The earth's magnetic poles and their impact on a compass (courtesy Addison Wesley Longman, Inc)

Navigation at night can easily be accomplished via stars and constellations but during the day, you must have an alternative means to determine north and south.  The easiest way is to construct a simple compass.

Components and magnetism

A compass acts as a pointer to magnetic north because the magnetized needle aligns itself with the lines of the Earth’ magnetic field.  Magnetism and the Earth's polesMaking a compass in the wild requires a magnetic needle and something to allow it to pivot.  Ferrous metal that is un-magnetized can be used and magnetized later.  Metal such as a needle or razor blade will suffice and can be suspended from a piece of thread or long hair.

You can magnetize (or polarize) a ferrous metal object by slowly stroking it in one direction on a piece of silk or through your own hair.  Metal can also be magnetized by stroking it at one end with a magnet.  Always stroke in the same direction.  As an alternative, insulated wire can be coiled around the metal object and both ends attached to a battery.  Then repeatedly insert one end of the metal object in and out of the coil.  This will magnetize the metal object.

Once the object has been magnetized, suspend if from a piece of nonmetallic string or floated on a small piece of wood, cork, or leaf in water (or some other low friction surface).  The metal object will align itself with a north-south line.

Magnet using needle and water

Magnetized needle and cork in waterYou can construct a more elaborate improvised compass using a sewing needle or thin metallic object, a nonmetallic container (for example, the cut-off bottom of a plastic container or soft drink bottle), and the silver tip from a pen. To construct this compass, take an ordinary sewing needle and break in half. One half will form your direction pointer and the other will act as the pivot point. Push the portion used as the pivot point through the bottom center of your container; this portion should be flush on the bottom and not interfere with the lid. Attach the center of the other portion (the pointer) of the needle on the pen’s silver tip using glue, tree sap, or melted plastic. Magnetize one end of the pointer and rest it on the pivot point.  The needle will align itself on a north-south line.

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