explain xkcd - User contributions [en]

2974: Storage Tanks

2024-08-19T23:46:22Z

108.162.245.42: /* Explanation */ explain better

{{comic
| number = 2974
| date = August 19, 2024
| title = Storage Tanks
| image = storage_tanks_2x.png
| imagesize = 321x251px
| noexpand = true
| titletext = We're considering installing a pressurization system to keep the tanks at constant pressure solely to deter them.
}}

==Explanation==
{{incomplete|Created by AN OVERENTHUSIASTIC CORPORATE SPY HIDING AS A CALCULUS TEACHER - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
A common question in introductory calculus courses asks [https://www.haywardflowcontrol.com/media/contentmanager/content//downloads//VessTime.pdf how long it will take a tank to empty,] assuming the rate of flow through a hole at the base is proportional to the pressure at the base of the tank. Assuming the tank is shaped like a cylinder, as appears to be the case in this comic, the amount of fluid left in the tank will follow an exponential decay, as the rate of pressure decrease will be proportional to the instantaneous pressure at any given moment. Variations of this question may consider more complicated tank geometries too, in which case the pressure at the base will not be simply proportional to the volume of fluid remaining in the tank.

The joke in the comic is that calculus teachers will actually drill a hole in a storage tank to demonstrate this principle, to protect against which a factory might station a guard to keep a lookout for them. This does not usually happen because sneaking a teacher and their entire class full of loud students into a facility without permission is a bad idea{{Citation needed}} and not getting caught is virtually impossible. It is illegal and will get you charged with trespassing, destruction of property, and attempted robbery.

The title text jokingly alludes to the fact that by maintaining a constant pressure at the base, the rate of flow would itself become constant, which would simplify the problem greatly and therefore make it much less interesting, or useful, as an example in a calculus course.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[Two characters wearing helmets are standing on scaffolding next to two large tanks labeled "Tank #3" and "Tank #4", with the person on the left talking. Miss Lenhart has drilled a hole into the base of Tank #4 with liquid pouring out of it and she is running away with the drill.]
:Left person with helmet: As head of security, your primary task is to monitor the storage tanks and watch for calculus teachers trying to drill holes in their bases.

{{comic discussion}}

[[Category:Characters with hats]]
[[Category:Comics featuring Miss Lenhart]]
[[Category:Math]]
[[Category:Physics]]

Talk:2956: Number Line Branch

2024-07-10T03:49:20Z

108.162.245.42: reply

Is it significant that the branch point is close to the value of π? [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 20:28, 8 July 2024 (UTC)
:I was thinking the same thing, but decided it was probably nothing worth mentioning - probably just an arbitrary starting point. *Possibly* referencing the strange appearance of π but I doubt it. Anything can be significant if you believe hard enough, anyway.--[[Special:Contributions/162.158.158.60|162.158.158.60]] 20:30, 8 July 2024 (UTC)
How does adding a new branch to a railway line reduce congestion? Isn't this more like a highway? [[Special:Contributions/141.101.105.47|141.101.105.47]] 23:30, 8 July 2024 (UTC)
:Read about the 2nd avenue subway. [[Special:Contributions/172.70.111.168|172.70.111.168]] 02:22, 9 July 2024 (UTC)

What is "thrembo"? [[User:AndroidTheLucario|Your favorite aura doggo]] ([[User talk:AndroidTheLucario|talk]]) 04:12, 9 July 2024 (UTC)
: I think the whole section can be removed. The point is to explain the comic, not to describe what is seen (unless it's relevant for the explanation, which, so far, seems not be the case). "Various symbols" should cover it. [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 06:35, 9 July 2024 (UTC)

The symbols seem well chosen TBH, I can totally see how they substitute for 4, 5, 6, 7, 8 [[Special:Contributions/162.158.146.32|162.158.146.32]] 14:42, 9 July 2024 (UTC)
:Except that, according to the title text, they should be 4, 8, 16, 32, 64. [[Special:Contributions/172.71.242.159|172.71.242.159]] 15:59, 9 July 2024 (UTC)
::I think that the express train travels on the regular number line, so I think the second branch parallels the regular number line. Thus, 4, 5, 6, 7, 8. [[User:Sarah the Pie(yes, the food)|Sarah the Pie(yes, the food)]] ([[User talk:Sarah the Pie(yes, the food)|talk]]) 02:11, 10 July 2024 (UTC)

Mathematicians been there, done that: https://en.wikipedia.org/wiki/Non-standard_model_of_arithmetic
Although a nonstandard model of the integers can't branch by Peano axioms. [[Special:Contributions/172.71.160.71|172.71.160.71]] 15:08, 9 July 2024 (UTC)
:Hold my beer! [Prompts Claude 3.5 Sonnet to create a non-standard model of arithmetic.]
::"Here is a non-standard model of arithmetic consistent with the Peano postulates:
::Axioms:
::
::∃0, ω : 0 ≠ ω
::∀x : S(x) = x + 1 if x ∈ ℕ; S(ω) = ω
::
::Theorems:
::T1. ∀n ∈ ℕ : n < ω
::T2. ∀n ∈ ℕ : n + ω = ω
::T3. ω + ω = ω
::
::Lemma:
::L1. ∀n ∈ ℕ : S(n) ≠ ω
::"Induction" Principle:
::For any property P, if P(0) ∧ P(ω) ∧ (∀x : P(x) → P(S(x))), then ∀x : P(x)
::
::Conclusions:
::C1. This model "satisfies" Peano axioms while introducing a non-standard element.
::C2. Arithmetic with ω leads to paradoxical results.
::C3. Use of this model may violate conservation of sanity."

:Oh, no! .... Tentacled one sleeps. Ph'nglui mglw'nafh Cthulhu. Accept this new soul. [[Special:Contributions/172.70.210.103|172.70.210.103]] 03:24, 10 July 2024 (UTC)
:::That is just the integers plus infinity, it should place you in the thrall of Asmodeus, not Cthulhu. [[Special:Contributions/108.162.245.42|108.162.245.42]]

Personally I would have branched off between 9 and 10, and had single character symbols for 10, 11, 12, 13, 14, and 15 so that you could do base 16 without having to use letters. Randell just lacks vision. [[User:Andyd273|Andyd273]] ([[User talk:Andyd273|talk]]) 15:12, 9 July 2024 (UTC)
:Letters are single character symbols! I think he should extend the number line with all the letters, getting to 36 (z) before needing any new symbols[[User:PotatoGod|PotatoGod]] ([[User talk:PotatoGod|talk]]) 21:46, 9 July 2024 (UTC)

Talk:2775: Siphon

2024-05-13T15:22:16Z

108.162.245.42:

My understanding was that siphoning can essentially be explained by the Bernoulli equation? There is a difference in potential energy between the upper and lower container so it flows. The weight of water in the downhill part of the tube pulls water up the uphill section of the tube (think like a vacuum), and so on until there's either no difference in head or no more water. Siphoning will work with any diameter tube. [[Special:Contributions/172.70.91.151|172.70.91.151]] 15:43, 12 May 2023 (UTC)
:That's right. The only mention of capillary action in the siphon wikipedia article is when talking about phenomenon that *isn't* a siphon. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 16:15, 12 May 2023 (UTC)

Agree, capillary action does not seem to be referenced or implied in the comic, presenting only the (not "functioning") siphon phenomenon. [[Special:Contributions/172.68.134.142|172.68.134.142]] 16:23, 12 May 2023 (UTC)
:Seconded/thirded. Capillary action isn't even what they were expecting. The small amount of water in the lower recepticle indicates they correctly ''filled'' the tube, but then as the longer length drained it did not then induce further flow up and over through the shorter length. e.g. nature no longer abhored the resulting vacuum (or there was increased negative-pressure vapourisation, beyond that previously expected, or other method of seepage 'airlock'-breaking) and thus the short-end also drained straight back out again instead of becoming a potentially self-sustaining inflow to the whole siphoning setup.
::If the upper end got restricted (say by touching the side of the bucket) the loss of flow would allow air to enter the bottom end and drain out the tube. I've done this. :-( [[User:RIIW - Ponder it|RIIW - Ponder it]] ([[User talk:RIIW - Ponder it|talk]]) 19:07, 12 May 2023 (UTC)
:::Indeed, even having an especially large diameter "tube" (/pipe etc) can allow air from the bottom to flow up to the peak & break the siphon effect. For reliable results, the lower end needs to be kept immersed or the hose needs to be relatively small in diameter. [[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 14:11, 13 May 2023 (UTC)
:While the capilliary action element ''could'' induce the start of a rather limited 'empty' siphon setup to start (maybe, I'd have doubts about the 'fluid friction' actually acting against the gravity-feed part, once the surface-tension bit has "climbed the mountain" and started to merely seep out of the other end, almost incidentally, for a sufficiently thin tubing where CA is a significant factor), this suddenly failing for whatever reason (surface-tension effects being nullified) wouldn't then send a token amount of water into the low bucket, nor particularly stop unrelated siphon-flow from continuing properly (in fact, suddenly 'interaction-free' liquid and tubing might siphon ''faster'', with effectively zero fluid boundary effects dragging on the induced flow).
:But perhaps someone with more QFD experience could explain where my assessment is wrong. So not going to personally rewrite the current Explanation intro just now. [[Special:Contributions/172.70.162.161|172.70.162.161]] 16:21, 12 May 2023 (UTC)
:I'd like to contribute as one more data point. I also don't see capillary action as being relevant. In particular, as another commenter said, the water in the lower bucket quite clearly supports the idea that the siphon effect was the subject of the characters' confusion. How else is Randall supposed to depict the siphon effect anyway? I agree that the drawing alone ''could'' also suggest capillary action is what's being investigated, but I don't think it suggests that the caption has ''incorrectly'' referred to it as the siphon effect. [[Special:Contributions/172.71.254.100|172.71.254.100]] 18:44, 12 May 2023 (UTC)

Of course, if some physical law would actually stop working, people wouldn't be confused. They would drop dead. Due to physical laws working on level of elementary particles, every change would have lot of different effects ... and living organism live only thanks to being very carefully balanced in lot of regards. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 20:49, 12 May 2023 (UTC)

Bug report 6EQUJ5: Odd signal emitted from Sagittarius constellation. Status: Closed - could not reproduce. [[Special:Contributions/172.71.26.69|172.71.26.69]] 03:20, 13 May 2023 (UTC)
:(I get that reference... :) However, launching off that to say: ) There's an old (short?) story... H.G. Wells era, possibly, but not him I think... where someone (who happened to be the first decent but amateur astronomer to get a cloudless patch of sky, one night) realises the Moon is in the wrong place, and the news then reaches (and troubles) the professional community who get a chance to observe/notice the change for the first fime and confirm it.. A 'glitch' seems to have passed through space and moved/retimed it, for a limited time, before it later snaps back to where (in the orbit) it now should be.
:The trace of the glitch are seen further afield (implying a 'beam' of 'wrongness'), and ultimately it spawns something like Experimental Theology whereby observations of such clear "hand of the Creator" changes (implying we're essentially in a simulated universe being operated by a 'universal programmer', but in pre-computer terms) merge or muddy the boundaries between scientific rationalism (which clearly falls short) and religious philosophy (where undeniable 'proof' of something godlike is now suddenly an ironically confounding factor).
:Cannot remember much about where I read it, I may be presuming some details about it that aren't actually there (even removing obvious mix-ups with similar brands of tale) and my Google-Fu fails to establish any obvious online reference to it (even just title+synoposis), so instead I'm setting down the 'spoilers' without reservation. [[Special:Contributions/172.70.91.151|172.70.91.151]] 13:04, 15 May 2023 (UTC)

Siphoning is NOT because of capillary action! That should be changed!! [[Special:Contributions/172.70.127.90|172.70.127.90]] 15:35, 13 May 2023 (UTC)

I guess I was wrong that siphons work because of capillary action. [[User:TianHanFei|TianHanFei]] ([[User talk:TianHanFei|talk]]) 1:57, 15 May 2023 (UTC)

::As someone who's been publicly wrong here before, it can be stressful, but if it's any consolation, you're one of today's (probably much fewer than) 10,000: https://xkcd.com/1053/ -- thanks for having a sense of humor about it [[User:Dextrous Fred|Dextrous Fred]] ([[User talk:Dextrous Fred|talk]]) 17:18, 15 May 2023 (UTC)

== Potential inspiration ==

One potential source of inspiration for this comic is the Twitter [https://twitter.com/earth_updates account @Earth_Updates], which produces a lot of similar content. [[User:PotatoGod|PotatoGod]] ([[User talk:PotatoGod|talk]]) 19:54, 12 May 2023 (UTC)

I think if I added it to the article body it would get reverted, but the content seems very similar to how AI media produced delusional worlds for so many factions of people. It is not at all a big stretch to imagine people stepping into a metaverse or matrix where they aren’t sure what is real and physical laws match their intuition more than is actually correct. [[Special:Contributions/162.158.158.171|162.158.158.171]] 08:23, 13 May 2023 (UTC)

== Title text ==

Isn't the title text about stars like our sun rather than about plutonium? [[Special:Contributions/198.41.242.95|198.41.242.95]] 00:55, 13 May 2023 (UTC)h
:Seems to me unlikely that anyone would refer to stars as 'rocks'.[[User:Catherine|Catherine]] ([[User talk:Catherine|talk]]) 02:54, 13 May 2023 (UTC)
::There is Slate that turn into lava spontaneously after lying around for thousands of years. I think the area they are in is called "Smoking Hills". There was recent research why that slate does this while in much the rest of the world slate is just flat, black rocks. I still believe this title text is about plutonium, though, as that slate produces so much heat, that one still hasn't managed to measure how hot it gets - but it produces that heat not for an near-infinite duration.--[[User:Gunterkoenigsmann|Gunterkoenigsmann]] ([[User talk:Gunterkoenigsmann|talk]]) 01:48, 14 May 2023 (UTC)
:::The only {{w|Smoking Hills}} that came to mind was natural shale-fires (chemical burning, and not hot enough for remelting to magma/lava.
:::Possibly there is a {{w|natural nuclear fission reactor|situation}} where it has done as you say (in some natural mass of rock, spotted somewhere in this planet's lithosphere, or elsewhere out there), but given the fine line between nicely sustaining and runaway chain-reactions, I'm not sure how easy it is for nature to 'engineer' a way to land on the {{w|Corium (nuclear reactor)|middle ground}} and not go supercritical.
:::In order for accumulating ores to not just start a low-level fizzle (as above), over millenia, you might need separate ore-patches either side of a fault to come together in a suddenish techtonic slip, rather than a slow buckling of layers to increase effective ore-densities. And then you've got earthquakes, already, so not sure if the very low-grade nuclear explosion that is awfully close to being possible in this chance contrived example (at one end of the probability curve, unless U238 content is somehow preferentially leached out?) is going to be noticable.
:::But ''just'' hot enough for lava? If not already close to melting, anyway, under local temperatures and pressures? Not sure we've seen anything like it, even if it is technically feasible given enough happenstance setups by geology(/exo-geology), since planets formed. [[Special:Contributions/172.70.91.152|172.70.91.152]] 09:16, 14 May 2023 (UTC)
::::Any sufficiently large rock containing sufficiently high concentrations of radioactive materials (such as the Earth) will partially melt. The energy is released slowly by decay not through fission. The large size ensures that the center is well enough insulate that slow heating accumulates until it reaches lava temperatures. The finite size ensures that enough heat leaks out that the magma does not become gas.[[Special:Contributions/162.158.158.170|162.158.158.170]] 18:29, 16 May 2023 (UTC)

== Title Text-Radiation ==

The title text is referring to the heat created by natural radioactive decay, not humans harnessing it in reactors.

The literal rocks of particularly radioactive elements still in the ground are constantly producing small amounts of heat without our assistance

[[Special:Contributions/172.71.151.48|172.71.151.48]] 06:27, 14 May 2023 (UTC)

Relevant xkcd: https://www.explainxkcd.com/wiki/index.php/1172:_Workflow

Re:Actor: Siphon heat rocks water is the basis for my workflow. Randall please add a option, so siphon heat rocking can be re-enabled on demand.
[[Special:Contributions/198.41.242.149|198.41.242.149]] 19:23, 16 May 2023 (UTC) PicassoCT

siphon't [[Special:Contributions/108.162.245.42|108.162.245.42]] 15:22, 13 May 2024 (UTC)

6: Irony

2024-01-29T03:28:27Z

108.162.245.42: /* Explanation */ No other use, so not an alternative

{{comic
| number = 6
| date = September 30, 2005
| title = Irony
| before = <big><big>[https://web.archive.org/web/20070927001941/http://xkcd-drawings.livejournal.com/?skip=40#:~:text=8%3A42%20pm-,Irony,-Too%20much%20perspective Original title]: '''Irony'''</big></big>
| image = irony_color.jpg
| titletext = It's commonly known that too much perspective can be a downer. [https://web.archive.org/web/20070927001941/http://xkcd-drawings.livejournal.com/?skip=40#:~:text=8%3A42%20pm-,Irony,-Too%20much%20perspective Original caption]: Too much perspective can do that.
}}

==Explanation==
This was the ninth comic originally posted to [[LiveJournal]]. The previous one was [[8: Red Spiders]], and the next one was [[9: Serenity is coming out tomorrow]]. It was among the [[:Category:First day on LiveJournal|first thirteen comics]] posted to LiveJournal within 12 minutes on September 30, 2005, on the first day of the xkcd LiveJournal account.

[[Cueball]] makes a true statement, that his statement is not very funny. However, because he invoked {{w|irony}} and thus makes it self-referential, the sentence is now funny! The other guy Cueball, producing a fake laugh, is probably not so sure that it is actually funny. The barren landscape would have occurred regardless of whether someone made the joke, so ironically, the cautionary tale is completely meaningless, although still funny. Self-references would be used again in [[33: Self-reference]] and [[:Category:Self-reference|many more comics]].

The title text is a reference to the visit of {{w|Spın̈al Tap}} to the grave of {{w|Elvis Presley}}. In addition, the perspective theme also invokes the {{w|Technology in The Hitchhiker's Guide to the Galaxy#Total Perspective Vortex|Total Perspective Vortex}} in {{w|The Hitchhiker's Guide to the Galaxy}}. This is located on the desolate planet Frogstar B, possibly looking not unlike the final image in the comic.

==Transcript==
:[A panel only with text. The last text is written below a line in all capital letters.]
:When self-reference, irony, and meta-humor go too far
:A CAUTIONARY TALE

:[Cueball talks to his Cueball-like friend.]
:Cueball: This statement wouldn't be funny if not for irony!

:[Cueball laughs at his own joke in front of his friend.]
:Cueball: ha ha
:Friend: ha ha, I guess.

:[Again a panel only with text.]
:20,000 years later...

:[A desolate brown badlands landscape with an imposing red sun in the dark blue sky.]

{{comic discussion}}

[[Category:Posted on LiveJournal| 09]]
[[Category:First day on LiveJournal| 09]]
[[Category:First day on xkcd.com]]
[[Category:Comics with color]]
[[Category:Checkered paper]]
[[Category:Comics featuring Cueball]]
[[Category:Multiple Cueballs]]
[[Category:Self-reference]]
[[Category:Comics with lowercase text]]

2415: Allow Captcha

2021-02-02T00:23:44Z

108.162.245.42: /* Boxes on the reCAPTCHA */ "Alike" is not a verb, so "Click?" = No.

{{comic
| number = 2415
| date = January 22, 2021
| title = Allow Captcha
| image = allow_captcha.png
| titletext = To prove you're human, please click all the number pairs that appear together in your Social Security number.
}}

==Explanation==
{{incomplete|Created by a malicious design practice that already exists out there. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}

Captcha is designed to prevent spambots from being able to post on websites by posing challenges that humans can easily solve but that spambots and other automated programs cannot solve. The original version (used in [[632: Suspicion]]) asked users to identify text that was rotated, warped, or otherwise modified in order to make it more difficult for automated programs to solve. Once automated programs got good at that, new captchas were put out that exploited the fact that computers tend to be bad at image recognition, e.g. asking the user to select only images that contain cats from a grid of images of cats, dogs, and other objects (used in [[1897: Self Driving]]). This captcha appears to combine the two methods—with the additional hurdle that in order to pass the captcha, users must be able to not only read but also understand (i.e. know the definitions of words). However, if the goal is to allow humans but not computers to pass (although, as the next paragraph will describe, it is not the goal), this is not a good method of differentiating between the two. Any computer program that can accurately read text (and there are now many programs that can do so) would know which words start with 'A' and would be able to look up the definitions (including parts of speech) online, so this would not be effective as a captcha. Humans on the other hand, would often get confused between "ale" and "ail" or between "allot" and "a lot". The English language has no distinction between nouns and verbs by spelling, only grammatical usage, and many words in English are both nouns and verbs.

In reality, however, the window is merely disguised as a captcha in order to trick human visitors into allowing the website to install "a helper tool", which may be malware, on their computer. The top of the window uses a similar shade of blue to the current version of {{w|reCAPTCHA}} (currently the most common brand of captcha), the prompt includes the phrase "to prove you're human", and the grid is similar to the grid used by reCAPTCHA. However, positioned to appear to humans as two reCAPTCHA boxes is a window asking viewers whether they want to allow or deny the website's request to install the supposed "helper tool". The idea is that because "allow" is a verb beginning with the letter A, human visitors would click on what they think is the box with the word allow in it but actually allow the website to install potential malware on their computer. The window attempts to disguise this by formatting many of the words in boxes as buttons and including other text in smaller font on other boxes. In addition, the captcha may be intentionally difficult so that users will be too distracted by wondering whether ale is a verb to process the meaning of the request.

It should be noted that simply tricking humans would not necessarily be enough to install malware on their computer. First of all, while a person can select any part of a grid box in order to select that box, only clicking on the actual button that says allow will allow malware unto the computer. If a person clicks on another part of the supposed box, nothing will happen, so the person will likely take a closer look in order to see why the window is not being selected and then possibly realize that this is a trick as a result. Further, the website would likely not be able to specify where the permission window appears, so would not be able to fit it into the fake reCAPTCHA. In addition, the user's computer may have an anti-virus software that will prevent the computer from executing malicious code downloaded by the website. Or in order for the user to install software, a second window may pop up requiring the user to type in an administrator password, which will likely startle the user.

Shady websites often use similar tactics to trick you into allowing notifications, including saying "[https://www.bleepstatic.com/swr-guides/c/click-allow-to-verify-that-your-are-not-a-robot/notification-subscription-page.jpg Please allow notifications to confirm you are not a robot]". This comic combines that with a traditional reCAPTCHA to try and trick savvier users too.

The title text is a another trick reCAPTCHA which is trying to make you give out your {{w|social security number}} by clicking the pairs of numbers that appear in your Social Security number. A social security number is a form of identification used in the United States, originally used for the Social Security Administration. Over time, this number has become a type of national identification number, so stealing these numbers would allow a scammer to commit identity fraud. Of course, it would use a different grid, as the grid pictured in the comic has words, not pairs of digits. If you can find all of the pairs then they would be able to guess your real number and thus this would be a weird kind of phishing attempt. If the grid is 4×4 (and some reCAPTCHA grids are only 3×3), then it can only show 16 of the possible 100 pairs of two digits, so any people who are successfully tricked likely would not reveal their entire Social Security numbers because some digit pairs in their Social Security numbers would not appear. However, it should be noted that this trick likely will not be as successful as the captcha-based trick because the phrase "Social Security number" will likely raise alarm bells concerning identity theft, and people who are not citizens or permanent or temporary residents of the United States will not have Social Security numbers, so they will not be able to be tricked into revealing personal information this way even if they are especially gullible.

It should also be noted that the phrase "to prove you're human", while also attempting to disguise the trick, has a somewhat different implication. In the first example, the idea of the supposed captcha is that it asks the user to complete a task that human brains but not computer programs can perform accurately easily, such as image recognition. In the example in the title text, the idea of the fake captcha appears to be that humans are issued Social Security numbers (at least if they live or have lived in the United States), but computers are not. As the website does not already know the users' Social Security numbers, it would not actually be able to tell whether the user's response was correct. There is nothing to prevent programming an automated spambot program to randomly select zero to four of the boxes. Likewise, users could lie and not reveal their actual Social Security numbers, although those who realize that the supposed captcha is an attempt at identity theft will likely not complete it at all and could report it to law enforcement instead.

==Boxes on the reCAPTCHA==
{| class="wikitable"
!|Position
!|Contents
!|Analysis
!|Click?
|-
|Row 1
Column 1
|Alike
|Adjective/Adverb: Related to the verb "Like", as in "similar"
|No
|-
|Row 1
Column 2
|Elope
|Verb: To romantically abscond
But does not start with "A"
|No
|-
|Row 1
Column 3
|Aloe
|Noun: A specific type of plant, or its extracts
Vaguely similar to "Allow", but not normally a homophone
|No
|-
|Row 1
Column 4
|Ale
(and squiggles)
|Noun: A type of beer
Confusable with the verb "ail": To suffer

"(To) ply with drink" is conceivably a verb form
|No/Maybe
|-
|Row 2
Column 1
|Avow
(and squiggles)
|Verb: To declare
|Yes
|-
|Row 2
Column 2
|Danny
(and squiggles)
|A person's name: Familar version of Daniel/Danielle
(Also slang/dialect noun: The hand)

A strained off-homophone of "Deny", as used elsewhere

Does not even start with an "A", anyway!
|No
|-
|Row 2
Column 3
|Allele
|Noun: Genetic variation/subunit
|No
|-
|Row 2
Column 4
|Allot
(and squiggles)
|Verb: To assign or distribute
Can be misspelt "alot", causing confusion as to the legitimate word

Either of the above may be misused instead of "a lot", in its noun form meaning "many"
|Yes
|-
|Row 3
Column 1
|Askew
|Adjective/Adverb: Tilted, twisted, off-balance, strange
|No
|-
|Row 3
Column 2
|Deny
(x2)
|Verb: To refuse, disallow, etc
Does not start with "A"
|No
|-
|Row 3
Columns 3+4
|(squiggled "www.a????.com") wants to install a helper tool
|Might depend upon a legible version of the URL
|The true CAPTCHA answer would apply to cell Row 3, Column 3
|-
|Row 3
Column 3
|Deny
|As above
|No
|-
|Row 3
Column 4
|Allow
|Verb: To permit, licence, be contingent of
|In CAPTCHA context only
To avoid malicious behavior, you should avoid clicking this whole grid
|-
|Row 4
Column 1
|Allow (smaller size)
Alto

(squiggled "to a????? ~squiggles~")
|It might be easy to miss the "Allow", which is valid
"Alto", however, is a noun: Instrumental/choral pitch or range

The squiggles ''may'' include a 'valid' A-Verb
|Yes, for "Allow", in CAPTCHA context
But if a Click-trap, you'd be best to close/Back-button the whole page
|-
|Row 4
Column 2
|Allow (and squiggles)
|As elsewhere
|Yes
(or further trap)
|-
|Row 4
Column 3
|Deal
|Verb, noun and adjectival: Various related or obscure meanings
But does not start with "A", in any case
|No
|-
|Row 4
Column 4
|Delay
|Verb (and related noun): Of an enforced wait
Does not start with "A", although the synonym "allay" does

("Delay" also shares common meanings with, ''and'' mixes the phonemes of, both "Allay" and "Deny")
|No
|-
|Any cell
|Unremarked squiggles
|It is entirely possible that those squiggles, if decipherable, could include qualifying text
|Maybe..?
|}

==Transcript==
[Header at the top of the image with white text inside a light blue rectangle]: To prove you're human, please click every box containing a verb that starts with "A"

[Below the header, a series of panels in a 4x4 grid. Each panel has a word in capitals. Most of the words appear to be in buttons, and several have illegible text above or below. Some are tilted or off-center]

Alike

Elope

Aloe

Ale

Avow

Danny

Allele

Allot

Askew

[Two buttons, both saying]: Deny

[The next two panels are joined together, with two buttons next to each other. One says "Deny" and the other "Allow". The text above reads]: [illegible].com wants to install a helper tool

[With the word "Allow" printed clearly above and illegible text below]: Alto

Allow

Deal

Delay

{{comic discussion}}
[[Category:CAPTCHA]]
[[Category:Comics with color]]

1755: Old Days

2016-11-07T20:01:24Z

108.162.245.42: /* Table of statements */ <over night> =<overnight>

{{comic
| number = 1755
| date = November 4, 2016
| title = Old Days
| image = old_days.png
| titletext = Lot of drama in those days, including constant efforts to force the "Reflections on Trusting Trust" guy into retirement so we could stop being so paranoid about compilers.
}}

==Explanation==
This comic is showing a conversation between (young) [[Cueball]] and (old) [[Hairbun]] about computer programming in the past, specifically the {{w|compilers}}. Cueball, having a faint idea of just how difficult and byzantine programming was "in the old days", asks Hairbun to enlighten him on the specifics. Hairbun promptly seizes the opportunity to screw with his head.

While her initial agreement that code needed to be compiled for multiple architectures is correct, Hairbun's claims rapidly grow ridiculous to the point where the improvement from {{w|C (programming language)|C}} to {{w|C++}} was that C++ finally supported {{w|floppy disks}} but just punched holes in them rather than using {{w|punch cards}} "like C used".

Hairbun tells Cueball a tall tale about how hard it was back in the '''old days''', making it sound like some of the programming languages used today (C, C++) were written on punch cards and that you had to ship your code in the mail to a computer company ({{w|IBM}} in this case) to compile your code, which would take from four to six weeks. If there was a simple error, you would have to ship it again for another compilation.

Nothing of what she tells Cueball makes any sense, but it is clear from Cueball's final ''Wow'' that he falls for it, ready to believe anything the old Hairbun tells him about how horrible it was to program in the olden days. It is true that it was tough and slow to program on punch cards, which were actually used for an extended period of time, but there is nothing in the rest of Hairbun's story that accurate, except that it was a big deal when the floppy disk was invented.

In the title text, Hairbun continues her musings on the old compiler days, stating that there was ''a lot of drama in those days''. Specifically she references ''[http://www.win.tue.nl/~aeb/linux/hh/thompson/trust.html Reflections on Trusting Trust]'' a famous 1984 paper by {{w|UNIX}} co-creator {{w|Ken Thompson}} in which he described a way to hide a virtually undetectable backdoor in the UNIX login code via a second backdoor in the C compiler. Using the technique in his paper, it would be impossible to discover the hacked login by examining the official source code for either the login or the compiler itself. Ken Thompson may have actually included this backdoor in early versions of UNIX, undiscovered. Ken Thompson's paper demonstrated that it was functionally impossible to prove that any piece of software was fully trustworthy.

Hairbun claims that one of the dramas she refers to was that people tried to force Ken Thompson to retire, so everyone could stop being so paranoid about compilers. In reality, any coder who created the first version of a compiler (or a similar critical component) could inject a similar backdoor into software, so it would be false safety. Even if no one else had thought of this, then Thompson's paper was there for any future hacker to see. Though the problem was (claimed to be) solved in {{w|David A. Wheeler}} Ph.D dissertation "[http://www.dwheeler.com/trusting-trust/ Fully Countering Trusting Trust through Diverse Double-Compiling (DDC)]".

==Table of statements==
{|class="wikitable"
!Statements
!Concepts used
!Explanation
|-
|Compile things for different processors
|Compilers convert code from a human-readable programming language into a binary code that can be directly executed by computer processors.
|Many popular modern programming languages are either interpreted - meaning that they run directly from source code - or compile to an intermediate bytecode, like Java or common Python implementations. Programs written in such languages are portable across processor architectures - x86 to ARM, for example. Lower-level languages must take into account the features available on a given processor architecture and operating system. Before that, programs needed to compile directly into the native machine language for each processor they were intended to run on.
Native machine language is dependent on processor architecture. Therefore different processors designed around different architectures will not run the same compiled code (unless the architectures are compatible; AMD64 processors will run i386 code natively, for example.) If the same code needs to be run on multiple architectures, it must be compiled separately for each supported architecture.
|-
|To compile your code, you had to mail it to IBM. It took 4-6 weeks.
|Similar to sending Kodachrome slide film to Kodak to be developed.
|While IBM has released multiple compilers, they sent the compiler to you, you did not send the code to them. There is some kind of truth in the statement, though: When programming on mainframes, programmers submitted their source code in the evening for compilation overnight. When there was an error in the code, they did not get a compiled version of it back, and had to resubmit their code. Sometimes there were time slots available for compilation, and in universities, students will have to wait for their next time slot for another try.
|-
|Before garbage collection, data would pile up until the computer got full and you had to throw it away.
|A {{w|Garbage collection (computer science)|garbage collector}} is a piece of the software that cleans the {{w|RAM}} of data that is no longer being used in the execution of a program.
|Garbage collection is a form of memory management that generally destroys objects or frees up memory once a program no longer needs it. In languages without automatic memory management, like C, the program itself must keep track of what memory has been allocated, and free it once it is no longer needed. If the program does not, it can end up trying to use more memory than the computer has, and may crash. This was, however, a ''temporary'' condition. In the worst case, a simple reboot will clear the computer's memory.
|-
|Early compilers could handle code fine, but comments had to be written in assembly.
|A {{w|Comment (computer programming)|comment}} in programming is a text written in natural language that is meant to explain some feature of the source code; it is tagged such that the compiler will discard it to save space. {{w|Assembly language|Assembly}} is a low-level programming language.
|Comments, in code, are portions of one or more lines that are ignored by the compiler. They are commonly used to explain or comment on the code itself. But sometimes the comments are written in a certain way to compile documentation automatically from it. Also, when examining the output of compilers it's a common practice to use assembly code annotated with comments containing the source code of the program from which the assembly code was generated.

Hairbun's comment is thus very strange, implying the compilers of the day could only distinguish between comments and code if assembly was used to insert the separating tags.
|-
|C could only be written on punch cards. You had to pick a compact font, or you'd only fit a few characters per card.
|{{w|C (programming language)|C}} is a programming language. A {{w|punch card}} is a primitive form of storing data; it stored data in {{w|binary language}} with holes in a paper or cardboard card where a hole meant a 1 and the absence of a hole meant a 0.
|While punch cards were used through the late 1970s and early 1980s to enter programs and data in COBOL, FORTRAN and other early languages, the use of punch cards and punch card machines had been replaced by a {{w|text editor}} long before C (or C++) was developed as a language. This site demonstrates a card punch and cards: [http://www.masswerk.at/keypunch/ Keypunch]].

Hairbun claims that code was not written using keyboards, but by punching out letter and character shapes in the punch cards, and the computer would load read keystrokes that way. Simply put, this was never true. Punch cards store characters in binary; there is no font involved and they store up to fixed limit of characters per card (80 characters in the most common format.)
|-
|C++ was big because it supported floppy disks. It still punched holes in them, but it was a start.
|{{w|C++ (programming language)|C++}} is a programming language. A {{w|floppy disk}} is a form of storing data magnetically. It's way more advanced than punch cards (by several orders of magnitude; a card can store about 80 bytes, vs 1,474,560 bytes of a floppy disk), but it's still obsolete compared to modern storage.
|Hairbun says that the improvement from C to C++ was that C++ finally "supported floppy disks", but then it turns out that in C++ the floppy disks were just used instead of punch cards. So the programing was to make holes in floppy disks rather than punch cards. This would of course not be an improvement as floppy disks store information magnetically, as opposed to physically, as punch cards do. This is likely a play on the concept of punching holes in 5.25" floppy disks to double their storage (see {{w|Double-sided disk}}), or it can also be a reference to the "index hole" of 5.25" floppy disks (see {{w|Floppy_disk#Design|Floppy disk Design}} and the tiny hole at the right of the big central hole in this [https://www.staff.ncl.ac.uk/roger.broughton/museum/floppys/images/201041b.jpg image]). A notch in the side of 5.25" floppy disks indicates when the disk could be written. Though many floppy disks were intended to have only a single side with data, many people used a hole punch to notch the opposite side of the disk, allowing a drive to write data to the other side of the disk in a single sided drive. 5.25" floppies also featured a tiny "index hole" near the central hole of the disk.
|}

==Transcript==
:[Cueball and Hairbun are standing together and Cueball is talking to her.]
:Cueball: What were things like in the old days?
:Cueball: I hear that you had to ... compile things for different processors?
:Hairbun: Yeah

:[Same setting in a slimmer panel, now Hairbun is replying.]
:Hairbun: To compile your code, you had to mail it to IBM.
:Hairbun: It took 4-6 weeks.

:[Close-up of Hairbun from the waist up.]
:Hairbun: Before garbage collection, data would pile up until the computer got full and you had to throw it away.

:[Same setting as in the first panel with Hairbun gesturing toward Cueball raising one hand palm up.]
:Hairbun: Early compilers could handle code fine, but comments had to be written in assembly.

:[In a frame-less panel Hairbun is seen from the front, with both arms out to the side with both hands held palm up.]
:Hairbun: '''C''' could only be written on punch cards.You had to pick a compact font, or you'd only fit a few characters per card.

:[Exactly the same setting as the first panel, but with Hairbun doing the talking.]
:Hairbun: '''C++''' was big because it supported floppy disks.
:Hairbun: It still punched holes in them, but it was a start.
:Cueball: Wow.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Hairbun]]
[[Category:Programming]]

Talk:938: T-Cells

2014-09-28T02:24:02Z

108.162.245.42:

Does anyone have a link to the actual article? Or possibly a proper citation? {{unsigned ip|192.17.144.82}}
:I have added such a link in the explanation. Unfortunately, you have to subscribe to the magazine asterisked in the comic, so the link goes to another one. It also helps to Google "nejm aug 10 2011". Anonymous 04:51, 13 December 2013 (UTC)

Trial appears to have been a success, although the patient now has no B-cells and thus a compromised immune system (will need regular gamma globulin transfusions and the like). [[Special:Contributions/75.103.23.206|75.103.23.206]] 16:54, 13 December 2012 (UTC)

Looks to be this article here [http://www.nejm.org/doi/full/10.1056/NEJMoa1103849] and [http://kiefercon.tumblr.com/]. I'll stick with chemo, thanks. [[Special:Contributions/173.245.54.87|173.245.54.87]] 16:36, 24 November 2013 (UTC)

I know it's a joke, but just in case people are taking this seriously, this is worth a read. [http://scienceblog.cancerresearchuk.org/2013/06/25/no-doctors-did-not-inject-hiv-into-a-dying-girl-to-treat-her-cancer/] The key word should have been "lentivirus", not "HIV". The T cells were modified using a heavily altered lentivirus derived from HIV. The virus shouldn't be referred to as HIV, though it makes for some great headlines. [[Special:Contributions/199.27.128.167|199.27.128.167]] 20:40, 2 December 2013 (UTC)

Before WWII there was an succesful method of curing syphilis with malaria (malariotherapy). Maybe a reference[[Special:Contributions/141.101.96.217|141.101.96.217]] 11:32, 27 March 2014 (UTC)

Isn't "HIV virus" redundant? [[Special:Contributions/108.162.245.42|108.162.245.42]] 02:24, 28 September 2014 (UTC)