The Land of the Long Night

by Paul B. Du Chaillu

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° 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° 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.