The Earth on June 21.
The total absence of the sun from the Arctic regions during a large part of each year makes the climate severe and the country desolate. Direct sun rays are necessary to insure warmth, and the regions within the Arctic circle receive at the best only slanting rays.
The Earth on December 21.
In the temperate zones the sun is never exactly overhead. For people who live within the tropics it is overhead twice every year. At all places along the equator the sun is overhead at noon on the 21st of March. Each day after, it comes overhead at noon at places farther north, until the 21st of June, when it is overhead at the tropic of Cancer. After this the sun appears to turn and go south, and on September 22 it is again overhead at noon at the equator. The sun then continues to move southward each day until December 21, when it is overhead at the tropic of Capricorn. And so it goes back and forth the year round.
While the sun is north of the equator, there is constant day somewhere within the Arctic circle; when the sun is south of the equator, there is constant night somewhere within the Arctic circle. The farther a region is from the equator, the longer are the days and nights at different seasons of the year. At the pole there is a night of six months and a day of six months. The night is sometimes lighted by the moon and sometimes by the aurora borealis.
Daily Motion of the Heavens as seen at the North Pole.
There are but two seasons in the Arctic regions—a long, cold winter and a short, dry summer. It is during the summer that the explorers do their work. Throughout the dark winter they can do nothing. Even in the summer, navigators meet with many perils, for Arctic navigation is not an easy matter. Besides the danger that the vessel may be frozen in an ice pack, or crushed between icebergs, the navigator is often blinded by fogs and snows, and has to face unknown tides and currents.