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Which way does a compass point in space?

You guys remember the “Sky Bar?” Yes? No? Anyway….

Just like most of you, I played with magnets when I was a kid. I played with some iron filings on a piece of paper. I remember seeing something that looks very much like the Earth’s magnetic field produced by a magnet. From a magnet, it comes out of the North Pole and curves round in two big ovals and comes back upwards at the South Pole. We on Earth can’t see that field and so when we’re on the ground, it’s going from the South Pole to the North Pole and so the compass points north. If you were right at the North Pole it would actually point straight downwards and if you were at the South Pole it would point straight upwards.

So what about in outer space?

The situation is not so clear. I mean theoretically, a compass is affected by the most prevalent and biggest magnetic source available, and would follow whatever lines of force there were. Depending on how far out a space vessel, carrying the compass is, that source might be the earth or even something in the vessel. NASA scientists have said that it was impossible to predict such behavior exactly from what is now known. Doing more research, I found, far outside the earth’s magnetic field, the compass needle would possibly just point randomly. If the compass could detect a magnetic field from any source, it would point accordingly. However, here on earth, it is the earth’s magnetic field that is detected. In deep space, the earth’s magnetic field would be too weak to be felt.

So if you were to fly around the world in a geosynchronous way (an orbit around the Earth with an orbital period of one sidereal day) so that you were parallel to the equator and going around at the same rate as the Earth, it should still point north-south.  But if you were to do an orbit Pole-Pole, like some of the weather satellites do, it would get confused as it went over the North Pole pointing straight down at the North Pole and rotating over and over its head as you go around.

Another theory comes from Dr. Ken Mellendorf Physics Instructor Illinois Central College:

“The compass will point toward the north pole of that magnet. Every magnet has a north pole and a south pole. A compass works on the Earth because the Earth is truly a giant magnet. If you were near something magnetic, maybe an asteroid with a lot of metal in it, the compass would point toward the magnetic asteroid’s north pole. If you were not near something magnetic, the compass would do nothing.” 

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