Scouts-L Mail Archive for June of 1999: Re: Finding north question and wandering North Star
Re: Finding north question and wandering North Star
Tue, 8 Jun 1999 19:08:55 -0400
Mark Arend wrote:
> What's interesting, though, is the more rapid change in the movement of the
> magnetic north pole--about 1 degree in 8 years according to a table I have.
> Apparently London hasn't measured 0'0" since 1657. In 1802 it was over 24
> degrees west and now appears to be heading back east.
Two things are at work I think.
1. Precession, which is the "wobble you observe in spinning tops and
toy gyroscopes also causes the observed position of the North Star to
vary from "True North". Earths precession cycle is something like
25,000 years (i.e. 1 complete "wobble" of the earth's axis). A real math
or physics maven can calculate this exactly for you :-)
2. Differences in the rotational axis of the earth at its core versus
the rotational axis of earth's surface. There's research going on about
this one but some think that a minute difference in the rotational axis
and velocity of the molten core from the earth's crust is causing the
"Magnetic Pole" to march North by Northwest across Canada at a rate of
about 10 miles per year.
Now if that doesn't liven up your first class compass requirements
discussion, I don't know what will (-: