Question Time!

[such_heights]

Calling my geologically inclined friends: please excuse a little lazy-webbing and help me resolve a debate with my father. Is there a non-arbritrary way of distinguishing a planet's north from its south, one that doesn't simply rely on convention? And if not, does that make all sci-fi talk of an unhabitated planet's southern hemisphere etc completely nonsensical?

... These are the things that keep me up at night.

Comments

[lorannah]

My understanding as an archaeologist (and feel I have to point out, that archaeologists rarely understand anything properly) is that the planet is naturally a magnet of sorts - hence that on a compass the arrow points one way. Humans decided at some point, that the way that arrow points should be North. Though I'm not sure when they did this.

We're not really sure how the earth developed it's magnetic field, though there are theories - so we're not really sure if all planets have the same phenomenon.

Interestingly though in the past there have been points when the planets poles have switched, so then North sort of would have been what we now think of as south. And the poles always wander around a little every year, so north on a map is never entirely accurate. The magnetic fields also how animals migrate, and my personal favourite fact is that it apparently affects which direction cows stand (unless they're near power lines)