explain xkcd - User contributions [en]

2238: Flu Shot

2025-01-15T11:07:45Z

172.69.195.27: Undo revision 362107 by Woofwooffire (talk) Revised undo. Presuming more useful than hoping. Re-added the full-stop in the *proper* place for it.

{{comic
| number = 2238
| date = December 6, 2019
| title = Flu Shot
| image = flu_shot.png
| titletext = "Wait, how often are you getting bitten by snakes? And why are you boiling water?" "Dunno, the CDC people keep showing up with complicated questions about the 'history of the property' and 'possible curses' but I kinda tune them out. At least one of them offered me the flu shot."
}}

==Explanation==

In this comic, [[Megan]] tells [[Cueball]] that she got a {{w|flu shot}}, which is a vaccine commonly prescribed in the winter months to prevent getting the {{w|common flu}}. She then goes on to claim she doesn't have to worry about being bitten by bats, but the worry with being bitten by bats is {{w|rabies}}, not the flu. (Interestingly, bats and biting in the context of diseases would start becoming a big topic that would eventually concern the entire world less than a month after this comic was published, which Randall presumably did not know anything about.) This implies she got the two confused and Cueball begins to correct her. But she just talks over him not listening to him. She then goes on to claim to now be immune to other conditions, such as {{w|poison ivy}}, {{w|snake venom}}, {{w|sunburn}}, contaminated water, and even {{w|computer viruses}}. It should be noted that a flu shot will not protect you from things other than the influenza virus.{{Citation needed}}

At the end of all this, Cueball has given up on her and proclaims that he supports her attempts to test the strength of her Flu Shot, perhaps mentally adopting the philosophy of the {{w|Darwin Awards}} that it is good if the genes that cause a person to do incredibly dangerous, stupid things are eliminated from the gene pool.

In the title text, Cueball asks Megan how often she gets bitten by snakes and why she boils water. She answers dunno (maybe to the water part, she must at least know how often she gets bitten). She then tells that some members of the {{w|U.S. Centers for Disease Control}} (CDC) keeps coming to her house asking about its history and possible curses, a humorous escalation which implies that Megan's absurd exposure to various forms of harm has brought them to the point of wondering if the supernatural may be involved. (Megan may have invoked a curse on herself or her residence when she and [[Rob]] desecrated an ancient Indian burial ground and smashed up a voodoo shop in [[782: Desecration]].) At the end of her reply, she mentions that she got the flu shot thanks to one (or more) of the CDC guys, and she is thankful for that. This is logical as she expects it to protect her from literally any danger she has ever put herself in.

===Explanation of "immunities"===
The flu shot consists of inactivated viruses from four different strains of the flu, which are those judged by the {{w|World Health Organization}} (WHO) to most likely be in wide circulation in the following flu season. Because the influenza virus comes in many strains and mutates rapidly, the flu shot is generally less than 60% effective at preventing flu infections; this is a positive effect for health outcomes, but it's not exactly what most people think of as "immunity", especially compared to e.g. the 97% effectiveness of the {{w|MMR vaccine}} against {{w|measles}}, {{w|Mumps}} and {{w|rubella}}. Statistics show that flu vaccine recipients are slightly less likely to die from a variety of other causes, but this is believed to be either because someone with the flu is more likely to have a heart attack, car accident, etc., or because of the {{w|healthy user effect}} (i.e. people who take the time to get non-mandatory vaccines are probably also taking better-than-average care of themselves in other ways, although this is clearly not the case with Megan in this comic strip). Even if there is a slight protective effect, it will certainly not completely prevent harm from coming to Megan by the other sources of infection or poison she mentions, except to the extent that all of these things will be even worse for her if she is also sick with the flu:

* '''{{w|Rabies}}''' is a near invariably fatal viral disease that causes brain inflammation, which in turn causes symptoms including aggression, fear of water, and violent uncontrollable limb movements. It can be carried by almost any vertebrate animal, but bats, raccoons, and wild dogs are the stereotypical carriers. There is a rabies vaccine, but it is generally only administered to pets and to humans who work extensively with animals or travel to regions with an elevated risk of contracting rabies. The rabies vaccine is also effective to prevent rabies after exposure, but only if administered before the victim starts showing symptoms.
* '''{{w|Poison ivy}}''' is a vine that produces an oil called {{w|urushiol}}, which chemically reacts with membrane proteins on the skin cells it contacts, tricking the immune system into attacking those cells, causing an itchy, irritating rash. Some people are not affected by poison ivy but, as it is an allergic reaction, those who do often become more sensitive to poison ivy upon repeated exposure. There is no known vaccine or other permanent preventative treatment against urushiol sensitivity, although there are several creams that can be applied in advance of expected poison ivy exposure to reduce the risk of coming into contact with the chemical.
* '''{{w|Sunburn}}''' is caused by exposing the skin to high levels of ultraviolet radiation, as found in sunlight. This can increase the risk of skin cancer later in life. As ultraviolet radiation is a form of electromagnetic energy, it cannot be prevented by vaccination, but the use of sunscreen with a high SPF ({{w|sun protection factor}}) can provide protection for a few hours.
* '''{{w|Snake venom}}''' is not one single compound, but several proteins and molecules produced by venomous snakes to inject into prey. Different snakes' venoms have different effects, so there is no single vaccine or antivenom for all snake bites, but {{w|antivenom}}s are produced by a process similar to vaccination. Small doses of venom are injected into host animals, such as horses, to provoke an immune response; the resulting antibodies are then stored to be injected into snakebite victims, where they will bind up and inactivate the toxic proteins and mark them for disposal by the immune system. Antivenom is more effective the sooner it is administered; for venomous snakes in North America, it is generally recommended to be treated within six hours of being envenomated.
* '''{{w|Raw water}}''' may be contaminated by bacteria, protozoa, parasites, and chemical pollutants. Boiling water will typically kill off most biological contaminants, preventing water-borne diseases such as {{w|cholera}}, {{w|dysentery}}, and {{w|giardiasis}}. Some of these diseases can be prevented by vaccines, but because there are so many microscopic life-forms in water, it is not possible to vaccinate against all of them.
* '''{{w|Computer virus|Computer viruses}}''' are computer programs that are now usually spread through networks via infected devices, attachments, and websites (early computer viruses were often spread by floppy diskettes). They can cause harm directly by taking up computer cycles and network bandwidth, but nowadays they often perform other tasks for their creators, such as exfiltrating financial information or encrypting files and demanding a ransom for the keys. Computer viruses can be recognized and blocked or deleted by antivirus software that scans incoming files and links against known computer virus patterns, which is analogous to vaccination, but there is no vaccine that can be administered to Megan which would protect her computer.
** Megan specifically mentions clicking on links that have "weird Unicode in them"; this may be referring to an {{w|IDN homograph attack}}, in which attackers register domain names that use Unicode characters that resemble ASCII characters to trick users into thinking they are visiting a website belonging to a trusted party. For example, an attacker could register a website with the URL "xkсd.com", in which the Latin letter "c" is replaced by the Cyrillic letter ''es'' (с), and then send emails to trick users into visiting that site and attempting to log in. The attacker can then attempt to use the supplied passwords on more important websites, as in [[792: Password Reuse]].

==Transcript==
:[Megan is walking with both of her hands held up in fists. She talks to Cueball who replies to her from off-panel. His presence is revealed in the second panel.]
:Megan: Yesss, I got my flu shot.
:Cueball (off-panel): Nice! I got mine a few weeks ago.
:Cueball (off-panel): Immunity buddies!

:[Megan spreading her arms wide in front of Cueball.]
:Megan: Now I can finally get bitten by all the bats I want!
:Cueball: No, that's rabies, that's not what-

:[Closeup of Megan's head, with Cueball's reply coming from off-panel.]
:Megan: I'll be able to roll and play in the poison ivy without a care in the world!
:Cueball (off-panel): Why would you do that even if the shot ''did''-

:[In a frame-less panel Megan is flexing her arms holding her fists up, she has turned partly away from Cueball who looks at her.]
:Megan: No more slathering on sunscreen. No more rushing for antivenom after a snakebite. And now I can stop wasting time boiling contaminated water before drinking it!

:[Megan is running away from Cueball, while she is holding one arm up, her hand making the like symbol with a thumbs up.]
:Megan: Gonna click on every URL in every email I get, even the ones with IP addresses and weird Unicode in them!
:Cueball: You know what, sure, go for it.

{{comic discussion}}

[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Biology]]
[[Category:Animals]]
[[Category:Computers]]

Talk:3034: Features of Adulthood

2025-01-07T03:23:44Z

172.69.195.27:

No comments yet? Probably everyone's still considering the filling in of the table. As for me, I just put a load of words in about the middle name(s), but perhaps it drifts and could be cut back a lot. However, I think we do know a lot of middle names of people, especially [[2393: Presidential Middle Names|politicians]]. Or at least use their middle initials (like with "John F[itzgerald]. Kennedy"), even if we don't use their full names (like with "Harry S. Truman"... :p ). Not that I've had much experience with middle names. Don't have one myself. Knew a couple of people at school who would admit to having them (one had "Colin", the other had "Douglas"), which weren't really names given to people our age and location, so they ''must'' have been grandparental honorifics (though I'm not sure the names were right for two generations back, either... never enquired further, but maybe they were being traditional ''middle'' names, inherited but never really used). To my knowledge, neither the "Colin" nor the "Douglas" ever went on to use those in post-school life, but at least one of them also changed from their first name as their habitual name to be known by, and likely they prefered to go for something altogether new. [[Special:Contributions/172.69.195.27|172.69.195.27]] 03:23, 7 January 2025 (UTC)

Talk:3026: Linear Sort

2024-12-20T09:52:26Z

172.69.195.27:

First in linear time![[User:Mr. I|Mr. I]] ([[User talk:Mr. I|talk]]) 13:28, 18 December 2024 (UTC)

Due to the fact that O(nlog(n)) outgrows O(n), the Linear Sort is not actually linear. [[Special:Contributions/162.158.174.227|162.158.174.227]] 14:21, 18 December 2024 (UTC)
:If your sleep() function can handle negative arguments "correctly", then I guess it could work. [[Special:Contributions/162.158.91.91|162.158.91.91]] 16:27, 18 December 2024 (UTC)

That was fast... [[User:CalibansCreations|'''Caliban''']] ([[User talk:CalibansCreations|talk]]) 15:35, 18 December 2024 (UTC)

Do I even want to know what Randall's thinking nowadays? [[User:Definitely Bill Cipher|⯅A dream demon⯅]] ([[User talk:Definitely Bill Cipher|talk]]) 16:02, 18 December 2024 (UTC)
:Does anyone every want to know what Randall is thinking nowadays? :P [[Special:Contributions/198.41.227.177|198.41.227.177]] 22:02, 19 December 2024 (UTC)

The title text would be more correct if Randall used e.g. Timsort instead of Mergesort. They both have the same worst-case complexity O(n*log(n)), but the former is linear if the list was already in order, so best-case complexity is O(n). Mergesort COULD also be implemented this way, but its standard version is never linear. [[User:Bebidek|Bebidek]] ([[User talk:Bebidek|talk]]) 16:35, 18 December 2024 (UTC)

According to my estimates extrapolated from timing the sorting of 10 million random numbers on my computer, the break-even point where the algorithm becomes worse than linear is beyond the expected heat death of the universe. I did neglect the question of where to store the input array. --[[Special:Contributions/162.158.154.35|162.158.154.35]] 16:37, 18 December 2024 (UTC)
:If the numbers being sorted are unique, each would need a fair number of bits to store. (Fair meaning that the time to do the comparison would be non-negligible.) If they aren't, you can just bucket-sort them in linear time. Since we're assuming absurdly large memory capacity. [[Special:Contributions/162.158.186.253|162.158.186.253]] 17:14, 18 December 2024 (UTC)

What system was the person writing the description using where Sleep(n) takes a parameter in whole seconds rather than the usual milliseconds? [[Special:Contributions/172.70.216.162|172.70.216.162]] 17:20, 18 December 2024 (UTC)
: First, I don't recognize the language, but sleep() takes seconds for python, C (et. al.), and no doubt many others. Second, the units don't have to be seconds, they just have to be whatever `TIME()` returns, and multiplicable by 1e6 to yield a "big enough" delay. Of course, no coefficient is big enough for this to actually be linear in theory for any size list, so who cares? To be truly accurate, sleep for `e^LENGTH(LIST)`, and it really won't much matter what the units are, as long as they're big enough for `SLEEP(e)` to exceed the difference in the time it takes to sort two items versus one item. Use a language-dependent coefficient as needed. [[User:Jlearman|Jlearman]] ([[User talk:Jlearman|talk]]) 18:02, 18 December 2024 (UTC)
: Usual where, is that the Windows API? The sleep function in the POSIX standard takes seconds. See https://man7.org/linux/man-pages/man3/sleep.3.html . [[Special:Contributions/162.158.62.194|162.158.62.194]] 18:57, 18 December 2024 (UTC)

If I had a nickel for every time I saw an O(n) sorting algorithm using "sleep"… But this one is actually different. The one I usually see feeds the to-be-sorted value into the sleep function, so it schedules "10" to be printed in 10 seconds, then schedules "3" to be printed in 3 seconds, etc., which would theoretically be linear time, if the sleep function was magic. [[User:Fabian42|Fabian42]] ([[User talk:Fabian42|talk]]) 17:25, 18 December 2024 (UTC)

This comic also critiques/points out the pitfalls of measuring time complexity using Big-O notation, such as an algorithm or solution that runs in linear time still being too slow for its intended use case. [[User:Sophon|Sophon]] ([[User talk:Sophon|talk]]) 17:46, 18 December 2024 (UTC)

Current text is incorrect, but I'm not sure how best to express the correction -- there do exist O(n) sorting algorithms, they're just not general-purpose, since they don't work with an arbitrary comparison function. See [https://en.wikipedia.org/wiki/Counting_sort counting sort]. [[Special:Contributions/172.69.134.151|172.69.134.151]] 18:25, 18 December 2024 (UTC)

Hi! I'm just gonna say this before everyone leaves and goes on their merry way. Significant comic numbers coming soon:
Comics 3100, 3200, 3300, etc, Comic 3094 (The total number of frames in 'time'), Comic 4000, Comic Whatever the next April fools day comic will be, and Comic 4096. Wait for it...[[User:DollarStoreBa'al|DollarStoreBa'al]] ([[User talk:DollarStoreBa'al|talk]]) 20:42, 18 December 2024 (UTC)
:Comic 3141.592654[[Special:Contributions/172.70.163.144|172.70.163.144]] 09:16, 19 December 2024 (UTC)

As everyone observed, the stated algorithm is not theoretically linear, but only practically linear (in that the time and space to detect O(n log n) exceeds reasonable (time, space) bounds for this universe). Munroe's solution is much deeper than that though - it trivially generalises to a _constant_ O(1) bound. [run a sort algorithm, wait 20 years, give the answer]. That's the preferred way of repaying loans, too. {{unsigned ip|172.69.195.27|21:46, 18 December 2024 (UTC)}}

Continues comic 3017's theme of worst-case optimization. [[Special:Contributions/172.70.207.115|172.70.207.115]] 00:32, 19 December 2024 (UTC)

It looks as though this function does not actually do the sort in Linear Time, it only returns in Linear Time.
The MERGESORT Function takes one parameter and does not have an obvious return value indicating that it performs an in-place sort on the input mutable list. This is also implied by the function signature that takes an input but has no return value, only having an externally visible effect if it mutates the data in the pass by reference input. This means that the list is sorted at the speed of the MERGESORT function, but flow control is only returned after Linear Time.
For a single threaded program calling this function there is no practical difference, but it would make a difference if some other thread was concurrently querying the list.
A clearer linear time sort might look like this:

function LinearSort(list):
StartTime=Time()
SortedList=MergeSort(list)
Sleep(1e6*length(list)-(Time()-StartTime))
return SortedList

Leon {{unsigned ip|172.70.162.70|17:31, 19 December 2024}}
:There's such a thing as pass-by-reference, variously implemented depending upon the actual programming language used. It's even possible to accept both ''list'' (non-reference, to force a return of ''sorted_list'') and ''listRef'' (returns nothing, or perhaps a result such as ''number_of_shuffles made''), for added usefulness, though of course that'd need even more pseudocode to describe. For the above/comic pseudocode, it's not so arbitrary that a programmer shouldn't know how to implement it in their instance.
:I might even set about to do something like use a SetStartTime() and CheckElapsedTime() funtion, if there's possible use; the former making a persistant (private variable) note of what =Time() it is, perhaps to an arbitrary record scoped to any parameterID it is supplied, and the latter returning the 'now' time minus the stored (default or explicitly IDed) moment of record. I could then have freely pseudocoded the extant outline in even briefer format, on the understanding what these two poke/peek functions are. Which is already left open to the imagination for MergeSort(). [[Special:Contributions/172.69.43.182|172.69.43.182]] 18:04, 19 December 2024 (UTC)

There are situations where you want to return in O(1) time or some other time that is not dependent on the input data to prevent side-channel data leaks. While the run-time of Randall's "O(n)" algorithm has an obvious dependencies on the input data, using the "Randall Algorithm" to obscure a different algorithm can reduce the side-channel opportunities. A more sure-fire way would be to have the algorithm return in precisely i seconds, where i is the number of seconds between now and the heat death of the universe. [[Special:Contributions/172.71.167.89|172.71.167.89]] 17:49, 19 December 2024 (UTC)

;Please write an explanation for non-programmers!
I don't understand this explainxkcd. The comic itself was less confusing. Can please someone who really gets this stuff write a section of the explanation that explains the joke to people like me who do not have a theoretical programming degree? I know that is a tall task but right now it reads as rambling and a bunch of 0(n) that makes no sense to me. I can cut and paste a bash script together and make it work. I can understand that putting a sleep for a million seconds in a loop somewhere makes it slow. But a layperson explanation of what makes a sort linear, what is linear, what is funny about that approach, would be better than all the arguing about 0(n) because we don't get it. Thanks in advance! You folks are awesome! [[Special:Contributions/172.71.147.210|172.71.147.210]] 20:51, 19 December 2024 (UTC)
:Maybe this would be a good start:
::--cut here--
::An algorithm is a step-by-step way of doing things.
::A sorting algorithm is a step-by-step way to sort things.
::There are several commonly used sorting algorithms. Some have very little "overhead" (think: set-up time or requiring lots of extra memory) or what I call "molassas" (yes, I just made that up) (think "taking a long time or lots of extra memory for each step") but they really bog down if you have a lot of things that need sorting. These are better if you have a small list of items to sort.

::Others have more "overhead" or "molasses" but don't bog down as much when you have a lot of things that need sorting. These are better if you have a lot of things to sort.

::A linear sorting algorithm would take twice as long to sort twice as many unsorted items. If it took 100 seconds to sort 100 items, then it would take 200 seconds to sort 200, 300 seconds to sort 300, and so on. Algorithms that take "twice as long to do twice as much" are said to run in "Order(n)" or "O(n)" time, where "n" is the number of items they are working on, or in the case of a sorting algorithm, the number of items to be sorted.

::For traditional sorting algorithms that don't use "parallel processing" (that is, they don't do more than one thing in any given moment), a linear sorting algorithm with very little "overhead" or "molasses" would be the "holy grail" of sorting algorithms. For example, a hypothetical linear sorting algorithm that took 1/1000th of a second to "set things up" (low "overhead") and an additional 1 second to sort 1,000,000 numbers (not much "molasses") would be able to sort 2,000,000 numbers in just over 2 seconds, 10,000,000 numbers in just over 10 seconds, and 3,600,000,000 numbers in a hair over an hour.

::The reality is that there is no such thing as a general-purpose linear sorting algorithm that has very little overhead (in both time and memory) and very little "molasses." All practical general-purpose sorting algorithms either use parallel processing, they have a lot of overhead (set-up time or uses lots of memory), a lot of "molasses" (takes a long time or uses lots of memory for EACH item in the list) or they are "slower than linear," which means they bog down when you give them a huge list of things to sort. For example, let's say the "mergesort" in Randall's algorithm doesn't have much "overhead" or "molasses" and it sorts 1,000,000 items in 1 second. It's time is "O(nlog(n))" which is a fancy way of saying if you double the number, you'll more than double the time. This means sorting 2,000,000 items will take more than 2 seconds, and sorting 4,000,000 items will take more than twice as long as it takes to sort 2,000,000. Eventually all of those "more than's" add up and things slow to a crawl.

::The joke is that Randall "pretends" to be the "holy grail" by being a linear sorting algorithm, but he has lots of "molasses" because his linear sorting algorithm takes 1 million seconds for each item in the list, compared to the 1,000,000 items per second in the hypothetical "linear sorting algorithm" I proposed.

::As others in the discussion point out, Randall's "algorithm" is "busted" (breaks, doesn't work, gives undefined results) if the mergesort (which is a very fast sort if you have a large list if items) is sorting a list so big that it takes over 1 million seconds per item to sort anyways. I'll spare you the math, but if the mergesort part of Randall's "algorithm" could do 1,000,000 numbers in 1 second with a 1/1000th of a second to "set things up," it would take a huge list to get it to "bust" Randall's "algorithm."
::--cut here--
:[[Special:Contributions/162.158.174.202|162.158.174.202]] 21:44, 19 December 2024 (UTC)

:Layman's guide to O(n) time, second try:
::--cut here--
::First, "O" is "Order of" as in "order of magnitude." It's far from exact.
::O(1) is "constant time" - the time it takes me to give you a bag that contains 5000 $1 bills doesn't depend on how many bills there are in the bag. It would take the same amount of time if the bag had only 500, 50, or even 5 bills in it.
::O(log(n)) is "logarithmic time" - the time is the time it takes me to write down how many bills are in the bag. If it's 5000, I have to write down 4 digits, if it's 500, 3, if it's 50, 2, if it's 5, only 1.
::O(n) is "linear time" - the time it takes me to count out each bill in the bag depends on how many bills there are. It takes a fixed amount of time to count each bill. If there's 5000 $1 bills it may take me 5000 seconds to count them. If there's 500 $1 bills, it will take me only 500 seconds.
::O(nlog(n)) is "linear times logarithmic time" - the time it takes me to sort a pre-filled bag of money by serial number using a good general-purpose sorting algorithm (most good general-purpose sorting algorithms are O(nlog(n)) time). If it takes me 2 seconds to sort two $1 bills, it will take me about 3 or 4 times 5000 seconds to sort 5000 $1 bills. The "3 or 4" is very approximate, the important thing is that "logarithm of n" (in this case, logarithm of 5000) is big enough to make a difference (by a factor of 3 or 4 in this case) but far less than "n" (in this case, 5000).
::O(n2) is "n squared" time, which is a special case of "polynomial time." "Polynomial time" includes things like O(n3) and O(n1,000,000). Many algorithms including many "naive" sorting algorithms are in this category. If I used a "naive" sorting algorithm to sort 5000 $1 bills by serial number, instead of it taking about 15,000-20,000 seconds, it would take about 5,000 times 5,000 seconds. I don't know about you, but I've got better things to do with 25,000,000 seconds than sort paper money.
::It gets worse (O(2n) anyone? No thanks!), but you wanted to keep it simple.
:[[Special:Contributions/198.41.227.177|198.41.227.177]] 23:30, 19 December 2024 (UTC)
::Personally, I've got better things to do than sort dollar bills, full stop.[[Special:Contributions/172.70.91.130|172.70.91.130]] 09:37, 20 December 2024 (UTC)

Friendly reminder that some users of this site are just here to learn what the joke is, and not to read the entire Wikipedia article on Big O Notation. Perhaps the actual explanation could be moved up a bit, and some of the fiddly Big-O stuff could be moved down? I'd do it myself, but I'm not really sure which is which. [[Special:Contributions/172.70.176.28|172.70.176.28]] 06:42, 20 December 2024 (UTC)
:I mean, it is fairly fundamental to the joke, and therefore to the explanation. It might be possible to slim it down a bit, but I don't think you can explain the joke without ''some'' explanation of Big O.[[Special:Contributions/172.70.91.130|172.70.91.130]] 09:37, 20 December 2024 (UTC)

Talk:3026: Linear Sort

2024-12-20T09:50:31Z

172.69.195.27:

First in linear time![[User:Mr. I|Mr. I]] ([[User talk:Mr. I|talk]]) 13:28, 18 December 2024 (UTC)

Due to the fact that O(nlog(n)) outgrows O(n), the Linear Sort is not actually linear. [[Special:Contributions/162.158.174.227|162.158.174.227]] 14:21, 18 December 2024 (UTC)
:If your sleep() function can handle negative arguments "correctly", then I guess it could work. [[Special:Contributions/162.158.91.91|162.158.91.91]] 16:27, 18 December 2024 (UTC)

That was fast... [[User:CalibansCreations|'''Caliban''']] ([[User talk:CalibansCreations|talk]]) 15:35, 18 December 2024 (UTC)

Do I even want to know what Randall's thinking nowadays? [[User:Definitely Bill Cipher|⯅A dream demon⯅]] ([[User talk:Definitely Bill Cipher|talk]]) 16:02, 18 December 2024 (UTC)
:Does anyone every want to know what Randall is thinking nowadays? :P [[Special:Contributions/198.41.227.177|198.41.227.177]] 22:02, 19 December 2024 (UTC)

The title text would be more correct if Randall used e.g. Timsort instead of Mergesort. They both have the same worst-case complexity O(n*log(n)), but the former is linear if the list was already in order, so best-case complexity is O(n). Mergesort COULD also be implemented this way, but its standard version is never linear. [[User:Bebidek|Bebidek]] ([[User talk:Bebidek|talk]]) 16:35, 18 December 2024 (UTC)

According to my estimates extrapolated from timing the sorting of 10 million random numbers on my computer, the break-even point where the algorithm becomes worse than linear is beyond the expected heat death of the universe. I did neglect the question of where to store the input array. --[[Special:Contributions/162.158.154.35|162.158.154.35]] 16:37, 18 December 2024 (UTC)
:If the numbers being sorted are unique, each would need a fair number of bits to store. (Fair meaning that the time to do the comparison would be non-negligible.) If they aren't, you can just bucket-sort them in linear time. Since we're assuming absurdly large memory capacity. [[Special:Contributions/162.158.186.253|162.158.186.253]] 17:14, 18 December 2024 (UTC)

What system was the person writing the description using where Sleep(n) takes a parameter in whole seconds rather than the usual milliseconds? [[Special:Contributions/172.70.216.162|172.70.216.162]] 17:20, 18 December 2024 (UTC)
: First, I don't recognize the language, but sleep() takes seconds for python, C (et. al.), and no doubt many others. Second, the units don't have to be seconds, they just have to be whatever `TIME()` returns, and multiplicable by 1e6 to yield a "big enough" delay. Of course, no coefficient is big enough for this to actually be linear in theory for any size list, so who cares? To be truly accurate, sleep for `e^LENGTH(LIST)`, and it really won't much matter what the units are, as long as they're big enough for `SLEEP(e)` to exceed the difference in the time it takes to sort two items versus one item. Use a language-dependent coefficient as needed. [[User:Jlearman|Jlearman]] ([[User talk:Jlearman|talk]]) 18:02, 18 December 2024 (UTC)
: Usual where, is that the Windows API? The sleep function in the POSIX standard takes seconds. See https://man7.org/linux/man-pages/man3/sleep.3.html . [[Special:Contributions/162.158.62.194|162.158.62.194]] 18:57, 18 December 2024 (UTC)

If I had a nickel for every time I saw an O(n) sorting algorithm using "sleep"… But this one is actually different. The one I usually see feeds the to-be-sorted value into the sleep function, so it schedules "10" to be printed in 10 seconds, then schedules "3" to be printed in 3 seconds, etc., which would theoretically be linear time, if the sleep function was magic. [[User:Fabian42|Fabian42]] ([[User talk:Fabian42|talk]]) 17:25, 18 December 2024 (UTC)

This comic also critiques/points out the pitfalls of measuring time complexity using Big-O notation, such as an algorithm or solution that runs in linear time still being too slow for its intended use case. [[User:Sophon|Sophon]] ([[User talk:Sophon|talk]]) 17:46, 18 December 2024 (UTC)

Current text is incorrect, but I'm not sure how best to express the correction -- there do exist O(n) sorting algorithms, they're just not general-purpose, since they don't work with an arbitrary comparison function. See [https://en.wikipedia.org/wiki/Counting_sort counting sort]. [[Special:Contributions/172.69.134.151|172.69.134.151]] 18:25, 18 December 2024 (UTC)

Hi! I'm just gonna say this before everyone leaves and goes on their merry way. Significant comic numbers coming soon:
Comics 3100, 3200, 3300, etc, Comic 3094 (The total number of frames in 'time'), Comic 4000, Comic Whatever the next April fools day comic will be, and Comic 4096. Wait for it...[[User:DollarStoreBa'al|DollarStoreBa'al]] ([[User talk:DollarStoreBa'al|talk]]) 20:42, 18 December 2024 (UTC)
:Comic 3141.592654[[Special:Contributions/172.70.163.144|172.70.163.144]] 09:16, 19 December 2024 (UTC)

As everyone observed, the stated algorithm is not theoretically linear, but only practically linear (in that the time and space to detect O(n log n) exceeds reasonable (time, space) bounds for this universe). Munroe's solution is much deeper than that though - it trivially generalises to a _constant_ O(1) bound. [run a sort algorithm, wait 20 years, give the answer]. That's the preferred way of repaying loans, too. {{unsigned ip|172.69.195.27|21:46, 18 December 2024 (UTC)}}

Continues comic 3017's theme of worst-case optimization. [[Special:Contributions/172.70.207.115|172.70.207.115]] 00:32, 19 December 2024 (UTC)

It looks as though this function does not actually do the sort in Linear Time, it only returns in Linear Time.
The MERGESORT Function takes one parameter and does not have an obvious return value indicating that it performs an in-place sort on the input mutable list (this is also implied by the function signature that looks to take an input but has no retuen, only having any externally visible effect if it mutates the data in the pass by reference input). This means that the list is sorted at the speed of the MERGESORT function, but flow control is only returned after Linear Time.
For a single threaded program calling this function there is no practical difference, but it would make a difference if some other thread was concurrently querying the list.
A clearer linear time sort might look like this:

function LinearSort(list):
StartTime=Time()
SortedList=MergeSort(list)
Sleep(1e6*length(list)-(Time()-StartTime))
return SortedList

Leon {{unsigned ip|172.70.162.70|17:31, 19 December 2024}}
:There's such a thing as pass-by-reference, variously implemented depending upon the actual programming language used. It's even possible to accept both ''list'' (non-reference, to force a return of ''sorted_list'') and ''listRef'' (returns nothing, or perhaps a result such as ''number_of_shuffles made''), for added usefulness, though of course that'd need even more pseudocode to describe. For the above/comic pseudocode, it's not so arbitrary that a programmer shouldn't know how to implement it in their instance.
:I might even set about to do something like use a SetStartTime() and CheckElapsedTime() funtion, if there's possible use; the former making a persistant (private variable) note of what =Time() it is, perhaps to an arbitrary record scoped to any parameterID it is supplied, and the latter returning the 'now' time minus the stored (default or explicitly IDed) moment of record. I could then have freely pseudocoded the extant outline in even briefer format, on the understanding what these two poke/peek functions are. Which is already left open to the imagination for MergeSort(). [[Special:Contributions/172.69.43.182|172.69.43.182]] 18:04, 19 December 2024 (UTC)

There are situations where you want to return in O(1) time or some other time that is not dependent on the input data to prevent side-channel data leaks. While the run-time of Randall's "O(n)" algorithm has an obvious dependencies on the input data, using the "Randall Algorithm" to obscure a different algorithm can reduce the side-channel opportunities. A more sure-fire way would be to have the algorithm return in precisely i seconds, where i is the number of seconds between now and the heat death of the universe. [[Special:Contributions/172.71.167.89|172.71.167.89]] 17:49, 19 December 2024 (UTC)

;Please write an explanation for non-programmers!
I don't understand this explainxkcd. The comic itself was less confusing. Can please someone who really gets this stuff write a section of the explanation that explains the joke to people like me who do not have a theoretical programming degree? I know that is a tall task but right now it reads as rambling and a bunch of 0(n) that makes no sense to me. I can cut and paste a bash script together and make it work. I can understand that putting a sleep for a million seconds in a loop somewhere makes it slow. But a layperson explanation of what makes a sort linear, what is linear, what is funny about that approach, would be better than all the arguing about 0(n) because we don't get it. Thanks in advance! You folks are awesome! [[Special:Contributions/172.71.147.210|172.71.147.210]] 20:51, 19 December 2024 (UTC)
:Maybe this would be a good start:
::--cut here--
::An algorithm is a step-by-step way of doing things.
::A sorting algorithm is a step-by-step way to sort things.
::There are several commonly used sorting algorithms. Some have very little "overhead" (think: set-up time or requiring lots of extra memory) or what I call "molassas" (yes, I just made that up) (think "taking a long time or lots of extra memory for each step") but they really bog down if you have a lot of things that need sorting. These are better if you have a small list of items to sort.

::Others have more "overhead" or "molasses" but don't bog down as much when you have a lot of things that need sorting. These are better if you have a lot of things to sort.

::A linear sorting algorithm would take twice as long to sort twice as many unsorted items. If it took 100 seconds to sort 100 items, then it would take 200 seconds to sort 200, 300 seconds to sort 300, and so on. Algorithms that take "twice as long to do twice as much" are said to run in "Order(n)" or "O(n)" time, where "n" is the number of items they are working on, or in the case of a sorting algorithm, the number of items to be sorted.

::For traditional sorting algorithms that don't use "parallel processing" (that is, they don't do more than one thing in any given moment), a linear sorting algorithm with very little "overhead" or "molasses" would be the "holy grail" of sorting algorithms. For example, a hypothetical linear sorting algorithm that took 1/1000th of a second to "set things up" (low "overhead") and an additional 1 second to sort 1,000,000 numbers (not much "molasses") would be able to sort 2,000,000 numbers in just over 2 seconds, 10,000,000 numbers in just over 10 seconds, and 3,600,000,000 numbers in a hair over an hour.

::The reality is that there is no such thing as a general-purpose linear sorting algorithm that has very little overhead (in both time and memory) and very little "molasses." All practical general-purpose sorting algorithms either use parallel processing, they have a lot of overhead (set-up time or uses lots of memory), a lot of "molasses" (takes a long time or uses lots of memory for EACH item in the list) or they are "slower than linear," which means they bog down when you give them a huge list of things to sort. For example, let's say the "mergesort" in Randall's algorithm doesn't have much "overhead" or "molasses" and it sorts 1,000,000 items in 1 second. It's time is "O(nlog(n))" which is a fancy way of saying if you double the number, you'll more than double the time. This means sorting 2,000,000 items will take more than 2 seconds, and sorting 4,000,000 items will take more than twice as long as it takes to sort 2,000,000. Eventually all of those "more than's" add up and things slow to a crawl.

::The joke is that Randall "pretends" to be the "holy grail" by being a linear sorting algorithm, but he has lots of "molasses" because his linear sorting algorithm takes 1 million seconds for each item in the list, compared to the 1,000,000 items per second in the hypothetical "linear sorting algorithm" I proposed.

::As others in the discussion point out, Randall's "algorithm" is "busted" (breaks, doesn't work, gives undefined results) if the mergesort (which is a very fast sort if you have a large list if items) is sorting a list so big that it takes over 1 million seconds per item to sort anyways. I'll spare you the math, but if the mergesort part of Randall's "algorithm" could do 1,000,000 numbers in 1 second with a 1/1000th of a second to "set things up," it would take a huge list to get it to "bust" Randall's "algorithm."
::--cut here--
:[[Special:Contributions/162.158.174.202|162.158.174.202]] 21:44, 19 December 2024 (UTC)

:Layman's guide to O(n) time, second try:
::--cut here--
::First, "O" is "Order of" as in "order of magnitude." It's far from exact.
::O(1) is "constant time" - the time it takes me to give you a bag that contains 5000 $1 bills doesn't depend on how many bills there are in the bag. It would take the same amount of time if the bag had only 500, 50, or even 5 bills in it.
::O(log(n)) is "logarithmic time" - the time is the time it takes me to write down how many bills are in the bag. If it's 5000, I have to write down 4 digits, if it's 500, 3, if it's 50, 2, if it's 5, only 1.
::O(n) is "linear time" - the time it takes me to count out each bill in the bag depends on how many bills there are. It takes a fixed amount of time to count each bill. If there's 5000 $1 bills it may take me 5000 seconds to count them. If there's 500 $1 bills, it will take me only 500 seconds.
::O(nlog(n)) is "linear times logarithmic time" - the time it takes me to sort a pre-filled bag of money by serial number using a good general-purpose sorting algorithm (most good general-purpose sorting algorithms are O(nlog(n)) time). If it takes me 2 seconds to sort two $1 bills, it will take me about 3 or 4 times 5000 seconds to sort 5000 $1 bills. The "3 or 4" is very approximate, the important thing is that "logarithm of n" (in this case, logarithm of 5000) is big enough to make a difference (by a factor of 3 or 4 in this case) but far less than "n" (in this case, 5000).
::O(n2) is "n squared" time, which is a special case of "polynomial time." "Polynomial time" includes things like O(n3) and O(n1,000,000). Many algorithms including many "naive" sorting algorithms are in this category. If I used a "naive" sorting algorithm to sort 5000 $1 bills by serial number, instead of it taking about 15,000-20,000 seconds, it would take about 5,000 times 5,000 seconds. I don't know about you, but I've got better things to do with 25,000,000 seconds than sort paper money.
::It gets worse (O(2n) anyone? No thanks!), but you wanted to keep it simple.
:[[Special:Contributions/198.41.227.177|198.41.227.177]] 23:30, 19 December 2024 (UTC)
::Personally, I've got better things to do than sort dollar bills, full stop.[[Special:Contributions/172.70.91.130|172.70.91.130]] 09:37, 20 December 2024 (UTC)

Friendly reminder that some users of this site are just here to learn what the joke is, and not to read the entire Wikipedia article on Big O Notation. Perhaps the actual explanation could be moved up a bit, and some of the fiddly Big-O stuff could be moved down? I'd do it myself, but I'm not really sure which is which. [[Special:Contributions/172.70.176.28|172.70.176.28]] 06:42, 20 December 2024 (UTC)
:I mean, it is fairly fundamental to the joke, and therefore to the explanation. It might be possible to slim it down a bit, but I don't think you can explain the joke without ''some'' explanation of Big O.[[Special:Contributions/172.70.91.130|172.70.91.130]] 09:37, 20 December 2024 (UTC)

3026: Linear Sort

2024-12-19T03:25:17Z

172.69.195.27: /* Explanation */

{{comic
| number = 3026
| date = December 18, 2024
| title = Linear Sort
| image = linear_sort_2x.png
| imagesize = 385x181px
| noexpand = true
| titletext = The best case is O(n), and the worst case is that someone checks why.
}}

==Explanation==
{{incomplete|Created in Θ(N) TIME by an iterative Insertion Sorter working on a multidimensional array - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
A common task in programming is to sort a list, a list being a collection of related elements of data that are stored in a linear fashion. There are dozens of algorithms that have been created for this through the years, from simple to complex, and each has its own merits with regards to how easy it is to understand / implement, how much space it uses, and how efficiently it operates on the data.

In computer science, the runtime of an algorithm can be described using {{w|Big O Notation}}, which categories the asymptotic, usually average, runtime (''O'') of a function of the number of elements (''n'') operated on (''f(n)'') as it grows larger and larger towards infinity; this creates the form O(''f''(''n'')) as the final description. Being asymptotic means that Big O Notation only considers parts of the function that scale with time and disregards fixed changes such as multipliers and additions to the scaling time. For instance, in an O(''n'') algorithm, ''f''(''n'') is simply ''n'', meaning it takes a constant amount of time per element operated on. A simple example would be examining pictures: if it takes one second to look at a picture, it would take ten seconds to look at ten pictures; if it took three seconds to look at a picture, it would take thirty seconds to look at ten pictures - both are described as O(''n'').

Generally, programmers seek to minimize the Big O Notation of their algorithms because it means they take less time. It can be proven that the best general-purpose sorting methods are O(''n'' log ''n''); since this is larger than ''n'' on its own, it means that algorithms will always begin to take longer per element as the number of elements increases.

Here are some examples of common runtimes expressed in Big O notation, from smallest to largest:
<ul><li>O(1) - Constant time, which means the execution time is independent of the size of the data</li>
<li>O(''n'') - Linear time, which means the execution time grows in direct proportion to the size of the data</li>
<li>O(''n'' log(''n'')) - The execution time grows proportionally to ''n'' * the {{w|logarithm}} of ''n'', with the added ''log(n)'' creating an increasingly larger multiplier on the runtime</li>
<li>O(''n''2) - Quadratic time, meaning the execution time grows proportionally to the ''square'' of the size of the data.</li></ul>

The code in the comic describes a 'linear' sort that first sorts the list using {{w|merge sort}}, which is known to take time O(''n'' log(''n'')), and then `sleep()`s (pauses with no activity) for a complimentary amount of time by subtracting the time taken for the sort from the number of elements multiplied by 1 million (1e6) seconds. This way, the total time always scales proportionately with the number of elements. This effectively converts the algorithm, through brute force, to fit the definition of linear time: it takes one million seconds — which is more than 11 days — per element, rather than a non-linear progression as the number of elements increases. Although this algorithm ''does'' run in O(''n''), it does not reflect that it is made to be significantly slower than the nominally 'worse' O(''n'' log(''n'')) performance that the embedded sort takes by itself.

It should be noted that for sufficiently large lists, the merge sort will take longer than the million seconds per element, which results in a negative value being passed to the sleep() function. This might halt the program with a runtime error, produce {{w|Integer overflow#Definition variations and ambiguity|unpredictably extra-long}} additional waits or skip any additional wait; all of these still leaving the issue of already having exceeded O(''n''). However, this issue will only arise for impossibly huge lists: if, for instance, a merge sort took ''n log(n)'' microseconds to complete (which would be considered slow, by today's typical processing times), then the comic's 'linear' sort target would be reached sooner only for lists longer than 21,000,000,000,000 ≈ 10300,000,000,000 elements — a number far larger than the number of atoms in the universe. The practical impossibility of this outcome might be why such a ridiculously high number of seconds was chosen.

The title text refers to the {{w|Best, worst and average case|best and worst case}} of a sort, which are additional measures of its runtime to describe the shortest and longest potential times. A more optimal sort may decide how much of a list needs to be passed over again after its first pass of shuffling elements around; scanning a pre-sorted list (and deducing that it has no more checking to do) could mean that no more effort is needed, resulting in a best case of O(''n''). Depending upon the algorithm, presenting a list that is in an ordering that happens to challenge it the most (such as exactly reversed) may mean even an 'average O(''n'' log ''n'')' process would have to exceed this, resulting in a worst-case number of operations that may be O(''n2''). It can be very useful to know that a given sorting method ''may'' take the average order of time, but have the possibility of a much shorter ''or'' longer runtime... especially when the method is expected to be [[1185: Ineffective Sorts|far, far worse than others]], where only particular and more idealistic input lets it approach the more satisfyingly fast average/best responses.

By forcing all practical searches to take O(''n'') time, regardless of how otherwise identical data is presorted, the best case (and worst case, for that matter) will also be O(''n''). The last part of the text then plays on the another meaning of best case and worst case, as best- and {{w|worst-case scenario}}s for a situation, by saying that the worst situation that could occur for the code's author is if someone decides to investigate the code (perhaps owing to its absurd runtime, or else just justifiably skeptical of the declared optimality), whereupon that investigator will discover the deception and destroy the author's credibility.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[The panel shows five lines of code:]
:function LinearSort(list):
::StartTime=Time()
::MergeSort(list)
::Sleep(1e6*length(list)-(Time()-StartTime))
::return

:[Caption below the panel:]
:How to sort a list in linear time

{{comic discussion}}

[[Category:Programming]]

Talk:3026: Linear Sort

2024-12-18T21:46:48Z

172.69.195.27:

Talk:3022: Making Tea

2024-12-10T07:53:52Z

172.69.195.27: Added query about boiling in a pot

I wonder where [https://en.wikipedia.org/wiki/Boston_Tea_Party making it in Boston Harbor, at ambient temperature, at scale] would fit on this scale. [[Special:Contributions/172.70.206.162|172.70.206.162]] 04:38, 10 December 2024 (UTC)
: A little to the left of the microwave thing. [[Special:Contributions/162.158.186.252|162.158.186.252]] 05:14, 10 December 2024 (UTC)
: Oh, no, much further to the right. You stole our colony from us, set up some tinpot, pretended 'country' in its place, and you didn't even have the class to make a decent cup of tea first. [[Special:Contributions/172.68.205.93|172.68.205.93]] 06:24, 10 December 2024 (UTC)
:: And, even if [https://www.bbc.co.uk/news/uk-68085304 this guy] is right, ''way'' too much salt... [[Special:Contributions/172.70.91.130|172.70.91.130]] 07:03, 10 December 2024 (UTC)

When I make ramen, I put the measuring cup in the microwave. Fight me. [[Special:Contributions/162.158.167.87|162.158.167.87]] 05:35, 10 December 2024 (UTC)

"...to the point virtually every home has an electric tea kettle as a standard appliance". If I'm reading it correctly, this and the comic suggests we (though not I, as I'm not a tea-drinker) make tea ''in the electric kettle''. Electric tea-urns, yes, or maybe a setup like a samovar. But, generally, the kettle itself (and, so far as I'm aware, always with an electric kettle) is used to heat the water, which you then pour into the tea''pot'' into which the requisite number of tealeaves/teabags are also put to steep. (Or, for the lazy way, into the mug-with-teabag.) I wouldn't be able to use my electric kettle to (for example) make my instant mashed-potato into the actual mash, if I'd have regularly used it to mash tea. Or top up the boiling saucepan that I'd realised I'd not quite enough water in to cover the pasta/vegetables/whatever. Or to easily add nust a little more heat (with less new water) to the washing-up bowl than would be possible from the hot tap, back to as hot as possible without scalding me. – Whether intentional or not, I suspect Randall has the role of kettle and teapot mixed up, and so (without the intent to parody) has the editor who wrote the above. [[Special:Contributions/172.70.160.135|172.70.160.135]] 05:49, 10 December 2024 (UTC)

I don't think the section on 'Boiling the water in a pot' refers to a teapot - I think it means boiling the water in a pot on the hob, and then making tea with it (in a pot/mug). [[Special:Contributions/172.69.195.27|172.69.195.27]] 07:53, 10 December 2024 (UTC)

520: Cuttlefish

2024-11-22T11:28:51Z

172.69.195.27: /* Explanation */

{{comic
| number = 520
| date = December 22, 2008
| title = Cuttlefish
| image = cuttlefish.png
| titletext = Unless the CS students finish the robot revolution before you finish the cephalopod one.
}}

==Explanation==
It appears that [[Cueball]] and [[Megan]] are {{w|physicists}} visiting a biology lab. Their guide, a {{w|biologist}} looking like Cueball, gives them a description of the humble {{w|cuttlefish}} that is both accurate and makes them sound like other-worldly creatures with highly advanced capabilities.

The scene takes an unusual turn when the scientist implies that the cuttlefish have been easily trained to improve their capabilities. He then demonstrates this by giving a simple command, whereupon the cuttlefish rise out of the water, only to attack and kill both Cueball and Megan, demonstrating an ability to fly, talk, and discharge lethal electric shocks in the process. (See also [[35: Sheep]]).

This is all revealed to be a dream, but it has given Cueball a warning not to underestimate the biologists. Apparently, they can be just as crazy and dangerous as any other kind of scientist. Cueball (who represents [[Randall]], as it is xkcd that salutes in the final panel) offers a toast to all biologists everywhere and plans an alliance with them against the {{w|chemists}}, hoping to prevent further attacks on physicists. He is then shown drinking from a laboratory flask, something that any scientist would be wary of.

In the past, Randall has been somewhat dismissive of the non-math/non-physics scientific disciplines, so this comic may be trying to mend some bridges with biologists. But not with chemists.

In the title text, CS stands for {{w|Computer Science}}. The "robot revolution" references events in film and literature, wherein robots, having become commonplace in the workforce, achieve independent thought and declare war on humanity, like in ''{{w|The Terminator}}'', ''{{w|The Matrix}}'', or the movie ''{{w|I, Robot}}''. Randall implies that the physicists will switch sides if the robot revolution arrives first. {{w|Cephalopod}} is the class of animals that encompasses cuttlefish, as well as {{w|squids}} and {{w|octopodes}}.

==Transcript==
:[A scientist (looking like Cueball) is pointing into an aquarium tank with two small animals floating in the water. He explains that they are cuttlefish to Cueball and Megan, who are on the other side of the tank looking into it, Cueball with a hand to his mouth. Above them there is a frame inside the panel with a caption:]
:We visit a bio lab:
:Scientist: These are cuttlefish.

:[Very detailed drawing of a cuttlefish, with its special W shaped pupils, all eight arms and two longer tentacles, and the striped body with waving parts shown waving down each side. The scientist tells about the animal with text above and below.]
:Scientist (off-panel): They're frighteningly smart, have manipulating arms and tentacles, have ink jets, can dart backwards and see the polarization of light through their w-shaped pupils.
:Scientist (off-panel): And their sides are 200 DPI display screens which they use for camouflage and communication.

:[Back to the original setting where the scientist stands a little farther back from the tank with his arms down. Cueball and Megan have also moved farther back and are even leaning away from the tank.]
:Scientist: When we realized how intelligent they were, we began to teach them.
:Scientist: They've advanced quickly.
:Scientist: '''Cuttlefish: GO.'''

:[The two cuttlefish float straight out of the tank (lines indicating the movement and water splashing at the surface of the tank). The scientist looks down at them, while Cueball and Megan are holding hands and leaning farther back and Cueball taking his hand back to his mouth.]

:[Pan to only the scientist, standing with one arm bend in front of him and the other holding a finger up to his mouth, and the tank from where the cuttlefish now fly toward Cueball and Megan, who are now off-panel. Lines behind the cuttlefish show that they fly right but bob up and down. The cuttlefish talk in a strange way where the letters are alternately up and down.]
:Cuttlefish: K<big>i</big>l<big>l</big> t<big>h</big>e P<big>h</big>y<big>s</big>i<big>c</big>i<big>s</big>t<big>s</big>
:Cuttlefish: K<big>i</big>l<big>l</big> t<big>h</big>e Ph<big>y</big>s<big>i</big>c<big>i</big>st<big>s</big>
:[Pan to Megan and Cueball, with the tank almost inside the left frame. Both cuttlefish are surrounded by their own zigzag lines, which then extend from them in a thin line to encompass either Cueball or Megan. Cueball was running away from them, when this happens, with legs bent at the knees and arms out, one bent. Megan has fallen, lying face down with her arms out.]

:[In this panel with faint gray shading, Cueball is waking up in bed from the dream, rising up to a sitting position suddenly as indicated with two movement lines behind his head. One arm is supporting him on the bed next to the pillow, and the other is pulling his sheet down away from his torso. The first sentence is maybe still part of the dream, as there is no line from Cueball to the sentence, and it is written high up. There is a line to the second sentence.]
:Cueball: Oh god.
:Cueball: I knew it.

:[This panel is divided into five segments. At the top, there is a large caption in two lines. There are three drawings following each other from left to right. First, a bottle is pouring liquid into a an Erlenmeyer flask (a conical laboratory flask) that is half full. Then, Cueball takes the flask and holds it up as a salute. Finally, he drinks from it, leaning his head way back. Below there is more text.]
:<big>xkcd</big>
:Salutes Bio Majors
:If we join you against the chemists, will you train your fleshy minions to leave us alive?

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Multiple Cueballs]]
[[Category:Dreams]]
[[Category:Chemistry]]
[[Category:Biology]]
[[Category:Animals]]

2989: Physics Lab Thermostat

2024-09-24T14:13:25Z

172.69.195.27: /* Explanation */ I liked it how it was. Suitably tongue-in-cheek. Then someone made it actively annoy someone else.

{{comic
| number = 2989
| date = September 23, 2024
| title = Physics Lab Thermostat
| image = physics_lab_thermostat_2x.png
| imagesize = 264x296px
| noexpand = true
| titletext = Hopefully the HVAC people set it to only affect the AIR in the room.
}}

==Explanation==
{{incomplete|Created by a BOLTZMANN BRAIN - Given the calculations mentioned in the comment, it would seem that the thermostat works normally in the way that turning it clockwise will increase the temperature. This should be mentioned and some kind of calculation like the one mentioned in comments section could be added for clarity/reference. Do NOT delete this tag too soon.}}

A thermostat is often used to regulate the operation of heating and/or cooling for a room. This may take the form of a simple dial, graduated by desired temperature values marked Celsius or Fahrenheit, depending upon {{w|Fahrenheit#Usage|location}}. Typically a person is expected to know what sort of temperature they will find comfortable, to have heating/cooling effects kick in as the wall-device detects a temperature more than a certain amount below/above that ideal. The basic design of a physical wall-mounted dial might relate the relative position of the dial against the current state of a {{w|Bimetallic strip#Thermostats|bimetallic coil}}, switching {{w|Bang–bang control|on or off}} the relevent systems once conditions locally drift away from the chosen ideal.

In this comic, the thermostat is installed in a physics lab, with those that work there clearly being expected to be familiar with the {{w|Boltzmann constant}}, a more fundamental method of measuring temperature which relates the average kinetic energy of a particle in a gas with the temperature of that gas. The Boltzmann constant is defined as 1.380649 × 10^-23 J/K (joules per kelvin).

Thus Randall imagines a physics lab having a dial that can alter the constant between 1.418 x 10^-23 J/K and 1.351 x 10^-23 J/K. If the average kinetic energy of gas particles remains constant when moving the dial, then changing the Boltzmann constant would change how this average energy is measured in {{w|kelvin}} (and therefore {{w|Conversion of scales of temperature#Comparison of temperature scales|any other measure}} of temperature), thus "changing the temperature". The equation is E=kT where k is the Boltzmann constant. Notice that if E is the same, lowering k implies a raised T, so the thermostat 'works' as intended. The effective range of the thermostat, presuming it is set to "room temperature" of 23°C (73°F) runs from 15°C to 29°C (59°F to 85°F). Rather than controlling the nature of the airflow into the lab (or convection heaters/coolers around it), it might be implied that this applies the effect directly across the whole lab at a fundamental level. Changing one of the fundamental constants of thermodynamics would have dangerous effects.{{acn}} 

There have previously been control panels for properties of the universe in [[1620: Christmas Settings]] and [[1763: Catcalling]].

Because the Boltzmann constant is primarily concerned with the nature of temperature within gas, the titletext expresses concern that it might not only be applied to the air (hence the capital letters) in the room. Aside from the possibility that those responsible for the {{w|heating, ventilation, and air conditioning}} (a.k.a. HVAC) of the room could perhaps directly enhance or suppress the temperature in all the solids and liquids within the room, in unknown and not necessarily conducive ways, there may also be a secondary joke in which {{w|high voltage}} forms of {{w|alternating current}} (also refered to as HVAC) are influenced, in the related but distinct use of the measure for '{{w|Boltzmann constant#Thermal voltage|thermal voltage}}'.

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

:[A black circular dial is shown with a white indicator line at the upper right. The label above the dial, enclosed in a rectangular box, says:]
:Local Boltzmann Constant
:[The two extremes of the dial are labeled as follows, the first value on the left and the second value on the right:]
:1.418 x 10-23 J/K
:1.351 x 10-23 J/K
:[The indicator line is pointing to a position on the dial somewhere around 1.375 x 10-23 J/K.]
:[Caption below the panel:]
:Physics Lab Thermostat

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

Talk:2986: Every Scientific Field

2024-09-18T08:12:02Z

172.69.195.27: /* This stupid site is malfunctioning. */

My reading of the comic is completely opposite to the current explanation. Rather than the large section being what 'a disproportionate amount of time is spent on', it's the small section, which is why we've heard of that stuff. To me, the large section represents the bulk of what is there to be studied, but is relatively poorly understood, so the point of the comic is emphasising how little we actually know about stuff in relation to what there is to be known. [[Special:Contributions/172.70.160.136|172.70.160.136]] 11:16, 17 September 2024 (UTC)
: I didn't like the word 'disproportionate' either, because to me it sounded like an accusation of too much time being spent in the wrong branch, which is not what Randall is saying. I reworded and fleshed out the description. Better now? [[Special:Contributions/172.70.111.167|172.70.111.167]] 11:38, 17 September 2024 (UTC)
: I disagree with "poorly understood" being the central issue, though, rather the branches the general public finds fascinating are often not the scientificially dominating ones. Wasps laying eggs in other insects isn't "poorly understood" at all. It's just that cute baby elephants or pandas draw huge crowds in zoos, whereas 'icky' wasps don't. And e.g. a gyroscope makes for great YouTube videos, but it's no longer a subject of fundamental physics research. [[Special:Contributions/162.158.154.238|162.158.154.238]] 13:04, 17 September 2024 (UTC)
: It's not really a matter of understanding, it's whether most of the public has even heard of it and knows that scientists are studying it. Randall's point is that most of what scientists study doesn't get much mention in the mainstream press and lay people don't know about it. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 14:27, 17 September 2024 (UTC)

== This stupid site is malfunctioning. ==

Hi chat. I'm the infamous #FreePalestine "troll". I would go into another rant, but there is a more pressing matter on our hands here. Whenever I try to access this site, I frequently encounter some "technical difficulties" message, claiming that I can't access the database. It occurs both on the school computers and my own device, so it's probably server-side. Can someone get to the bottom of this?

Cheers! [[Special:Contributions/141.101.105.48|141.101.105.48]] 19:35, 17 September 2024 (UTC)

:This has been happening to me too. Reloading the tab almost always fixes it, but it’s still annoying nonetheless. [[User:Trogdor147|Trogdor147]] ([[User_talk:Trogdor147|talk]]) 23:49, 17 September 2024 (UTC)
::seems to have been fixed now :) [[Special:Contributions/162.158.33.237|162.158.33.237]] 07:42, 18 September 2024 (UTC)
:::Can we make it so that it it only does this for trolls and vandals?[[Special:Contributions/172.69.195.27|172.69.195.27]] 08:12, 18 September 2024 (UTC)

2984: Asteroid News

2024-09-14T07:36:45Z

172.69.195.27: /* Explanation */ proper names

{{comic
| number = 2984
| date = September 11, 2024
| title = Asteroid News
| image = asteroid_news_2x.png
| imagesize = 376x288px
| noexpand = true
| titletext = Their calculations show it will 'pass within the distance of the moon' but that it 'will not hit the moon, so what's the point?'
}}

==Explanation==
{{incomplete|Created by a VERY EXCITED EDITOR, LIKE ALL THE OTHERS. Do NOT delete this tag too soon.}}
[[Blondie]] as a [[:Category:News anchor|news anchor]] presents an image where an {{w|asteroid}} is seen zooming past {{w|Earth}} outside of the {{w|Moon}}'s orbit.

The comic is about an unspecified asteroid that is predicted to approach Earth in 2063. It could possibly be related to the recently discovered asteroid [https://www.esa.int/ESA_Multimedia/Images/2024/06/Close_approach_of_asteroid_2024_MK 2024 MK], which made a close approach to Earth on June 29, 2024, but it could be any of the {{w|Sentry (monitoring system)|Sentry Objects}} of the {{w|Jet Propulsion Laboratory}}'s Center for Near Earth Object Studies [https://cneos.jpl.nasa.gov/sentry/ ].

Blondie mentions that according to the astronomers, the asteroid only has 'a one-in-6000 chance of "doing something cool",' meaning that there is only a small chance that the asteroid will have a direct impact on Earth's surroundings. What is described as "something cool" would presumably be that the asteroid hits the Earth or the Moon. She then states that further observations have shown that this will not happen and the asteroid will just be yet another boring dot in the sky.

The joke is that most people are afraid that a near-Earth asteroid would actually hit, and hope to hear that it will not. If the asteroid in this comic gets close enough that it will actually be a visible dot, then given the normal sizes of {{w|Near-Earth object|near-Earth asteroids}}, it would indeed be very close to Earth. Many people interested in the night sky would find it interesting to see an asteroid with their naked eye.

The title text may refer to another asteroid that gets even closer than the one depicted, because this one should come closer than the Moon according to calculations (presumably by the astronomers). However, this asteroid will not hit the Moon even though it gets close, so the astronomers ask, "What's the point?". The comic is mute on the question whether the asteroid will hit the Earth, although this is generally very unlikely even for an asteroid passing closer than the Moon. Again Blondie implies that the astronomers hope for some visible effect.

This is the fourth comic in the last seven about space.

==Transcript==
:[Close-up of Blondie as a news anchor speaking, alongside an image to the left of an asteroid passing by Earth. The path of the asteroid is shown as a dashed line near the top-left, with the Moon orbiting the Earth below it.]
:Blondie: Astronomers initially said there was a one-in-6,000 chance that the newly-discovered asteroid might "do something cool" in 2063, but further observations determined it will be "just a boring dot like all the others."

{{comic discussion}}

[[Category:Comics featuring Blondie]]
[[Category:News anchor]]
[[Category:Astronomy]]
[[Category:Space]]

Talk:2981: Slingshots

2024-09-05T18:23:41Z

172.69.195.27:

We don't put tables in the transcript, which is supposed to be screen-readable. Tables are not screen-readable. [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 04:25, 5 September 2024 (UTC)
:I now see the hidden "Tables are bad?" content in the incomplete transcript notice! Cute! [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 04:33, 5 September 2024 (UTC)
::anybody want to change the transcript? not too confident on how to write it. [[User:42.book.addict|42.book.addict]] ([[User talk:42.book.addict|talk]]) 17:06, 5 September 2024 (UTC)
:::Given it a go. Could add "regular column" and "gravitational column" pre-descriptors to each subsequent pair of row elements, or go the other way and remove the [Row N] bit. Also chose to use the [label]s of [Tick] and [Cross] in place of the 'fancy' characters; could have gone with [Ticked], [Marked with a tick], [Affirmed], etc, but this seemed sensible. Obviously still open for editing.
:::If I'd have started from scratch, I would have used the (previously identical) table-markup version in the Explanation but have put the "Yay/Nay/freetext" explanation in there with it. But that's not to say that it doesn't look fairly ok (if not better?) in the paragraph-by-paragraph treatment as it currently is, with the table there as visual repeat only.
:::YMMV on all aspects of my choice/complicit acceptance, naturally. [[Special:Contributions/172.69.194.143|172.69.194.143]] 18:20, 5 September 2024 (UTC)

We should clarify that it's the American Dennis and not the British one. There are differences, which I learned the hard way :( [[Special:Contributions/172.69.43.184|172.69.43.184]] 06:48, 5 September 2024 (UTC)
:I expanded (and moved to a Trivia section) the interesting facts of this coincidence. (And I didn't add [https://www.plagiarismtoday.com/2010/10/18/the-odd-case-of-dennis-the-menace/ this link there], but maybe it's of "not even Trivia" interest, so you can have it here instead.) [[Special:Contributions/172.70.86.37|172.70.86.37]] 10:53, 5 September 2024 (UTC)

I'm really surprised that "regular slingshot" is "no" for spacecraft instead of something like "not yet". [[User:SystemParadox|SystemParadox]] ([[User talk:SystemParadox|talk]]) 09:46, 5 September 2024 (UTC)
:There's definitely spring-type "delivery systems" (analogues of the elastic slingshots, arguably) which hasten the detatchment of items on a multi-launch 'racked' delivery system. There's also the (proposed, SFAIK not yet tried in anger) rotating-tether release system, akin to biblical sling(shot)s, that would actually be what the gravitational slingshot is most similar to by pure analogy.
:If we ever get a space-elevator and 'drop' things off from the counterweight station, then that would effectively be a biblical slingshot on a planetary scale. (If we time the drop right, or very wrong, with a heavy enough load or even most of the counterweight itself, such that it ends up eventually impacting Earth or any other inhabited lump of rock, it could well also be a matter of a ''planetary'' slingshot with effects on a ''biblical'' scale!) [[Special:Contributions/172.70.86.37|172.70.86.37]] 10:53, 5 September 2024 (UTC)

Gravitational slingshot & Used for Sport shooting would also be a "not yet".
Imagine a couple of millenia from now, where gravitational slingshoting is a sport, and is called shooting for one of many reasons.
ok, fair. It's a stretch. But I felt I had to mention it.
[[Special:Contributions/162.158.222.142|162.158.222.142]] 12:45, 5 September 2024 (UTC)
: In Futurama they use Gravitational slingshot for [https://futurama.fandom.com/wiki/Leo_Wong%27s_%22Miniature%22_Golf_Course "Miniature" golf]

This comic comes the same week as the release of a movie called Slingshot about the gravitational kind.

Isn't David supposed to be using a sling in his fight with Goliath, not a slingshot? That is, a long bit of material that you can use to throw a projectile with higher velocity? There seems to be similar confusion in describing a slingshot as using "mechanical advantage and rotation". A slingshot doesn't really involve rotation, nor does it involve mechanical advantage, really. Mechanical advantage is force amplification, right? And most slingshots don't amplify force, they simply are better than human bodies at delivering that force while moving quickly - that is, they amplify power. Maybe that's splitting hairs. [[Special:Contributions/172.68.71.102|172.68.71.102]] 14:52, 5 September 2024 (UTC)
: I see now that the text has been edited, distinguishing a sling as "an earlier form" of the slingshot. I still don't think that's accurate. They both accelerate a projectile, but they're not at all the same mechanism. Slingshots store deformation energy, and slings store kinetic energy. If we're talking ancient weapons that a slingshot is comparable to, it's far more like a bow than it is a sling. [[Special:Contributions/172.71.22.58|172.71.22.58]] 15:16, 5 September 2024 (UTC)
:: Indeed, the [https://www.etymonline.com/word/slingshot etymologists] tell us that "hand-held implement for throwing stones" is the original meaning of the word "sling", and it dates to 1300. Whereas "slingshot", with "hand catapult" given as a synonym (implying the cleft-stick version), dates only from 1849. The etymologists also tell us that, by the 14th century, "sling" had acquired the additional meaning of "loop for carrying heavy objects", and, by the 18th century, "cloth for suspending an injured arm". These meanings, I argue, gained prominence, while the sling (weapon) fell out of favor, in armies and in language. I daresay that a person with deir arm in a sling would shudder at the prospect of that arm being hurled at an oncoming foe. It appears to me that, at least in the USA where I reside, "slingshot" is now applied to both the "hand catapult" and the "sling (weapon)" to avoid confusion with the sling (object carrier). [[Special:Contributions/172.68.23.190|172.68.23.190]] 15:42, 5 September 2024 (UTC)
::: I'm also in the US, but slingshot to me specifically evokes something where you store and release elastic energy. People often *hear* sling and think it's referring to a slingshot, because they're unfamiliar with an actual sling (weapon). Although slingshot and sling are certainly etymologically related, they are not technologically related. You might argue that a "gravitational slingshot" is a misnomer, in that its arc around a body is more akin to a sling than to a slingshot, I suppose. But a sling is not an earlier form of the "regular slingshot" in this comic. [[Special:Contributions/172.71.31.46|172.71.31.46]] 16:56, 5 September 2024 (UTC)
:: I come from where the Y-Stick-with-rubber-'bowstring' is termed a catapult, and always associated "slingshot" as being the "shot" (projectile) that was slung (either in a David/Golith 'swung sling' or a Dennise The Menace 'pulled elastic' version), where actually deliberately manufactured/harvested beforehand (typically cast lead, as per muskets, or else specific riverbed pebbles) for consistency of mass and convenience of size rather than just relying upon randomly available rocks and stones grabbed from the ground-clutter as and when needed.
:: But when I went looking for references, it seems there's a general merging of terms (apparently also "pea-shooter", among others, although I'd say ''that'' was a short blowpipe/thick straw that a dried pea or pea-sized wad of mashed up paper can be quickly expelled from just by lung-power). And while some 'catapults' might also be the slung type, with the neolithic-era "stout cords and cradle" design, generally the comic-book type (rather than full blown onagers, mangonels or trebuchets) match what both UK and US alternatives of Dennis tend to use, so clearly that's what Randall is talking about. [[Special:Contributions/172.70.91.27|172.70.91.27]] 17:23, 5 September 2024 (UTC)

I vote we use gravitational slingshots to hunt stray probes. Anyone wanna try taking down Voyager I? [[Special:Contributions/172.69.90.237|172.69.90.237]] 14:57, 5 September 2024 (UTC)
:If we fire at Voyager I (or II, especially) and perhaps ''miss'', we then likely set a new record for fastest/furthest object sent out into the universe by man. Win-Win! [[Special:Contributions/172.70.91.27|172.70.91.27]] 17:23, 5 September 2024 (UTC)