How Can the Sun Shine at Midnight?
“HOW can the sun never set?” As a Finnish missionary serving in Papua New Guinea, I often heard questions like that one. In the Tropics the number of daylight hours changes little from month to month. So the idea that in the Arctic the sun does not set for months is hard for residents of the Tropics to imagine. And when I tried to explain that in winter the sun never rises, many were even more puzzled.
How, then, does the sun shine at midnight? This remarkable phenomenon has to do with the fact that in the earth’s annual trip around the sun, earth’s rotational axis remains tilted 23.5 degrees away from vertical. Thus, during summer in the Northern Hemisphere, the North Pole is tipped toward the sun, while in winter it is tipped away from it. Since the earth rotates on its axis once a day, at the Arctic Circle on one night a year—about June 21—the sun does not set. Likewise, on one day a year—about December 21—the sun does not rise, though at noon the landscape may be bathed in predawn twilight.
In fact, the farther north you go above the Arctic Circle, the more summer nights will be graced by the midnight sun and the more winter days will be sunless. At the poles, day and night both last for six months.a
How do the inhabitants of polar regions sleep in the summer, and how do they cope with the long winter nights? In the past in some cultures, people slept more than twice as many hours a night during the winter as they did during the summer. Adopting a more modern way of life has reduced that difference for many. But the long days of summer still imbue dwellers of the Northland with added energy. “When it is broad daylight at 11:00 p.m., I just don’t feel like going to bed,” says Patrick, who lives in Alaska. “Sometimes I go out and cut the grass or perform some other task.”
On the other hand, months of daylight or darkness can be wearing—physically and psychologically. Thus, some people try to block the light from entering their bedroom in the summer and expose themselves to bright lights in the winter, all in an effort to balance out their sleep mechanisms and ward off exhaustion and depression. Despite the challenges, however, residents and visitors agree that experiencing the midnight sun is unforgettable.—Contributed.
a The Antarctic experiences these same phenomena, but the Antarctic has summer when the Arctic has winter.
[Diagram/Pictures on page 31]
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Earth’s tilted axis puts the poles in constant sunlight in summer and constant darkness in winter (Example shown is for the Northern Hemisphere)
● ● ● ● ●
Winter ● ◯ ●
● ● ● ● ●
Earth spins on its axis once a day
[Picture on page 31]
Time-lapse photo of midnight sun
© Paul Souders/WorldFoto