What will we do with all the antique compasses when the Earth's magnetic field
flips? Can we just put the labels on upside down?
Mark
________________________________
From: owner-triumphs@autox.team.net on behalf of Randall
Sent: Wed 12/04/2006 8:29 PM
Cc: Triumphs@autox.team.net
Subject: RE: [TR] Quest
> If one were super pedantic, one would point out that Variation is the
> difference between True North and Magnetic North which is very exactly
> determined worldwide by the geological surveying people
Except that the US Geological Survey calls this the magnetic declination,
not Variation.
http://geomag.usgs.gov/
> and marked on maps
> and charts with a date and accompanying information about the the annual
> change of Variation for that epoch as they call it.
Right, but the annual change is only known precisely after it happens.
Anything else is just a projection, subject to error. There are also
significant short term variations, and even things known as "magnetic
storms" where all h*** breaks loose for a few days. The link above has an
entertaining plot of the storm of Oct 29-31 2003, and if you poke around on
that site, you'll also find near-real-time plots of the current variation.
> Also in high
> latitudes the angle of Dip (be quiet that dirty minded boy at the back)
> becomes significant.
Of course, until near the magnetic pole there is no horizontal component at
all and your magnetic compass just spins uselessly.
> The thing you have to deal with concerning your TR compass is Deviation
> which is the difference on any given heading between magnetic
> North and your
> compass reading. This is local to your car
Not necessarily just the car. There are also local variations, due to iron
ore deposits and whatnot.
> and Randall himself are theoretical
Gee I always wanted to be theoretical ! Thanks !
Randall
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