Location: Outside U.S.
Date: Winter 2012-2013
A compass needle is not always parallel to Earth's surface ,but one may dip downward. Why?
Earth's magnetic field at the magnetic poles is perpendicular to the ground. At the equator, it is parallel. Angle of dip varies by latitude between these locations.
If you think of the shape of the field like that around a bar magnet, at the poles, the field is perpendicular to the bar, but between the ends, it is parallel to the bar.
Nathan A. Unterman
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Update: November 2011