Text 2073, 66 rader
Skriven 2005-01-07 22:17:11 av Peter Karlsson (2:204/254.222)
   Kommentar till text 2056 av Michael Cronsten (2:205/412.444)
Ärende: Sydpolen (vid gränsen mot Tjeckien?)
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> Nån som har alla fakta till hands?

Wikipedia har en lång utläggning i ämnet magnetisk norpol på
<URL:http://en.wikipedia.org/wiki/North_Pole>:

Magnetic North

Magnetic North is one of several locations on the Earth's surface known as the
"North Pole". Its definition, as the point where the geomagnetic field points
vertically downwards, i.e. the dip is 90°, was proposed in 1600 by Sir William
Gilbert, a courtier of Queen Elizabeth I, and is still used. It should not be
confused with the less frequently used Geomagnetic North Pole. Magnetic North
is the place to which all magnetic compasses point, although since the pole
marked "N" on a bar magnet points north, and only opposite magnetic poles are
attracted to each other, the Earth's magnetic north is actually a south
magnetic pole.

Magnetic poles can flip flop from north to south and back again. The Earth's
poles have done this repeatedly throughout history, and 500,000 years ago, the
south magnetic pole was at the North Pole. It is thought that this occurs when
the circulation of liquid nickel/iron in the Earth's outer core is disrupted
and then reestablishes itself in the opposite direction. It is not known what
causes these disruptions.

The first expedition to reach this pole was led by James Clark Ross, who found
it at Cape Adelaide on the Boothia Peninsula on June 1, 1831. Roald Amundsen
found Magnetic North in a slightly different location in 1903. The third
observation of Magnetic North was by Canadian government scientists Paul Serson
and Jack Clark, of the Dominion Astrophysical Observatory, who found the pole
at Allen Lake on Prince of Wales Island. The Canadian government has made
several measurements since, which show that Magnetic North is continually
moving northwest. Its location (in 2003) is 78°18' North, 104° West, near Ellef
Ringness Island, one of the Queen Elizabeth Islands, in Canada. During the 20th
century it has moved 1100 km, and since 1970 its rate of motion has accelerated
from 9 km/a to 41 km/a (2001-2003 average; see also Polar drift). If it
maintains its present speed and direction it will reach Siberia in about 50
years, but it is expected to veer from its present course and slow down.

This movement is on top of a daily or diurnal variation in which Magnetic North
describes a rough ellipse, with a maximum deviation of 80 km from its mean
position. This effect is due to disturbances of the geomagnetic field by the
sun. A line drawn from one magnetic pole to the other does not go through the
centre of the Earth, it actually misses it by about 530 km.

The angular difference between Magnetic North and true North varies with
location, and is called the magnetic declination.



Det står inte lika mycket om den magnetiska sydpolen
<URL:http://en.wikipedia.org/wiki/South_Pole>:

Magnetic South Pole

The Magnetic South Pole is the point nearest the Geographic South Pole where
the field lines of Earth's magnetic field point directly into the ground. It
does not coincide with the Geomagnetic South Pole.

On January 16, 1909 an expedition led by Ernest Shackleton found the Magnetic
South Pole.


[Text från Wikipedia faller under GNU Free Documentation License]

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