So OT as to be extra-planet! Compass needles - which end points north?

On or around Sun, 25 Feb 2007 19:29:45 +0000, steve Taylor enlightened us thusly:

that's 'cos it's a circular motion and from where we're sitting it moves at a speed governed by a sinusoidal relationship. exactly like the way day-length varies, only over a longer period.

The fastest changes are at the midpoint, which is in a few years for magnetic north (or mebbe in a year or so) and in about a month for day-length.

one map here says 4 degrees west of grid north and shifting half a degree in

another one says 5½ degrees west in 1986, moving by half a degree in the next 3 years.

if you find old maps, from say about 1940, it was about 11 degrees.

"> > I know where NSEW are here. It was a purely intelectual question based

Med. The satnav is so accurate it can tell you which end of the boat you are on, but the charts which were last surveyed in the 1800's, can be up to a mile out! TonyB

We don't know how long a flip takes, not what effects it might have on the solar wind. At least we're not so dependent on magnets for navigation as we were even 20 years ago.

The timing isn't predictable, but there might be enough warning to get a lead-lined hat. I reckon it's one of those things that is currently best regarded as something to keep scientists away from the dangeous stuff.

Sun rises in the East sets in the West, so get uo at sunrise and find North then paint needle. You could also use a GPS hand set and set it ???!!!???

Is'nt there a way of using the hands on a watch and studying the shadow produced by a twig placed at the centre with the hour hand pointing to the sun ?

Avast me hearties and prepare for boarding!

Richard ;-)