2577: Sea Chase

Explain xkcd: It's 'cause you're dumb.
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Sea Chase
There are two rules on this ship: Never gaze back into the projection abyss, and never touch the red button labeled DYMAXION.
Title text: There are two rules on this ship: Never gaze back into the projection abyss, and never touch the red button labeled DYMAXION.


In this comic, Randall returns to one of his pet subjects: map projections. Unusually, this time it is seen from the perspective of people living — or, in this case, sailing — upon the world that is quite literally being projected differently.

Two sailing ships, of circa 18th-century design, are engaged in a close chase across the Atlantic, the aggressor flying the Skull and Crossbones of a stereotypical pirate vessel. It can be seen from the flags of both ships that they are tacking into the wind, the trailing ship seeming to be lighter and yet deploying more effective canvas with two active sails than the forward one can with three. The ship being chased has a plan to escape and the means to do so. At a crucial moment, Cueball is told to flip a large incongruous switch that (like several other artifacts in the xkcd universe) alters the nature of their reality.

Whereas beforehand the world is directly represented upon a simply contiguous map, the Robinson projection, it is now changed to one (which is actually the new reality) known as the Goode homolosine projection in which the flattening of the world mitigates localized warping of angle, distance, and area by introducing discontinuities in relatively "unused" parts of the mapped world, such as the center of the Atlantic.

By precisely timing the change (as they cross a particular meridian, possibly the 40°W one), they leave the pursuer now on the wrong side of the very real gap, allowing the pursued ship to escape whatever fate they were trying to avoid. Though there is still an oceanic connection, it requires sailing down the edge towards the tropics, rounding this particular rent in the planet's surface, and heading back up the other side. This is vastly further than Cueball's ship needs to travel to reach (presumably) any European port in which they can safely moor.

The title text elaborates on the policies of the ship: crewmates are never to look into the "projection abyss" and to never hit the red button labeled "DYMAXION."

The first rule suggests that changing the projection of physical reality produces a gap in reality — a void. This may be dangerous to gaze into or simply unnerving to crew-mates, hence the rule. This may also be a reference to a well-known quote by philosopher Friedrich Nietzsche: “He who fights with monsters must take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you.” See Beyond Good and Evil at Project Gutenberg

Dymaxion projection of the world

The second rule references a button that seems to do the same thing as the lever but changes the world into a Dymaxion projection. The Dymaxion map projects the Earth onto 20 triangles, which are typically chosen such that landmasses are contiguous while adding many discontinuities in the oceans. This would make navigating by ship in such a 2D world even more difficult than in the Goode homolosine projection. In particular, crossing the Atlantic ocean becomes impossible because of the introduction of a projection abyss from Norway to the Caribbean.

The Robinson, Goode Homolosine, and Dymaxion projections have been referenced in 977: Map Projections.

A similar chase but in space, was represented in 2646: Minkowski Space. Here the pursued spaceship tried to escape by jumping to Minkowski space, and after that failed, the title text mentions jumping to Hilbert space worked. This is similar to the title text here, also mentions other modes of escaping.


[A pirate ship flying the Skull and Crossbones is sailing after a merchant ship. Two sailors' voices come from the merchant ship.]
Merchant ship sailor #1: They're closing in!
Merchant ship sailor #2: Hang on, we're almost at the meridian!
[A map of the Earth in the Robinson projection, with two red dots in the middle of the Atlantic Ocean. A voice comes from the red dot further to the east.]
Merchant ship sailor #2: Now! Throw the switch!
[In a frameless panel, Cueball, representing merchant ship sailor #1, pulls down a giant lever switch labeled "Projection", from "Robinson" to "Goode Homolosine".]
[A map of the Earth in the Goode Homolosine projection, with one red dot on the American side of the split and one red dot on the European side of the split.]

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The flag on the lefthand ship (port-side, if you will :P) looks like the Rising Sun Flag that the Japanese Navy uses as its ensign. 02:31, 5 February 2022 (UTC)

Actually, that the Navy used in 1889 (not uses). 02:31, 5 February 2022 (UTC)
I reckon it looks more like a Jolly Roger. 02:44, 5 February 2022 (UTC)
Ah, you're right. I was thinking Union Jack for a minute but thought there were too many streaks. The upper and lower portions of the skull nearly touch the edge of the flag, making it look like something akin to a sunburst. 02:46, 5 February 2022 (UTC)
If you look at the 2x size image and zoom in it is very clearly the Skull and Crossbones flag from pirates. Which makes a lot of sense. --Kynde (talk) 17:27, 13 February 2022 (UTC)

Okay, I added an initial description for the title text and made a bunch of edits. I'll stop now to let other people get in on the action. :P 02:54, 5 February 2022 (UTC)

Yeah, I kept edit-conflicting (except the first time, when I ended up just appended to some else's first edit) and I think I have reached the point where I've unruined everything of everyone else's that I didn't fully intend to change or add to. But it's late (GMT) and I need my sleep so if I've accidentally rushed through some stuff I shouldn't have then please fill your boots and tweak it back (or onwards) to how it should be. G'night! 03:07, 5 February 2022 (UTC)
G'night. I think we were conflicting. It was my first experience live editing and it was fun. lol 03:08, 5 February 2022 (UTC)

If that is the goode one, I'd like to keep clear of the Baad Homolosine. 14:08, 6 February 2022 (UTC)

What's the reason for thinking the ships are sailing towards Europe? The prevailing wind in the north Atlantic is more or less westerly, so ships tacking into the wind are more likely to be heading west. 20:00, 6 February 2022 (UTC)

They're pointing right, which matches the map? (Was posting the following comment, but might as well answer this straight away.) Also, being chased by a pirate towards all those lovely New World riches seems funny idea, on balance. Although of course it depends on when and how a privateer discovers a possible prize... for some reason in the very middle of the Atlantic rather than in a more bottlenecked part of the trade-routes. Perhaps the merchantman was spotted leaving the vicinity of Bermuda (they have the sails for it!), with signs of carrying cargo of value, and it was considered worth chasing all the way to the mid-Atlantic, just about catching them up. The voice 'from the map' comes from the Easterly ship, as well, so that can really only mean that it went just a little more east prior to the gap-in-the-map appears and it would make Europe the most practical destination afterwards. As for the winds, matching the map position with prevailing/trade-wind diagrams, they could easily be caught in a north-westerly/north-easterly zone that naturally forms a gyre in the atmospheric flow (on average, and of course passing weather systems can send contrary winds any which way off the various edges of a rotating or counter-rotating pressure-system as it moves loosely across the ocean. On the whole I think it was a reasonable assumption to make that they're Europe-bound (by inclination and/or because that's the way the chase takes them), based upon both illustrative convention and the general logistics of the situation, but then with the possible top-mast flags 'error' I'm not sure exactly how strictly Randall intended this all to be. He could have colour-coded the dots, individually, if he was even that bothered - not just made them both red. 20:23, 6 February 2022 (UTC)
Very long explanation for nothing ;-) That they are sailing east is clear from the fact that the red dot closest to Europe is the one being chased, and it just crosses the meridian from the west to the east so they can throw the switch. End of all other arguments. ;-) --Kynde (talk) 17:27, 13 February 2022 (UTC)
Westerlies blow from the West to the East. It could be argued they're within the Trade Wind latitudes, but the ships are positioned far enough up North for me to believe they're meant to be in the Westerlies. 21:35, 28 February 2022 (UTC)

So by my (less than encyclopedic) reckoning, that's a fast gaff-rigged sloop flying chasing what appears to be a more cumbersome gunter-rigged (or bermuda?) schooner (iffy on that one, but it's not a ketch). What's most strange is that they're triangular, not square, as a merchantman/non-raider should need (especially in a chase such as this) as much sail as possible just to get its deeper and wider hull moving. Neither are using topsails, maybe because the wind conditions are contrary. Yes, the top-flags are pointing backwards, but then that's also a common artist error (with anything other than a modern wingsail), while both ships are flying clearly foreward sails (not spinnakers, I'm sure) and the chased one seems distinctly inflated to the direction of travel. Era-specific peculiarities are beyond my easy assessment (or indeed what century such an encounter might actually be in). 20:23, 6 February 2022 (UTC)

I think it is safe to say that Randall did not think too much about how the ships sails worked. For one if the ship has the wind in from the back, then the flags would blow the other way, since the ship will never sail as fast as the wind. --Kynde (talk) 17:30, 13 February 2022 (UTC)
Nah. Randall knows full well how sails and flags work. I reckon he deliberately drew it that way to drive traffic to this site. We should thank him. :-) -- 16:06, 1 March 2022 (UTC)

It should be noted that the Dymaxion map used afloat would almost assuredly be of the "contiguous oceans" variety of projections, not one of the versions that splits the oceans to produce contiguous land masses... 16:21, 7 February 2022 (UTC)

Changing the projection would be extremely unhelpful for any other ships traveling the Atlantic between North America and Europe which hadn't arrived at the meridian yet, as they would have to travel hundreds of miles out of their way to continue their journey. Not to mention, any ship that was on the meridian elsewhere in the ocean would be split in half. -- 21:42, 7 February 2022 (UTC)

The strange large anachronistic square incongruous inscribed otherworldly ¿synthetic? reality-warping switch....

Interesting edits about the switch, along the way. Generally I think compounded adjectival descriptors go by the order of opinion, size, age, shape, (existential) quality, colour, origin, material and purpose - though there are disagreements and alternate versions of that list. What is incongruousity? An opinion or a quality (or origin, at a push?), I'd guess, making each order potentially valid. (In advance of any further arguments, I suggest "strange large" rather than an edit-war, though I personally like its incongruousness being mentioned, and incongruousicity in general. YMMV.) 17:22, 5 February 2022 (UTC)