http://www.physics.hku.hk

physics.hku.hk

It’s not like I was planning a vacation (but you never know); I was just curious, and decided to find out exactly where on the planet the North Pole is. The answer wasn’t as easy as I thought…

As a matter of fact, there are several ‘North Poles’ (the following is somewhat ‘borrowed’ from a Scientific American article…):

  • North Pole, Alaska. This town isn’t close to any of the other North Poles in this post, but the town gets a lot of mail just prior to Christmas every year.
  • Geographic North Pole, the point where all the lines of longitude of a map meet: known as true north to cartographers.
  • Celestial North Pole, a whimsical point that is defined by extrapolating the Earth’s axis of rotation into the heavens. If we imagine the celestial North Pole as a hub, the universe of stars — the celestial sphere — rotates around it. This is an important point for the set-up of sundials (Polaris — the North Star — is located surprisingly close to the Celestial North Pole).
  • Instantaneous North Pole, where the Earth’s rotational axis meets its surface. The instantaneous North Pole is not a fixed point: it whirls in an erratic, spiral dance called the Chandler wobble (i.e.: the Earth wobbles, as discovered in 1891 by Seth Carlo Chandler).
  • The North Pole of Balance is defined as the center-point of the Chandler wobble (see above).
  • Magnetic North Pole, where the Earth’s magnetic field is vertical (also called ‘the magnetic dip pole’: if you stand at this point, a compass needle will try to point (dip) straight down). Similarly to the instantaneous North Pole, the magnetic North Pole is not a static point; it moves as much as fifty kilometers per year. Currently, the magnetic North Pole is moving from northern Canada toward Siberia. And, to be factual, the magnetic North Pole is somewhat of a misnomer because it actually behaves like the south pole of a magnet (by definition, a magnet’s flux lines describe a vector away from the north pole and toward the south pole: the opposite of Earth’s north/south pole magnetic field vectors).
  • Geomagnetic North Pole is an attempt to treat the complexity of Earth’s magnetic field as a dipole bar magnet. Geomagnetic north is of little use to navigators — magnetic north is much more useful — but if you happen to be a space physicist, geomagnetic north might interest you because the further you travel from our planet the more it approximates the characteristics of a dipole bar magnet.

In summary, I have no idea which North Pole Santa calls home; also, if you’re planning a trip to the North Pole, you’d best decide which one you want to arrive at before setting out.

.

.

.