explain xkcd - User contributions [en]

3242: Aperiodic Table

2026-05-08T15:27:31Z

82.132.185.192: /* Transcript */ "the the"->"the", and allowing for variation (or absence) of exact colouring practices in otherwise 'standard' tables.

{{comic
| number = 3242
| date = May 6, 2026
| title = Aperiodic Table
| image = aperiodic_table_2x.png
| imagesize = 740x464px
| noexpand = true
| titletext = Scientists occasionally invent alternative periodic table layouts, which is usually a sign that they don't have enough enrichment in their enclosures.
}}

==Explanation==
{{incomplete|This page was created APERIODICALLY. Don't remove this notice too soon.}}
The {{w|periodic table of the elements}} is a diagram often used to show the properties of the {{w|chemical elements}} that make up the world. Its structure represents several properties of the elements. Atoms increase in {{w|atomic number}} from left to right and continue on each new row, going top to bottom. Elements in a single column will have similar chemical properties, with allowance for any crossing of the {{w|dividing line between metals and nonmetals}}, and each row exhibits a similar trend to adjacent rows for the gaining or losing electrons and other physical properties.

[[Randall]] spoofs this concept by creating a similar view that is much less useful. The original table is "periodic" because it has consistent, repeating patterns that are represented by the horizontal position of the elements. Randall's 'table' is "aperiodic", meaning it has no consistent, repeating patterns. Instead, it is just a meandering line ordered by atomic number. To fit into a compact space, the sequence snakes back and forth and (roughly) down the page. This presentation is not actually helpful,{{cn}} since it contains little information other than the atomic number of each element. Faint colouring on each box does show its category, but due to the dull colours that is also quite inconvenient to use, and depicts this information in an unnecessarily unhelpful and hard-to-read format.

The title text suggests that the creation of {{w|Types of periodic tables|alternative periodic table layouts}} is due to scientists not having enough work to do. However, it frames this by comparing them to animals kept in enclosures, with a lack of {{w|Behavioral enrichment|enrichment activities}} to keep them occupied and satisfied in their lab, implying that this is a form of aberrant dysfunctional behaviour. Researcher enclosure enrichment was previously mentioned in [[3052: Archive Request]]. The reference to 'enrichment' could also be a pun on the process of chemical enrichment (particularly of [https://www.energy.gov/ne/articles/uranium-enrichment-explained uranium]), or on the {{wiktionary|enrichment}} of scientists by gaining funding.

This comic may be a critique about how an excessive variety of ways to display the periodic table have been created over the years, many of which make Randall's periodic table look fairly normal by comparison. Alternatively, it may be intended to highlight how useful the original idea of the periodic table was, since the version in the comic is essentially what scientists were faced with before it was invented.

==Trivia==
* Element 81, Thallium, should be labeled "Tl" (with a lowercase "L"), but is incorrectly labeled "Ti", which is the abbreviation for Titanium (element 22).

==Transcript==
{{incomplete transcript|Don't remove this notice too soon. All 118 elements and their number should be included in a full transcript.}}

:The Aperiodic Table of the Elements
:[Rectangles showing the atomic symbols and atomic numbers from H (1) through Og (118) are arranged in a serpentine chain. Each rectangle has the atomic number in small numerals at the upper left and the atomic symbol in large letters. The color of each rectangle matches the pattern of a similarly keyed standard periodic table. For example, the noble elements all have a red background.]

{{comic discussion}}<noinclude>

[[Category:Comics with color]]
[[Category:Comics with lowercase text]]
[[Category:Periodic table]]
[[Category:Chemistry]]

3242: Aperiodic Table

2026-05-08T15:21:56Z

82.132.185.192: /* Transcript */

{{comic
| number = 3242
| date = May 6, 2026
| title = Aperiodic Table
| image = aperiodic_table_2x.png
| imagesize = 740x464px
| noexpand = true
| titletext = Scientists occasionally invent alternative periodic table layouts, which is usually a sign that they don't have enough enrichment in their enclosures.
}}

==Explanation==
{{incomplete|This page was created APERIODICALLY. Don't remove this notice too soon.}}
The {{w|periodic table of the elements}} is a diagram often used to show the properties of the {{w|chemical elements}} that make up the world. Its structure represents several properties of the elements. Atoms increase in {{w|atomic number}} from left to right and continue on each new row, going top to bottom. Elements in a single column will have similar chemical properties, with allowance for any crossing of the {{w|dividing line between metals and nonmetals}}, and each row exhibits a similar trend to adjacent rows for the gaining or losing electrons and other physical properties.

[[Randall]] spoofs this concept by creating a similar view that is much less useful. The original table is "periodic" because it has consistent, repeating patterns that are represented by the horizontal position of the elements. Randall's 'table' is "aperiodic", meaning it has no consistent, repeating patterns. Instead, it is just a meandering line ordered by atomic number. To fit into a compact space, the sequence snakes back and forth and (roughly) down the page. This presentation is not actually helpful,{{cn}} since it contains little information other than the atomic number of each element. Faint colouring on each box does show its category, but due to the dull colours that is also quite inconvenient to use, and depicts this information in an unnecessarily unhelpful and hard-to-read format.

The title text suggests that the creation of {{w|Types of periodic tables|alternative periodic table layouts}} is due to scientists not having enough work to do. However, it frames this by comparing them to animals kept in enclosures, with a lack of {{w|Behavioral enrichment|enrichment activities}} to keep them occupied and satisfied in their lab, implying that this is a form of aberrant dysfunctional behaviour. Researcher enclosure enrichment was previously mentioned in [[3052: Archive Request]]. The reference to 'enrichment' could also be a pun on the process of chemical enrichment (particularly of [https://www.energy.gov/ne/articles/uranium-enrichment-explained uranium]), or on the {{wiktionary|enrichment}} of scientists by gaining funding.

This comic may be a critique about how an excessive variety of ways to display the periodic table have been created over the years, many of which make Randall's periodic table look fairly normal by comparison. Alternatively, it may be intended to highlight how useful the original idea of the periodic table was, since the version in the comic is essentially what scientists were faced with before it was invented.

==Trivia==
* Element 81, Thallium, should be labeled "Tl" (with a lowercase "L"), but is incorrectly labeled "Ti", which is the abbreviation for Titanium (element 22).

==Transcript==
{{incomplete transcript|Don't remove this notice too soon. All 118 elements and their number should be included in a full transcript.}}

:The Aperiodic Table of the Elements
:[Rectangles showing the atomic symbols and atomic numbers from H (1) through Og (118) are arranged in a serpentine chain. Each rectangle has the atomic number in small numerals at the upper left and the atomic symbol in large letters. The color of each rectangle matches the the pattern of a standard periodic table. For example, the noble elements all have a red background.]

{{comic discussion}}<noinclude>

[[Category:Comics with color]]
[[Category:Comics with lowercase text]]
[[Category:Periodic table]]
[[Category:Chemistry]]

Talk:3106: Farads

2026-05-08T15:17:38Z

82.132.185.192:

Who wrote this description? It's complete nonsense. A capacitor can't throw a stone. A 1 F capacitor is also not remotely dangerous unless it's charged to a high voltage — except that a 1 F capacitor and a 0.01 F capacitor can be charged to essentially the same maximum voltage!

Unlike other units of measure where a single unit is non-extreme, "The capacitance of the Earth's ionosphere with respect to the ground is calculated to be about 1 F." [https://en.wikipedia.org/wiki/Farad] Most capacitors in practical use are measured in pico, nano, or micro farads. 03:04, 25 June 2025 (UTC)

Please note that the pound, shown in panel 2, is not an SI unit. The corresponding SI unit is the kilogram; an item with a mass of one kilogram is still commonplace. [[User:Troy0|Troy0]] ([[User talk:Troy0|talk]]) 03:11, 25 June 2025 (UTC)
:I added Trivia to mention that (and another thing), sorry that I didn't read here first but I think I've covered your thoughts on the subject. [[Special:Contributions/82.132.246.160|82.132.246.160]] 13:07, 25 June 2025 (UTC)
:Kilogram is a unit of mass, while pound is a unit of force (weight is a measure of the force of gravity on a particular mass). So no, the kg is not quite the corresponding unit to the lb; that would be the Newton (N), equal to about 0.223 lb. [[Special:Contributions/170.85.70.249|170.85.70.249]] 18:12, 10 July 2025 (UTC)

When my father was a young engineer, the old guys would haze the new kids by asking them to fetch a "one farad capacitor". But everybody in the lab said "Sorry, I ran out, go ask Fred on the top floor", "Go ask Tom in the basement", "Try Peter's Parts on Vine St", etc--- give the kid a run-around. The joke was: at the time, 1F was likely large than a large garbage can and many hundred (non-SI) pounds. But the world changed, and in recent years you can easily buy 1F @ 16V, about the size of a soup can, to smooth car sound power feeds. --[[User:PRR|PRR]] ([[User talk:PRR|talk]]) 03:27, 25 June 2025 (UTC)

:[I used to work with a guy who'd fall for all of the gags, going off to fetch striped paint, a glass hammer (there are such things in fact), a spirit level bubble, etc. Turns out he'd just goof off, completely aware he was on a wild goose chase.] {{unsigned ip|81.109.188.229|19:47, 27 June 2025}}

This explanation would benefit from some elaboration on how and why supercapacitors are dangerous. [[Special:Contributions/195.252.226.234|195.252.226.234]] 04:41, 25 June 2025 (UTC)

Funnily enough, the wikipedia page for "Farad" (https://en.wikipedia.org/wiki/Farad) currently has a 1 farad supercapacitator as the title image. It looks pretty unassuming. [[User:Mouse|Mouse]] 08:54, 25 June 2025 (UTC)

Top of the page says June 23 even though it looks like this came out on June 25. Should it be changed? [[Special:Contributions/85.76.9.43|85.76.9.43]] 05:15, 25 June 2025 (UTC)
:Randall-time, it was 24/Jun (or Jun/24, being leftpondian with potentily mixedendian dates). It's not unnown for it to be an early-hours-of-day-after (EST) release, though late-hours-of-day-after is rather unusual. I'm guessing awkward commitments took over, perhaps even the prescheduled timer (if left 'in charge', not having even been put to the test in a while) didn't work when/how it should have.
:We've also had surpisingly ''early'' releases (noon or earlier, UTC, making it very-early-on-day-of-release), but I haven't any specific memory of it being so early that it ended up ''preceding'' the scheduled day (off-schedule additions don't count), other than perhaps when he was currently on a book-tour and (e.g.) in Europe so probably doing his prefered time-of-day (or when it was most convenient for his schedule) in UTC/UTC+1/UTC+2 'mode', though it was still "yesterday" back home.
:Best suggestion is to see when [[3107]] comes out. If it's a Wednesday(ish)-compatible time, this was just overdue for ...reasons. But if it's Friday(ish), then we can re-examine its true position (with much arguing, I suspect) in the schedule.
:It ''could'' also be an attempt to subtly shift what number pops up when (I think a past "whole week series", or two, were conjectured to alter the numbers to reasonably engineer the landing of [[404]] upon April 1st), but that's probably beyond speculation until we at least can assess what has happened by the end of this week. (''Then'' start looking for what numbers land (near) where, up to arbitrary points in the future.)
:Also something to add to Trivia, ''when'' we can rule out some of the possibilities (or be prepared to be wrong/overly-comprehensive, like here, and remove the wronger bits later). [[Special:Contributions/82.132.246.160|82.132.246.160]] 13:07, 25 June 2025 (UTC)
::The official archive at https://xkcd.com/archive/ lists it as released at 2025-6-23. We should follow that listing, as we have done before at (vary rarely) delayed comics. [[Special:Contributions/2001:16B8:C731:2E00:9AC:BBD8:8775:315D|2001:16B8:C731:2E00:9AC:BBD8:8775:315D]] 15:34, 25 June 2025 (UTC)

I agree with [[User:Troy0|Troy0]] that having a non-SI unit in there (1 pound) is incongruous, and it should instead be a sugar crystal weighing 1 gram. [[Special:Contributions/121.98.227.79|121.98.227.79]] 06:52, 25 June 2025 (UTC)

"most consumer electronics use at most a nanofarad" -> nah... Several hundreds of microfarads are quite common. But so are tens-of-picofarad, mostly in HF/RF filters etc. Calculating an average over all capacitors in all consumer electronics makes no sense anyway... But I'd say "Most consumer electronics use capacitors in the picofarad to milifarad range".
"To prevent static electricity from building lethal charge, unused supercapacitors are usually stored and transported with a "keeper", a steel or aluminum bar shorting the terminals." -> Static charge won't change the voltage of a 1 F capacitor much... V=q/C with small q and large C... The shorting is for high voltage capacitors that 'recharge' themselves trough {{w|Dielectric_absorption|dielectric absorption}}... Interesting, but completely different. -- [[User:Gautee|Gautee]] ([[User talk:Gautee|talk]]) 07:52, 25 June 2025 (UTC)
:Even a supercapacitor is not necessarily lethal. It depends on the voltage. A project I'm working on has a 6v supercapacitor (to keep the clock running for a few days when power is disconnected). And they're not even expensive parts. For example [https://www.mouser.com/ProductDetail/KYOCERA-AVX/SCMT32H755MRBB0?qs=l7cgNqFNU1iVPH0cf9oilA%3D%3D this one] is 7.5F (!) at 6v. They're not very large and only cost $9. Touching the terminals when it is charged will hurt a lot, but it will hardly kill you. [[User:Shamino|Shamino]] ([[User talk:Shamino|talk]]) 14:40, 25 June 2025 (UTC)
::It really doesn't (directly) depend upon the voltage, either. It's a function of the volts ''and amps'' (but ultimately, how much energy there is, and ''where'' it manages to go).
::Personal anecdote: Physics lesson (tertiary education level), one experiment used a High Tension Power Supply to provide a high (selectable) voltage to some equipment, already set up with a rope(-like) barrier around it that one had to stay beyond when it was powered up. HTPSU's selector-switch had a screw 'stop' to limit the selection to only 'very high' voltage (already way beyond 230+V mains, with generally up to 13A fuse). During a classroom break, I thought I'd see what results a 'ludicrously high' voltage would give, unscrewed the stop, turned the dial up beyond it, and from beyond the boundary-'barrier' turned the power on. *ZAP*, I actually got shocked! (Can't now remember if it blew a fuse/RCD, or if it was part of the experiment that a discharge naturally stopped it, it was decades ago and the finer details of the encounter are well and truly blurred, including what the activity was - but a Jacob's Ladder could well have needed thousands to tens of thousands of volts running through it, if it was that, or the HTPSU was ultimately capable of running one, rather than what 'low voltage' thing I was doing.)
::Hurridly turned it all off, possibly earthed the bit you had to remember to earrh when you were leaving it for the next person's turn, dialled it back down, reinserted the limiter-screw, went off on the break that the rest of the class (and supervising tutor) had gone off to. It would have been very low ampage (lucky for me), maybe also I only got a fraction of the discharge, sharing it with nearby lab-fixtures (sink/gas-taps?), etc, and it probably did not cross my body (the most dangerous effect) but I felt it (and remember not being sure from where the shock might have actually jumped).
::Nobody the wiser (''possibly'' the next experimenter found the fuse blown, when they tried to power up, but maybe even not that if was just temporarily RCDed at most), except maybe myself... Tended to respect 'screwstops' on dials from then on.
::And only other significant 'shock' I've ever had, apart from static ones resulting from man-made fibres in clothjng/carpets, was when I touched a plucked dandelion stalk (or similar) to an electric fence when ''much'' younger, curiosity getting the better of me in a slightly different scenario that turned out to be more shocking than I perhaps expected. Was I thinking it'd be a mere tingle, the current having to pass through a plant stem..? I think I already knew the old adage about "there are good electricians, bad electricians and dead electricians" - good ones have a current-detecting screwdriver-thingy (sufficiently high resistance), bad ones forget to bring one and have to test maybe-off wires with the back of their hand (if not off, muscles contract and contact quickly lost), dead ones ''grasp'' any mysterious wire and then ''can't let go'' until the power cuts for any other reason (high-rating household fuse, maybe, could be too late). OK, so there's some acinowledged inaccuracies (or historical assumptions) in the above, but the gist is pretty much there. [[Special:Contributions/82.132.244.34|82.132.244.34]] 15:47, 25 June 2025 (UTC)

We now have an exact answer to the question "how tall is Cueball?"--[[Special:Contributions/86.13.226.126|86.13.226.126]] 09:16, 25 June 2025 (UTC)
:Assuming that Cueball's holding the stick in a plane parallel to the comic frame. [[User:Legowerewolf|Legowerewolf]] ([[User talk:Legowerewolf|talk]]) 13:23, 25 June 2025 (UTC)
:If the stick really is parallel, Cueball's height is 1.78 m, or 5'10" for the Americans, or 9.02×106 ħc/eV for the Proxima b-ans. [[User:MinersHavenM43|MinersHavenM43]] ([[User talk:MinersHavenM43|talk]]) 15:19, 25 June 2025 (UTC)
::in my neck of the woods we usually use centimetres for people's heights. It's more convenient to not need to use a decimal separator. [[User:Bicorn|Bicorn]] ([[User talk:Bicorn|talk]])
:I've [https://i.imgur.com/NUOjpw4.png done the measuring], and I found a beautiful easter egg: The stick is held at a 23° angle, and when rotated to vertical is 100 px! So I get Cueball at 180 cm, or 1,8 m, [https://en.wikipedia.org/wiki/Decimal_separator#Countries_using_decimal_comma as it's written in my neck of the woods]. --[[Special:Contributions/80.71.143.166|80.71.143.166]] 09:38, 10 July 2025 (UTC)

In agreement with the first discussion point, this description remains low quality. It claims that after the unwarranted panic, Megan and White Hat "ask why he [Cueball] is carrying it [the 1-farad capacitor] around." This does not occur at any point in the comic or the Title Text, and should be removed. [[Special:Contributions/198.147.146.254|198.147.146.254]] 10:21, 25 June 2025 (UTC)

I'm sure the Farad is going to drive all sorts of commentary. My nitpick with the description: a 1F 30V+ capacitor can be held in hand (e.g. Cornell Dubilier DSM105Q030W075PB, Nichicon LNR1V105MSE). I don't recall the hazard criteria for stored energy right off, so I can only say that @30V there is no shock hazard in dry environment human handling, but the energy stored still present other hazards (e.g. fire or burns from conductors) [[Special:Contributions/12.171.61.178|12.171.61.178]] 14:39, 25 June 2025 (UTC) JourneymanWizard

Could the 1V battery be not a 1.5V alkaline battery, but a 1.1V lithium battery? Still somewhat discharged, but not nearly as much. [[Special:Contributions/2600:1009:B092:310F:4D22:1073:190A:E328|2600:1009:B092:310F:4D22:1073:190A:E328]] 17:04, 25 June 2025 (UTC)

"This litre of water is at 1 ''T''P" [[Special:Contributions/60.240.13.138|60.240.13.138]] 22:30, 25 June 2025 (UTC)

For different capacitors of a given physical size, what is the approximate relationship between capacitance and max voltage, all other factors also being equal? Simple inverse? Is it even a reasonable question to ask? Clearly, a gigantic capacitance and low voltage isn't dangerous; a tiny capacitance and extremely high voltage also isn't, if for no other reason than that it would discharge through the air. [[User:BunsenH|BunsenH]] ([[User talk:BunsenH|talk]]) 00:39, 26 June 2025 (UTC)
:Inverse square. If you want double the voltage your insulation needs to be double as thick, which halves the capacitance. However with double the insulation you can fit only half the area, which halves the capacitance again 14:20, 8 May 2026 (UTC)[[Special:Contributions/2A02:B027:8F06:5D6E:76F:A213:3F7B:AACE|2A02:B027:8F06:5D6E:76F:A213:3F7B:AACE]] 14:20, 8 May 2026 (UTC)
::''Slightly'' more complex, as the insulator/non-insulator division of thickness would need to be considered, which ''could'' be doubled-and-halved, but needn't be. Starting with 1/3 of available space as insulator, doubled, would become 2/3 with the remaining counterpart volume going from original 2/3 to now 1/3 (halved, yes)... But a 1/4=>2/4 doubling would be 3/4=>2/4 (two-thirdsing) on the other side of the split. 1/2 as insulator, initially, sends the counterpart from (also) half down fully to zero, and anything already greater than half for the former sends you into negative utility (if that were physicaly possible) now available to fulfil the latter aspect.
:And, even if that's balanced to handle the proportionaty change (whatever it is) equally proportionate 9n the other side (thus is proportionate-squared, as the end effect, for that specific degree of change), if you're thinning the conducting element it might no longer rate properly for the increased voltage that the insulator's thickness (and rating) has been increased in order to handle. I would presume that a given design, and size, of capacitor is probably already somewhat tuned to match the two (or more) internal ratings needed for the proposed loading, perhaps only slightly off to make its failure mode (upon being overpowered) involve the least problematic practical limit being breached... Rearranging the proportions alone, especially to try to double the performance in any way, is going to just make it significantly non-optimal overall.
:Exactly how, may depend upon what "all else being equal" base design you're working with. Might be more effective to entirely switch designs (and materials) to a trickier (and more expensive) construction of capacitor that sits in the same footprint but does a premium job that the original was never ever capable of handling. Unless you can find an 'original' that's so under-engineered that it can trivially be improved merely by doing the tweaks that should already have been done. [[Special:Contributions/82.132.185.192|82.132.185.192]] 15:17, 8 May 2026 (UTC)

Although he threw in one pound, I think the point is that some base metric units are impracticaly large or small. The MKS system has a kilogram as a "base" unit rather the gram. The CGS system used grams but centimeters instead of meters. Nobody uses ares or bels. [[Special:Contributions/2600:8800:4880:66B:809:D867:2F4C:D77A|2600:8800:4880:66B:809:D867:2F4C:D77A]] 03:41, 26 June 2025 (UTC)

I'd just like to point out that the confidence with which the explanation declares the capacitor to be low energy and therefore safe is exactly the sort of confidence that gets you electrocuted.[[Special:Contributions/2602:FF4D:128:D56:8114:9FE5:5A4D:499F|2602:FF4D:128:D56:8114:9FE5:5A4D:499F]] 16:19, 26 June 2025 (UTC)
:Yes, and "low-energy" needs definition. It's easy to find caps in the ballpark of 1F, >30V rating, hundreds of milliohms ESR, under $50, and small enough to easily hold in your hand. This could have an energy around 1000 J and could supply tens of amps for a significant fraction of a second. It's not as dangerous as, say, a grenade, but enough that I would be careful to avoid accidental self-discharge, especially across the body. And this assumes that the previous user didn't charge it *above* the rated voltage! [[Special:Contributions/174.126.217.139|174.126.217.139]] 17:46, 26 June 2025 (UTC)

All that panic about Farad ... I wonder what would they say if he was holding something creating a magnetic field of one Tesla. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 18:32, 3 July 2025 (UTC)
:I tried to something similar with an item one Kelvin, thinking that people would be interested, but just ended up being given the cold shoulder. [[Special:Contributions/92.23.2.228|92.23.2.228]] 19:27, 3 July 2025 (UTC)

See also: [https://www.youtube.com/watch?v=KmfdeWd0RMk A joke about measurement]. He constructs a consistent system of measurement based around the speed of light, the calorie, and Middle C. Once you have that you can start deriving other units, such as power. It's measured in "middle-C calories" and works out to 1094.64 Watts, the "first derived unit that's actually a convenient size." [[Special:Contributions/69.14.74.137|69.14.74.137]] 03:38, 13 July 2025 (UTC)

3242: Aperiodic Table

2026-05-08T14:43:45Z

82.132.185.192: /* Explanation */

{{comic
| number = 3242
| date = May 6, 2026
| title = Aperiodic Table
| image = aperiodic_table_2x.png
| imagesize = 740x464px
| noexpand = true
| titletext = Scientists occasionally invent alternative periodic table layouts, which is usually a sign that they don't have enough enrichment in their enclosures.
}}

==Explanation==
{{incomplete|This page was created APERIODICALLY. Don't remove this notice too soon.}}
The {{w|periodic table of the elements}} is a diagram often used to show the properties of the {{w|chemical elements}} that make up the world. Its structure represents several properties of the elements. Atoms increase in {{w|atomic number}} from left to right and continue on each new row, going top to bottom. Elements in a single column will have similar chemical properties, with allowance for any crossing of the {{w|dividing line between metals and nonmetals}}, and each row exhibits a similar trend to adjacent rows for the gaining or losing electrons and other physical properties.

[[Randall]] spoofs this concept by creating a similar view that is much less useful. The original table is "periodic" because it has consistent, repeating patterns that are represented by the horizontal position of the elements. Randall's 'table' is "aperiodic", meaning it has no consistent, repeating patterns. Instead, it is just a meandering line ordered by atomic number. To fit into a compact space, the sequence snakes back and forth and (roughly) down the page. This presentation is not actually helpful,{{cn}} since it contains little information other than the atomic number of each element. Faint colouring on each box does show its category, but due to the dull colours that is also quite inconvenient to use, and depicts this information in an unnecessarily unhelpful and hard-to-read format.

The title text suggests that the creation of {{w|Types of periodic tables|alternative periodic table layouts}} is due to scientists not having enough work to do. However, it frames this by comparing them to animals kept in enclosures, with a lack of {{w|Behavioral enrichment|enrichment activities}} to keep them occupied and satisfied in their lab, implying that this is a form of aberrant dysfunctional behaviour. Researcher enclosure enrichment was previously mentioned in [[3052: Archive Request]]. The reference to 'enrichment' could also be a pun on the process of chemical enrichment (particularly of [https://www.energy.gov/ne/articles/uranium-enrichment-explained uranium]), or on the {{wiktionary|enrichment}} of scientists by gaining funding.

This comic may be a critique about how an excessive variety of ways to display the periodic table have been created over the years, many of which make Randall's periodic table look fairly normal by comparison. Alternatively, it may be intended to highlight how useful the original idea of the periodic table was, since the version in the comic is essentially what scientists were faced with before it was invented.

==Trivia==
* Element 81, Thallium, should be labeled "Tl" (with a lowercase "L"), but is incorrectly labeled "Ti", which is the abbreviation for Titanium (element 22).

==Transcript==
{{incomplete transcript|Don't remove this notice too soon. All 118 elements and their number should be included in a full transcript.}}

:The Aperiodic Table of the Elements
:[Rectangles showing the atomic symbols and atomic numbers from H (1) through Og (118) are arranged in a serpentine chain. Each rectangle has the atomic number in small numerals at the upper left and the atomic symbol in large letters. The color of each rectangle matches the the pattern of a standard periodic table. For example, the noble elements all have a red background.]

{{comic discussion}}<noinclude>

[[Category:Comics with color]]
[[Category:Periodic table]]
[[Category:Chemistry]]

2385: Final Exam

2026-05-08T14:25:49Z

82.132.185.192: /* Explanation */ Simpler templated link format. (Aesthetically identical, but more compact/standardised markup.)

{{comic
| number = 2385
| date = November 13, 2020
| title = Final Exam
| image = final_exam.png
| titletext = For those of you also taking Game Theory, your grade in that class will be based on how close your grade on this exam is to 80% of the average.
}}

==Explanation==
In this comic, Ponytail appears to be administering a group sitting for cybersecurity exam. However, at the beginning of the exam, she informs her students that they have all failed, despite not having taken a test yet. She then informs them that their grades are stored on the department server and will be submitted the next day. The implication here is that the true test, rather than being a traditional exam, is actually whether the students can hack into the server and change their grades. This may be a jab at education security which is known to be vulnerable to assault, which is not the first time xkcd has made such a [[327: Exploits of a Mom|joke]]. In real life, students have attempted to change their grades in this manner, with occasional success.

The title text adds a twist to this. In order for a student to get a good grade in the {{w|game theory}} class, they need to get a below-average grade on this final exam. This incentivizes the students to also change the grades of other students when they change their grade. However, this is more complicated than it seems, and depends on various factors, such as the fraction of students who take game theory in addition to cybersecurity. If, for example, half of the students also take game theory, then for all of them to get 80% of the average score, even assuming that all their non-game-theory classmates get maximum possible score, they would have to target for 2/3 (or about 67%) of the maximum possible score, to get 80% of the final average. While that would make their game theory grade perfect, it might noticeably worsen their cybersecurity grade. This gets progressively worse with the increasing fraction of students who take game theory along with cybersecurity.

In the extreme case of all cybersecurity students also taking game theory class, this degenerates into another common game theory problem: {{w|Guess 2/3 of the average}} of everybody's guesses. The only group-wide winning strategy is, of course, for everyone to guess 0, which means that 2/3 of the average will be 0. This assumes {{w|perfect rationality}} of all players with respect to the game theory problem. The catch is that here we have the same number as a grade for the cybersecurity exam and for the game theory guess. We'd like one to be as high as possible, and the other to be zero or close to zero, which are obviously conflicting goals.

To improve their overall results, students could resort to various compromises and strategies, such as increasing other students' scores against their will, or making alliances with students who might not mind taking a hit to their game theory grade (perhaps in exchange for other incentives) - these are all topics that the game theory class would have been dealing with. Specifically, this test seems to refer to the {{w|prisoner's dilemma}} and {{w|tragedy of the commons}}; if one student changes their grade to 80% of the average, they will receive high marks, but if more and more students attempt this, the gain for each one drops and tends towards zero.

The combination with cybersecurity adds another layer of complexity, in that students could, for example, also attempt to lock each other out of the server to achieve maximum control over the results to their benefit.

In the strip, there is no actual test to take. But if there was one, there would still be strategies to optimize performance without hacking the grades. One option would be to take the test normally, and then change every fifth answer to the bubble below it; using this strategy your overall grade will drop to 80% if you were at 100%, and may even raise your score if a student performed particularly poorly. The trick, though, is that other students (assuming rationality) would try this strategy as well; thus, a student may need to overcorrect more, weigh the possibilities of whether any of their classmates had followed this as well, and perform this recursively until it is most likely that the score is 80 percent of the average.

Note: All of the above is based on the assumption that the game theory mark will be directly (and not inversely) proportional to how close the cybersecurity grade is to 80% of the average. This is left ambiguous in the formulation.

Note: The above also assumes the system accepts a maximum of 100%. If (as is likely) the system allows for extra credit you could reach a Nash equilibrium by setting the non-game theory students to an arbitrary, but very high, number (say 2000%) C and then the game theory students to (C*g)/(.25+g) where g is the percentage of students not in game theory.

Note: The solution becomes trivial if the game-theory grade is stored on the same server but submitted after the cybersecurity grade. Students would simply give themselves full marks on cybersecurity, then edit the game-theory grade after cybersecurity has been submitted, demonstrating a classical {{w|time-of-check to time-of-use}} vulnerability.

==Transcript==
:[Ponytail is standing in front of a whiteboard addressing someone off-panel to the left.]
:Ponytail: Welcome to your final exam.
:Ponytail: The exam is now over.
:Ponytail: I'm afraid all of you failed.
:Ponytail: Your grades have been stored on our department server and will be submitted tomorrow.
:Ponytail: Class dismissed.

:[Caption below the panel:]
:Cybersecurity final exams

{{comic discussion}}

[[Category:Comics featuring Ponytail]]
[[Category:Computer security]]
[[Category: Psychology]]

1623: 2016 Conversation Guide

2026-05-08T14:07:49Z

82.132.185.192: /* Explanation */ Correcting the misaligned "not yet"+"now it is" sense of the exited sentence. (Noting the two products mentioned may be best linked. And I doubt these are the *only* such examples that have comparatively achieved such statuses.)

{{comic
| number = 1623
| date = December 30, 2015
| title = 2016 Conversation Guide
| image = 2016_conversation_guide.png
| titletext = The real loser in an argument about the meaning of the word 'hoverboard' is anyone who leaves that argument on foot.
}}

==Explanation==
[[File:Electric Flying Cars -- Advertisement, 1958 (51438281706).jpg|thumb|right|1958 poster advertising an electric future of freedom and horrible crashes]]
As each year turns (or other milestone dates, perhaps set out in popular fiction) it is common enough to remember that what is now the present was once considered ''the future!''

This [[:Category:New Year|New Year comic]], published just prior to the start of the {{w|New Year}}, 2016, aims to clarify a number of the things one might have expected by now. (Another New Year comic followed on New Year's Day: [[1624: 2016]], making it two in a row with titles beginning with 2016...) The classic target of personal futurology is the ability to levitate or fly, to varying degrees. This topic was discussed before in [[864: Flying Cars]], where [[Megan]] suggests that the real advances in futuristic technology are in computers and electronics, rather than methods of flying.

;Flying car
Various forms of {{w|Flying_car_(aircraft)|flying car}} have had varying {{w|AVE_Mizar|degrees}} of {{w|Moller_M400_Skycar|success}} (although it's debatable whether these examples are actually cars or just small airplanes), but the comic points out that the regular {{w|helicopter}} is as close as most of us would ever get to levitating personal vehicles. But the company Alef has successfully designed a flying car.

;Jetpack
"Where's my {{w|jet pack}}?" is a common {{tvtropes|IWantMyJetPack|trope}}. There are various systems and {{w|Astronaut propulsion unit|analogues}} that could be considered jet packs in some sense, but devices to let individuals fly on Earth would be extremely dangerous, even if they could be made practical. A functioning jetpack would risk elevating people to dangerous altitudes while potentially accelerating them to dangerous velocities, make it both difficult and dangerous to steer. The high likelihood of fatal crashes means that a viable product is unlikely to ever exist - unless technologies will allow to augment humans (such as genetic engineering or cybernetics) to such degree, that they could ram the ground at top speed and remain unharmed.

;Moon colony
The basic {{w|Apollo_program| science and engineering}} {{w|International Space Station|exists}} exists to build some form of permanently manned settlement on the Moon, but doing so would be extremely expensive. The technology to exploit lunar resources, either for construction or life support, has not yet been developed, so all equipment and supplies would need to be continually transported from Earth. Commercial potential of such a base would be extremely limited, and no organization or group has been willing to spend the kind of money it would take.

;Self-driving car
Randall notes that these are "coming surprisingly soon." Self-driving cars have not become nearly as ubiquitous as was frequently predicted in 2016. As of 2024 (9 years after the release of this comic), there are various forms of self-driving with various degrees of advancement. The most impressive would be [https://www.tesla.com/support/autopilot Tesla's full self-driving beta], which is capable of performing acceptably in most situations, except for parking lot navigation. Other than Tesla, companies such as Google, Waabi, and Euler Motors are working on self-driving vehicles, though Tesla remains the [https://electrek.co/2023/07/13/tesla-most-wanted-car-brand-us-study/ most well-known amongst the general public]. All these vehicles still require a human driver present.

Self-driving cars has become a [[:Category:Self-driving cars|recurring topic]] on xkcd and they were mentioned again already in the title text of [[1625: Substitutions 2]] just two comics after this one.

;Floating sky city
Various science fiction sources imagined the idea of floating cities (e.g. {{w|Bespin}}, {{w|Mortal Engines Quartet}}). In reality, this seems highly unlikely to happen in the foreseeable future. Absent some form of levitation technology that doesn't even exist as a concept yet, the only ways to keep things floating inside a planet's atmosphere are to make use of either buoyancy or continually providing thrust and/or lift. But "cities are heavy". The amount of mass that any kind of city would have would require either an implausibly large volume to float by buoyancy, or an incredible amount of energy (continually provided) to supply thrust or lift. With any foreseeable technology, that's unlikely to ever be practical.

;Hoverboard
[[File:Red self-balancing two-wheeled board with a person standing on it.png|thumb|right|A self-balancing scooter, marketed as a "hoverboard"]]
The {{w|Hoverboard|levitating Hoverboard}} has been popularised by the {{w|Back_to_the_Future_Part_II|''Back To The Future'' franchise}} of films, with several attempts to fully emulate such a device with air-blast or magnetic levitation, but the ''term'' "Hoverboard" has ended up being applied to a {{w|Segway}}-like {{w|Self-balancing_two-wheeled_board|personal transport system}} that has at least become a mass-produced device (albeit with a number of {{w|Self-balancing_two-wheeled_board#Safety|safety concerns}}) even if it doesn't fly or levitate. The very concept of the hoverboard was therefore predicted to be reduced mostly to arguments between opposing camps of opinions; and then, in the title-text, the conclusion that giving up and resorting to old-fashioned walking is inferior to ''any'' of the possible alternatives.

;Robot butler
A long-held science fiction vision is a robot (presumably humanoid), that can perform household tasks, taking that burden off people. Randall mentions "Jeeves", saying "he wasn't that great". This is presumably a reference to the early search site {{w|Ask Jeeves}}, which used a stereotypical butler name. The concept was that the search engine could take on tasks for you, much as a butler would. However, it was only a search engine, incapable of performing any physical tasks, extremely limited in the non-physical tasks it could perform, limited in its accessibility, and not even a particularly good search engine in the first place.

In a broader sense, there do exist an increasing number of automated systems to do specific household tasks (such as {{w|Roomba|vacuuming}}), and voice-activated systems that can perform virtual tasks, like keeping schedules and looking up information, are {{w|Amazon Alexa|increasingly widespread}}. Since the comic, a generalized robot that can perform variety of physical tasks now exists in the form of the neo x1. Robots (both humanoid and otherwise) that can move and operate semi-autonomously are under development, but are neither sufficiently advanced nor sufficiently cost effective to replace human labor in most instances.

==Transcript==
:[A chart with three columns of text with only one entry to the left - which is written in the middle of the panel. Then there is one line going right from this text but soon it splits into seven lines going either up (3), almost straight (2) or down (2) ending in arrows that points to the next column with seven entries for different possible future inventions. From each of these entries a horizontal arrow continues to the last column at the right with seven more entries commenting on these inventions.]

:It's 2016 – Where's my...

::Flying car → They're called "helicopters"

::Jetpack → Turns out people are huge wimps about crashing

::Moon colony → No one has put up the cash

::Self-driving car → Coming surprisingly soon

::Floating sky city → Turns out cities are heavy

::Hoverboard → This question is now ambiguous thanks to a new scooter thing (and will lead to an argument about the meaning of "hoverboard" which is way less interesting than either kind of hoverboard)

::Robot butler → He was called "Jeeves" and he wasn't that great

{{comic discussion}}

[[Category:New Year]]
[[Category:Charts]]
[[Category:Robots]]
[[Category:Self-driving cars]]
[[Category:Back to the Future]]