Tropic of Cancer, parallel of latitude at 23°30− north of the equator; it is the northern boundary of the tropics. This parallel marks the farthest point north at which the sun can be seen directly overhead at noon; north of the parallel the sun appears less than 90° from the southern horizon at any day of the year. The sun reaches its vertical position over the Tropic of Cancer at about June 22, the summer solstice in the Northern Hemisphere. When the Tropic of Cancer was named, the sun was in the constellation Cancer at the time of the summer solstice.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.