Читать книгу The Land of the Long Night - Paul B. Du Chaillu - Страница 10

Table of Contents

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° 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.

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
Vardö	22nd
Hammerfest	21st
North Cape or Nordkyn	18th
Where the sun is first seen again, begins at:
Karasjok	January 16th
Vardö	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.