Polar Night

Also found in: Wikipedia.

polar night

[′pō·lər ′nīt]
The period of winter darkness in the polar regions, both northern and southern.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Polar Night


a night lasting more than 24 hours, occurring in polar regions north of the arctic circle and south of the antarctic circle. At points in the northern hemisphere with a geographic latitude ϕ, the sun will not rise above the horizon at certain times of the year. This occurs whenever the sun, in its apparent annual motion along the ecliptic, enters an area of the sky that is not visible at that given latitude. At such times, the

Table 1
Geographic latitude (degrees)Polar night (24-hour periods)Polar day (24-hour periods)

sun is located south of the parallel of declination δ = —(90° — ϕ). At points along the arctic circle the sun will not rise once each year; this occurs on the winter solstice (December 21 or 22), when the sun is at maximum south declination δ Θ = –23°27’. As ϕ increases, the arc of the ecliptic in the region of the sky that is not visible also increases. The polar night lengthens, and at the pole itself, it is six months long, lasting from the autumnal equinox to the vernal equinox. At points along the antarctic circle the sun will not rise on the summer solstice (June 21 or 22), and at the south pole the polar night lasts from the vernal equinox to the autumnal equinox.

The refraction of light complicates this phenomenon, and as a consequence the polar night becomes somewhat shorter. Table 1 gives lengths of the polar night and polar day at various geographic latitudes of the northern hemisphere (with refraction taken into account).


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
"Neither solar, nor wind could ensure uninterrupted electricity supply in polar night, when there is no wind and temperatures are well below zero."
"There is always cold air over the Arctic in the polar night and the question is whether it sits there, or it breaks out," Trenberth told the Daily Caller.
In "When The Stars Come Out", children ages 8-11 will delve into the magical realm that is our universe at night, discovering what makes it so extraordinary from moonbows to shooting stars and from the polar night to the northern lights.
The Polar Night - when the sun never appears above the horizon - paints the landscape in an eerie blue twilight.
On the 5th January 2019, Anna McGuire will join many others for an Arctic running experience in the polar night!
With the new data they found that during the southern polar night (mostly during July and August), temperatures right at the surface actually plummeted as low as -97.8[degrees]C (-144[degrees]F), about 5[degrees]C colder than they had previously reported.
Pre-orders begin April 20 and will be available in either Polar Night Black or Sky Gray.
"Northern Greenland is still in the polar night and the temperatures usually average -20 to -30degC.
Experts predict the Arctic could inch above freezing during the polar night for the first time in February since records began.
A total of eight Daimler test drivers simulated two typical working weeks for truckers at a site in during the long polar night in wintry road conditions Finland to allow a research team from Daimler to ask that question.
The Polar Night Nitric Oxide experiment, or PolarNOx, was launched on a Black Brant IX sounding rocket to an altitude of nearly 176 miles.