This may be intentional (WE might be the volunteers).

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
Types of Scientific Paper

We put a camera somewhere new

Hey, I found a trove of old records! They don't turn out to be particularly useful, but still, cool!

My colleague is wrong and I can finally prove it

The immune system is at it again

We figured out how to make this exotic material, so email us if you need some

What are fish even doing down there

This task I had to do anyway turned out to be hard enough for its own paper

Hey, at least we showed that this method can produce results! That's not nothing, right?

Check out this weird thing one of us saw while out for a walk

We are 500 scientist and here's what we've been up to for the last 10 years

Some thoughts on how everyone else is bad at research

We scanned some undergraduates

{{comic discussion}}

2451: AI Methodology

2021-04-17T15:02:54Z

172.70.38.94: /* Explanation */

{{comic
| number = 2451
| date = April 16, 2021
| title = AI Methodology
| image = ai_methodology.png
| titletext = We've learned that weird spacing and diacritics in the methodology description are apparently the key to good research; luckily, we've developed an AI tool to help us figure out where to add them.
}}

==Explanation==
{{incomplete|Created by a BOT (91%). TRAINED BY AN ADVERSARIAL AI (72%). If you are knowledgeable about AI, please rewrite at least one paragraph for us. The current content was completely fudged by amateurs. Do NOT delete this tag too soon.}}

The joke in this comic is that the people are using AI without understanding how to. That classifier is trained on data that doesn't include the causes of the results, and then not testing it at all, producing a model that is both random and heavily overfitted. Such a model appears perfect but makes random predictions on new data. The flavor text is describing this happening, and how. For an introduction to machine learning, you can visit https://fast.ai/ .

This comic shows Cueball giving a presentation of some description. He is reassuring his audience of the validity of his research's methodology, which he says is "AI-based". There are many issues that can arise from an AI-based methodology, such as lingering influence from its training data or a bad algorithm reducing the quality of the investigation.

Cueball seeks to reassure his audience by quantifying the quality of his methodology. He does this by creating yet another AI to rank methodologies. This would not actually improve the confidence of any audience member, as any flaws of the methodology AI would likely be shared by the ranking AI, due to being created by the same team.

Furthermore, the ranking AI heavily favours the methodology of Cueball's AI, and may be biased. It shows a normal distribution, with a singular outlier to the far right with an arrow above. It can be inferred [from the arrow] that this data-point represents the AI's methodology. It is a significant outlier, and as such it is probably not an accurate representation of Cueball's AI. Alternatively, this could be taken as AI 'nepotism', where Cueball's methodology AI is more likely to select AI-based approaches over others. This type of algorithmic bias is mentioned in [[2237: AI Hiring Algorithm]]. Another explanation would be that the x axis measures something other than "how good the methodology is" (eg, rate of highly significant results), and the fact that Cueball's AI is not within the normal distribution should have been a red flag indicating a problem with their methodology, but the ranking AI didn't notice the skew / correctly interpret the meaning of the data. (However, the title text seems to indicate that the x axis was indeed labeled by "quality of methodology", albeit defining this quality by very strange criteria.)

The title text is likely a continuation of Cueball's dialogue, saying that when the classifying AI was shown good research methodology descriptions, the AI identified weird spacing and diacritics as the indicators of a good methodology. Cueball then used his AI to figure out where to put these into his own methodology description to improve his research report. Adding weird symbols into a text doesn't improve the quality of the text {{Citation needed}} and hence Cueball may be doing something very similar to p-hacking, where data is manipulated to decrease the p-number, which represents the likelihood the data is a fluke. P-hacking is mentioned in [[882: Significant]]

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

:[Cueball stands in front of a projection on a screen and points with a stick to a histogram with a bell curve to the left and one bar to the far right marked with an arrow]
:Cueball: Despite our great research results, some have questioned our AI-based methodology.
:Cueball: But we trained a classifier on a collection of good and bad methodology sections, and it says ours is fine.

{{comic discussion}}
[[Category:Artificial Intelligence]]
[[Category:Comics featuring Cueball]]

1578: Squirrelphone

2021-04-05T15:20:55Z

172.70.38.94: Why would you do that?

{{comic
| number = 1578
| date = September 16, 2015
| title = Squirrelphone
| image = squirrelphone.png
| titletext = After a while, the squirrel starts making that beeping noise and doesn't stop until it hops back up onto the stump.
}}

==Explanation==
"Squirrelphone" is a {{w|Compound (linguistics)|compound word}} combining "{{w|squirrel}}" and "{{w|phone}}".

In this comic, we see a squirrel pretend to be a telephone, only to bite [[Cueball]] who tries to pick it up and use it as one. This is humorous because a living squirrel is not an appropriate creature to maintain a phone call{{Citation needed}}. This could be seen as an example of {{w|mimicry}} in nature, or parasitism where one creature gains a benefit from another.

It may be an allusion to the {{w|Tufted ground squirrel|vampire squirrel}} which was [https://www.washingtonpost.com/news/speaking-of-science/wp/2015/09/11/vampire-squirrel-caught-on-camera-for-the-first-time-ever/ documented recently] that allegedly 'attacks and kills' deer. The comic follows the absurd conclusion that the squirrel uses mimicry to 'attack and kill' humans. Cueball may be lucky to still be alive{{Citation needed}}.

The sounds the squirrel makes correspond to the tones that the terminals make when you use the POTS (Plain Old Telephone Service) in the US:
*When someone else calls you and the receiver of your phone is on the hook, the phone makes loud and long "riiing riiiing" tones. This is the case in the first frame of the comic.
*When you pick the receiver up, the phone call is established and no extra noises are made.
*When no phone call is established and you pick up, a continuous humming tone is heard, meaning the service is up and you can dial someone else's number (A {{w|dial tone}}).
*If a phone is left off hook for too long, a loud {{w|Off-hook tone|howler-tone}} is played. This is to alert anyone present that the phone is off-hook. In this case, you should hang up so that you can receive calls. Once on-hook, the receiver can be picked up again to dial. Many cordless phones will also beep if left off their cradles for too long, to warn that their rechargeable batteries are getting drained.

[[:Category:Squirrels|Squirrels]] have been used frequently in xkcd, also in [[what if]], where it has for instance been used as a cute animal to replace a drawing of something scary or unpleasant like in [http://what-if.xkcd.com/98/ Blood Alcohol] or [http://what-if.xkcd.com/105/ Cannibalism]. So this is some twist for the cuteness factor of squirrels in xkcd.

It may also be the case that "squirrelphone" is a reference to the popular web-mail software [http://squirrelmail.org/ SquirrelMail].

The title text takes the joke further by showing the squirrel possesses another phone feature: that cordless phones need to recharge frequently, either by setting them at their cradles or by connecting them to a charger, in the case of mobile phones. When they sense the battery is low, they emit a beeping noise every few minutes. In this case, the stump is the squirrel's cradle.

==Transcript==
:[Cueball is approaching a stump with a squirrel perched on it. A ringing noise is coming from the squirrel's back.]
:Squirrel: Riiiiing
:Squirrel: Riiiiiing

:[Cueball has picked up the squirrel and is holding it to his left ear.]
:Cueball: Hello?

:[The squirrel bites Cueball's head.]
:Squirrel: Chomp!
:Cueball: Ow!

:[Cueball holds his hand to his cheek while the squirrel leaps away, fleeing.]
:Cueball: ???

{{comic discussion}}
[[Category:Squirrels]]
[[Category:Comics featuring Cueball]]
[[Category:Phones]]