Comment by tanzam75 | Hacker News Reader

Comment by tanzam75 | Hacker News Reader

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> As said earlier in the thread: Because of the North Star.

But that doesn't explain why north points up. It only explains why the compass rose points north.

As the article says: "These maps had no real up or down — pictures and words faced in all sorts of directions, generally pointing inward from the edge of the map."

So now you have another step: you have to orient the map. Why north at the top? Why not "orient" the map so that east faces up? Or west? Or south? The compass rose is just a reference -- you could face it in any way.

This is why the article comes up with all sorts of explanations and then finally says that it was just a convention established by Ptolemy. Because at every step of the way between the North Star and north-up, you could ask "Why this way? Why not the other way?" And then when that is answered, you could ask "Why?" again. And so on.

But when something is arbitrary, then there is no "Why?" to be answered. It's just arbitrary.

I think that goes too far. We have a context: the convention of reading with the letters facing up, orienting pictures with words, etc.

You want to see where a hand compass is pointing, you turn until the needle points ahead or 'up'; then you read off the heading (or the other way around). Not too far from that, to writing it on paper that way.

> You want to see where a hand compass is pointing, you turn until the needle points ahead or 'up'; then you read off the heading (or the other way around). Not too far from that, to writing it on paper that way.

No, that's not how you use a compass to determine which way you're facing. (Perhaps that's what you meant by "or the other way around.")

To use a compass, you turn it until the magnetic needle points to "North" on the dial. Then you read the heading from the top of the dial, and that's the direction you're facing.

Note that the needle might point in any direction. The magnetic needle only points ahead (up) if you are facing north." What you're accomplishing by turning the compass is calibrating* the dial, so that it is aligned with the local magnetic field. In other words, so that "North" on the dial is actually magnetic north.

The only thing that your example says is that you have a strong cultural expectation that north is up. So you face north, and the compass needle points up. Circular reference.

But suppose we'd stuck with the traditional European map orientation -- with east being up. (Hence the verb "to orient," related to the adjective "oriental.") Then we'd think it perfectly natural for the compass rose to point left.

Hold a compass straight in front of you. Now walk due east without re-orienting yourself. That is in essence what you are doing if you use the N star as a guide, but insist on orienting the map with east on top.

> Hold a compass straight in front of you. Now walk due east without re-orienting yourself. That is in essence what you are doing if you use the N star as a guide, but insist on orienting the map with east on top.

Take out the compass and rotate yourself until the needle points left. You are now facing due east. Start walking.

Anyway, what does this have to do with north facing up on maps? The procedure does not change based on which direction north faces on a map. Up, down, left, or right, it's irrelevant to the task of walking due east using a compass.

And what does "without re-orienting yourself" mean? Should I face north and walk sideways? I don't get it. It's usually best to re-orient yourself to face in the direction that you're traveling.

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