Date: Thu, 18 Nov 2004 12:43:20 -0800
Author: "John Welch"
Subject: compass flipping
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Here's a puzzle that I am having a hard time with-
I have a bunch of cheap compasses in a box on a shelf with lots of =
magnetic demos, including magnets.
Some of the compasses have the red side of the needle pointing north, =
and the others have the red side pointing south. I just figured that =
this was because they were cheap and the manufacturer didn't pay =
attention. So I labeled them according to their orientation in order to =
have two consistent sets. Now a few weeks later, many of the labels are =
wrong, so some compasses must have flipped. What I can't figure out is, =
if a compass is free to orient itself along whatever magnetic field it =
is in (in 2 dimensions at least), why would its magnetic orientation =