North Pole

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  1. The northernmost point on the Earth, as determined by the earth's rotation. This is known as the "geographic" north pole, and has a known fixed position.
  2. The north magnetic pole, being the magnetic pole of the Earth's magnetic field. It is so named due to its proximity to the geographic pole, but is in fact a south magnetic pole. (Either that, or every magnet is mislabelled. Magnetic opposites attract, and your magnet "N" points North!)

Astronomers define the north "geographic" pole of a planet in the solar system by the planetary pole that is in the same ecliptic hemisphere as the Earth's north pole. For the magnetic poles, their names are decided upon by the direction that their field lines emerge or enter the planet's crust. If they enter the same way as they do for Earth at the north pole, we call this the planet's north 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 poles was at the North Pole. It is thought that this is 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.

Saturn's moon Hyperion is the only object in the solar system that is known to lack a geographic north pole. It rotates chaotically due to a combination of its irregular shape and tidal influences from nearby moons.

The axial tilt of the planet Uranus is very nearly 90 degrees relative to the ecliptic plane, so that labelling one pole or the other to be the "north" pole is still a matter of some dispute.


See also South Pole