Arctic Circle, imaginary circle on the surface of the earth at 661/2°N latitude, i.e., 231/2° south of the North Pole. It marks the northernmost point at which the sun can be seen at the winter solstice (about Dec. 22) and the southernmost point of the northern polar regions at which the midnight sun is visible.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.