The New Student's Reference Work/Poles

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The New Student's Reference Work (1914)
Poles
See also Pole on Wikipedia, and the disclaimer.


Poles (Greek polos, a turning point), in geography are the two extremities of the axis round which the earth revolves, the north pole being 90° north of the equator and the south pole 90° south.  In astronomy the poles, which for distinction are called celestial poles, are those points in the heavens to which the earth’s axis is directed and round which the heavens seem to revolve.  Unfortunately no stars mark the exact position of the celestial poles, and therefore the polestar is used for this purpose, its exact position being determined by noting the point between its upper and lower culminations.  The term poles also has a wider application as denoting the extremities of a line passing through the center of a great circle perpendicular to its plane.  Thus we have the poles of the horizon (which are the zenith and the nadir), the poles of the ecliptic and the poles of a meridian.  In the same sense the terrestial and celestial poles are spoken of as the poles of the equator and the equinoctial, respectively.  Poles in physics denote those points of a body at which its attractive or repulsive force is concentrated.