Samuel Rivier scripsit:

> The North Pole is determined by magnetism. Uranus is
> flipped across so the poles are on its sides. We still
> know which one is north magnetically though. Just
> think of how a magnetic compass works. Well, the south
> pole of a magnet always points north and vice versa.

At present.  But the Earth's magnetic field has repeatedly reversed
direction; during some periods, the South Magnetic Pole is near
the North (geographical) Pole.  And at some periods, the Earth
has had no perceptible magnetic field at all.

At any rate, the presence or absence of a magnetic field does
not determine north and south.

John Cowan                                   [log in to unmask]
One art/there is/no less/no more/All things/to do/with sparks/galore
        --Douglas Hofstadter