explain xkcd - User contributions [en]

Talk:3089: Modern

2025-05-14T19:12:40Z

172.71.182.126: early modernity

Hate to be that guy, but wow, it’s empty [[User:Broseph|Broseph]] ([[User talk:Broseph|talk]]) 19:04, 14 May 2025 (UTC)

This strip reminded me of the comments in [[3063]]. Historians / historiographers typically define (early) "modernity" to begin around 1500. {{w|early modernity}} [[Special:Contributions/172.71.182.126|172.71.182.126]] 19:12, 14 May 2025 (UTC)

Talk:3003: Sandwich Helix

2024-11-25T00:32:34Z

172.71.182.126: Sandwich Helix = DNA

Sandwich presumably refers to {{w|compliment sandwich}}, but I don’t know what the helix is. --[[User:Galaktos|Galaktos]] ([[User talk:Galaktos|talk]]) 14:03, 25 October 2024 (UTC)
:I think sandwich refers to the context itself, as in, the context of something is both what is before that and what is after. [[Special:Contributions/172.71.222.236|172.71.222.236]] 15:19, 26 October 2024 (UTC)
: Maybe {{w|Models of communication#Dance}}? --[[User:Galaktos|Galaktos]] ([[User talk:Galaktos|talk]]) 14:12, 25 October 2024 (UTC)

:The word "Helix" may be a reference to the previous comic. [[User:CategoryGeneral|CategoryGeneral]] ([[User talk:CategoryGeneral|talk]]) 14:36, 25 October 2024 (UTC)

:The moral of this story is "People will try to find meaning in anything, even things that are directly stated to be meaningless."[[Special:Contributions/172.70.176.43|172.70.176.43]] 23:01, 26 October 2024 (UTC)

That title text makes me reasonably upset. What nitwit decided "smart quotes" AND incompatible default encodings was a good idea? [[Special:Contributions/172.70.174.203|172.70.174.203]] 16:45, 25 October 2024 (UTC)
: I'm inclined to blame Apple because [https://en.wikipedia.org/wiki/Mac_OS_Roman Mac OS Roman] (1989) postdates [https://en.wikipedia.org/wiki/Windows-1252 Windows 1252] (1987). Both of these extended [https://en.wikipedia.org/wiki/ISO/IEC_8859-1 ISO 8859-1] with curly quotes but chose different code points. [[User:Davidhbrown|Davidhbrown]] ([[User talk:Davidhbrown|talk]]) 03:26, 28 October 2024 (UTC)
:: Hi, Davidhbrown. Speaking of curls, note the difference between "[https://en.wikipedia.org/wiki/Mac_OS_Roman Mac OS Roman]" and "{{w|Mac OS Roman}}". And come into the edit to see how neater the source is! (Even compared to [[]]s marked to go to "wikipedia:..."). HTH, HAND. [[Special:Contributions/172.68.205.151|172.68.205.151]] 11:33, 28 October 2024 (UTC)

It seems that something like this could happen over time naturally if it's a saying that "everyone knows" so that real meaning stops being said, and then eventually that bit of information disappears. For instance KISS "Keep it simple, stupid" has a negative connotation, but the idea is very sound. So people keep saying the abbreviation but stop saying the full version, and new people hearing it the first time might get the basic idea without knowing why. Eventually even the meaning could be lost, and it could just become something that people say without knowing why. Maybe the assume the ancient designers and engineers liked to make out when they saw complex things. [[User:Andyd273|Andyd273]] ([[User talk:Andyd273|talk]]) 17:58, 25 October 2024 (UTC)
:Frums - Options [[Special:Contributions/162.158.91.14|162.158.91.14]] 04:18, 26 October 2024 (UTC)
:''KISS Keep it simple, stupid'' was originally ''keep it stupid simple''. An emphasis, not an insult. --[[User:PRR|PRR]] ([[User talk:PRR|talk]]) 05:12, 26 October 2024 (UTC)
:: "Keep it stupid, simple" still sounds like an insult. [[User:These Are Not The Comments You Are Looking For|These Are Not The Comments You Are Looking For]] ([[User talk:These Are Not The Comments You Are Looking For|talk]]) 03:07, 27 October 2024 (UTC)
::: https://en.wikipedia.org/wiki/KISS_principle#Origin --[[User:PRR|PRR]] ([[User talk:PRR|talk]]) 18:31, 27 October 2024 (UTC)
:::: Note for recent editors... You can use that link as <code><nowiki>{{w|KISS principle#Origin|~insert some link text here~}}</nowiki></code> to get it to look like {{w|KISS principle#Origin|~insert some link text here~}}. I think we're getting some new users who seem not to be aware of this handy template, and/or being lazy about it. (I also indented your comment, for the circumstances.) [[Special:Contributions/162.158.74.118|162.158.74.118]] 19:01, 27 October 2024 (UTC)
::maybe keep it stupidly simple?{{unsigned ip|172.69.34.176|04:56, 27 October 2024}}
:: Nope. That's a sweet thought, but comes from the US Navy in 1960, and indeed started as "Keep it simple, stupid!". [[Special:Contributions/172.68.71.159|172.68.71.159]] 15:52, 28 October 2024 (UTC)

Infodump: To my knowledge the only five encodings resulting in "â€™" for utf-8 encoded "’" are Windows-125X where X is an even decimal digit. {{unsigned ip|162.158.154.78|15:25, 27 October 2024}}

This is similar to the number 42 in Hitchhikers Guide to the Galaxy, in that the answer is known, but the exact question (=the context) has been lost. See [https://hitchhikers.fandom.com/wiki/42 HHGG Fandom wiki] --[[User:Cavac|Cavac]] ([[User talk:Cavac|talk]]) 09:33, 28 October 2024 (UTC)

Minor grammatical point; please feel free to skip this. I just tweaked "a communication technique [...] which meaning has not been lost." to "a communication technique [...] whose meaning has not been lost.". "''Of'' which ''the'' meaning" or "whose meaning" both work, but the latter is less contrived. People keep forgetting that "whose" can refer to objects, as well as to people. <https://en.wiktionary.org/wiki/whose#Determiner>

The first rule of communication is "Always talk about communication." [[User:RegularSizedGuy|RegularSizedGuy]] ([[User talk:RegularSizedGuy|talk]]) 15:36, 25 October 2024 (UTC)
: I'm pretty sure the first rule is "Context Matters" and "Helix Sandwich" conveys that by the lack of it.[[Special:Contributions/172.70.126.228|172.70.126.228]] 20:28, 27 October 2024 (UTC)

Possibly the best real-world example of this is the Biblical Book of Revelation. It's an example of apocalyptic writing, which means 'writing in code', not necessarily 'talking about the end of the world' (although it does also do that, which is where the confusion has arisen). And that's sort of the point - most of the context which would enable us to understand the book properly has been lost. For example, scholars generally accept that the 'beast' whose number is 666 is a reference to a real historical person, and that the number 666 is supposed to tell the reader that person's identity... but there's no consensus on who that person is. The fact that there is evidence to suggest that the number was altered (from 616) by later editors doesn't help. [[Special:Contributions/172.70.90.109|172.70.90.109]] 05:47, 28 October 2024 (UTC)

I don't think the "helix" refers to software development. It could be about the helical model of communication, which conveys communication as a non-linear process.

This is perhaps a joke with these simplistic "rules" of communication (like the compliment sandwich), which portray communication as something much simpler.

If we assume that communication is complex and non-linear (as the helical model of communication portrays), we might conclude that there is no such thing as "#1 rule of communication"; something that could be observed by the misuse of the "compliment sandwich". {{unsigned ip|172.70.47.87|15:38+, 25 October 2024}} (Assuming all the above is the same IP editor, tweaking their comment.)

:Ah, thank you. I added the Spiral (for development) because I couldn't find the Helix one (for communication), and I thought this was the best linkable item out there. Now I know it's ''Helical'', I've found it and I can put a link on your addendum and perhaps remove my original 'placeholder'. That's collaborative communication! ;) [[Special:Contributions/172.70.91.77|172.70.91.77]] 15:56, 25 October 2024 (UTC) (PS, please sign Talk contributions, and wikilinks are a good idea if you can add them. ;p )

I took the opposite point from that in the explanation so far, especially with the title text: Even if the encoding is wrongly specified, it's possible to figure out what was meant by some sequence of bytes. I imagine the teacher using a different nonce every time to make the point about the #1 rule of communication: Words don't have inherent meaning, it is acquired through use. (Though if I'm the only one with this interpretation it kind of sinks my idea I guess). [[User:Hcs|Hcs]] ([[User talk:Hcs|talk]]) 10:18, 26 October 2024 (UTC)

Is it not true that Cueball could basically be demonstrating the #1 rule, i.e. context is important, and that sometimes language is self-repairing? [[Special:Contributions/172.69.214.109|172.69.214.109]] 14:42, 26 October 2024 (UTC)

:<=========>
: ∞∞∞∞∞∞∞
:<=========>

Helix sandwich. That did not render well.- TenGolf [[Special:Contributions/172.69.58.19|172.69.58.19]] 18:20, 27 October 2024 (UTC)
:Like it now? (There are better ways, but is the simplest.)[[Special:Contributions/172.68.205.134|172.68.205.134]] 18:28, 27 October 2024 (UTC)
I think that people are missing that the Sandwich Helix is the DNA molecule where nucleic base pairs are stacked like the layers in one of Dagwood's sandwiches. This molecule "communicates" a lot of information but we don't know how to interpret a lot of it (much of the non-translated regions). This notwithstanding, we can list consensus sequences for many organisms. I.e. we have the message but not the encoding (for all of it). [[Special:Contributions/172.71.182.126|172.71.182.126]] 00:32, 25 November 2024 (UTC)

2520: Symbols

2024-10-10T11:42:37Z

172.71.182.126: /* Explanation */ Context for the 10^44 kg figure

{{comic
| number = 2520
| date = September 24, 2021
| title = Symbols
| image = symbols.png
| titletext = "röntgen" and "rem" are 20th-century physics terms that mean "no trespassing."
}}

==Explanation==
This comic refers to elements of (mostly mathematical or engineering) notation commonly used in various fields of math and science. Each piece of notation is presented as "symbolizing" not what it specifically means, but a typical ''context'' in which it might be encountered, see [[#Symbols|below]].

Many of the individual descriptions look like verbiage that might be found on informational or warnings signs or placards, although typically with a silly edge.

The title text refers to two non-SI units of radiation measurement, {{w|Roentgen (unit)|röntgen}} and {{w|Roentgen equivalent man|rem}}. In the mid-20th century when they were in use, the dangers of radiation weren't as well understood as today, so an area with radiation that was noteworthy back then is [https://archive.md/v3dME probably dangerous], hence the no trespassing part.

Later [[Randall]] made a similar comic, [[2586: Greek Letters]], regarding the use of Greek letters in math.

===Symbols===
'''d⁄dx: An undergrad is working very hard''' d/dx is the symbol for a single-variable {{w|Derivative|derivative}}. This is one of the basic operations in {{w|calculus}} and consequently is ubiquitous in the work of undergraduates in the sciences. A hard-working undergraduate in the relevant fields would churn through exercises using this symbol.

'''∂⁄∂x: A grad student is working very hard''' The replacement of the standard "d" letters with the curly letters "∂" denotes the partial derivative, which generalizes the ordinary derivative to multi-variable calculus. Problems with partial derivatives, especially partial differential equations, can be extremely challenging. Although PDEs would typically be first taught at an undergraduate level, difficult partial derivatives would be encountered in graduate-level work.

'''ħ: Oh wow, this is apparently a quantum thing''' ħ (pronounced "h-bar") is a symbol used for (the reduced) {{w|Planck's constant}}, a universal, fundamental constant in quantum physics. h, the normal version of Planck's constant, is equal to the energy of a photon divided by its frequency. ħ is equal to h/2π, and angular momentum in quantum mechanical systems is measured in quantized integer or half-integer units of ħ.
Classical physics appears as a limit of quantum physics if all "actions" (quantities of dimension energy * time, momentum * length, or angular momentum) are much larger than ħ. Conversely, you can also formally set ħ=0 to get classical results from quantum formulae. This means that effects that are proportional to some power of ħ cannot be explained classically, and instead are "a quantum thing".

'''Re: Someone needs to do a lot of tedious numerical work; hopefully it's not you''' The {{w|Reynolds number}} (which is usually denoted by "Re," not "Re" as it appears in the comic) is the most important dimensionless group in fluid mechanics. Named for Osborne Reynolds, Re characterizes the relative sizes of inertial and viscous effects in a moving fluid. Large values of Re are indicative of turbulent flow, which cannot usually be retrieved analytically, and so numerical modeling is necessary. Accurate numerical studies of high-Reynolds-number flows are notoriously difficult to create and program.

Alternatively, Re could stand for electronic {{w|transition dipole moment}} in a molecule. This appears in quantum-mechanical calculations of transition probabilities and also includes a lot of unpleasant numerical work. Re is also a term used for the radius of the Earth at mean sea level, though this is not necessarily a complex term in and of itself.

Another alternative is that Re could refer to Relative Error, a measurement of precision or accuracy. Used often in the analysis of scientific data and numerical analysis.

'''(Ta4 - Tb4): You are at risk of skin burns''' The {{w|Stefan-Boltzmann law}} says that a perfectly absorbing ("black body") source emits electromagnetic radiation with a power per unit area of σT4, where σ is a known constant and T is the absolute temperature. The quantity (Ta4 – Tb4) thus appears in any calculation of purely radiative energy transfer between two bodies, one at temperature Ta and the other at Tb. When the radiative transfer is large enough to be the most important form of heat interchange, it is normally also large enough to sear the skin with thermal or ultraviolet burns.

'''NA: You are probably about to make an incredibly dangerous arithmetic error''' NA, or {{w|Avogadro's number}}, is the number of molecules in a mole of a substance, approximately the number of carbon atoms in exactly 12 grams of carbon-12. This is an enormous number, exactly 6.022 140 76 × 1023, or 602 214 076 000 000 000 000 000. Working with NA, it is easy to accidentally divide by it instead of multiplying or vice versa, leading to erroneous and nonsensical answers such as ~10-23 molecules (even though you can't have less than 1 whole molecule) or ~1046 moles (>1043 to 1045 kilograms, depending on the chemical - tens to hundreds of times the estimated mass of the Milky Way Galaxy) of a substance.

'''µm: Careful, that equipment is expensive''' {{w|Micrometre|Micrometer}}s are a very small unit of distance. Micrometers are commonly used to measure wavelengths in the infrared, and infrared detectors are very expensive, compared with visible wavelength counterparts. Of course, micrometers are used as a measurement of distance in other contexts, but any distance-measuring device capable of accurately measuring micrometer distances would also be expensive. Similarly, tools used to create or calibrate items within micrometer tolerances can also be expensive.

'''mK: Careful, that equipment is very expensive''' {{w|Kelvin}} is a temperature scale roughly speaking similar to Celsius, but taking absolute zero as its zero point instead of the freezing point of water (rigorously speaking, its definition is now {{w|2019_redefinition_of_the_SI_base_units#Kelvin|based on the Boltzmann constant}}). {{w|Millikelvin}}s (1/1000 of a Kelvin) are used for high precision temperature work. Frequently this is used in processes of cooling temperatures to nearly absolute zero - such as superconductors or other quantum effects that occur when atoms are almost still. This is suggesting that the symbol appears on a sensitive experimental system probing quantum mechanical behavior that would likely only exist in an advanced laboratory. Any equipment that works down at mK temperatures, or at least to mK precision and accuracy, is likely to be very expensive.

'''nm: Don't shine that in your eye''' {{w|Nanometre|Nanometer}}s are frequently seen in the listed wavelengths for lasers. Pointing a visible or infrared laser at someone's eye is notoriously dangerous; the tightly-focused coherent light can cause permanent damage very quickly.

'''eV: Definitely don't shine that in your eye''' {{w|Electronvolt}} energies are typical of moderate-energy particle beams, produced by accelerating electrons (or protons) over macroscopic voltages. These particle beams can be {{w|Anatoli Bugorski|even more damaging (and are probably a direct reference to Anatoli Bugorski)}} to soft tissues than optical-wavelength lasers.

'''mSv: You're about to get into an Internet argument''' The {{w|millisievert}} is a unit of radiation dose absorbed. It is a very small dosage, but the joke refers to Internet trolls debating the effects of low-dose radiation sources, such as 5G wireless networks. [[Randall|Randall's]] comment may also be referring to [[Radiation]].

'''mg/kg: Go wash your hands''' This unit measures the dose of a drug or other chemical in milligrams per kilogram of body mass. If the appropriate dose - or worse, the lethal dose - is measured in mg/kg (parts per million), then the substance may be quite toxic.

'''µg/kg: Go get in the chemical shower''' A unit 1/1000 times the size of mg/kg. If a dosage is measured in micrograms per kilogram (parts per billion), any accident probably requires whole-body decontamination procedures.

'''π or τ: Whatever answer you get will be wrong by a factor of exactly two''' π is defined as the ratio of a circle's circumference to its diameter, while τ is defined as the ratio of a circle's circumference to its radius (and is therefore equal to 2π). {{w|pi|π}} has been used as the primary constant for describing the circumference and area of circles millennia ago, but proponents of {{w|Turn (angle)|τ}} claim that τ is more natural in most contexts since it makes working in radians more straightforward. Actually, the "Pi" symbol used to be occasionally used for the constant now called Tau. The joke here is that whichever constant you use, it will probably be the wrong one (off by a factor of two, one way or the other) for the formula you are trying to use. The debate over Pi vs. Tau was solved by Randall in this compromise: [[1292: Pi vs. Tau]].

==Transcript==
:[A list with 14 different scientific constants/symbols are shown. Next to each symbol is a description. Above the list is a heading and beneath that a subheading.]
:::::<big>Symbols</big>
::::And what they mean

:::d⁄dx    An undergrad is working very hard
:::∂⁄∂x    A grad student is working very hard
:::ħ       Oh wow, this is apparently a quantum thing
:::Rₑ     Someone needs to do a lot of tedious numerical work; hopefully it's not you
:(Ta⁴ - Tb⁴)    You are at risk of skin burns
:::NA    You are probably about to make an incredibly dangerous arithmetic error
:::µm    Careful, that equipment is expensive
:::mK    Careful, that equipment is very expensive
:::nm    Don't shine that in your eye
:::eV     '''''Definitely''''' don't shine that in your eye
:::mSv  You're about to get into an internet argument
::mg/kg      Go wash your hands
::µg/kg      Go get in the chemical shower
::π or τ      Whatever answer you get will be wrong by a factor of exactly two

{{comic discussion}}

[[Category:Math]]
[[Category:Physics]]
[[Category:Chemistry]]
[[Category:Biology]]
[[Category:5G]]