I sent this note out last week but changed the thread name to "Polar
Confusion". (see Larry Smith's original posting of
Date: Mon, 10 May 1999 14:36:48 -0600, Subject: Earth's Magnetic Field)
Perhaps this was a mistake as several of you to whom I have
spoken never saw the reply. So, here I go again!
This kind of gibberish that Larry has found in the instructions for "The
Model 28000 Magnetizer" is exactly why I'm afraid to let students read
instructions that come with equipment before I have a chance to do the
same. You should see the nonsense that comes with some of our
demonstration compasses. From the inappropriate tense and ordering of the
explanations, I usually assume that the text was originally written in
some other language (commonly Chinese) and then "transliterated" into
something approximating English. But this would hardly explain the errors
in science of which they are mostly composed.
I goes like this: (BTW: If you want a really complete explanation see
Benjamin Franklin's "On the Magnetics of Compasses".)
The north end of a compass needle was chosen as north because that's the
geographic direction to which the point of a proper compass needle will
orient itself. And that simple statement DEFINES the magnetic poles of a
compass. We are the ones that have selected the the direction of the
magnetic field lines --- we could have as easily chosen the reverse.
[Notice that I will slip to the singular word definition (as opposed to
definitions), as does Franklin, because defining one end of a compass
needle (pole) as north necessarily defines the other end (pole) as south.]
Once this definition has been made, it necessarily follows that the "north
geographic pole" is in actuality a "south magnetic pole" and the "south
geographic pole" is in actuality a "north magnetic pole".
Also, let me assure you that sailors are rarely "confused when directed to
steer a course". This despite the US Army's statement to Congress that
they can only train approximately 18% of the GI's (General Inductees) to
properly use a compass. It was this statement that lead to the
developmental funding for "miniaturizing" the GPS Location Device. This
is why these boxes are now available at such a low cost (I just talked to
a friend that received one free from Shell Oil in some promotion).
And I cannot pass up the opportunity to point out that we train every Boy
Scout you'll meet to use a compass very effectively or they don't even
make Tenderfoot. I must wonder how may GI's the Army really trains to
"properly use a compass" since at least part of their stated 18% must have
been Boy Scouts at one time! Perhaps we could improve the Army's results
if we could make sure to send every GI to Boy Scout camp for a week for
Orienteering Merit Badge. Certainly, we could hardly do worse! I would
also mention that the Marine Corps doesn't have much trouble training its
recruits to use a compass. Perhaps this is because of the association of
the Marine Corps with the Navy or possibly because 41% of them have spent
some time in the Boy Scouts.
In any case, I feel certain that the "confusion" mentioned in the
instructions for "The Model 28000 Magnetizer" is mainly on the part of the
manufacturers who are simply unwilling to admit that they have mislabeled
the polarity of their instrument.
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ERTEL SENDS.
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