The
poles
The idea of standing on the top or bottom of the Earth or being
where the compass needle points directly straight up or down has always
raised the imagination of explorers and scientists alike. The points
on Earth known as "the Poles" are not just two points, but
four points, the North and South Geographic poles and the North and
South Magnetic Poles.
The Geographic Poles
The North and South Geographic Poles are the points
on the Earth's surface defining the axis of rotation of the Earth. They
are located in the Arctic Ocean, and within the continent of Antarctica.
The axis is not perpendicular to the plane of the Earth's orbit around
the Sun; that is, the axis does not point straight "up and down"
with respect to the orbit. Instead, it is tilted about 23.5 degrees
to the perpendicular.
It is because the Earth's axis remains pointing in roughly the same
direction in space that the Sun appears to move north and south over
the course of a year. However, the axis is slowly changing direction
over a long period of time, completing one cycle about every 26,000
years. This effect is like a spinning top slowing down, as it slows
it starts to wobble, with its axis of rotation moving in a slow circle.
The Magnetic Poles
The Earth's magnetic field is tipped in relation to its geographic poles.
The field is rather complicated, and there are different possible definitions
for the Magnetic Poles. A basic magnetic field that provides the best
approximation to the Earth's field is tilted by about 11 degrees to
the Earth's rotation axis. However, the North and South Magnetic Poles
that are most often referred to are the two points on the Earth's surface
where the Earth's magnetic field points straight up and down.
The poles are presently situated at about 107°W, 80°N (in the
Arctic Ocean, north of Canada), and at about 139°E, 64°S (off
the coast of Antarctica). However, they do drift: the South Magnetic
Pole is currently moving north west at about 5km per year, while the
North Magnetic Pole is also moving north-west, but at about 20km per
year.
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