All magnets are dipoles, their poles being identified typically as north and south. You can measure the strength of the magnetism with fairly simple devices, and you can even see a representation of the "lines" of magnetism with something as simple as iron filings. But I'm wondering, aside from bringing another magnet near to it, is there any way of determining whether a given magnetic field is a north pole or a south pole? In other words, what it is about a magnetic field that makes it a a north pole or a south pole? It's certainly not the strength of the field. I wouldn't think it's determined by the direction of the field, since both fields seem to "look" the same. What characteristic of a magnetic field gives it its south-ness or north-ness?