xkcd.WTF!?

Explanation ➲

Megan and Cueball are installing wall-to-wall carpeting (also known as fitted carpet), which usually runs from the inner edge of one wall to the inner edge of a facing wall. Somehow, they have managed to mistakenly start laying the carpet against the outer edge of the wall without noticing. Despite encountering unfinished and uneven surfaces, plants, rocks, and other obstructions, they have not realized their error, and have simply continued laying carpet for an unknown distance. Presumably, they would continue doing so until they encountered the outer wall of another building. Alternatively, if they check whether the wall is actually the other end of their room, they may keep going even then. Provided they can overcome the various geographical obstacles they might encounter — including oceans — they could eventually reach the other wall of their building by circumnavigation. They may run into a more immediate problem that prevents either approach, though, as it appears their last roll of carpet is about to run out. One wonders whether Cueball and Megan are topologists, since the inside and outside of a room (a closed loop) on a sphere (Earth) are topologically equivalent.

According to the title text they have failed to notice another rather large clue to their problem — that there is a big open sky above them. Instead, they have, rather improbably, interpreted this as an extremely large skylight — a window on the ceiling designed to add light to a space of a building.