Making a compass from magnet and needle -- which end is north?
I was watching one of those Discovery Channel wilderness survival shows last night and one of the "survivors" made a compass from a piece of wire tie and an earbud's magnet.
He stripped the plastic from the tie and rubbed the magnet in a single direction on one end of half the wire, then suspended it from a thread.
How would he know which end of the wire was north? As best I can tell, if you don't know the orientation of the magnet, you can't determine the orientation of the needle. Did magnetizing only one end of the wire make a difference?
Edit:
In their scenario, it was daytime, but in a jungle. The view of the sky was pretty obscured and I believe it was somewhat overcast. I figured if they couldn't actually determine east from west (they wanted to go east), they couldn't tell north from south to calibrate the compass by the light/sun. I believe it was midday.
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Having watched what I believe to be the episode of the program in question (and if not, it was something very similar), I would say that in my recollection the specific direction of travel was not important (the two survivors did not know where in the jungle they were, nor which direction had the best chance of rescue/encountering civilization.
The point of the crude compass, per the dialogue/explanation, was not to have them traveling in any specific direction, but rather to prevent them from getting lost and traveling in circles.
One direction, regardless of which direction it was, is what they needed, and what they achieved. It doesn't matter if their "North" was actually "South" so long as it was the same direction that they were traveling before.
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Even in an overcast jungle, the sun still cast's a shadow, they'll just be more diffuse and not as ray traced, but if there is light, it is possible to determine which direction it is coming from. The only caveat being at high noon right on the equator during equinox when the sun is literally directly overhead. Having the sun directly overhead doesn't help you, but even then, only 15 minutes later you can have your bearings.
Use a tree, or use a stick planted in the ground. A clear floor of any size will make things easy for you, plant your stick, then look for whatever you might think looks like the darker side of it. Mark this with a stone or leaf or something. Wait 15 minutes, then do the same thing again. You'll have two different points, and easily be able to determine which hemisphere of the sky the sun is in.
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What you would have to know beforehand, is which way is generally north, by other methods, like the North Star, or from the direction of the sun. I don't mean that you could tell which way is north precisely without a compass or gps, but one of the ends should be obviously wrong. For instance in the northern hemisphere, the end pointing towards the sun is the south end.
Then you could mark which end of the improvised magnet pointed north.
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