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North Pole

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Frederick The Monk
57185.  Sun Mar 05, 2006 2:05 pm Reply with quote

Apologies if we've done this before:

Question: How many North Poles does the Earth have?

Forfeits: 1 (The North Pole); 2 (Geographic and magnetic poles)

Answer: 4 (but none of them is actually on the axis of earth's rotation).

1/.Geographic - where the Earth's axis of rotation meets the surface; also known as 'True North'.Classically (19th century) this pole was exactly where people believed the pole of rotation met the Earth's surface, but soon astronomers noticed a small apparent variation of latitude as determined for a fixed point on Earth by observing stars. This variation had a period of about 435 days and the periodic part of it is now called the Chandler wobble after its discoverer. It is desirable to tie the system of Earth coordinates (latitude, longitude, and elevations or orography) to fixed landforms. Of course, given continental drift and the rising and falling of land due to volcanos, erosion and so on, there is no system in which all geographic features are fixed. Yet the International Earth Rotation and Reference Systems Service and the International Astronomical Union have defined a framework called the International Terrestrial Reference System that does an admirable job. The North pole of this system now defines geographic North and it does not quite coincide with the rotation axis so, quite interestingly, the one place that isn;t the North Pole is the exact point of the rotational axis.

2/. Geomagnetic - point where the Earth's magnetic dipole meets the surface. Somewhat confusingly, it is technically the south pole of the dipole.

3/. Magnetic - where geomagnetic field lines point vertically into the ground

4/.Arctic - farthest point from any coastline; also called the 'Northern Pole of Inaccessibility'.This is at 8403?N 17451?W. Similar poles exist in the Pacific and Indian oceans, and there is a dry land pole of inaccessibility in the Antarctic.

Links to:



Researcher: JP


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