How come you can always travel east or west, but north will eventually become south and vice versa?


if you go east non stop around the world, you’ll always be going east until you turn around. but if you travel north, you’ll eventually stop going north once you hit the pole and will be going south without changing your direction. how come this phenomenon doesn’t exist east/west?

In: Other

Looking from outside the earth you would be going right, then left if travelling east (left when you were on the ‘back’ side of the earth). Or up, then down if travelling north/south.

Or course to you, relative to the earth, you are always travelling in one direction. The difference with north/south is that we have magnetic poles, and so have deemed you to be travelling north when going towards the North Pole, and south when going the other way. There aren’t similar poles east/west.

It is to do with the rotation of the planet. The north and south directions on a compass are named after the poles of our planet. Since the poles are points on the opposite sides of a sphere, if you walk past one you are automatically walking towards the other. The east and west directions are not based on points but rather the direction of rotation of the planet. West is opposite to the direction of rotation and east is in the direction of rotation. Because it is based on objective direction rather than convergence towards a point, you can indefinitely walk east or west without changing compass bearing.

Moving “north/south” means “moving towards the North/South pole”. You’re traveling towards a specific point.

Moving “east/west” means “moving in the direction of/in the opposite direction of the Earth’s rotation”. Or “moving with North directly to your left/right”.

East and west are not defined as leading to a specific point, therefore they’re “never-ending”

North, south, east and west are just a consequence of the coordinate system we chose to use. We could very trivially use a different coordinate system where you can always go north or south but east will eventually change to west and west to east.

It is mostly to do with the fact that in order to think about directions to move in relative the ground, we need to pick a point of reference. While there are good reasons for it, the points of reference we ‘happen’ to use are the North and South Poles. Moving North or South will always be taking you to one of the poles, and once you cross it you change your orientation to the pole and begin heading towards the other. Because East and West refer to moving in either direction at a 90deg. angle from the poles, you can continue in either direction forever but that original 90deg. orientation to the pole never changes.

It might make more sense to think of it like; if we moved the poles from the tops to the sides we would have the opposite. East and West would be poles, and if you traveled far enough either way, you would eventually cross the pole and now be headed to the opposite one. While moving North or South would be moving you at a 90deg. angle to the East and West poles, so you could continue on forever in the direction you where facing.

Long story short, the words North, South just happen to be the ones used to describe moving up or down along the line between the poles, and East and West just happen to be the ones that describe moving perpendicular (at a 90deg angle to) from them. The fact that you can continue on eternally in two directions, but constantly swap between the others is something of an accidental consequence of all the other reasons that we decided to use The North and the South poles as the main references for how we describe our orientation relative the earth.