explain xkcd - User contributions [en]

Talk:3041: Unit Circle

2025-01-24T09:42:32Z

172.69.195.200:

First [[Special:Contributions/162.158.175.72|162.158.175.72]] 23:00, 22 January 2025 (UTC)

This would actually be so helpful for my geometry class right now '''[[User:42.book.addict|42.book.addict]][[User talk:42.book.addict|Talk to me!]]''' 23:06, 22 January 2025 (UTC)
:Are you saying you have problem with abstract thinking? Why should matter if the unit circle had radius 1 yard, 1 foot, 1 meter or 1 lightsecond? -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 23:12, 22 January 2025 (UTC)
::I don’t like having things defined as “x” and like to have exact measurements. The diagram just looks cleaner to me that way '''[[User:42.book.addict|42.book.addict]][[User talk:42.book.addict|Talk to me!]]''' 23:38, 22 January 2025 (UTC)
:::There's nothing stopping you from considering non-dimensional lengths to be whatever unit you want. If you just write in, for example, "cm" after any linear dimensions, and corresponding units for areas and volumes, that's fine.[[Special:Contributions/162.158.158.169|162.158.158.169]] 14:24, 23 January 2025 (UTC)
::I prefer units of light-nanoseconds or the metric version parnsecs (don't think about it too hard :P) {{unsigned|SammyChips}} SammyChips 23:58, 22 January 2025 (UTC)
:::I like [[3038|square acrminutes per steradian]] '''[[User:42.book.addict|42.book.addict]][[User talk:42.book.addict|Talk to me!]]''' 02:38, 23 January 2025 (UTC)
:::Please sign off with <code><nowiki>~~~~</nowiki></code>, or change your signature to include a link to either your talk page or user page. Thank you! '''[[User:42.book.addict|42.book.addict]][[User talk:42.book.addict|Talk to me!]]''' 01:25, 23 January 2025 (UTC)
::::I did sign with <code><nowiki>~~~~</nowiki></code>, but the option for treating my signature as plain text was enabled. [[User:SammyChips|SammyChips]] ([[User talk:SammyChips|talk]]) 15:57, 23 January 2025 (UTC)
:::SammyChips, if that is supposed to be Parallax nano-seconds, you should understand that that is probably more like a Giga-Parsec. The parsec is the distance at which an object appears to move one second of arc when the Earth moves halfway around its orbit. (though I'm not sure which orientation.) [[User:Divad27182|Divad27182]] ([[User talk:Divad27182|talk]]) 03:34, 23 January 2025 (UTC)
::::I told you not to think too hard for that very reason :P It's actually parsec-nanosecond per year, but in a nod to the recent comics dealing with [[3038|unit cancelation]] and [[3040|making up personal scientific jargon]], I collapsed it into its own unit. For those who didn't get it, a light-nanosecond is pretty close to a foot, and the "parnsec" is pretty close to a meter. SammyChips 15:50, 23 January 2025 (UTC)
::::: You Americans will use anything but the metric system![[Special:Contributions/172.70.58.45|172.70.58.45]] 16:30, 23 January 2025 (UTC)
:::parallax giga-seconds?[[User:Lordpishky|Lordpishky]] ([[User talk:Lordpishky|talk]]) 19:20, 23 January 2025 (UTC)
:::My Millennium Falcon gets 14 parsecs to the Kessel Run, and that’s the way I likes it! [[Special:Contributions/172.68.186.34|172.68.186.34]] 06:26, 23 January 2025 (UTC)
:::I'm going to take all these desires for weird units with a barn-megaparsec of nackle. [[Special:Contributions/172.69.195.160|172.69.195.160]] 07:00, 23 January 2025 (UTC)
:yo Tori, [https://www.youtube.com/watch?v=VEJWE6cpqw0 ''this''] might help you with geometry too ;) [[User:CalibansCreations|'''Caliban''']] ([[User talk:CalibansCreations|talk]]) 11:14, 23 January 2025 (UTC)
::I’ve watched that video before-it’s really cool and it’s one of my favorite videos ever '''[[User:42.book.addict|42.book.addict]][[User talk:42.book.addict|Talk to me!]]''' 16:10, 23 January 2025 (UTC)

Are "they" also searching for {{w|Doubling the cube|Apollo's doubled altar}}? [[User:Divad27182|Divad27182]] ([[User talk:Divad27182|talk]]) 03:22, 23 January 2025 (UTC)

I guess the correct wording is that $\pi$ is a trancendent number. Some irrational numbers e.g. $\sqrt{2}$ can be constructed by compass and ruler. {{unsigned ip|172.68.185.165|07:12, 23 January 2025}}
:To be more precise, constructable irrational numbers are those that can be obtained through taking square roots, even repeatedly. Transcendental numbers are out, but so are things like cube roots. Note also that the fact that there are no "absolute units" of length is a quirk of Euclidean geometry -- in, say, hyperbolic world, a unit circle like this could actually work. [[Special:Contributions/172.68.213.153|172.68.213.153]] 09:10, 23 January 2025 (UTC)
::Watch out you don't make that unit circle too big, or the square's vertices might {{w|Ideal_triangle|stretch out to infinity}} and [[809|ignite the atmosphere]]! [[User:SammyChips|SammyChips]] ([[User talk:SammyChips|talk]]) 16:14, 23 January 2025 (UTC)

Didn't the unit kilogram lose some of it's mass? It may be working if something similar happened to this unit circle. [[Special:Contributions/172.69.214.117|172.69.214.117]] 15:43, 23 January 2025 (UTC)
:It probably gains mass. (Hard to tell, when the reference mass is the mass that may be changing... But it's what tends to be observed from how the IPK copies change. Could be the addition of small amounts of hydrogen onto the surface, or even mercury vapour escaping from the themometers/etc that tend to be around the reference masses. [[Special:Contributions/172.70.58.6|172.70.58.6]] 21:43, 23 January 2025 (UTC)

The unit circle has a diameter of 2 units by definition, as a circle's diameter is twice its radius. In this comic, the diameter of the circle is 89 pixels, measured from the center of the outline on one side to the center of the outline on the other side. This implies that at the scale of this scene, the "unit" is 44.5 pixels. Cueball is 201 pixels tall, making him 4.5 "units" tall. Are characters' relative heights consistent enough in ''xkcd'' for this to be meaningful? --[[User:Tepples|Tepples]] ([[User talk:Tepples|talk]]) 18:22, 23 January 2025 (UTC)

The only true unit of length is ~1.616*10^(-35) meters. Whether you want that to be the circle's radius or diameter would be a matter of convention, although it might help to point out that the Schwarzchild "radius" of a unit mass is two length units, which makes me think of a diameter instead. [[Special:Contributions/172.68.245.206|172.68.245.206]] 20:00, 23 January 2025 (UTC)

I'm surprised that this explanation doesn't cover the joke inherent in "dimensional analysts": This is obviously a reference to [https://en.wikipedia.org/wiki/Dimensional_analysis dimensional analysis], the process of cancelling out units in long chains (and the topic of [[3038: Uncanceled Units]]). [[User:Trimeta|Trimeta]] ([[User talk:Trimeta|talk]]) 01:52, 24 January 2025 (UTC)
:That all goes back to (at least!) [[687: Dimensional Analysis]], and has been covered since several times (I think at least one What If? mentions it), mildly surprised to see that there is not yet a Dimensional Analysis category.
:Though, if there was, I'm not sure I would add this to that. It would cover, in my view, all the cases where unit-type cancellations/uncancellations/recombinings are used for surprising(/blatantly incorrect) purposes, or as a comment on how they ''could/should'' (as per 3038). The dimensional analysts in ''this'' comic aren't changing how length is used (i.e. suddenly using it for for a surprising <length*weight unit>/<weight unit> reduction), and seem to be styled as ultra-practical mathematicians (getting their hands dirty with expeditions to find mythical objects) rather than ultra-theoretic ones (darned be what the real world is like, to experience, they'll imagine the world how [[224: Lisp|they want]] — or even [[505: A Bunch of Rocks|try to make it work that way]], though that probably involves getting one's hands dirty in a ''different'' way). One incarnation of the edit even had them as practically Indianna Joneses (named them as (action-)archeologists, having dug this object up, which I was glad to be changed, as there's little sign it was excavated and not just found in plain sight), which puts me at odds with them being actually called "dimensional analysts" in the aforementioned Dimensional Analysis sense, as they're not messing with the dimensional qualities. They're "arbitrarily de-abitrising" in a completely different way, setting up a single (non-compound) measurement unit in terms of [[2198: Throw#Table of distance units|all other similar units]], under the (mis?)impression that their newly considered one is fundamentally more 'true', not "having fun with unit''s''(-plural)".
:I'm sure the Explanation ''could'' cover Dimensional Analysis (perhaps try to explain their group-profession name to me, I'd have perhaps called them "practical mathemologists", or something like that), and you're free to do so if you think you have a handle on it, but I (for one) never saw a useful link between the two (even, tenuously, as being entirely opposite ends of the actual practical/theoretical spectrum), so didn't even start to think to link it up with an additional bit of explanation in this direction. Can't speak for anyone else, though, and perhaps your comment (and a complete disagreement with my own voiced interpretations) will inspire something of what you initially sought in vain... That's the beauty of the collaborative wikidocumentation process. ;) [[Special:Contributions/172.69.195.200|172.69.195.200]] 09:42, 24 January 2025 (UTC)

Talk:3016: Cold Air

2024-11-27T00:13:43Z

172.69.195.200:

Back In The Day, one of the idiot youngsters in a first-year chemistry lab, before leaving at the end of the afternoon, connected a water faucet to a natural-gas line (used for Bunsen burners) with a rubber hose, and opened both taps. By the next morning, much of the natural-gas network in the heart of the city was flooded. It took a while to get everything working again, and the cleanup wasn't cheap. [[User:BunsenH|BunsenH]] ([[User talk:BunsenH|talk]]) 22:50, 25 November 2024 (UTC)
:You have the right username to mention this! ;)
:Also, the 'big trick', back in my day, was to be at the (correct end of) the science-lab bench and briefly blow into a pipe (temporarily unplugged from the burner) just as you turn your tap on. Then watch as the rest of the row (downstream of your connection to the supply) have their active flames go out. ...but I leave it to your imagination the ''three'' main problems (and various other less major ones) with trying that, with the benefit of hindsight. [[Special:Contributions/172.69.195.201|172.69.195.201]] 00:02, 26 November 2024 (UTC)

Anyone understand the physics here? It seems clear that adding tanks of cool, dry air will make storms (and particularly tornados) far worse, not better, as the incoming hot, wet air will react with any released air to make even worse/dramatic weather patterns. But is there more to it? If the tanks are sealed, then effect could be muted by simply not releasing the stored air once the problem is realized, but this would be countered by at least two factors: First, the title text indicates that an additonal error was made resulting in it beingg impossible to seal the stored air completely (it escapes through the water system). But also, any time weather got bad enough to open leaks in the system, I think this would produce a catastrophic result as the storm mixed with all the cold dry air at once? [[User:Mneme|Mneme]] ([[User talk:Mneme|talk]]) 23:01, 25 November 2024 (UTC)
:My understanding is generally that explosive failure of a container with sufficient "anti-tornado" air inside is going to be non-trivial (and you face this threat constantly, in the settlement that has an "air tower", whereas tornados are relatively infrequent and mostly cross countryside). ''post-edit: And the editor who set up the current explanation seems to have had much the same idea... gratifying to know I'm on the same wavelength as at least one person!''
:And the water-connection would be bad due to (first) extremely pressurised water and (immediately afterwards) almost as pressurised air pushing through the areas plumbing systems, with unknown secondary effects such as effectively blowing empty any water-heaters that ''really'' shouldn't be left to be 'boiled dry' (after enough air bubbles in, the remaining water will soak up the burner heat and evaporate beyond design limitations, adding to the gas pressure ''and'' no longer moderating the effects on the boiler body itself; not sure exactly what will go wrong, but it may not be pretty). [[Special:Contributions/172.69.195.201|172.69.195.201]] 00:02, 26 November 2024 (UTC)

Without knowing which 'city' the diagram might be of (or, indeed, how figurative Cueball's illustrative figure might be), I checked the first "tornado alley" city I could think of and came up with {{w|One Kansas City Place}} as how tall the taller buildings might be. In that case, just shy of 200m (with spire on top) and 40-odd floors. The dimensions of the 3000psi tank (external, but ignoring support infrastructure) is somewhere around 400m in height, perhaps 600m side to side, presumably oblate spheroidal, so approaching (less thickness of container walls) 75 ''million'' m³ of compressed air. Which is compressed, and would otherwise be around 15,000 million m³ (15 km³!) of atmosphere if ever released. As a very vague upper limit. Notwithstanding the apparent use of an existing (ex-)water-tower in the titletext. But obviously there's possibly abstract and definitely reinterpretable alternative interpretations of the quantities that might be involved. [[Special:Contributions/172.69.195.225|172.69.195.225]] 00:48, 26 November 2024 (UTC)

It seems that the wiki math package <pre><math> </math></pre> Does not work properly, and returns an error Failed to parse <pre>(Missing <code>texvc</code> executable. Please see math/README to configure.):</pre> when I attempted to add the math describing the speed of the air using LaTeX [[Special:Contributions/172.68.22.92|172.68.22.92]] 01:06, 26 November 2024 (UTC)
:This is a long-standing error (at some point, one bit of update invalidated the rendering process, and nobody is currently able to update the other component/configuration).
:There are plenty of alternate ways to format a newly needed formula, without TeX, and anything that's the same as when it was pre-rendered will continue to show as the inline "formula image" (which I think is potentially worse, anyway, when it comes to accessibility issues). It's really not too hard to do it without the math-tag extension working properly, though. e.g. <table style="display: inline-table; line-height: 0.6em; text-align: center; vertical-align: middle; font-size:10pt; font-style: italic; text-size-adjust: none;"><tr><td style="border-bottom: 1px solid black;">p1•v1</td><td rowspan="2">=</td><td style="border-bottom: 1px solid black;">p2•v2</td></tr><tr><td>t1</td><td>t2</td></tr></table> ...as quick example with just a little bit of fine tuning applied. [[Special:Contributions/172.70.160.134|172.70.160.134]] 01:44, 26 November 2024 (UTC)

The statement that 3000PSI is 6x higher than known high pressure systems is false. Scuba tanks contain air at this pressure (240bar/3000psi) and the systems used to fill scuba tanks are twice that. {{unsigned ip|172.71.26.101|09:28, 26 November 2024}}
:Perform the wiki magic and add that source!--[[User:FrankHightower|FrankHightower]] ([[User talk:FrankHightower|talk]]) 15:04, 26 November 2024 (UTC)

[https://www.google.com/search?q=40+Bar+to+psi My calculator (Google)] says 400MPH is 644 KPH (not 500). Also 40 Bar seems to be well on the high side of 500psi (580psi).

''"winds of about 40-400 mph [1] (about 50-500 kph)" "about 40 bar [2] (about 500 psi)."''

--[[User:PRR|PRR]] ([[User talk:PRR|talk]]) 01:11, 26 November 2024 (UTC)
:The source says tornadoes go up to 318 mph (512 kph) but the [https://en.wikipedia.org/wiki/1999_Bridge_Creek%E2%80%93Moore_tornado strongest tornado on record] exceeded that. I couldn't confirm when I wrote whether that was ''actually'' the strongest, and since the only purpose of the number is to say "Cueball's windspeeds are way, way worse", I decided an upper bound of 400 covered it.--[[User:FrankHightower|FrankHightower]] ([[User talk:FrankHightower|talk]]) 15:04, 26 November 2024 (UTC)

"I decided an upper bound of 400 covered it." Somebody edited my words and omitted the key point: ARITHMETIC. English to Metric is NOT 4:5. --[[User:PRR|PRR]] ([[User talk:PRR|talk]]) 23:32, 26 November 2024 (UTC)
:Hmmm... "English to Metric". Strange phrase, for ''various'' reasons. ;) [[Special:Contributions/172.69.195.200|172.69.195.200]] 00:13, 27 November 2024 (UTC)

3014: Arizona Chess

2024-11-20T15:37:17Z

172.69.195.200: /* Explanation */

{{comic
| number = 3014
| date = November 20, 2024
| title = Arizona Chess
| image = arizona_chess_2x.png
| imagesize = 740x315px
| noexpand = true
| titletext = Sometimes, you have to sacrifice pieces to gain the advantage. Sometimes, to advance ... you have to fall back.
}}

==Explanation==
{{incomplete|Created by a DAYLIGHT SLAYING BOT - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

[[White Hat]] and [[Cueball]] are playing a game of chess, perhaps at a championship. White Hat is in the advantage, as he has one more pawn than Cueball and has more time on the {{w|chess clock|clock}}. However, Cueball has an unexpected advantage. The building is sited across the border of Arizona with another state, with White Hat on the Arizona side, and the game is being played at a very particular time of year. As Arizona doesn't do {{w|daylight saving time}}, unlike neighboring US states, only one clock gains an hour. White Hat's time remains normal, but Cueball's time "falls back" one hour, as his departure from daylight saving time occurs. Due to the way the timer apparently calibrates its display (perhaps in part based upon something like the self-adjusting [https://en.cppreference.com/w/c/chrono/localtime localtime()] function), Cueball is suddenly given more time in the game. White Hat, whose timer instance is governed by a different locale, protests as this is not typically how these clocks would function.

The title text is a pun with the idea of "falling back" strategically from an attack and the term "fall back" in the mnemonic used to remember which way the clock changes when we go in and out of DST: "spring forward, fall back" (we advance the clock forward when entering DST in the spring, and move it backward when leaving it in the fall).

Hawaii also doesn't observe DST, but since it's an achipelago it doesn't share a land border with any other state, so a game like this is not possible.
==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

:[White Hat and Cueball are sitting across from each other playing chess. The time, shown above them in white on a black screen, reads 6:35 for White Hat, and 0:28 for Cueball.]
:White Hat: It’s late, I’m up a pawn, and you’re out of time. It’s over.
:Cueball: Ah, you’re forgetting something.

:[Cueball gestures with one hand above the chessboard. His time now reads 0:19.]
:Cueball: Did you know this building straddles the Arizona border?
:Cueball: It actually runs right through the table. You're on the Arizona side.

:[Cueball raises his hand further to gesture at his time. It beeps and is now blank and white.]
:Cueball: This tournament started Saturday, November 2nd. Now it's almost 2AM on the 3rd.
:Cueball: And there's something you should know about Arizona.
:Chess clock: BEEP

:[White Hat raises his head slightly to look at the timer. Cueball's time now reads 60:07.]
:White Hat: '''''What?!''''' No! That's not how... '''''No!!'''''
:Cueball: Looks like it's daylight '''''slaying''''' time.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring White Hat]]
[[Category:Chess]]
[[Category:Daylight saving time]]

3013: Kedging Cannon

2024-11-20T10:57:40Z

172.69.195.200: /* Explanation */ Not very well justified (more than obvious, but why?)

{{comic
| number = 3013
| date = November 18, 2024
| title = Kedging Cannon
| image = kedging_cannon_2x.png
| imagesize = 740x259px
| noexpand = true
| titletext = The real key was inventing the windmill-powered winch.
}}

==Explanation==
{{incomplete|Created by a HEADCANNON. Do NOT delete this tag too soon.}}

Prior to the invention of powered ships, oceangoing vessels moved primarily by means of wind power, which meant that they were restricted by the direction and power of the winds. If a sailing vessel needs to travel upwind (against the wind), they typically make use of a technique called {{w|Tacking_(sailing)|tacking}} (or "tacking against the wind") which involves zigzagging across the wind's direction. This method is significantly slower and more difficult than traveling downwind, but it makes upwind navigation possible.

This comic portrays a fictional scenario where a ship's captain, apparently unfamiliar with tacking, has developed an alternative method based on {{w|kedging}} (also known as warping).

The basics of kedging are not dissimilar to the comic: a boat affixes a rope or chain to an anchor point (such as a literal anchor) and winches itself closer. Traditionally kedging involves deploying an anchor from the vessel, either manually or via a smaller boat, and then {{w|winch|winching}} the ship toward the anchor point using ropes or chains. This is a real method, but is clearly very slow and labor intensive. Generally kedging is only effective in shallow waters and employed when tacking is not an option, as for example in harbors or narrow channels where space is tightly constricted. The captain in this strip appears to be using it for long-distance travel, which would be highly impractical. What's more, he deploys his anchor with a cannon, wasting large amounts of gunpowder (although with the setup as depicted, wasting gunpowder would be the least of a ship's concerns, as firing something the weight of an anchor any meaningful distance would require so much force it would outright rupture just about any age of sail artillery piece{{acn}}), all while a confused Cueball looks on, wondering why the Captain isn't trying to use tacking instead.

This approach to transportation has been used in war when the wind halts{{acn}}, with ongoing gunfire. This may be where the concept of using a cannon to deploy the anchor came from, as such a situation may involve an excess supply of gunpowder.

Where the water is too deep for the anchor to reach the bottom, a so-called {{w|sea anchor}} could theoretically be used, but would be even less practical. Kedging with a sea anchor would effectively be a very slow and inefficient version of rowing, which is an alternative (albeit labor-intensive) method to travel against the wind.

The title text indicates that the captain's system has evolved to incorporate a windmill mechanism that harnesses wind power to draw in the kedging rope. This implies that there is indeed sufficient wind that could be used for tacking, as otherwise the windmill would be ineffective. Likely this is a ridiculously inefficient {{w|Rube Goldberg machine|Rube-Goldberg-like}} solution to wind propulsion, if tacking has been discovered, and an ingenious energy saver (if heavy and expensive) if not. An analysis of the efficiency is below.

==In real life==
On some rivers, {{w|Chain_boat|chain boats}} were used for about a century. A chain would be laid the length of the river, and the boat used a winch to pull itself along the chain. Rudders and booms could replace the chain in the center of the river even around bends. It turned out to be very difficult to drive the chain with enough force - several techniques were attempted.

{{cot|Speed and economic analysis of dual wind-winched kedging cannons compared to tacking}}
A dual-anchor kedging cannon system for sailing upwind, consisting of:
* Two kedging cannons firing 16 kg anchors
* 6-meter diameter windmill powering winch system
* Dual-winch setup for continuous operation
* Operating in 15 knot headwind conditions

Vessel specifications:
* Length: 30 feet (9.1 meters)
* Displacement: 10,000 lbs (4536 kg)
* Sail area: 600 sq ft (55.7 m²)
* Wetted surface: 40 m²
* Frontal area: 8 m²

;Wind power generation
Available wind power is given by:
''P'' = ½''ρAv''³''η''
where:
* ''ρ'' = 1.225 kg/m³ (air density)
* ''A'' = ''π''(''D''/2)² = 28.3 m² (windmill area)
* ''v'' = 7.72 m/s (wind speed)
* ''η'' = 0.245 (combined efficiency)

This yields 1.95 kW of usable power.

;Drag forces
Total drag combines water and air resistance:
''F''drag = ''F''water + ''F''wind
where:
* ''F''water = ½''ρ''w''C''d''A''w''v''²
* ''F''wind = ½''ρ''a''C''a''A''f''v''²

Using:
* Water density (''ρ''w) = 1025 kg/m³
* Hull drag coefficient (''C''d) = 0.04
* Wetted area (''A''w) = 40 m²
* Air density (''ρ''a) = 1.225 kg/m³
* Air drag coefficient (''C''a) = 0.8
* Frontal area (''A''f) = 8 m²

Total drag force = 1053.4 N

;Anchor ballistics
For 300 m range with 45° launch angle:
* Required velocity = 54.7 m/s
* Launch energy = 23.7 kJ
* Black powder energy per shot = 680.4 kJ
* Launch efficiency = 3.5%

;System performance
* Winch speed = 3.60 knots
* Cycle time = 194.7 seconds
* Effective speed = 3.04 knots
* Compared to tacking speed = 4.95 knots
* Speed ratio (kedging/tacking) = 0.61

;Economic analysis
* Shots needed per nautical mile: 6.1
* Black powder cost per shot: $10 (0.5 lbs @ $20/lb)
* Cost per nautical mile: $60.76
* Powder consumption: 9.2 lbs/hour
* Operating cost: $184.90/hour

Example 100 nmi journey:
* Total powder cost: $6,076.12
* Journey time: 32.9 hours

;Conclusion
The dual-anchor kedging cannon system is both slower and significantly more expensive than traditional tacking:

Speed disadvantage:
* Achieves only 61% of tacking speed
* 100 nmi journey takes 32.9 hours vs 20.2 hours tacking

Economic disadvantage:
* High powder costs ($60.76 per nautical mile)
* Requires significant powder storage (303 lbs for 100 nmi journey)
* Additional wear and tear on mechanical systems

Key limiting factors:
* Limited wind power available (1.95 kW from 6 m windmill)
* High drag forces (1053.4 N total)
* Poor ballistic efficiency (3.5% of powder energy converts to useful launch)
* Long cycle times due to realistic winching speeds

The system could potentially be improved by:
* Larger windmill (though practical size limits on boats)
* More aerodynamic anchor design
* More efficient powder-to-launch energy conversion
* Reduced transfer time between anchors

Therefore, given both the energy constraints and economic factors, traditional tacking remains far more practical for upwind progress. The key insight is that while the kedging cannon seems to "cheat" the wind by going straight upwind, it actually requires converting wind energy to mechanical work less efficiently than a well-designed sail plan, while also consuming expensive gunpowder. The indirect path of tacking makes better use of the available wind force with no consumable costs.
{{cob}}

==Transcript==
:[A two-masted sailing ship with its sails up is floating on a calm sea with tiny waves. Two tiny figures can be seen at the ship's bow. One of them is speaking. In the next panel it becomes clear this is the captain.]
:Captain: I hope someday someone invents a way to sail upwind.
:Captain: Using the kedging cannon just wastes so much gunpowder.

:[Close-up on the deck of the ship, showing two persons behind the taffrail. Cueball is standing behind the ship's captain and talking to him. The captain is wearing a black bicorne navy hat and aiming a cannon containing an anchor forward. Chains are draped from the cannon.]
:Cueball: The '''''what?'''''
:Cueball: Wait, do you not know how to sail upwind? Is that why your ship takes forever to--
:Captain: Stand by...'''''Fire!'''''

:[Distant shot showing the anchor and its chain being launched out in front of the ship, towards the right of the panel. Cueball and the Captain can still be seen behind the cannon. The cannon has exhaust fumes coming out in front and the sound it makes is indicated:]
:Cannon: ''Boom''

:[Same setting but the anchor is now under water and the chain has become taut as the ship is dragged forward to the right. Movement lines behind the ship indicated its progress and it is also further into the frame than the previous panel. The movement is caused by pulling the chain back in on the ship. This produces a series of sounds:]
:Dragging chain: ''Click click click''

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Characters with hats]]

Talk:Header text

2024-11-18T15:33:33Z

172.69.195.200:

;Localized versions

Currently to me the header text is in German (as I live in Germany):
:Triff Randall Munroe in Berlin am 15. Oktober 2019!
:Hier die deutsche Ausgabe vorbestellen!
(Meet Randall Munroe in Berlin on 15th of October 2019! Preorder the german version here) where "Hier" (here) is a link.
4 odd things I noticed about this:
*It mentions the German version, but not the German verison of what. The book isn't even mentioned.
*When I (re)load the page, for a moment I get the image about winning a stick-figure-sketch of myself.
*XKCD does not use means like other pages (e.g. [[713: GeoIP]] to identify my language. As I am using a swedish VPN, I usually get advertisements in swedish (and redirections to swedish homepages, etc.). Maybe it is my browser settings which are set to German. Can someone identify the method used?
*The link leads to "https://www.xkcd.com/%22https://www.randomhouse.de/Buch/HOW-TO-Wie-man-s-hinkriegt/Randall-Munroe/Penguin/e547637.rhd?utm_source=autorenblog&utm_medium=banner&utm_campaign=how_to\%22" - a 404 page. (getting rid of the part before the 2nd https gets you to the page of the german publisher.
Someone got an idea on how to put this into the wiki properly? Are there other language versions as well? --[[User:Lupo|Lupo]] ([[User talk:Lupo|talk]]) 06:38, 16 August 2019 (UTC)

Yeah there is, in the UK the text changes to "I'll be coming to the UK for [https://xkcd.com/how-to/#tourdates the book tour]." There is Javascript in the page which sends a request to https://c.xkcd.com/how-to/news which is simply redirected (for me to https://xkcd.com/ukNews ) presumably based on GeoIP, definitely not a browser locale setting. Not sure how you would get them all, maybe iterate country codes through the start of the URL? I tried deNews which worked. [[Special:Contributions/162.158.34.172|162.158.34.172]] 17:57, 30 August 2019 (UTC)

;Black lives matter

As a note to whoever archieves this (I don't have the time to do it properly myself right now), today I noticed the first time, that the header text, which I think was empty recently changed to a cueball stating "black lives matter" and a link "how to help" to joincampaignzero.org. It might have been up for a few days. --[[User:Lupo|Lupo]] ([[User talk:Lupo|talk]]) 06:48, 4 June 2020 (UTC)

{{done}}; sorry I didn't notice your post here on the talk page before adding it. It seems like we should feature this article page more prominently somehow so people become aware of it. I'm not sure how that should be accomplished. [[User:JohnHawkinson|JohnHawkinson]] ([[User talk:JohnHawkinson|talk]]) 19:00, 9 June 2020 (UTC)
:No need to be sorry. I could've done it myself, but there seems to be (as you mention in the post below) a quite formal structure to the page, and currently I don't find the time to spend as much time on this wiki as I used to, so instead I just thought I'd put together a note, in case it is noticed in the future, to then have a rough starting date.--[[User:Lupo|Lupo]] ([[User talk:Lupo|talk]]) 06:01, 10 June 2020 (UTC)

;Formatting this page as a visual gallery?

It seems like there would be a lot of value in having this page as a visual archive of all of the header illustrations, not merely reducing them to plain text. Is there a reason that approach was not chosen, and are there any thoughts about how best to format and manage it? [[User:JohnHawkinson|JohnHawkinson]] ([[User talk:JohnHawkinson|talk]]) 19:01, 9 June 2020 (UTC)
:I guess it is because it is a much larger task to include all those images. But feel free to begin. I have created most of he text on this page, so I have already used a lot of time. There are links to the web archive where they can be seen. This was seen by me as a transcript of these, so it is possible to search for text bites. It will be a very long page to load if you include pictures directly here as well. But a link to the images placed in another page could be a possibility. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 07:53, 20 July 2020 (UTC)

;Recent BLM edits

I disagree with most of [[:User:Kynde]]'s [https://www.explainxkcd.com/wiki/index.php?title=xkcd_Header_text&oldid=194829 edits] from just now:
* Links to "Black Lives Matter" should remain to the url https://blacklivesmatter.com/ rather than hiding it behind an anchor, as [https://blacklivesmatter.com/ Black Lives Matter], because "Black Lives Matter" is not a clear unambiguous entity, and where the point is to show the URL, we should do so.
* That necessarily implies https://joincampaignzero.org should get the same treatment.
* By removing the June 17 section and combining into the June 3 section, it makes no sense to now say "The link goes to" and list where it went on June 3–16 but went elsewhere from June 17–present.
* "Fill it in when it changes" just looks bad. It is a comment to editors, not readers, and the wiki is for readers. It should be deleted or restored to a comment.

I would make all of these changes, but they have the appearance of edit warring, so I wanted to raise them here first. Thank you. [[User:JohnHawkinson|JohnHawkinson]] ([[User talk:JohnHawkinson|talk]]) 18:02, 18 July 2020 (UTC)
:I just tried to use the same format I have used on all the other changes to header texts over the last couple of years. I have also inserted link like this before. I can see this matter is much more sensitive than any previously used in the header (or at least where any noticed this page.). If you feel strongly about this, then please feel free to change it back, or change my edits somehow. I would prefer this entry does not diverge from the format of all the others, but since this header means a lot to many people, I will not change it back if you think it should be formatted differently than the rest. If you really wish, undo my changes, I will not redo them then. But I think this is just the same header, with a new link and thus did not warrant a new entry. I have done similar with other headers where just a small thing changes (yes I know the link is the important part here, and thus not a small change, but it did not change the header text or image!) --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 07:57, 20 July 2020 (UTC)

;Ideas about the Jan 31, 2022 countdown?
It seems like the countdown's code is on github: https://github.com/munvoseli/xkcd-countdown
I can't seem to find any hints there what it's about, though.
--[[Special:Contributions/162.158.159.29|162.158.159.29]] 13:01, 11 January 2022 (UTC)
Nevermind, that's just the code of a progress tracker at https://munvoseli.github.io/xkcd-countdown/ .
--[[Special:Contributions/172.70.90.173|172.70.90.173]] 13:19, 11 January 2022 (UTC)

;1047

Comic 1047 (Approximations) has unique header text. [[Special:Contributions/172.70.110.245|172.70.110.245]] 16:12, 31 January 2022 (UTC)

;Comic-specific section incomplete

The section on comic-specific headers seems to be missing many examples. I found quite a few from just a couple minutes of browsing random comics (405, 432, 433, 826, 896), so I suspect a thorough search would turn up a lot more. [[Special:Contributions/162.158.146.136|162.158.146.136]] 15:21, 3 July 2023 (UTC)
:Unfortunately you're right. This page needs much more attention, I added an incomplete tag. --[[User:FaviFake|FaviFake]] ([[User talk:FaviFake|talk]]) 21:31, 3 July 2023 (UTC)

;Missing "A Smarter Planet comics unique header text

The [https://web.archive.org/web/20190102070937/https://xkcd.com/asmarterplanet archived page of xkcd.com/asmarterplanet] shows this header text: "Bonus xkcd comics done for IBM's "[http://asmarterplanet.com/ A Smarter Planet]" initiative.", and it's missing fromt the page --[[User:FaviFake|FaviFake]] ([[User talk:FaviFake|talk]]) 09:10, 18 August 2023 (UTC)

;Word salad
This sentence in the header is not comprehensible: "In recent times there has been very long between the old go to text has been used for extended periods though." I'm not actually sure enough what it means to correct it. [[User:Nitpicking|Nitpicking]] ([[User talk:Nitpicking|talk]]) 14:15, 18 November 2024 (UTC)
:I'm guessing something like "In recent times there has '''not''' been very long between '''changes. T'''he old go'''-'''to text has been used for extended periods''',''' though."
:i.e., there have been rapid turn-arounds (to a topical update, then back to 'normal'). But, more time than not, it tends to sit on a more general non-topical message.
:I've not actually checked if this is true, or what edits might have been incrementally made to saladise the words that are there. [[Special:Contributions/172.69.195.200|172.69.195.200]] 15:33, 18 November 2024 (UTC)

1611: Baking Soda and Vinegar

2024-09-13T13:13:59Z

172.69.195.200: /* Transcript */

{{comic
| number = 1611
| date = December 2, 2015
| title = Baking Soda and Vinegar
| image = baking_soda_and_vinegar.png
| titletext = Sure, it may not meet science fair standards, but I want credit for getting my baking soda and vinegar mountain added to the Decade Volcanoes list.
}}

==Explanation==
In popular fiction (and maybe in part in fact) the "{{w|Sodium bicarbonate|Baking Soda}} and {{w|Vinegar}}" {{w|volcano}} is often a staple image of the science nerd at the science fair (see [https://sciencebob.com/the-erupting-volcano/ example here]), unless all the science nerds are doing ''real'' imaginative science and the student(s) with the volcano exhibit are dragging out the old hackneyed stereotype. It may also be age-dependent, this being something that is relatively advanced science for the lower grades but rather a childish experiment in the hands of older students.

[[Ponytail]] is about to point out any one of a number of flaws with the trope. For one thing, while the project may exhibit interesting physical phenomena of the sort that some scientists study, the project itself doesn't actually teach anything about the scientific method. {{w|Science fair|Actual science fairs}} are usually intended to teach students about the scientific method by exercising it firsthand: subjecting hypotheses to appropriately rigorous experimentation and reporting on the results. The cliché volcano exhibit doesn't teach any of this and may instead reinforce the idea that science is about cool explosions and not a system of inquiry. Further, the exhibit doesn't (usually) actually demonstrate anything about volcanic activity: it is relatively simple chemistry involving the reaction of acetic acid in vinegar and sodium bicarbonate in baking soda to produce sodium acetate and (notably) a vigorous froth made up of bubbles of carbon dioxide. It is often dressed up to look more impressive, such as by using dye or other additives to make the 'eruption' look more 'realistic,' but it often fails to replicate important features of actual volcanic eruptions, such as the flow of lava, associated seismic events or the collapse of part of the volcanic crater. Most people doing soda volcano projects don't even explain what's happening.

[[Jill]] has made a little more of her volcano, however, as it seems to go beyond simple chemistry. The model replicates many of the dangers (aside from the pure lava) of a volcano and appears to have been given scaled-down vehicles (not visible in the comic) trying (and failing) to escape the dangers of the resultant mud-flows (a.k.a. {{w|lahar|lahars}} in professional terminology) being modeled. Ponytail contradicts her early reaction by also not liking the more realistic model, although it is the carnage she dislikes, not that it has more correct details of the eruption itself.

Even more, this is not an isolated 'model volcano' but a vinegar-powered representation of a geological 'hot spot', such as with the islands of Hawaii, in which the spot moves with respect to the Earth's crust (or vice-versa) and generates a new volcano some way off. Despite this model being supported on a table, it appears that the 'project' extends some way beyond that and has somehow contrived further eruptions away from the table, the room and probably even the building.

The 'project' seems to be turning into a very thorough model of a much larger geological process (a {{w|Supervolcano}} like {{w|Yellowstone Caldera|the one}} under {{w|Yellowstone National Park|Yellowstone}}) and destined to produce a ''very real'' {{w|volcanic winter}}. Where a magma-powered volcano could produce vast clouds of dust, preventing the sun's energy from warming the Earth, in this case it's the airborne salt (probably sodium acetate) from the chemical reaction that appears to be in danger of causing crop failure. There's no mention of the corresponding environmental effects of the vast amounts of carbon dioxide (and/or aqueous carbonic acid) necessarily released in proportion to the ejected salt (presumably itself not left in solution).

It is especially troubling that the child even mentions that her model volcano is an offshoot of a baking soda ''super''volcano. Supervolcanoes are massive volcanoes, far larger than even those on the list of {{w|Decade Volcanoes}} (mentioned in the title text), whose eruption would likely trigger species-level extinction events comparable to the dinosaur extinction. The best hope humanity has here is that the baking soda supervolcano is as small compared to supervolcanoes as the girl's baking soda volcano is to real volcanoes; the ratio is about 1:600 (for a cinder cone volcano), implying that the baking soda supervolcano, if modeled after Yellowstone, would only be about 80 meters by 120 meters in size. Unfortunately, the climatological and economic symptoms witnessed outside and on the grain market suggest that the model supervolcano is not very small.

When someone (presumably Megan) says she wants to stop learning, Jill grimly states that "Soon, we all will", alluding to their impending doom.

[[Randall]] has mentioned supervolcanoes before in [[1053: Ten Thousand]] (title text) and [[1159: Countdown]], making it a recurring interest of his. The volcano [http://www.explainxkcd.com/wiki/images/6/6a/Entire_Volcano_zoom_out.png Mount Doom] was depicted to the far left in the game [[1608: Hoverboard]] released a week before this comic. It may not be a supervolcano, but quite potent anyway... Later this comic was directly referenced in the seventh panel of [[1714: Volcano Types]], where it is up to the reader to decide it, this is Jill's model people or what happens outside on her supervolcano.

In the title text the student expects extra credit for getting her model volcano added to the Decade Volcanoes list, a list maintained by {{w|International Association of Volcanology and Chemistry of the Earth's Interior}} of the world's most dangerous volcanoes (currently 16). It is either an absurd notion or a very troubling achievement that a science fair project could achieve the threat level posed by the likes of {{w|Mount Vesuvius}} (which destroyed ancient Pompeii in Italy, and threatens modern-day Naples in the same manner), {{w|Mount Rainier}} (whose lahars could potentially destroy parts of Seattle) or {{w|Mauna Loa}} (which could create a massive landslide, triggering a major tsunami that would threaten all of Hawaii). But if the volcano erupting outside is scaled down to match the scale of her original model volcano, at least that means that it was only a "local" volcano event and not a supervolcano event that she created, so it would only doom the local area.

==Transcript==
:[Ponytail is standing behind Jill who has one hand up. They are looking at a table with a model volcano.]
:Jill: My science project is a baking soda and vinegar volcano!

:[A larger frame that includes Megan who stands to the right. Ponytail is a little further back and Jill has taken her hand down. The baking soda volcano erupts in a small upwards explosion.]
:Ponytail: Why do people make these? It isn't really even a science project. It doesn't teach anything about-
:Volcano: '''''Foom!'''''

:[Smaller frame again. Ponytail has moved closer to the table, Jill moves around the table to the right, pointing at the volcano while Megan walks closer. The "lava" flows down the volcano on both sides.]
:Jill: See how the baking soda and vinegar mix with mud and ice to form deadly flowing lahars?

:[Zoom in on Jill's head close to the stream of lava going down the lower part of the volcano's right slope.]
:Jill: You can see the tiny cars trying to flee.
:Jill: Whoops! Too slow.

:[Zoom in on Ponytail.]
:Ponytail: Um. This is a bit grim.
:Jill (off panel): Learning!

:[Jill stand to the right of the table looking at the now still volcano. Shaky lines surround a sound effect written over the top of this slim frame:]
: ''Rumble''

:[Back to showing all three as before. Jill lifts a finger in the air.]
:Jill: And now we're learning that this volcano is an offshoot of a vinegar hotspot rising from deep within the earth.
:Jill: ''Annnd...''

:[Jill turns away from the table looking right as a loud noise can be heard off-panel, depicted in white text on a wavy black bubble:]
:<big>''Boooom''</big>

:[Megan has walked over to a window to the right. It has the blinds drawn down. She opens a hole in the blinds by pulling down in the middle. It is dark outside. The other two are outside the frame to the left.]
:Jill (off panel): The baking soda supervolcano erupts, injecting clouds of salt into the stratosphere.
:Megan: Why is it getting dark outside?
:Jill (off panel): Learning is fun!

:[We see Jill standing close to the table, of which only the right leg can be seen. She holds up a tablet with a graph showing a rising trend. The other two are both out of the frame.]
:Jill: Sunlight dims. The earth cools. Summer frosts form. Crops die. We check the markets. Grain prices are rising.
:Megan (off panel): I want to stop learning now.
:Jill: Soon, we all will.

==Trivia==
{{w|Campi Flegrei}} is a real-life example of her project.

{{comic discussion}}

[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Jill]]
[[Category:Science]]
[[Category:Geology]]
[[Category:Volcanoes]]

2922: Pub Trivia

2024-04-19T14:12:41Z

172.69.195.200: /* Explanation */

{{comic
| number = 2922
| date = April 19, 2024
| title = Pub Trivia
| image = pub_trivia_2x.png
| imagesize = 422x666px
| noexpand = true
| titletext = Bonus question: Where is London located? (a) The British Isles (b) Great Britain and Northern Ireland (c) The UK (d) Europe (or 'the EU') (e) Greater London
}}

==Explanation==
{{incomplete|Created by a TRIVIAL BOT - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

The comic shows Cueball reading off bad trivia questions which are either confusing or don't have an answer.
The caption states that this is because he was paid to sabotage other bars that offer trivia so that people will want to go to the one that hired him.

1. Which member of BTS has a birthday this year?

BTS is a K-Pop group. Every member would have a birthday in 1 year.

2. How many sides does a platonic solid have?

4, 6, 8, 12, or 20 in Euclidean 3-space

3. What is the smallest lake in the world?

Unknowable as there are many small bodies of water in the world, and determining which is the smallest while still being large enough to count as a lake is a complicated question.

4. Which Steven Spielberg movie features more shark attacks? Jaws (1875) or Lincoln (2012)

Jaws, as Lincoln has a surprising lack of shark attacks.

5. How many planets were there originally?

Question lacks context, since it doesn't define what originally means, and there is no way to know when humans first found out that the wandering stars were actually other worlds, or that Earth is a planet.

6. What NFL player has scored the most points outside of a game?

As points are not usually scored outside of games, this is a nonsense question.

7. The Wright brothers built the first airplane. Who built the last one?

Since airplanes are built continuously, there is no way to know who built the last one.

8. Is every even number greater than2 the sum of two primes?

This is [https://en.wikipedia.org/wiki/Goldbach%27s_conjecture|an open question in math].

9. Not counting Canberra, what city is the capitol of Australia?

Nonsense question, since each country only has one capitol (citation needed)

10. Who played the drums?

Lots of people, needs context.

The alt-text bonus question:

Bonus question: Where is London located? (a) The British Isles (b) Great Britain and Northern Ireland (c) The UK (d) Europe (or 'the EU') (e) Greater London

All choices are technically correct as they are all names for the same geographical area.

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

{{comic discussion}}