Arctic regions have day and nights that are not just 24
hours long, but much more than that. These regions have a six month of what may be
described as day followed by six months of what may be described as
nights.
The cycles of days and nights is caused by rotation
of earth along a north south axis. This causes different pars of the earth to face the
sun during one complete rotation of earth which takes about 24 hours to complete. The
relative direction of axis of rotation of earth and the orbit of earth around the sun
are arranged in such a way that as the earth orbits round the sun the duration of for
which different parts of the earth face the sun during the one rotation of earth varies
from place to place on earth, and from time to time during one complete orbit round the
sun.
The axis of rotation of earth is tilted at an angle of
23.5 degrees with respect to the plane of rotation of earth round the sun. As a result
the area in the arctic region which falls beyond 66.5 (90 - 23.5) degrees north and
south and longitude remain exposes to or hidden from the sun for continuous period of
six months, result in days and nights of six
months.
Because of tilt of axis of earth, at one time
during its orbit round the sun - around January 14 every year - the north pole is tilted
maximum towards the sun, while the south pole is tilted maximum away from the sun. As a
result the the area around the South Pole pole up to 66.5 degrees south is exposed to
the sun for the complete rotation of earth resulting in day for the entire 24 hour
period of rotation. Similarly, area around north pole up to 66.5 degree north is hidden
from the sun resulting in night for the entire 24 hour period of
rotation.
The relative position of the North and South Pole
with respect to sun gets reversed when the earth comes to the exactly opposite of its
orbit after completing half of its orbit. The the North Pole faces the sun for entire 24
hour rotation of the earth while the South Pole remains hidden from the
sun.
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