WHAT THE ARCTIC CIRCLE IS.--DESCRIPTION OF THE PHENOMENON OF THE LONG
NIGHT.--REASONS FOR ITS EXISTENCE.--THE ECLIPTIC AND THE
EQUINOXES.--LENGTH OF THE LONG NIGHT AT DIFFERENT PLACES.
Now I was ready to go further northward beyond the Arctic Circle, and
roam in "The Land of the Long Night."
The Arctic Circle is an imaginary line, just as are the Equator and the
two Tropics, going round the earth, and begins at 66 deg. 32' north latitude
and is 1623 miles from the North Pole. It is the southernmost limit of
the region where the sun disappears in winter, under the horizon, for
one day.
At the North Pole on the 22nd of September the sun descends to the
horizon and then disappears till the 20th of March, when it reappears
and remains in sight above the horizon until the 22nd of September. So
at the pole the year is made of one day and one night. On the 22nd day
of December it disappears at the Arctic Circle for one day only. The
space between the Arctic Circle and the pole is therefore called the
Arctic region, or the Frigid Zone. Consequently, the further one
advances to the north, the longer the duration of the night.
I will tell you the causes of this phenomenon of the Long Night. The
earth revolves about the sun once every year, and rotates on its axis
once in twenty-four hours, which makes what we call a day.
Rotate means to move round a centre; thus the daily turning of the earth
on its axis is a rotation. Its annual course round the sun is called a
revolution.
The axis about which the daily rotation takes place is an imaginary
straight line passing through the centre of the earth, and its
extremities are called poles, hence the names of the North and the South
pole. The diurnal movement is from West to East and takes place in
twenty-four hours.
The earth's orbit, or the path described by it in its annual revolution
about the sun, is, so to speak, a flattened circle, somewhat elongated,
called an ellipse. The axis of the earth is not perpendicular to the
plane of the orbit, which is an imaginary flat surface enclosed by the
line of the earth's revolution, but is inclined to it at an angle of 23 deg.
28', which angle is called the obliquity of the ecliptic. The ecliptic
is the path or way among the fixed stars which the earth in its orbit
appears to describe to an eye placed in the sun, for the sun is the
fixed centre and not the earth. The earth, therefore, in moving about
the sun, is not upright, but inclined, so that in different parts of its
course it always presents a half, but always a different half, of its
surface to the sun.
Twice in the year, 21st of March and 21st of September, the exact half
of the earth along its axis is illuminated. On these dates, therefore,
any point on the earth's surface is, during the rotation of the earth on
its axis, half the time in light and half the time in darkness,--that
is, day and night are twelve hours each all over the globe.
These two dates are called equinoxes, March 21st being the vernal, and
September 21st being the autumnal, equinox.
As the earth moves in its orbit after March 21st, the North Pole
inclines more and more towards the sun, till June 21st, after which it
turns away from it. On September 21st day and night are again equal all
over the earth, and after this the North Pole is turned away from the
sun, and does not receive its light again till the following March.
It will thus be seen that from the autumnal to the vernal equinox the
North Pole is in darkness and has a night of six months' duration,
during which time the sun is not seen. Therefore, any point near the
pole is, during any given twenty-four hours, longer in darkness than in
light.
The number of days of constant darkness depends on the latitude of the
observer. At the pole the sun is not seen for six months, at the Arctic
Circle it is invisible, as I have said, for only one day in December. At
North Cape and Nordkyn the sun disappears November 18th, and is not seen
again till January 24th. That is the reason I have called the land
between North Cape and the Arctic Circle "The Land of the Long Night."
This "Land of the Long Night" commences at Nordkyn, or the most northern
point of the continent of Europe,--or at North Cape, but five miles
distant--on the 16th of November. The whole sun appears on that day, its
lower rim just touching above the horizon at noon. The next day, 17th of
November, the lower half of the sun has disappeared, and the following
day, the 18th, it sinks below the horizon and does not show itself again
until the 24th of January--hence the night there lasts sixty-seven days
of twenty-four hours each. And at the Arctic Circle the sun is only
completely hidden on the 22nd of December.
The following table shows you the dates of the disappearance of the sun,
and of its reappearance at the principal places to which we are going.
THE CONTINUOUS NIGHT
_Where the sun is last seen, begins at:_
Karasjok November 26th
Vardoe 22nd
Hammerfest 21st
North Cape or Nordkyn 18th
_Where the sun is first seen again, begins at:_
Karasjok January 16th
Vardoe 20th
Hammerfest 21st
North Cape or Nordkyn 24th
I hope that I have been successful in giving you an idea of day and
night in the Frigid Zone.