Re: Which way is north?

On Wed, 27 May 1998, Roman J. Smith wrote:

>We know that if we set two bar magnets side by side, the positive pole of
>one must line up with the negative pole of the other for them to stick
>together. We also call the positive pole "North" and the negative pole
>"South". So if the positive needle of the compass points North, the compass
>needle must be aligned with the opposite poles of the Earth. So the
>positive compass needle points to the negative pole of the Earth. That
>means that the magnetic north pole of the Earth is at the Earth's South Pole.
>
>So we now have a distinction between the "North magnetic pole" (in the
>Artic) and the "Magnetic north pole of the Earth" (in the Anartic).
>
>The only way that all of this could be wrong is if the negative needle of
>the compass points north. I do not have a bar magnet available to me to
>test my compass. Can anyone verify all of this?

The point about this is that it is totally arbitrary which end of a
magnet we call North - there is no way of telling which end of a magnet is
north and which is south, without using another magnet (or a
electromagnetic field). Hence the "North" Pole of a compass or
any magnet can be defined as the end which points north, or more
accurately the end which points to the Earth's magnetic "North Pole",
which is the magnetic pole closest to the true North Pole.

David


--------------------------------------------------------
David Ball
Ridcully@Kami.Keble.Ox.Ac.Uk
Nonsuch Venture Scout Unit, Epsom and Ewell, Surrey, UK.
Oxford University Scout and Guide Group, Oxfordshire, UK.

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