explain xkcd - User contributions [en]

Talk:605: Extrapolating

2025-05-15T07:05:05Z

172.71.178.56:

If I post a comment on this page, this page will someday consume all the bandwidth of the world. Eh, what the heck.[[Special:Contributions/108.162.216.158|108.162.216.158]] 02:45, 1 September 2015 (UTC)

: Don't worry. That's not how bandwidth works. And even it was, its growth can also be extrapolated. [[User:Flewk|flewk]] ([[User talk:Flewk|talk]]) 09:59, 8 January 2016 (UTC)

What is we extrapolate at the time point just before she has one husband? {{unsigned ip|108.162.222.75}}

Why does doing this with my paycheck / payday never work? Though it seems this is the logic bills follow. [[Special:Contributions/108.162.216.166|108.162.216.166]] 19:25, 27 July 2017 (UTC)

This reminds me of the Steven Wright joke: "When I turned two I was really anxious, because I'd doubled my age in a year. I thought, if this keeps up, by the time I'm six I'll be ninety."

This comic also demonstrates the problem with not using enough data points. If all the days of her life were to be plotted on the x-axis, then adding a value 1 on her wedding night could look like an outlier and would be ignored. Even if the one different data point was included, the line of best fit for extrapolation would still be very close to 0. [[User:Nutster|Nutster]] ([[User talk:Nutster|talk]]) 22:53, 7 March 2021 (UTC)

Did anyone notice that the graph is negative before yesterday? What does a negative number of husbands even mean? {{unsigned ip|162.158.91.129|05:35, 15 May 2025}}
:Depends upon the scale. Could be a positive number of wives/boyfriends/friends-with-benefits/toy-boys/sugar-daddies/room-mates/personal-clones/roombas/dragons... [[Special:Contributions/172.71.178.56|172.71.178.56]] 07:05, 15 May 2025 (UTC)

2859: Oceanography Gift

2023-11-25T19:51:41Z

172.71.178.56: /* Explanation */

{{comic
| number = 2859
| date = November 24, 2023
| title = Oceanography Gift
| image = oceanography_gift_2x.png
| imagesize = 740x272px
| noexpand = true
| titletext = Shipping times vary. Same-ocean delivery may only take a few years, but delivery from the Weddell Sea in Antarctica may take multiple decades, and molecules meant for inland seas like the Mediterranean may be returned as undeliverable by surface currents.
}}

==Explanation==
{{incomplete|Created ten years ago by a WATER CURRENT - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
In this comic, [[Randall]] seems inspired by the timing of {{w|ocean current}}s, much as he has previously been with [[2805: Global Atmospheric Circulation|air currents]], although he may even have already considered some of the technicalities [[1675: Message in a Bottle|prior to that]]. As supporting evidence, he provides a DOI reference to a 2016 Jönsson & Watson open-access article in Nature Communications, '[https://www.nature.com/articles/ncomms11239 The timescales of global surface-ocean connectivity]'.

In this specific (fictional) example, the water dumped into the ocean today will take ten years to circulate round to the depicted neighbouring coastline (wherever that is). Which implies significant planning ahead is necessary before posting water to someone. And a lot of presumption about the lack of any other dispersal/dilution, or that some degree of fungibility is acceptable, so long as it is ''{{w|Ship of Theseus|philsophically}}'' the same group of molecules involved.

The title text mentions that "same-ocean delivery" may only take a few years, as the coast lines are in the same general body of circulating water, and doesn't have to pass around large obstacles (like continents) or through small gaps (straits). But if you wish delivery from {{w|Weddell Sea}} it may take decades. The Weddell lies near the {{w|Antarctic Peninsula}}, part of the {{w|Southern Ocean}} whose circulation can be considered largely isolated from the neighbouring bodies of water by the {{w|Antarctic Circumpolar Current}}. In particular, that area contains the {{w|Weddell Gyre}} one of the two {{w|ocean gyre}}s in that area.

The title text also mentions {{w|inland sea}}s, which can be generalised as bodies of water that are very large in area but either completely surrounded by dry land or connected to an ocean only by a river or a strait. He mentions the {{w|Mediterranean Sea}} which is only connected to the {{w|Atlantic Ocean}} through the narrow {{w|Strait of Gibraltar}}; the intention of the title text is to suggest that water molecules dumped in an ocean would not get to appear in such a sea (except by {{w|evaporation}} and re{{w|precipitation}}) into its catchment area) and thus they can only ever circulate back to the dumping point (deemed 'undeliverable').

In reality, the Mediterranean Sea is not completely cut off from the main oceans and surface currents actually do reach into and around the Mediterranean. The natural loss from evaporation is not fully compensated for by the inflow of the incident rivers from southern Europe, North Africa and Asia, directly or via other attached bodies of water (e.g. the Black Sea). The movement of water also involves the deeper Levantine Intermediate Waters layer (a subsurface current) which exits via Gibraltar and helps to further draw current inwards at the surface level. As such, except for a limited amount of water which reverses direction within the extreme western end the Mediterranean, it is more true to say that ''surface'' currents cannot actually transport water from within the sea outwards into the Atlantic (and beyond).

The {{w|Caspian Sea}} is a real inland sea that has no outlet to any oceans and only inlets from rivers, one of a number of [[2325: Endorheic Basin|endorheic basins]] that are also {{w|Endorheic lake|lakes}}, and thus trivially isolated from all other maritime currents.

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

:[Cueball and Megan are standing thigh deep, at either edge of a stretch of water between two steep but walkable shorelines.]

:[Cueball, at the left, is apparently opening bottles of water and pouring them into the sea while recording himself.]
:Cueball: Happy birthday!
:Cueball: I got you these water molecules.
:[Sound effects:] (click) (pour)

:[The water between has a morass of short swirling arrows indicating movement. In the air above this there is a square-bracketted 'label']
:[Label:] 10 years pass 

:[Megan, at the right, is dipping bottles into the water to fill them]
:Megan: Aww, thank you!
:[Sound effect:] (scoop)

:[Text below comic:]
: Global surface ocean connectivity times are ≤10 years (Jönsson & Watson, 2016, DOI:10.1038/ncomms11239), so if you're willing to plan ahead, you can pour water into the ocean while wishing someone a happy birthday, and then in 10 years let them know they can pick up their gift at the nearest coastline.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics with lowercase text]]

2519: Sloped Border

2023-11-21T22:20:54Z

172.71.178.56: Undo revision 329410 by Pie Guy (talk) Looking at what this edit 'simplified', it stopped explaining most of what it had done. Yes, maybe an edit needed, but clearly hadn't been read and understood.

{{comic
| number = 2519
| date = September 22, 2021
| title = Sloped Border
| image = sloped_border.png
| titletext = "The slope will be 74° at ground level." "Okay, I think we can hack together a ... wait, why did they specify ground level? It's 74° everywhere, right? ... Oh no, there's a whole section in the treaty labeled 'curvature.'"
}}

==Explanation==

Every country has land and sea {{w|international borders}} that demarcate the extent of their territory and their legal jurisdiction. These borders are established through law, treaty, or consensus. Establishing an international border is maintained by present-day customs, immigration, and security checks. Some countries (like {{w|Cyprus}}) have established a {{w|buffer zone}} outside of their international border in order to gain additional protection during a conflict, and most countries have an offshore {{w|Exclusive Economic Zone}} in order to preserve exclusive proprietorship of marine resources such as oilfields and fishing grounds.

In this comic, Cueball and Blondie have established a "sloped" international border through a treaty. Usually borders are perpendicular to the ground{{citation needed}} so that all the air(space) above the ground belongs to the same country. This is called {{w|Air sovereignty}}. Thus it suffices to define the border on the earth surface, as 1D lines across the curved 2D surface. The precise definition is that a line from the center of the Earth through the point of the border is drawn. Sloped terrain is immaterial to the border of the air sovereignty which is still vertical, even if not perpendicular to the terrain.

If the borders were sloped (with respect to the horizontal ground level) an airplane would need to know its precise height to decide if another country's jurisdiction currently applies. With the help of the {{w|Global Positioning System}} this would be in principle possible, although the height information of GPS is less reliable. (It might be possible to program a computer to use altitude data from the airplane's altimeter along with latitude and longitude data from the GPS and a relevant ground relief database to make an accurate determination.)

Most countries would not agree to a border that cuts into their airspace and shrinks their territory as the altitude increases; most cases of countries losing area have come about as a result of trying to avert, or losing, an armed conflict. It is entirely possible that Cueball's country has compelled Blondie's country to accept its demands, of which the redrawn border is one. Alternatively, Cueball's country may be deliberately reducing its own airspace purely because it will cause problems.

There is at least one famous case of a border being affected by elevation: the Franco-Swiss border bisects the staircase of the {{w|Hotel Arbez}}. Hence, although part of the upper floor is geographically in France, the entire floor is Swiss territory, because it is only accessible through Switzerland.

The mathematical computation for an angled air sovereignty seems relatively straight-forward at low level and could be expressed with a single line of code or a single equation, although the people acting on the information are likely unfamiliar with code and equations and likely use tools with completely no support for sloped borders. The mention of curvatures in the title text may reveal some emergent problems that need accounting for.

A totally straight line drawn far enough upwards at an angle will find the surface of the Earth curving away beneath it (not even considering terrain undulations) and the angle to the local vertical will reduce as it continues, tending towards vertical as you head towards infinite altitude.

Alternately (although it seems this is not the case) the profile of the sloped border may be assumed to remain at a constant angle to the shifting vertical, in which case it describes a certain {{w|Logarithmic spiral|form of spiral}} (which will eventually loop around the earth).

A third option is that it gains altitude at a constant rate, with respect to the passage of land measured on its surface track, to form a {{w|Archimedean spiral|different spiral}}, in which case it will still loop around the Earth but at an angle that increasingly tends towards horizontal.

While the comic doesn't mention this, such a boundary should probably also extend underground, in the opposite direction. (The straight-line version, if implemented, will eventually reach a depth at which it is tangential to the radius and then rise back through the surface an equal distance further around the planet.) This would then impact, at practical depths for such things, planning rights for property foundations and, at deeper levels, mining rights for minerals.

Practically, an upper-limit to a nation's claim (somewhat below satellites, e.g. the Karman Line) and a lower limit (well before reaching the Earth's mantle) will prevent many of these complications, together with intersections with other (probably vertical) 'territorial volume' borders that will supercede in any compound claims to ownership. - However, it is still ''very important'' to specify exactly which curve (i.e. with respect to what) the boundary is designed to be respecting.

"GIS" refers to {{w|geographic information system}}, a set of tools and methods for capturing, analyzing and presenting spatial and geographic data. While altitude is already an (optional) element in the blocks of information, people developing these systems would be inconvenienced by the additional requirements demanded by the border described in the comic.

It is possible this comic is inspired by such boundary disputes as the {{w|Beaufort_Sea#Border_dispute|Beaufort Sea 'wedge'}} which, while in this case perpendicular to the surface, suffers from alternative interpretations of how to extend it from the shoreline out towards international waters.

==Transcript==
:[Cueball and Blondie are standing on a podium. They are holding a document together between them, filled with unreadable text. On either side of the podium are two informational graphics each on a stand. They are placed a bit behind the back side of the podium. The graphic to the left shows a cross-sectional view of a non-vertical border, shown as a dotted line going up between Cueball and Blondie, who both are standing on the ground. The angle is indicated and noted, and the line tilts towards Blondie's side. The graphic on the right shows a skewed perspective of a similar setup of the non vertical border, shaded so what is behind it becomes gray. There are also some lines on this plane to indicate where it is. It almost looks like a window, but people can move through it. There are also two more persons than on the left, Megan, who is on the same side of the border as Cueball, and another Cueball-like guy standing next to Blondie. Megan is entirely on Cueball's side of the plane, but the other three are positioned so they are intersected by the 'shaded plane' of the border, with the effect that some or most of their bodies are beyond the sloped boundary, in the gray area, but not all. Cueball and Blondie are posed in a mutual greeting across this border, as the others look on.]
:Cueball: With this treaty, we are proud to announce the creation of the world's first '''''sloped''''' international border!
:Angle: 74°

:[Caption below frame:]
:If I'm ever put in charge of a country, I'm going to spend all my time trying to think of new ways to make life a nightmare for GIS people.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Blondie]]
[[Category:Comics featuring Megan]]
[[Category:Multiple Cueballs]]
[[Category: Geography]]

2852: Parameterball

2023-11-08T17:51:42Z

172.71.178.56: /* Explanation */

{{comic
| number = 2852
| date = November 8, 2023
| title = Parameterball
| image = parameterball_2x.png
| imagesize = 518x371px
| noexpand = true
| titletext = The ball's density also varies, but players don't learn the value until after choosing their raquets. The infamous 'bowling ball table tennis' region of the parameter space often leads to equipment damage.
}}

==Explanation==
{{incomplete|Created by a BALL THE SIZE OF 3.14 BEACH BALLS, HEAVIER THAN A CUBIC METER OF CONCRETE, FLYING OVER A NET SHORTER THAN AN ANT, ON A FIELD THE SIZE OF NEW JERSEY - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

A racquet (misspelled as "raquet" in the comic) game is a 2 player point game, with a net, ball, 2 racquets, and a court. The objective of the game is, usually, to hit the ball in a way that it bounces on your opponent's side in a way that it hits the floor before they can hit it onto your side. The two most notable examples of this kind of game are {{w|Tennis}} and {{w|Table Tennis}} (also known as Ping-Pong).

In this comic, a game called "Parameterball" is proposed, where net size, ball size, and court size are randomized. There are 4 different instances of Megan and Cueball playing this game, each in one corner.

In the top left, the court is small while the ball is massive, about half the size of a person. This would be very hard to play, since hitting the net would be easy and the ball would be hard to move.

In the top right, Megan and Cueball are essentially just playing tennis, with a court, net, and ball sized about the same as it.

In the bottom left, Megan and Cueball are essentially just playing ping pong, much like the top right.

In the bottom right, Cueball is struggling to keep the ball from hitting the ground, as it is much bigger than him and the net is basically impossible to hit over due to being taller than Cueball and the ball combined.

The title text mentions that the ball's density is also randomized, and that an infamous incident where the net size, ball size, and court size were similar to that of a Ping-pong match, but with a ball as dense as a {{w|Bowling ball|bowling ball}}, not only led to equipment damage, but does so on several occasions. Despite this, the participants ''do not'' learn the density until ''after'' the racquet is chosen, meaning that they have no way of determining whether the racquet they chose is durable enough until it's already too late. (Choosing an excessively robust item could be detrimental to trying to play with a light ball, conversely, as it proves detrimental to reacting against volleys by a more aptly-equipped opponent.)

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

:[Megan and Cueball are playing a game that looks similar to tennis. There are courts, but on each multiple parts of the game are different. On each, Cueball is on the right and Megan is on the left.]
:[Top left: The court is small, each half slightly wider and deeper than a person is tall, and the ball is extremely large, about twice the height as the players' heads. The ball has just bounced on Cueball's side very slowly, and he is about to hit it.]
:[Top right: The court, ball, and net closely match a regular tennis game, albeit perhaps a slightly more ground area than a doubles'-court. Cueball has just hit the ball, and it is currently flying towards Megan's side.]
:[Bottom left: The ball, and net are much as with table tennis, but the 'court' is a much smaller tabletop. The ball has just hit Megan's side, and she is about to hit it.]
:[Bottom right: The court is slightly larger than the top left, while the net and ball are massive, with the ball at least double the radius and the net significantly over twice the height of the players. Cueball is apparently fighting to push the huge ball high enough to get over the net, indicated by movement lines in which he is barely manage to keep the ball up, never mind the extra amount necessary to be above the net top.]

:[Caption below the panel:]
:Parameterball is a raquet game divided into four quarters, with ball size, court size, and net height randomized each quarter.

{{comic discussion}}