QUESTION #31

# Is the geographic NORTH pole of the earth a magnetic NORTH pole? Once you have reached the north pole of the earth, what happens to your compass? Which way would it be pointing?

Asked by: Chuck Hendrick & C. J. Price

### Answer

There are two North Poles: the geographical and the magnetic North Pole.

The geographical pole is the point at 90' northern latitude. It is very near to the point at which the rotation axis of the earth passes through the surface. This is the North Pole that is shown on most maps.

The magnetic pole is the point were the magnetic field lines are vertical and enter the earth. This pole wanders around and is currently somewhere off Western Greenland at about 77'N 102'W (see http://sarbc.org/north5b.html).

A magnetic compass needle will always try to align itself with the magnetic field lines. When you are far away from a pole the field lines are nearly parallel to the earth's surface and the compass will point towards the magnetic pole. When you get near the pole the field is stronger and its lines are directed into the earths surface. Therefore the needle is pulled down vertically. If you tilt the compass slightly forward the needle is pulled forward and you think North is ahead. If you then tilt the compass backwards, the needle is pulled around to the back and you think North is behind you. Near the North and South magnetic poles compasses are useless.
Answered by: Michael Ewart, Researcher at the University of Southern California