Magnetic compass

The presence of the geomagnetic field was 1st noticed in ancient times. Some rocks, known as lodestones, when are hung by strings would orient themselves a certain direction. This was attributed correctly to the presence of a force in the air. Even though it was some time before the details were understood fully, this effect was put to use by early sea farers and land explorers. A magnetic compass can still be a valuable navigation aid, which is used by mariners, backpackers, and others who travel far from the familiar landmarks.

The geomagnetic field and the magnetic field around the compass needle interact, so that the force is exerted on the little magnet inside the compass. This force works not in a horizontal plane, but vertically at most latitudes. The vertical component is zero at the geomagnetic equator, a line running around the globe which is equidistant from both geomagnetic poles. As geomagnetic latitude increases, towards north or south geomagnetic pole, magnetic force pulls up and down on the compass needle more. You may have noticed this when you hold the compass. The one end of the needle seems to insist on touching the compass face, while other end tilts up toward glass. The needle tries to align themselves parallel to the magnetic lines of flux.