Anyone who has been at sea or has simply become lost
hiking in the woods (before the satellite age) knows the importance of a compass, an
ancient device which works on the principles of magnetism. A compass is a magnetically
sensitive device that is capable of indicating the direction of the magnetic north of
the earth's magnetosphere, or regions dominated by the magnetic field of celestial
objects.
This device was invented in China in the second
century, A.D., and was used for navigation by the eleventh century. By 1300, the dry
compass was invented in Europe; this compass has been replaced by the liquid-filled
magnetic compass of the twentieth century. A gyrocompass or an astrocompass can be used
now to find "true North" since it is unaffected by magnetic fields, power circuits which
may be nearby, or close masses of ferrous (iron) metals.
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