"It's just that I get nervous about heights."
Image Transcription: XKCD Comics image
[Megan is seated at a desk, in front of a laptop. The scene is rotated by 150° clockwise, so she appears to be upside down and angled.]
[Cueball enters the scene from the right side, behind Megan. He has three question marks below his head, oriented upright in frame.]
Megan: They announced that "down" is relative to Mars today.
Cueball: Ugh, I hate when they make another planet the coordinate system origin.
If up is defined as the other way to mars' centre, as it is on earth, then mars would be somewhere in the top left direction in the comic.