Sea Chase
Sea Chase
[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.]

In this comic, Randall returns to one of his pet subjects: map projections . Unusually, [ citation needed ] this time it is from the perspective of people living — or, in this case, sailing — upon the world that is quite literally being mapped.
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 Goode Homolosine 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 crewmates, 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
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 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.]
