Midnight
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.
Midnight
the moment at which, for a given point on earth, the center of the sun (the true sun or the mean sun) is in the lower culmination. The apparent midnight corresponds to a meridian transit by the true sun, while the mean midnight corresponds to a transit by the mean sun. The time at which midnight occurs depends on the geographic longitude. Midnight begins one hour later for every 15° of longitude to the west. All data in astronomical almanacs are calculated for mean midnight at the Greenwich meridian, from which universal time is figured.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.