Magnetic north is of interest because it is the direction indicated as north on a properly
functioning (but uncorrected) magnetic compass. The difference between it and true north is
called
the magnetic declination (or simply the declination
where the context is clear). For many purposes and physical circumstances, the error in
direction
that results from ignoring the distinction is tolerable; in others a mental or instrument
compensation, based on assumed knowledge of
the applicable declination, can solve all the problems. But simple generalizations on the
subject
should be treated as unsound, and as likely to reflect popular misconceptions about terrestrial
magnetism.
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While the choice of north over south as prime direction reflects quite arbitrary historical
factors,[which?] east and west are not nearly as natural alternatives as first glance might
suggest. Their folk definitions are, respectively, "where the sun rises" and "where it sets".
Except on the Equator, however, these definitions, taken together, would imply that
Reasonably accurate folk astronomy, such as is usually attributed to Stone Age peoples or later
Celts, would arrive at east and west by noting the directions of rising and setting (preferably
more than once each) and choosing as prime direction .